Title Page
 Table of Contents
 Part 1: Basic principles of...
 Part 2: Radiological health
 Part 3: Civil defense
 Part 4: Panel discussion
 Back Matter

Radiological health and civil defense
Full Citation
Permanent Link: http://ufdc.ufl.edu/UF00005079/00001
 Material Information
Title: Radiological health and civil defense Fourth National Public Health Engineering Conference, March 27-30, 1951
Series Title: Bulletin series ;
Physical Description: 107 p. : ill. ; 28 cm.
Language: English
Creator: University of Florida -- Engineering and Industrial Experiment Station
Conference: Public Health Engineering Conference, 1951
Publisher: The Station
Place of Publication: Gainesville, Fla
Publication Date: 1951
Subjects / Keywords: Radiation -- Physiological effect -- Congresses   ( lcsh )
Radiation -- Health aspects -- Congresses   ( lcsh )
Radioactivity -- Congresses   ( lcsh )
Nuclear weapons -- Safety measures -- Congresses   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
bibliography   ( marcgt )
conference publication   ( marcgt )
non-fiction   ( marcgt )
Bibliography: Includes bibliographical references.
Statement of Responsibility: sponsored by the Engineering and Industrial Experiment Station.
General Note: "November, 1951."
 Record Information
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: ltqf - AAA6367
ltuf - ANX7687
oclc - 13145014
alephbibnum - 002847287
System ID: UF00005079:00001

Table of Contents
    Title Page
        Page 1
    Table of Contents
        Page 2
        Page 3
        Page 4
    Part 1: Basic principles of radiation
        Page 5
        Page 6
        Page 7
        Page 8
        Page 9
        Page 10
        Page 11
        Page 12
        Page 13
        Page 14
        Page 15
        Page 16
        Page 17
        Page 18
        Page 19
        Page 20
        Page 21
        Page 22
        Page 23
        Page 24
        Page 25
        Page 26
        Page 27
        Page 28
        Page 29
    Part 2: Radiological health
        Page 30
        Page 31
        Page 32
        Page 33
        Page 34
        Page 35
        Page 36
        Page 37
        Page 38
        Page 39
        Page 40
        Page 41
        Page 42
        Page 43
        Page 44
        Page 45
        Page 46
        Page 47
        Page 48
        Page 49
        Page 50
        Page 51
        Page 52
        Page 53
        Page 54
        Page 55
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        Page 58
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        Page 60
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        Page 70
        Page 71
        Page 72
        Page 73
        Page 74
        Page 75
        Page 76
        Page 77
    Part 3: Civil defense
        Page 78
        Page 79
        Page 80
        Page 81
        Page 82
        Page 83
        Page 84
        Page 85
        Page 86
        Page 87
        Page 88
        Page 89
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        Page 93
        Page 94
        Page 95
        Page 96
        Page 97
        Page 98
        Page 99
    Part 4: Panel discussion
        Page 100
        Page 101
        Page 102
        Page 103
        Page 104
        Page 105
        Page 106
        Page 107
    Back Matter
        Page 108
        Page 109
        Page 110
Full Text



Bulletin Series No. 48

/APkowcam /1951


Wo. V. & //




(Fourth National Public Health Engineering Conference)

March 27-30, 1951

Sponsored by the

Engineering and Industrial

Experiment Station

Bulletin Series No. 48

November, 1951

Published monthly by the


College of Engineering * University of Florida 0 Gainesville

I' nlered as second-class matter at the Post Office at GailnsTille, Florida


(Fourth National Public Health Engineering Conference)

March 27-30, 1951

PART 1: Basic Principles of Radiation . . . . . . . . . . . . . . . . . . . . . . ... 5

Historical Sketch of Radiation Protection Experience and Increasing
Scope of Radiation Protection Problems, Karl Z. Morgan . . . . . . . . 5

Nuclear Structure and Nuclear Reactions, R. T. Overman . . . . . ... 13

Units of Radiation and Radioactivity, Elda E. Anderson . . . . . ... 18

Detection of Radiations, R. T. Overman . . . . . . . . . . . . . . . . ... 22

PART 2: Radiological Health ................... ............. 30

Biophysics Methods of Radiation Detection, A. A. Bless ...... . . 30

Some Quantitative Aspects of Naturally Occurring Radioactivity,
George K. Davis ................... . .............. 34

Quantitative Limits of Permissible Exposure of Personnel,
Karl Z. Morgan ................................... 37

Basic Principles of Radiation Protection, Elda E. Anderson . . . . . 47

Internal Radiation Hazards, Cyril L. Comar . . . . . . . . . . . . . .. 51

Radioisotopes in Medicine, Gould A. Andrews . . . . . . . . . . . . .. 54

Industrial Applications of Radioactivity, George G. Manov ... . . . 57

Disposition of Radioactive Sources, C. C. Ruchhoft ........ . . . 64

Radiological Health Program, Edwin G. Williams . . . . . . . . . . ... 69

Problems of Control and Disposal of Radioactive Waste Materials,
Roy J. Morton .................................... 73

PART 3: Civil Defense ..... . ........ . .. .... . . .. .. ...... .. . 78

Medical Aspects of Civilian Defense Against Atomic Weapons,
George A. Hardie ................................. 78

Decontamination of Radioactive Areas, Francis E. Ray . . . . . ... 83

Coordination Between Fire, Police, Health, Welfare, and Rescue Page
Workers,W. D. oiner .............................. 85

Mutual Aid and Mobile Support, H. H. Woeljen . . . . . . . . . . . ... 87

Defense Against Biological Warfare, Richard S. Green . . . . . . ... 89

Chemical Warfare Defense Problems, Harry P. Kramer . . . . . ... .. 92

PART 4: Panel Discussion ................... ..............100

Permission is given to reproduce or quote any
portion of this publication provided a credit line
is given acknowledging the source of information.


The Fourth National Public Health Engineering Conference was held March 27-30, 1951 in
Gainesville under the sponsorship of the Engineering and Industrial Experiment Station, College
of Engineering, University of Florida.

The program for the first two days was arranged with the view of serving public health person-
nel and practicing physicians interested in radiological health and medical applications of radia-
tions and radioactivity. The remainder of the program was intended primarily for health officers,
public health nurses, sanitary engineers, sanitarians, water and sewage treatment plant operators,
and other persons interested in radiation aspects of civil defense.

After the second day the program was common for the Nineteenth Annual Short Course on Water
and Sewerage, and the Third Annual Short Course for Sanitarians, sponsored by the General Exten-
sion Division of the University. The combined conference and short courses were arrangedin co-
operation with the Florida State Board of Health, the office of the Stare Director of Civil Defense,
the State Medical Society, and other interested groups. The Planning Committee for the conference
was comprised of the following persons:

Dr. John S. Allen, Vice President, University of Florida.
Dr. A. P. Black, Head Professor of Chemistry, University of Florida.
Dr. James L. Borand, President, Florida State Medical Society.
Dr. C. L. Brumback, Director, Palm Beach County Health Department.
Hon. Gordon T. Butler, President, Florida League of Municipalities.
Dr. T. Z. Cason, Director, Department of Medicine, Graduate School, University of Florida.
Dr. Geo. K. Davis, Professor of Nutrition, Agricultural Experiment Station, University of Florida.
Dr. Roland B. Eursler, Assistant Dean, College of Business Administration, University of Florida.
Professor W. F. Fagen, Electrical Engineering Department, University of Florida.
Dr. James V. Freeman, President, Dural County Medical Society.
Dr. E. R. Hendrickson, Professor of Sanitary Engineering, University of Florida.
Col. R. G. Howie, State Director of Civil Defense.
Professor John E. Kiker, Civil Engineering Department. Chm., Planning Committee, University of Florida.
Professor Albert L. Kimmel, Chemical Engineering Department, Unversity of Florida.
Col. H. N. Kirkman, Director, State Department of Public Safety.
Mr. David B. Lee, Director, Bureau of Sanitary Engineering, State Board of Health.
Dr. John M. McDonald, Director, Division of Industrial Hyg., State Board of Health.
Mr. W. T. Mcllwain, President, Florida City Managers Association.
Dr. K- E. Miller, Assestant to State Health Officer, State Board of Health.
Dr. Ralph A. Morgan, Director, Fla. Engineering and Industrial Experiment Sa., University of Florida.
CoL. James M. Morris, Director of Civil Defense, Alachua County.
Dr. L. L. Parks, Director, Field Technical Staff, State Board of Health.
Professor Earle B. Phelps, Civil Engineering Department, University of Florida.
Dr. Francis E. Ray, Director, University of Fla. Cancer Research Laboratory, University of Florida.
Mr. Earl M. Sawyer, Department of Physics, University of Florida.
Dr. Wilson T. Sowder, State Health Officer, State Board of Healih.
Professor William T. Tiffin, Mechanial Engineering Department, University of Florida.
Dean Joseph Weil, College of Engineering, University of Florida.

Much of the success of the conference was due to the support of the outside groups represented
by the foregoing committee. Major credit is also due to those who took part in the program. The
papers were well prepared and the discussions were presented enthusiastically.

The total registration for the conference was 432, including 308 out-of-town registrants from 11
states.We of the University are gratified bythis attendance and bythe interest shown inthe papers.

John E. Kiker. Jr.
Professor of Public Health Engineering

part I 12aic principles of Radlation

Historical Sketch of Radiation Protection Experience and Increasing
Scope of Radiation Protection Problems

Director, Health Physics Division
Oak Ridge National Laboratory
Oak Ridge, Tennessee

M AN has always been subjected to a certain
amount of naturally occurring ionizing ra-
diation. Cosmic rays from outer space come
into our atmosphere producing secondary ioniz-
ing radiation, which has a maximum intensity
cqual to about 50 times the sea level value at an
elevation of about 13 miles. Cosmic ray intensity
at 2,000 meters increases by 331' in going from
u0 to 50" geomagnetic latitude. Therefore, the
latitude and elevation at which a man lives de-
termine the amount of cosmic ray exposure. In
addition to the radiation received from cosmic
rays, man is incessantly bombarded by the radia-
tion from about 50 naturally occurring radioiso-
topes. Moat of these radioisotopes are members
of three radioactive chains, designated as ura-
nium, actinium and thorium series. The uranium
chain is shown in Fig. 1. In addition to the
naturally occurring heavy radioisotopes. there
are a few naturally occurring light radioisotopes.
such as K*U, RbST and C1. The concentration of
these radioisotopes in our food and water varies
considerably for different areas. For example,
the radium content in the New York area drink-
ing water is about 5 x 10-1�; pt/cc: the value is
about 5 x 10 1" /e/ce in the Rochester water sup-
ply ; and 10-' pc/ce in some mineral spring
water from various parts of the world. These
naturally occurring radioisotopes become de-
posited in our bodies so that from the day of our
conception to the grave we are bombarded by
this background radiation, which may average
from about 0.5 mrep/day to 2.0 mrep/day. Thus
we are forced to the conclusion that although
man has probably not profited from ionizing ra-
diation, he certainly has managed to develop in
spite of it.
This low level of background radiation has
probably had some biological effect on man. Most
of the deleterious effects of radiation, such as
damage to the hematopoeitic system, require
large doses (much larger than levels of natural
background) before there are any observable
effects. In other words, there seems to be a
threshold below which either no damage occurs
or the damage is repaired at the same rate at
which it develops. Some biological damage, such
as genetic changes or shortening of the life span,
apparently does not require a threshold dose be
fore damage results, but the resulting damage
varies linearly with the dose so that evni small
exposures such as those from background radia-
tion produce an effect. It is believed that each
rep of ionizing radiation produces about 3 x 10 -

mutations per gene. If a person is exposed to
about 0.6 mrep/day during the first 45 years of
life (approximately to the termination of the
child-bearing period), this would account for
3 x 10-7 mutations per gene. This increase in
mutation rate in not significant, however, since
the spontaneous rate is about 10-5 mutations per
gene, indicating that there are many sources
responsible for mutations other than ionizing
According to calculations of R. D. Boche, each
rep of ionizing radiation reduces the life span by
about 10 0. In other words, if a person received
0.6 mrep/day for a period of 70 years, it might
be expected that the life span would be reduced
about six weeks (if animal experiments can be
extrapolated to man). This reduction in life span
is of no importance, however, in view of the fact
that many of our commonplace and eagerly sought
after overindulgences lop off years from our
average life.
Problems of radiation protection began with
the discovery of x-rays and radium. For example,
Mr. Grubbe, who was an experimenter and manu-
facturer of vacuum tubes, was studying the fluor-
escence of chemicals with the use of a Crookes'
tube and, while making these studies, he exposed
his hands between the tube and fluorescent
materials over a period of several days and re-

u a nm,

Jn tior
. oK

L^a"f .A k A

Flg. I.

clived a dermatitis which became so acute that
he sought medical aid. This was during the latter
part of January, 1896, less than a month after
Roentgen announced the discovery of x-rays.
Another example of early radiation damage oc-
curred when H. Becquerel, a few years after he
discovered uranium, carried a glass tube contain-
ing radium-bearing barium chloride in a small
pasteboard box inside his vest pocket for about six
days and later observed a red spot on his body,
which developed into an ulcer that healed within
a few months, leaving a permanent scar. Thus we
see that from the very beginning of the discovery
of x-rays and radium man has suffered the con-
sequences of overexposure because of carelessness
or ignorance concerning proper protective meas-
ures. Ionizing radiation, like all great tools of
science, can be used either to bring man under-
standing and happiness and a better way of life or
can cause misery, suffering and death.
During the First World War the x-ray and
radium industries carried on a flourishing busi-
ness. In spite of the fact that a great deal was
known about the proper handling of sources of
ionizing radiation, few precautions were taken.
X-rays were used routinely for the examination of
war materials for flaws, and many persons were
employed in the radium dial industry. During
this same period many persons considered radium
as a cure-all, and a number of people drank ra-
dium water or were injected with radium. Most
of these persons did not detect any immediate
damage, but 10 to 20 years later became the
victims of bone sarcoma and other defects caused
by radiation. Several persons, such as S. Russ
(1915) who made recommendations to the British
Roentgen Society, endeavored to establish radia-
tion protection measures during this period but
with no success. Had such recommendations been
heeded, much suffering and loss of life following
World War I as a result of the careless use of
ionizing radiation would have been avoided. Table
I outlines the early radiation protection meas-
ures that were taken following World War I.
Radiation protection problems became of much
greater magnitude as a result of the development
of high voltage accelerators and nuclear reactors.

1. The Britlah X-Ray and Radiiu Proteetion Committuee (121
pr'tented its firs radiation protection measure.
. The American Ro ntgen Ray Society ll92) published Its first
radiation rotection measures.
t The Steno Initernational Congress uo Radiu ra meeting in
Stockhaom 1is28) fored the international Commlllee on X.Ra
and Radium Protetion.
I International Committee on X-Ray and Radium Protecton
(1934) recommended a tolerance dose of f. roeten t per day
Ir I 0 roueaens per week.
. he U. S. , Advisory Commttee on X-tRy aild Uaelum Prolelion
endorsed the value of 02 r/day in 1981 anl the vdlua of 0.1
i/day in 10le.
0 The U. X-Ray and Radium Protection Comminitee 11I)
0.1 ps rdllun deposited in the body as 1tolerance limit. thl
limit it conldlered to corresond to Ito-' e of tiadon/e ofr
inhrled air or t10o* c of radon re in expired air.
7 Thi U S Atomic Energy Projects (1942) adplted i,] r/day as
tit malitmum permnist ble exposure to X and annmil radlatrol

Before this period only small sources of radiation
were available, and these produced only low en-
ergy alpha, beta, gamma and x-radiation. To-
day with our new sources of radiation we not
only have the same radiations available at much
higher energies and in much greater quantities,
but also new types of radiation-fast neutrons.
slow neutrons, thermal neutrons, mesons, etc.
Early in 1942 when plans were being made for
the construction of large nuclear reactors at Oak
Ridge and Hanford, it was recognized that un-
precedented radiation hazards would result. At
that time there were only about two pounds of
radium available to man in all the research lab-
oratories and hospitals. In a single nuclear re-
actor the radiation produced would be equivalent
to that from hundreds of tons* of radium.
Realizing the magnitude of the radiation pro-
tection problems the directors of the Atomic En-
ergy projects at the University of Chicago or-
ganized, during the summer of 1942, what was
the beginning of a new science called health
physics. When the first nuclear reactor was op-
erated on December 2. 1942, there were only three
health physicists.* Since then many new atomic
energy projects have been organized and radioiso-
tones are being sent from the reactors at Oak
Ridge, Tennessee, Chalk River, Canada, and Har-
well, England, to laboratories all over the world.
The need for health physicists has paralleled the
expansion in the field of atomic energy and from
a small beginning in 1942 this science of radiation
protection has expanded so that today there are
approximately a thousand persons devoting full
time to health physics work in this country alone.
These persons are giving their attention to the
study of ionizing radiation and to the develop-
ment of methods and procedures for minimizing
radiation damage. The outline that follows indi-
cates some of the major problems with which
the larger health physics groups are engaged.

Duties of the Health Physicist
ONE of the best ways of understanding how the
radiation protection programs have been so
successful is to outline some of the duties of the
health physicist. These are as follows:
1. Aid in the selection of sites that are suitable
locations of atomic reactors and for work with
large quantities of radioactive material. These
sites must be suitable from the standpoint of
density of population, underground and surface
waste disposal, and proper dilution of air-borne
2. Aid in the design of new piles. "hot" labora-
tories and associated equipment, such as hoods,

'The total gamma ray energy from radlum and its daughter
products per disintegration of Ran st 1 m1ne and there are
3.6 x 100 disintegrations p.r icond per rain of Ra. The total
amrma ray energy per fission is about I3 mc and there are about
3 x I0' fission per second per watt, therefree, a pile operating
with a power of 10t watts would produce samma rndiltlon equva-
lent 1 660 tons of radium.
*Thle three health physicist at that time at ihe University of
Chicuao were E 0 WOl.AN. . C C, CAlF Ts trii, and if M

radiation shields, fixed instrument , alarm mech-
anisms, etc., in order to incorporate ill the neces-
sary features of radiation protection.
1. Provide personnel monitoring meters for all
persons subject to radiation exposure. make thy-
roid counts of persons working with radioiodine:
make urine and feces analyses to delermmne the
possible accumulation of certain radinisotopes in
the body, notify a1l personnel and their supervi-
sion when appreciable radiation exposure is re-
ceived: and maintain accurate and interpretable
rrcordn of ladlltionl explosuHle for the protection
of both laboratory personnel and plant manage-
4 The health ph.sirs siinryors mike frequent
radiation surveys of all ieliipment and all ac-
cassible areas about the piles and in the radio-
ch amical laboratories.
5. SLe Lhat all plant .Mlup Il isrn is pllrperl lI-
lormcd of the various radiation hazards. of the
permissible working time in each area. the radia
tion protection measures, schli ;a renlote control
equipment, protective clothing. masks, etc, that
are desirable for each operaLnon The health
physicist mRiOl rmolnti I gil.nl fin ecking out
new radiation hazards befur.. rather than ;tfter
radiation pxpLOIIrp rou'llt
6. Make a continuous survey of all environ-
mental hazards to see that the liquid, solid and
gaseous radioactive material emanating from
the plant does not at any time exceed the maxi
mum permissible exposure level
7. Aid in all emergency operations, "uch as
fires, floods, and explosions if there can he an
associated radiation hazard.
8. Furniih and maintain in proper calibration
all health physics instruments for survey and
monitoring purposes.
9. Conduct educational programs for plant
personnel, to trail new health physicists for other
operations and to point.out the responsibilities to
outside groups that have an interest in these
problems-such as medical iIen, public health
officials, insurance personnel, sanitary engineers,
safety engineers, etc. The Health Physics Divi-
sion at ORNL has trained a number of groups
of military officers in theoretical and applied
health physics. In 1950 top-level personnel ap
pointed by the governors of the various states
were sent to Oak Ridge, Brookhaven, U. C. L. A.,
Read College and Illinois Institute of Technology
to receive civil defense training It was intendelI
-and has developed in many cases-that the
trained personnel should organ.l/.e the civil de-
fense training in radiation protection in their
respective states. It is Iheir responsibility to
teach the teachers in their state who, in lurn,
will instruct larger groups of personnel regard-
ing radiation problems associated with civil de
fense. At present. 40 Atomic Energy Commis-
sion fellowship students are in training in the
Oak Ridge-Vanderbilt Universily iand the Brook-
haven-University of Rochester Health Physics
graduate programs. Those who complete the re-
quired work will receive the M.S degree.

10. Assist in prolienls relating to national
11, Carry on research in order to keep abreast
of the field and so that divrlopmpnts in health
plh)'ics ill keep pawc with other tievelopi nt in
atomic energy. For example, a waste-disposal
program has been carried on at ORNL jointly
with the U, S, Public Health SLivice for the past
several years. Some of the important objectives
of this program are In determine the effective-
ness of conventional water purification systems
and waste disposal plant in removing radioiso-
topes and to find out what changes can he made
to improve their effectiveness. This group is also
working with the Tennessee Valley Authority on
an ecological program in an effort to detect any
environmental changes that ainy have resulted
in plant and animal life that have lived in White
Oak Lake, a lake that h;as I ee contaminated
with mixed fission products for the past seven
years. Another impoituani research project has
been that of developing new and better radiation
detection instruments. The instruments now
available are far superior to those that could be
procured when the projects began in 1942. Never-
theless, there is much room for improvement, and
a number of interepstinp and important instru-
ment developments are under way at present. A
considerable amount of fundamental information

1 (Ilnti i Nlatonal lmibratorI (nuw hlik h id, .N ilmnTal Lab
oi1o()> in . .1 1,e a 1.i ae/" r 14 nii i. 0. M Cre of
llllitirium in .i11 Thi, -oner ntlitulo- h.- .inc Inen uled as
The man-imumn tieiinm -ibie 'dlu for ill thur iliha emiltini
iuaiioimloi� %,cth ihe excelolfn or n.tiit l nf aitrring radion
anil thurn an I their rhori hiv l lhliltihlu' II|'I[[UII .
Sne ,ru he MiPi nilf nnilll iin ltm 1 n na hn � been lt t
from Iol to io0 p /ll ,f al
SAt a meeting inn Rochehie. N Y.. telrn'lia 2, I"19 a MPCof
2'p frir %oILhie *i nnrluhle c-- inlimuin olf inmuiiii -1 il air .
Siner i ti\\ the- gerir-l MPC tif hbei ,in�! ninmmn emitting radio-
i . oi iu. n ei iti Ri dge Nnaioni L ,e i tn has been
eI- tc or or
Tihe confejence otil wsilr isr .til canlldli0 thri i,0nllen D.i-.
olun of ihe Ar .mlr ineiVg Cnmml--1n in W~nhinlton, D C..
nn September 21. IIB, Wnet a. MP nf I-' pr/re ref C fi hargedt
i C l |iihiv TABLE IIl.
ATOMIC ENERcY Piaru.ots rillM 1942 TO 1949
Since T'l OR i hn. Iet iS ursi I . ir d.i . li ,1 limuni bita

at the t ln o, f li -'c h or ]n It , Whitle ink Cr 0ti t
l, ha iry p,1 t . uh.i1I .intlll W il . .llO nk i l were aet a
5 0 I //e foi ,ti tinil iiiima t 'llR in I,.I ur/er fr i n ,nhn
An - --ilitnl n lilution r'iletd it i rTin trt, I -1o to "cv .rl
l - ,l u.m l-' enuli be countI l Ii .. rl 1her lilut* thil
"ater "henm i enTrhtu ihr hlind R"r .mIi Iwrnrr it IO 1he
SThre Cnnfcrence n. Wraise rhilhl n lh . h .i cri4oi. I ore oI
iiiin* he T o nmc E'[,T'I' V iniii{kin mfi V, i ntinc , t, C-
1a) S i 0 - pc/c. nf . i ,rnvuh**I the toitil nctivite dns'
, it, w 0 r. oeork " M t or ' ir c provided each
mi ti" ilmi*iiechhvi' mii with I Ini nmitnstimn liFidl
I1~ Ir lcr re of P1' p-ro0l0ii ceh nm was thoroughly
ml.nl whi In gmo phothoronu tA a phosphate e

Fig. 2. Fg. 3.

remains to he accumulated in order to understand
better how to design more effective and cheaper
radiation shields and how to calculate the per-
missible radiation exposures from various types
of radiation over a wide range of energies. These
are just a few of the health physics research pro-
grams in progress.
Except for the few general statements about
radiation protection relative to x-rays and radia-
tion from radium as listed in Table I, very few
recommendations of levels of maximum permis-
sible concentrations of the various radioisotopes
in air and water were officially accepted until
after the atomic energy projects began in 1942.
Tables II and III list some of the maximum per-
missible concentrations of radioisotopes in air
and water, respectively, that were used by the
U. S. Atomic Energy Projects from 1942 to 1949.
More recent values will be discussed in my next
The best way to see how health physicists op-
erate would be to take a tour through one of the
larger AEC laboratories. Since this is impossi-
ble, we will look at a few illustrations which give
us an inside view of health physics in action at
the Oak Ridge National Laboratory.
Fig. 2 shows personnel entering the laboratory.
Each is picking up two pocket meters and a film
badge. These are returned to the proper slots
in the clock alleys at the close of the work day
Health physics technicians read the pocket meters
rach evening by means of a nllnometer. The films
are developed and read with a densitometer once
each week unless the pocket meters indicate .
radiation over-exposure during the week; in such
case the film is developed and read immediately.
Radiation overexposures are detected by means
of these meter readings and are reported to the
supervisor responsible for the persons who are
overexposed before the beginning of the next
work shift in order to avoid a repetition of the
overexposure. Careful records are maintained
of all overexposures to radiation.

Fig 3 shows two health physics surveyors mak-
ing a routine survey of a lunch room in which
personnel, who work with radioactive material,
eat. One of the surveyors is making measure-
ments with a "walkie squawkie" and the other is
taking smear samples with filter paper. These
smear samples will be checked later for alpha,
beta and gamma activity by means of propor-
tional counters and Geiger counters Although
smear sampling gives only qualitative data. it
does, at times, indicate the presence of contami-
nation that may be rubbed off and transferred to
the clothing or body. Such surveys are made, not
because radioactive Ciontamination is commonly
found in these aLeas, but rather because one
must be sure that it does not accumulate there.


Fg. 4.

Fig. 6.



Fig. 4. Before going into areas that are po-
tentially contaminated, per-onnel are required to
put oi protective clothing. This Iprotetllve cloth-
ing nustl be removed before entering the cafe-
tprii Ilrea or before going home.

Fig, 5. Protective clothing and street clothing
must be checked frequently for contamination.
This is usually done with a Geiger counter.
Hands and feet cant he hecrkld rapidly with a
four-fold had land Foot counter, as .hown in the
background. Proportional counters are usually
used to check for alpha contamination.
Fig 6. Sometimes it is necessary to repair
contaminated hoods, or to enter hot cells where
air-l)orne contamination is probable. Under such
conditions in addition to the usual protective
clothing, heavy gloves and a mask with its own
supply of oxygen must be worn.
Fig 7. In spite of all precautions, spills of
radioactive materials occur. This figure shows
personnel using filter-type masks and making
measurements with a Zeus-type ion chamber


Fig 9.

Fig. I .
Fig 8. After the contaminated clothes are re-
moved. they must be checked with Geiger counters
for beta and gamma activity, and proportional
counters for alpha activity. Then they are washed
in a decontamination laundry, after which they
are again checked to make certain the level of

Fg. IZ.
activity is below the maximum permissible value
Fig. 9. This illustrates a routine operation of
the health physics surveyor as be takes measure-
ments continually in the various laboratories, to
make certain that the work is carried on safely.
Fig. 10. Some of the work with high levels of
radioactive material must be carried out behind
thick lead or concrete barriers After the com-
pletion of such operations, materials removed
from the hot area are handed with remote con-
trol equipment, and radiation measurements are
made with a fish-pole type probe in order to
minimize the hazards to personnel.
Fig. 11. An important part of work with radio-
active material is to make certain that the radio-
active waste-liquid, solid, gas-is disposed of
safely. The liquid waste that is not held up in
large underground tanks or removed by evapora-
tion, is discharged at safe levels into the White
Oak Lake system. This picture shows the White
Oak Lake which contains several hundred cries
of mixed fission products. This lake is in the
control area and contains a normal population of
fish and cther marine life so f:r ps enrr:al ob-
servations can determine. Ecological studies are
now being undertaken in cooperation with the
Tennessee Valley Authority, to determine
whether this level of contamination over a period
of about seven years has brought about any de-
tectable changes in the plant and animal life.
Fig 12. Many methods are employed on the
various projects for the disposal of solid contain
inated waste. At ORNL, contaminated waste is
buried in deep trenches in the restricted area,
which is off the shores of White Oak L;le. Some
of the AEC contractors have special incinerators


in which they reduce combustible waste that is
contaminated with radioactive materials. In such
cases, elaborate filters must be provided in order
to remove the air-borne particulate activity.
Other AEC laboratories l mix the radioactive
waste material with concrete and, after the mix-
Lure is hardened, it is carried out and discharged
o at sea, or placed in a desert area.
Fig. 13. The air-cooled nuclear reactors, such
a s the one at Oak Ridge, and all chemical opera-
lionls wilh I;adioatitlve matl.rials discharge certain
S mounits of radoalctive material into the atmos-
ihere. This picture shows a typical air monitoring
Sr _station in the neighborhood of the laboratory.
Srnstrumeonts at this station make continuous
-, measurements and recordings of the air contami-
l i7nation, ond frequent inspection of the records
' i o gunranteet that ihe permissible levels of air
activity are not exceeded.
S illHaving completed our toui of the Laboratory,
'k it might be of interest to examine some of the
records of radiation exposure, ii order to estl-
mate how well the health physicists have carried
out their program of radiation protection. Radia-
ation exposures may occur from a variety of
Fiq 13 �nouces at ORNL. and they may result both from
external and internal sources (lo be discussed in
detail in a subsequent lecture).
Fig. 14 illustrates a typical exposure record
of a person who works with large quantities of
radioactive material. As illustrated here, most of
Backgrouand4 mr/week the weekly exposures are below the maximum per
missible value of 0.3 r/week, and the average
exposure is considerably less than this permis-
sible value. During the six-month period ending
July 1, 1950, approximately 12% of the personnel
at Oak Ridge National Laboratory received one
or more single weekly exposures in excess of
o0.250 rep * per week and only 0 26% received an
1 3 4 5 6 7 average exposure in excess of 0.3 rep per week.
e One of the six persons involved in the latter in-
Trme weeksl
Show us weekly external exposures that average$ less stance barely exceeded 0.1 r - per week as meas-
than the mazmun permissible limit of 0.3 r/week. ured by the blackening of that portion of the
film located behind the shields in the film meter.
F;g 14. The other five exposures were appreciably less
than 0.1 r per week.
Fig. 15 illustrates the type of exposure that
might be expected if a person takes a single dose
of radioactive material into the body. As illus-
>manlmum per.mssible exposure treated here, the initial exposure is very large but
decreases somewhat exponentially with time, ow-
ing to the radioactive and biological decay fac-
tors. The accumulated radiation exposure from
all types of radiation hazards must be kept below
the permissible value of 0.3 remi/week.
Fig. 16 illustrates the type of build-up that
Lime, by inhalation or ingestion were to take
radioactive material into the body.

Time weeks)
Showng an internal exposure due to a single Ll Clieni of
body intake of a aire amount off adioracve mnIt niL.
Fig 15

'Thr lr*smurr ucord& itli RI e th.ri. tiht nr r nriesule-d hI
the blacketnig u the portion of tht fllm that - unshielded and
tlilbr int by uranni tm bn e i liinrn. Thai furnlihe what is
iprlIbly thI, nwotl onrna tive .tn mrlt A ihr ,r A ibtur. The
ruinrrm'tna ,f r 1ill of which it. I.-r . e. than 0.3 r/weelk)
,it dindipilv m-r, ornatete e dtimort iif the natunt exposune.

A.mln -h r Hl Lsijii)-1I . to e .X o-'ul pCrrni blb
a *i ture l Hto trm rk tt] oI ' r r Ia iotope ID the
),", irl ti L r. oir Or trn i ,r *n< ii ter,-
Fig. 16.

Fig. 17 illustrates the general lype problem in
which we have a variety of effects.
Fig. 18 indicates the relative exposure of per-
sonnel working with radioactive material and
x-ray equipment. Curves A and B indicate the
percent nt ORNL personnel receiving exposures
greater than indicated values. Curves C, D and
E are from data taken from Nlcleonics, 1949
(Dec.), indicating what might be a typical ex-
posure to radiation of personnel working outside
AEC laboratories. It is noted that ORNL expo-
sures are much less than those of other groups,
and no ORNL personnel are receiving greater
than 0.3 r/ounek if averaged over a few weeks.
Table IV compares the accident rate at ORNL
with other large industries and indicates that
work with radioactive materials, if properly con
trolled, can be done safely and that it is one of the
safest industries of its type. It is because of this
record that insurance rates of laboratory person-

Fig. 17,

nel of the various Atomic Energy Projects are no
higher than those of corresponding chemieil and
engineering industries. In other words, the radi-
ation hazards are considered to be reduced to
minor importance relative to other commonly
recognized hazards of industry.

Lumbering Industry 49.04 47.72
Air Transport 15.05 12.97
Shipbuuilding O.14 8.86
Automobile 8.47 6.35
Steel 5.86 4.96
All Chemical Industries 7.51 5.72
All Industries 11.49 1.14
Oak Ridge National Ialaorntlor.
1948 2.03
1949 1.28
1950 1.56
'Reports of Industrial istablishments to the National
Safety Council.

A- tPo&flS DF ISS OlR' FU, BADDEC UUS AS d A 'l0Il 6ll0 OH al I*N '8R
ia oNTh r P raon I-1- I to T' 50 P
B- Ip OSuit. l14B OO& UAQE Mr4I Ao IIs.LAT O T -Ih4LD 0 EAs 1fO
R I IS I I**4 I-a
1 1-I A _1 -
eC -POsiuE O s FLUS or 144 AADIiaftOt eafts r�R 6 MalhTH PCo-e. .

s- 0 u - 02 0-04 s0-s0700 e

Fig. 18.
Exposure in roentgens or reps per week.

Reprinted from the Manual of the Lectures presented at
The Inservice Training Course in Radiological Health,
University of Michigan, School of Public Health, February 5-8, 1951.



R. T. Overman, Chairman

Special Training Division
Oak Ridge Institute of Nuclear Studies

One of the most firmly established laws in the
thinking of most scientific and technically trained men
is the so-called Coulombs law of the interaction of
charged bodies. Even the layman uses the terminology
"like charges repel, unlike charges attract." The laws
involving forces between particles likewise are extreme-
ly important in the field of nuclear science. The dif-
ference in thinking between the more common physics
and the concepts involved in nuclear physics lie pri-
marily in the range or distances over which the forces
act, and the somewhat surprising nature of these forces.
Very little is known about tfe actual nature of the
nuclear Forces, but it is possible to discuss some of the
more qualitative aspects of the nuclear picture.

One way of describing the nucleus lies in the use
of diagrams such as have been commonly used for the
description of an atom. It must be pointed out that
such diagrams are only useful simplifications of the
rigorous mathematical formulas which adequately de-
scribe our present state of knowledge. Such a diagram
might be constructed as shown in Fig. 1. Let us assume
that two positively charged units are suspended in
space. If these panicles are at an infinite distance
apart, there is no repulsion between them. Now, if they
are brought closer together, they then begin to repel
each other according to the well-known Coulombs law
exactly in the manner in which we are accustomed to
think. This repulsion continues to increase as the par-
ticles come closer and closer, and we might predict
that the repulsion would reach a tremendously high
value if we continued to bring them closer to each

Bhen the two particles reach a certain distance,
however, a surprising thing happens. 1xhen one particle
comes to approximately 10"13 cm. distance from the
other, the repulsion ceases to increase and instead
drops to zero and proceeds to negative repulsion which
would be represented by an attraction between the
charged particles. If the particles are brought closer
together no change in the potential energy, that is, the
attractive or repulsive force, is observed. The diagram
represented in Fig. I is common) referred to as the



"potential barrier" or "potential well" model of the
nucleus. The first refers to the barrier of energy over
which a particle would have to be pushed to make a
particle enter the nucleus, and the second refers to the
fact that once a particle has reached the distance at
which the nuclear forces surpass the coulombic forces,
the particle "drops into" the well and is thus held
tightly by the nucleus. Interesting aspects of this pic-
ture are that inside the region of the well, which is by
definition the nucleus, a proton attracts a proton with
very nearly the same attraction as a neutron and, sur-
prisingly, two neutrons attract each other with essen-
tially the same force. It should be pointed out that
while the diagram only indicates one direction of ap-
proach of the particles, the actual nucleus would be
represented as a three dimensional well to include all
possible directions of approach of the particle. In other
words, this diagram represents only half of the cross-
section of the nucleus.

Vile the picture as to the behavior and position of
the nuclear particles inside the nucleus is not at all
cleared up, it is probably safe to say that they are ar-
ranged in some kind of order similar to the position
of the electrons in the atom outside of the nucleus.
Many nuclear physicists feel that the nuclear particles
are arranged in shells inside of the nucleus. These
might be represented by levels inside the well as indi-
cated by the parallel horizontal lines in Fig. 1. The
important thing in this picture is that in a stable nucleus
all of the particles are in their lowest state. In the case
of an atom, we think of two electrons as inhabiting the
first level in the atom, with there being a possibility
of up to eight electrons in the second level and so on.
If, for any reason, an electron is lifted from a lower
level to a higher one, it will return to its vacancy in the
lower level and give off the energy which was required
to lift it to the higher level in the form of one bundle
(photon) of electro-magnetic radiation. This type of
radiation is called X-radiation, and is extremely useful
in both medical and industrial practice.

In the same way, if a nuclear particle is lifted to
a higher level in the nucleus and returns, a pulse of ra-
diation is emitted on its return. This is called gamma
radiation, and is one of the two types of radiation (the
other being beta radiation, discussed below) which is
commonly encountered in work involving artificially
produced radioactive materials. Radiations from members
of the radium family also may emit a third type called
alpha radiation.

One characteristic of the diagram in Fig. 1 is that,
as the label indicates, the ordinate is the total amount
of energy which is present in the nucleus. This means
that in addition to the repulsive or attractive force,
the potential energy of the nucleus also includes the
mass of the nuclear particles expressed in energy
units. This mass and energy are related by the famous
Einstein expression

E=m 2

in which E is the energy, m the mass, and c the velo-
city of light.

According to this concept, then, if a particle is
added to an already existing nucleus whose particles
are at position a on the diagram the total energy may
be represented by indicating that the particles are at
position b in the diagram. In other words, the nucleus
is "excited"; that is, it contains more total energy
than it did before it captured the incoming particle.
If such a process of particle capture occurs as may be
the case when a nucleus is bombarded in a cyclotron

or in a nuclear chain reactor (sometimes called simply
a "pile"), the nucleus will remain in this highly ex-
cited stare for a period of time ranging from 10-13 to
10' seconds before losing its excess energy. This
excess energy may be given off in one of several ways
in order to attain a more stable stare.

Let us consider, for example, the case of the neu-
tron bombardment of aluminum. Natural aluminum is
composed entirely of atoms with a mass number of 27;
that is, they each contain 27 particles. Since the mass
number of a neutron is one, the nucleus which is formed
by the capture of a neutron has a mass number of 28,
but is still aluminum since it contains only 13 protons.
If we consider the diagram given above, one important
difference should be noted. In the case described in-
volving the bringing up of a charged particle, the in-
crease in repulsive force would be observed which would
then be followed by the attractive forces as closer
distances were obtained. In the case of neutron bom-
bardment, there is no repulsion between the neutron and
the nucleus so that one would observe a constant energy
as the neutron approaches the nucleus. When the proper
distance is reached, however, the attractive forces do
come into place, and the neutron "falls into" the well
in the same way as the charged particle did so that
an attractive force is observed in this case, also. The
nucleus is represented as being in position b in either
case, and stays there for a very short time. This might
be illustrated by the following equation

At27 + n 1 - (AI 28)

in which the Al28 is starred to represent the excited

The question now arises as to how the excited
aluminum28 gives off its excess energy to regain its
lower energy state. This may happen by one of several
paths. The simplest method might be expected to in-
volve the emission of a gamma ray photon from the ex-
cited nucleus leaving an unexcited Al28 nucleus. Ac-
tually, this is usually the method of "choice" since
it involves the emission of energy, and thus would
occur spontaneously.

Another possible mode for lessening the energy
of the excited nucleus might be the "boiling off" of
particles from the nhot" nucleus by essentially the
same mechanism used in describing the boiling off of
molecules of water from a hot liquid surface. That is to
say, one particle might happen to obtain sufficient
energy to overcome the "surface tension," and thus
remove itself from the nucleus. Below are listed several
of the possibilities for reactions of this type in the

competition for carrying away the energy of the excited

A127 n-l (A128). - A128 + y (a)

SMg27 + p (b)

SNa24 + 4 (c)

SA26 + 2n1 (d)

Reaction (a) involves only the emission of gamma
radiation while the other reactions involve the "boiling
off" of nuclear particles. It is evident that if one of the
last three reactions occur, a nuclear transmutation has
occurred with a different nuclear species being formed.
The electrons quickly rearrange themselves in the levels
corresponding to the new atom and the newly formed
atom has all of the chemical properties of any other
isotope of the element.

One further point should be examined in this com-
petition for energy loss. If one determines accurately
the mass of the Al27 and of the neutron, the mass of the
excited compound nucleus will be the total of the two
masses. If one now determines the mass of the A128
formed by the emission of the gamma ray, it is found
that, as he might expect, it is less than that of the
compound nucleus. The difference in mass between the
reactants and the product nucleus is equal to the energy
of the gamma rays given off. On the other hand, in the
second reaction if one determines the mass of the Mg27
the toEal mass of the two particles is greater than the
total of the reacting particles. This is also the case in
equations 3 or 4 in the formation of both the Na24 and
the Al26. This indicates that these reactions will not
occur spontaneously unless some additional energy or
mass is made available to the reactants. This is accom-
plished by increasing the kinetic energy of the neutron
to such a level that the total masses are equal. The
first reaction is said to be exoergic (cf. exothermic)

(AJ FI"F)9 Tf

Mg2' Mqg9 Mg



,hiile the last three are called endoergic reactions.

o' a further step must be taken in the examination
of the nuclear concept. If one analvzes the nuclei which
are found free in nature on an instrument called a mass
spectrometer he may determine which nuclei are stable.
Shat is, those nuclear species which are observed in the
ordinary elements are said to be either stable or have
decay periods which are long with respect to the age
of the earth. Let us draw a diagram to represent those
that are found in nature by plotting the mass number
against the atomic number. Such a diagram for the region
of nuclei discussed above is given in Fig. 2 in which
the square blocks represent those which are found in
nature. Ve observe that Na23, g24, 25 26, and Al27
and Si28, 2 30, are all stable. however, in the pre-
vious discussion it has been shown rhat it is possible
to produce the atoms of Na24, lMg7, and Al26, 28 by
neutron bombardment. If these are not found in nature
it must be because they do not represent the nuclear
particles as being in the bottom shell of the appropriate
nucleus; that is to say, that they still have excess
energy which must be removed before they will become
stable. Such nuclei or atoms are said to be radioactive
and will give off the extra energy (almost entirely in the
form of emitted particles) with half-lives ranging from
a few millionths of a second or less up to a billion or
more years. While the life of none of these atoms can
be predicted, each kind of nuclear species has a decay
pattern which gives the statistical probability for the
disintegration of a single acom. This average life of the
atom is usually expressed in terms of (actually the re-
ciprocal of) a disintegration constant usually denoted
by the Greek letter lambda (A). The disintegration con-
stant is determined from the half-life value by dividing
it into 0.693, the value of the natural logarithm of 2.

At first glance, it might seem that the manner in
which the radioactive decay takes place might be the
emission of a neutron or proton with the resulting for-
'mation of the adjacent stable nucleus of the same ele-
ment. Actually, this process rarely, if ever, occurs
after the immediate break up of the compound nucleus.
Instead three other modes of decay occur commonly,
depending on the position of the radioactive element
relative to the stable series.

One case might include those nuclei which are
heavier than the corresponding stable nuclei. One of
the laws of nature is that there is only one most stable
nucleus for a given number of nuclear particles. In the
case of A128 which is made of 13 protons there is only
one stable nucleus that can contain this number of pro-
tons. If an extra neutron is inserted in it, it can no

longer exist indefinitely as aluminum. In cases such
as that of A12 where the neutron to proton ratio is
higher than it is for the stable nucleus, there is (with
one exception only), one nerhod by which the return
to stability can take place. This process consists
of the breaking up of a neutron into a proton and a
negative electron. The proton remains in the nucleus
and increases its aton ic number one unit while the
electron passes off into space. In the case of Al, this
leaves behind the nucleus, characterized by 14 protons,
which is silicon with a mass number of 28. An electron
formed in this way is called a beta particle, and the
radiation emitted from a number of such radioactive
nuclei is called beta radiation. They are actually
streams of electrons arising in the sample. These are
the particles which may damage tissue by passage
through it, and also the radiation which is measured
in our Geiger counters and ionization chambers by which
we may detect the presence of radioactivity. This gives
rise to a tool for scientific research which has been
called the greatest discovery since the invention of
the microscope.

It should be pointed out that the present picture is
that the electron is not actually a separate component
of the nucleus, but its mass is included in the mass of
the neutron. One other item should be included here.
The present nuclear theory requires that in the emission
of an electron or beta particle from a radioactive nu-
cleus, another particle called the neutrino is also emit-
ted in the process. It is thought to have a very small
mass, but it carries some of the energy away from the
nucleus during the disintegration process. It has not
been observed experimentally, but certain evidence is
very suggestive of its actual presence.

The emission of a negative beta particle is essen-
rially the only method by which nuclei with high neu-
tron-proton ratios return to stability. On the other
hand, if the radioactive nucleus has too few neutrons
in comparison with the number of protons in the stable
atom, it cannot return to stability by this method.

There are two methods by which a nucleus with
a low neutron-proton ratio can return to stability. One
of these is the process of electron capture. In this
case, the nucleus with the high charge can trap an
electron from one of the electron levels outside of the
nucleus, and pull it in where it can combine with a
proton to form a neutron. Since the electron which is
captured is usually from the innermost or K electron
level, this process is usually referred to as K electron
capture or simple K capture. It is possible to capture
L electrons, although the probability is not high. After

the combination of the electron and proton, the resulting
nucleus contains one less proton and, consequently,
is the nucleus of the next lower atomic number. Al-
though no radiation is given off in the primary process
of K capture, X-radiation is observed when an electron
in a higher level falls into the K level to replace the
first electron, and gives off its extra energy. The pro-
cess of K-capture is observed by measuring the X-
rays which are given off from the atoms after the capture
has taken place.

One other possibility for a nucleus with a low neu-
tron-proton ratio presents itself. This involves the
disintegration of one of the extra protons into a neutron
and a positive electron or positron. The theory of posi-
tron emission is not a simple picture, but the process
can cake place whenever there is at least 1.02 Mev
energy available for the transition. This energy is re-
quired to form the positron and the disintegration does
not take place spontaneously unless it is available.
As a result, only the K-capture process can take place
if the nucleus has less than this energy, but the pro-
cesses may compete with one another when more than
this energy is present. The positron behaves essen-
tially like a negatron (negative electron) in its passage
through matter, but it is characterized most significantly
by the fact that when it comes to rest, it unites with a
negative electron. After the positron and negatron have
united, it is observed that the particles literally anni-
hilate themselves with the formation of two gamma rays,
each having an energy of 0.51 Mev.

It was noted above that gamma radiation must be
considered in radioactive decay. In addition to that
which is emitted, following the capture of the incident
particle in the nuclear reaction, this radiation may raise
in the decay of the radioactive nuclei. Any of the pro-
cesses of radioactive decay may leave the daughter
nucleus (i.e. the product of the radioactive decay) in
a state having excessive energy. If this is the case, the
excess energy is emitted in the form of electromagnetic
or gamma radiation from the nucleus. This radiation is
not really radiation from the disintegration process,
but follows immediately the actual decay. A given
nucleus may thus decay by any one of the three pro-
cesses outlined, which process may or may not be fol-
lowed by gamma radiation emission. It should, however,
be pointed out that a given type of radioactive atom al-
ways follows the same decay process although it is
often a very complex combination of beta and gamma

In conclusion, it must be pointed out that a good
theory of the nucleus and its properties and reactions
may only be expressed in mathematical terminology.
One must he rather wary of forcing the mathematics to
give mechanical concepts because much of the newer
mathematical theory is not amenable to explanation in
terms of our classical concepts of physics. However, it
is quite interesting to trained scientists in whatever
field of endeavor they are working to know something
of the qualitative pictures which have been developed
in this new and fascinating realm of thought on a veri-
table frontier of science.



Eldo E. Anderson, Director

Health Physics Training
Oak Ridge National Laboratory

An important part of any discussion of a scientific
subject is the question of measurement, and the units
in which the measurements are to be made. We begin
to know something about a physical quantity when we
can measure it. If we are to assess the hazards asso-
ciated with radioactivity, if we are to use the radiations
for therapy, for biological research, in industry, etc.,
we must be able to measure the strength of our radio-
active source. We must be able to measure the radiation
dose received, and to do so we must have units in which
to make the measurements.

As in any science which is still growing and ex-
panding and in which ou knowledge is still limited,
agreement between measurements made in different
laboratories is not perfect, and as yet agreement on
terminology and in the magnitudes of all units has not
been reached. Some confusion results, but we can re-
duce such confusion by a knowledge of and exactness
in the terms we use.

Let us turn first to units for measuring the activity
of a radioactive source. Determination of the absolute
activity of radioactive samples is highly important in
dose determinations and is based on the number of
atoms disintegrating per second. Conventionally, the
unit of activity or quantity of radioactive material is
the curie. When the principal radioactive element in
general use was radium, there were two well-defined
units for expressing the quantity of radioactive material.
One was simply a gram of radium which could be deter-
mined by weighing. Amounts of radium were then deter-
mined by comparing the gamma radiation of the unknown
sample with that of a carefully weighed standard, condi-
tions of filtration, instrument for measuring the radia-
tion, and geometry all being the same. Since in many
cases radon is used in place of radium, a second unit
named the "curie" was defined as that quantity of radon
(0.66 mm3 at 00 and 760 mm/Hg) in radioactive equilib-
rium with 1 gm of radium. Later in 1930, the curie was
extended to include the equilibrium quantity of any
decay product of radium; i.e., it is that quantity (mass
in grams) of a decay product of radium which has the
same disintegration rate as a gram of radium, or that

has the same number of atoms disintegrating per unit
time as one gram of radium. Measurements of the abso-
lute decay rate of radium are not in perfect agreement;
hence, the number is not precisely known, and in 1930
the International Radium Standard Commission recom-
mended using the value of 3.7 x 1010 disintegrations
per second. Thus a curie is that quantity of a product
of radium which decays at the rate of 3.7 x 10 dis-
integrations per second.

The curie has become widely adopted as a measure
of the quantity of any radioisotope and not limited to
members of the radium family as recommended by the
Commission. Thus one millicurie of P32, Na24, or C14
means the amount of the isotope (mass in grams) nec-
essary to provide disintegrations at the rate of 3.7 x 107
atoms per second. Thus the relation between grams and
curies is different for different isotopes. For an iso-
tope that decays at a slow rate the mass per curie is
greater than in case of a rapidly decaying isotope. Fail-
ure to distinguish between total ionizing events and
total disintegrations in the case of isotopes that do
not have simple decay schemes has led to confusion and
error in the use of the curie. For example, with a radio-
isotope that emits both a beta and a gamma ray in a
single disintegration, (if there are internal conversion
electrons, that is if some of the gammas give up their
energy to eject K electrons from an atom) we have a
gamma replaced by an electron; then measurement of the
beta particles will lead to a disintegration rate too
high. If only the gammas are measured, a disintegration
rate too low results. Unless the number of gammas lead-
ing to conversion electrons is known, the disintegration
rate will not be correct and the amount of the radio-
active isotopes expressed in curies will be incorrect.
Likewise consider the error which could arise in meas-
uring the activity of Mn52 which has a half-life of 6.5
days and decays by positron emission in 35% of the
transitions and by electron capture in 65% of the tran
sitions. One millicurie of Mn 2 emits only 0.35 x 3.7
x 107 positions per second, even though there are
3.7 x 107 disintegrations per second. The use of the
curie to describe any radioactive source which pro-
duces the same gamma ray response as one curie of

radon is another serious misuse of the curie unit. The If we select as our unit of dose the ionization per

objection is that the gamma ray response depends on
the detection instrument used; for example, the ratio
of the apparent gamma ray intensity of a source of 8-day
1131 to a source of radon is four times as great if meas-
ured with a platinum cathode counter as when measured
with a copper cathode counter. The curie should he
used strictly to mean that quantity of radioactive materi-
at which has 3.7 x1010 disintegrating atoms per second.

Since there is a discrepancy between the number of
disintegrations per second from one gram of radium and
the number adopted by international agreement, Curtis
and Condon proposed a new unit for radioactivity, the
Rutherford, defined by them as that quantity of a radio-
isotope decaying at the rate of 106 disintegrations per
second. However, the unit has not come into widespread
use. The roentgen per hour at unit distance is used to
compare source strengths and we shall define it after
we have discussed the roentgen.

A unit of radiation dose should be readily repro-
ducible, and should be measurable in terms of simple
physical quantities by means of routine instrumentation.
In most cases, the ultimate information desired is the
biological damage produced by a given dose of radiation;
hence, it would be desirable to have our unit of radia-
tiondose proportional to the biological damage produced.
However, the factors involved in radiation damage are
so complex and so little known that it has not been
possible to devise a unit having both these physical
and biological characteristics. The physical quantity
selected must be capable of being measured with rea-
sonable accuracy and of being expressed in absolute
units. Thus, the unit of dose may be either the energy
absorbed from the radiation per unit mass or the ioni-
zation produced per unit of mass.

If we select as our physical quantity, the energy
absorbed per unit mass of tissue, we may measure the
energy m ergs or multiples of ergs; i.e., joules. (1 joule
is 10,000,000 ergs.) In recent years another energy
unit has come into widespread use because of its con-
venience, the electron volt, which is defined as the
energy an electron would acquire in falling through a
potential difference of one volt. Frequently used is
the unit Mev, which is one million electron volts, or
that energy an electron would acquire in falling through
a p. d. of 106 volts. Today particles with energies of
many Mev's are commonplace. Since both ergs and
electron volts measure the same quantity they must be
numerically related, and we find that 1.6 x 10"12 ergs
is equivalent to one electron volt or 6.2 x 1011 .v.
1 erg.

unit mass produced by the radiation, we would measure
it in terms of the number of charges formed per unit
mass. The unit of charge we shall use is the electro-
static unit. UXhichever unit of dose, energy absorbed
per unit mass or ionization per unit mass, is employed
the ionization produced per unit volume is the physical
quantity actually measured. The roentgen is "that quan-
tity of X or gamma radiation such that the associated
corpuscular emission per 0.001293 grams of air produces
in air ions carrying one electrostatic unit of quantity
of electricity of either sign." The quantity of air referred
to is one cc of dry air at 0�C and 760 mm i!g. The
roentgen (r) is aunit of radiation exposure or dose and is
based on the effect of X or gamma radiation on the air
through which it passes and applies only to X or gramra
radiation in air. The unit considers the ionization
caused by the secondary particles (electrons) ejected
from some known volume of air ( 1 cc at standard condi-
tions). The ionized tracks of these particles may go
outside of the known volume, but it is important that
their total ionization be collected wherever it occurs.
The roentgen is not a radiation unit, it does not de-
scribe directly the number of photons in the beam nor
their energy; it merely gives the effect of that radiation
in one cc of air. It is based on what this energy does to
air; namely, on the ionization it produces. Part of the
energy of the radiation is given to the air in producing
photoelectrons, Compton electrons or in pair production,
and these secondary particles (electrons and positions)
in turn produce other electrons and positive ions. When
all ions of either sign are counted and are found to be
one esu, then one roentgen of X or gamma radiation has
been absorbed by the original volume of air. Since this
concept is so important, let us repeat it in slightly
different words, but meaning the same thing. Thinking
of 0.001293 gram of air as occupying one cubic cm,
we can imagine many interactions occurring between die
photons and the air atoms in this volume, resulting in
the ejection of secondary electrons in different direc-
tions with different speeds. For a given quantity of X-y
radiation in ergs/sq. cm of a given A or energy passing
through this cubic cm of air there is a definite number
of electrons with certain energies produced in this
air volume. These secondary electrons which are set in
motion in the cubic centimeter of air constitute the
corpuscular emission associated with the given quantity
of radiation in the cubic cm of air. If the quantity of
radiation increases the number of such corpuscles
increases. V'hen the ion pairs produced by these second-
ary electrons within the cubic cm of air and in the
surrounding air into which they may travel reach such a
number (2 x 109) that they give 1 esu of quantity of
charge of either sign, the amount of radiation absorbed

in the cubic cm of air corresponds to I roentgen. Since
the charge on one electron is 4.8 x 10-10 esu, the one
esu of charge represents 1 or 2.083 x 109
4.8 x 10"
electrons. This is also the number of ion pairs per esu,
since only one partner of the ion pair is measured.
Thus the roentgen may be defined as chat quantity of X
or gamma radiation such that the associated corpuscular
emission per 0.001293 gms of air produces in air 2.083
x 10 ion pairs. A unit mass of air (1 gm) could be used
as well, then 773 esu of quantity of electricity of either
sign or 1.61 x 1012 ion pairs per gm of air would be
produced by 1 r. Since the energy required to form an
ion pair in air is 32.5 e.v., the roentgen represents
energy absorption of 6.77 x 104 Mev/cc of air, or 5.24
107 Mev per gm of air, or 5.24 x 1013 e.v. x 1.60x
10-12 ergs/e.v. = 83.8 ergs/gm of air.

Thus one roentgen of X or gamma rays is that quan-
tity of radiation such that approximately 83.8 ergs are
absorbed per gm of air. Thus a dose of one roentgen
received at any point means (official 1937 definition):

I esu of ion pairs produced per cc of air
2.083 x 109 ion pairs produced per cc of air
1.61 x 1012 ion pairs produced per gm of air
6.77 x 104 Mev absorbed per cc of air
5.24 x 10 Mev absorbed per gm of air
83.8 ergs absorbed per gm of air

Think of the dose of radiation in roentgens as
energy absorbed per gram of air from a quantity of
radiation in ergs per square cm passing through the
material. The more penetrating the radiation is, the
greater the ergs per square cm must be to give one
roentgen since a smaller proportion is absorbed per
gm of air or per cc of air. One roentgen of X or gamma
rays is that dose of radiation such that 83.8 ergs are
absorbed per gm of air, but in substances of different
atomic number and different density, the amount of
energy absorbed per unit volume for the same quantity
of radiation will be different. In soft tissue the energy
absorbed per gm of tissue per roentgen is approximately
93 ergs, while in bone it may be higher. While the rela-
tive amounts of energy absorbed in different substances
show wide variation, the dose is still one roentgen if
the same quantity of radiation produces one esu of
charge of either sign per 0.001293 gms of air at the
point under consideration. The dose expressed in roent-
gens is totally independent of the absorbing medium
exposed to the radiation and of the amount of energy
that the particular medium absorbs. Nor does the roent-
gen depend on the time required for the production of the
ionization; as long as one esu of charge of either sign

is produced by the radiation in one cc of standard air,
the dose delivered is one roentgen regardless of whether
it took one second or one hour to produce the one esu.
Consequently, dosay rates are given in roentgens per
hour. For example, if a constant dosage rate of 2 r/hr
is continued for 5 hours, the total dose delivered is
10 r, and in the one cc of standard air 10 esu of charge
is produced.

Since the definition of the roencgen requires that
the total ionization produced by the secondary electrons
formed per cubic cm of standard air be measured, and as
some of the secondary electrons may have ranges of
several meters, large and cumbersome apparatus would
be needed. To avoid such large unwieldy apparatus,
"air wall" r chambers or "thimble chambers" have
been developed. Their use is based on the principle
that when a tiny cavity such as a small ionization
chamber, is placed in a large homogeneous absorbing
medium which is uniformly irradiated, the atmosphere
of secondary electrons in the cavity is identical in
every respect with the electron atmosphere which ex-
isred in the medium before the cavity was introduced.
If the chamber gas is air, and if the walls are composed
of materials having an atomic number near that of air,
then the ionization per gram of air in the chamber will
be substantially the same as the gamma-ray energy loss
pergram of air at the point where the chamber is located.

The roentgen applies only to X ray and gamma ra-
diation; however, ionization in tissue if often produced
by radiations other than photons; that is, by betas,
alphas, neutrons, and protons. Thus there is need for
a dose unit applicable to corpuscular radiation, which
will be a measure of the energy absorbed in tissue ex-
posed to these radiations. The roentgen-equivalent-
physical introduced by H. M. Parker, is defined as that
dose of any ionizing radiation which produces energy
absorption of 83 ergs per gram of tissue. Thus if the
energy loss of ionization in the tissue is the same as
the energy loss for one roentgen of gamma radiation
absorbed in air, the dose is referred to as one roentgen-
equivalent-physical (rep). The name implies physical
equivalence with the roentgen, but in general such
equivalence does not exist for the rep is not equal to
the energy absorbed per gram of tissue exposed to one
roentgen. The energy absorbed in tissue exposed to
gamma radiation depends on atomic composition and
density of the tissue as well as on the energy of the
photons, while a rep is always 83 ergs per gram of
tissue independent of kind of tissue or the energy and
type of the corpuscular radiation. In soft tissue, a
dose of one roentgen corresponds to the absorption
of approximately 93 ergs per gram. There has been

considerable discussion in favor of changing the rep
to 93 ergs per gram of tissue and some persons prefer
the use of 95 or 100 ergs per gram.

The biological evidence indicates that the effects
of the various ionizing radiations are not the same and
that a different degree of tissue damage can be expected
from the absorption of 100 ergs of alpha ray energy than
from L00 ergs of beta-ray energy or from 100 ergs of
neutron energy. The roentgen-equivalent-man (rem) Is
that dose of any ionizing radiation which delivered to
man is biologically equivalent to the dose of one roent-
gen of X or gamma radiation. The rem is not a measure
of energy absorption or of ionization produced in tissue,
but is rather a measure of a quantity of radiation that
produces certain observed biological effects. Extensive
experimental studies have been made of the relative
biological effectiveness (RBE) of the ionization pro-
duced in tissue by the various types of ionizing radia-
tions and an equal amount of tissue ionization due to
gamma rays. The values obtained for the various radia-
tions show rather wide variations with effects (blood
counts, median lethal dose, etc.) and with different
species of mammals. The present accepted values for
RBE are:

Beta rays
Alpha rays
Fast neutrons
Thermal neutrons

In terms of energy, 1 rem = 9 2 rgi ., or in
RBE gm tissue
terms of the rep: I rem = reL. Thus for alphas: 1 rem =
95 (4.75) ergs/gm tissue; 1 rem = rep = 0.05 rep.
20 20

The maximum permissible tissue dose for X rays
and gammas is 0.3 rep per week, while for alphas it is
0.015 rep per week, for fast neutrons it is 0.03 reps
per week; or expressed in rem/week, for X and gammas
0.3 rem/week, for alphas 0.3 rem/week for neutrons
0.3 rem/week. Since a rem of alphas produces the same
biological damage as a rem of gammas or a rem of neu-
trons, doses expressed in rems are additive. Thus an
exposure to 100 m rem of gammas and 200 m rem of
neutrons is a total dose of 300 m rems.

Having defined the roentgen, we can now discuss
the unit of radioactive source strength, the roentgen-per-
hour-at-unit distance. For a particular radioactive sub-
stance which emits gamma rays, it provides a means
of stating the amount of that substance without knowl-
edge of its disintegration scheme. The roentgen-per-
hour-at-one meter (rhm) is that amount of a radioactive
isotope whose unshielded gamma ray emission produces
one roentgen per hour in air at a distance, one meter
from the source. By use of a standard instrument read-
ing in r/hr, a standard technique, and the rhm, the
source strength of various gamma ray emitters can be
compared and expressed in terms of the number of roent-
gens per unit time produced at some arbitrary distance.
The unit has the advantage in thar the disintegration
scheme need not be known while to express quantity
of radioactive material in curies, it must be known.

These then are the units used to express quantities
of radioactive materials, the curie and the rhm; to ex-
press dose, the roentgen, the rep, and the rem. With
these units it is possible to correlate the effects of
radiation on living tissue with external measurements of
the exposure, or with calculated internal doses.

The Detection of Radiation

Chairman, Special Training Division
Oak Ridge Institute of Nuclear Studies, Inc.
Oak Ridge, Tennessee

ION coLLEiCTON PIENO.'ENA. Since the inter-
action of the various types f radiation with
matter is accompanied by ionization, the obviou>
method of detecting the radiation is by collecting
the ions produced. Since Ihe fundamentals of the
behavior of electrons in electrical circuits have
been so well developed, it is a relatively simple
matter to design a device which can collect the
ions formed by the radiation The essential fea-
tures of such a device are ;i electrode system, ini
which the ions may le collected, and a circuit
through which a current passes when ions are
attracted to the charged electrodes. While plate
electrode systems can he used. other geometrical
arrangements are possible. and frequently a cylin-
drical geometry is utilized. This incorporates a
wire, or electrode, in the center of a cylinder.
which acts as the other electrode and is separated
from the central wire, or electrode, by an efficient
insulator. These electrons are connected through a
suitable resistance which permits a potential dif-
ference to be applied to the electrodes. The resist-
acee may be one which is inserted into the circuit
or it may be only the parts of the circuit them-
Although ionization is produced when radia-
tion passes through any kind of matter, one of the
most suitable mediums from which the ions can
be collected is a gas. If a cylinder containing a
central electrode, as was described above, is filled
with a gas, and a source of radiation is brought
into the vicinity so that the radiation passes
through the gas and causes ionization in it, these
ions are then attracted to the electrodes. If, for
example, the center wire is charged positively
with respect to the outer electrode, any negative
ions formed will migrate to the center electrode
while the positive ions will migrate to the wall.
Since the negative ions are usually electrons, they
will cause a charge to be collected on the center
wire as they arrive.
Under suitable conditions, a current may pass
from the center wire through the external cir-
cuit to the other electrode. Consequently, the
basic problem of the detection of radiation re-
solves itself into one of the detection and meas-
urement of small currents arising from the ion
collection in the detector system.
There are two problems which must be con-
sidered in the study of the detection of ionizing
These are the problems as to the behavior of
the ion in the tube as a function of the collection
voltage, and the problems involved in the detec-
tion of very small currents in the external system
of the instrument.

ELECTRODE VOLTAGE. To study this problem, one
may determine the amount of charge which is
-ile-cted on an electrode as a function of the
p'ltential across the electrode system. For a given
geometrical arrangement of the electrodes, the
charge collected after the passage of the two
given particles may vary because of the different
numbers if ions formed by the particles as they
traverse the gas in the collecting system. This
may be either the result of differing specific ioni-
zation for the two radiations or a difference in
the path length of the particle in the sensitive
volume of the detector.
If a curve is plotted showing the amount of
charge collected on the electrode as a function of
voltage, it will appear as in Fig. 1. Two curves
Ire shown in the low voltage region to represent
the case of the charge produced by different types
of radiation. The passage of an alpha particle
through the detector is shown in the upper curve
and the passage of a beta particle through it is
shown in the lower curve. It is found that at very
small voltages only a fraction of the number of
ions formed in the detector are collected because
the electrostatic field around the central electrode
does not extend to the walls and some of the ions
recombine before they are collected. As the volt-
age increases, the field extends to the walls of
the tube and all of the ions produced inside the
detector are collected. This is shown by a level-
ling off of both curves so that both represent
the collection of a constant charge as the voltage
is increased for several hundred volts. These
plateaus are called "saturation" values or the
region of saturation voltage, and are indicated by
the segments BC for the beta, and B'C' for the
alpha radiation.
In each case, the saturation plateau continues
,i the voltage is increased, as long as all of the
so-called "primary" ions are being collected. This
plateau continues until a voltage is reached, at
which the ions, formed by the initial interaction
between the nuclear radiation and the gas, i.e..
the primary ions are accelerated in the field of
the center electrode to such a point that they may
produce secondary ionization by their interae-
Lion with other gas molecules. The result is that
more ions reach the collecting electrode than
were formed in the original collisions and the
amount of charge collected increases over the
saturation value. This is called a process of gas
If the voltage is increased above this point,
more and more secondary ions are created and
the curve of charge collected rises rapidly with
increasing voltage.

Ionization Proportional
Chamber Countar
R region I region



10 .

Collecting Voltage
10* . �G^

Curve showing relationship between charge
The increase in the charge collected at the
electrode is no longer independent of the applied
voltage, as in the saturation region (BC and
B'C'), but is proportional to the voltage. This
voltage range is then referred to as the propor-
tional region of ion collection and is designated
CD and C'D' in Fig 1. It should be noted that the
slope of the curve which corresponds to the rate
at which the collected charge changes with in-
creasing voltage is the same for both alpha and
beta radiation. However, the number of ions
collected will remain proportionately different
in the two cases because of the different number
of primary ions formed by the radiation. In this
region, the discharge is localized to a small
portion of the tube.
It would seem that the process of secondary
ion production which is caused by the accelera-
ton of the ions toward the collecting electrode
would continue to increase the charge indefinitely
as the voltae is increased higher and higher.
During this increase of voltage, the ionization
discharge would spread over successively larger
portions of the tute. However, another factor
enters the picture as the voltage is increased. If,
as we assumedd ahove, the central wire or elec-
trode of the tube is positively charged, the nega-
tive oni will be attracted to it Now, since the
electrons are so light in comparison with the
positive atomic residues, they are swept out of
the collecting gas very rapidly, leaving behind
an atmosphere of positive ions. These ions give
rise to what i- known as a "space-charge effect."
In addition, the positive ion sheath has the effect
of increasing the diameter of the central electrode
which reduces the electrostatic field intensity in
the tube. The result is that an upper limit of
voltage is reached at which these factors effec-
tively limit the number of ions which may he
collected at the positive electrode. This mrena s

ollected as a function of collecting voltage.
that the multiplication of secondary ionization
cannot continue to increase indefinitely with in-
creasing voltage.
This region in which there is not a strict pro-
portionality between the voltage and the amount
of charge collected is called the limited propor-
tional region, and is shown as the segment DE
and D'E' in Fig. 1 In this region, the slope of
the curves for the two types of radiation is noi
the same because of the limiting value of the
amount of charge that can be collected imposed by
the particular characteristics of the tube in use-
If the voltage increases still further, one finds
that the charge collected is not at all dependent
on the type of the radiation or the number of
primary ions initially formed, but only on the
voltage applied to the elctrode. In this region,
the field intensity about the center electrode is
so high that any ion formed, whether of primary
or secondary origin, can be accelerated enough
to cause additional ionization in the gas. A chain
reaction is thus instituted and an "avalanche" of
ions is created in the tube. In principle, any
particle giving rise to a single ion pair in a de-
tector operating above this particular voltage
would he sufficient to cause the collection of the
same amount of charge at the electrode as a par
title giving rise to many thousands of ion pairs
initially. The actual charge collected from either
type of radiation does increase slowly as thr
voltage is further increased, but its amount does
not depend on the type of radiation or the energy
of the particle which causes the initial ionization.
This region was first investigated by Geiger
and has since been called the "Geiger region" of
ion collection. This is represented by the seg-
ment EF in Fig. 1.
If the voltage on the collecting electrode is fur-
ther increased, a limit is reached at which the
tube discharges in a "continuous manner." With

Imany types of Geiger tubes, permitting the tube
to discharge in such a way damages it. This
shouldd be guarded against, but if it happens in-
advertently, the voltage should be immediately
lowered to a safe value.

chambers are instruments characterized by the
une of collection voltages in the saturation region,
as indicated in Fig. 1. Thus far in the discussion,
little mention has been made of the method of
determining the amount of charge which has
been collected on the electrode. As a matter of
fact, the total amount of charge collected is not
often the quantity which is of interest to the
experimenter. He is most often interested in
determining only the rate of radiation emission.
This is usually equivalent to the rate of ion col-
lection. in order to determine the rate at which
ions are collected by a given electrode system.
uoe of two general methods is used. In the first
method, the actual rate of the charging or dis-
charging of an electrical capacitance is measured.
This may be done simply, as in the case of the
discharge of a gold leaf or quartz fiber electro-
scope or, more elegantly, by the actual use of a
condenser in an electrical circuit. In this method,
the actual rate of drift of the leaf or of a needle
of an electrometer galvanometer is used as a
measure of the rate of charge collection and is
thus a measure of the rate at which the radiation
is affecting the detector. A galvanometer is not
used directly since it cannot usually detect a cur-
rent corresponding to less than about 10-' am-
peres while the current generated by the detee-
tion of a beta particle may be as low as 1011
The second general method of current measure-
ment involves the use of the well-known Ohm's
law. (Of course, all current measurements utilize
this law, but some are not evident immediately.)
This law is usually expressed by the following
in which V is the voltage produced by a current,
I. passing through a resistance, R.
In this method of ionization current measure-
ment, the current from the detecting tube is
passed through a resistor and the voltage drop
across the resistor is measured. The deflection of
the voltmeter is, then, proportional to the amount
of ionization being collected by the detector elec-
trude. Thi, voltage would vary if the rate at
which the radiation passed through the detector
changed and would also vary with different types
of radiations as a result of their different specific
ionizations in the detector tube.
It is easily seen that the rate of drift method
measures the time required to collect a given
amount of charge. The potentiometer or voltage
mer.surement gives a measure of the steady state
lonizatiun being produced at a given time by the
pa-sage of ionizing radiation through the detee-

tor. Neither of these methods measures directly
the number of particles passing through the
detector, but gives only the total effect of the
radiation on the detector.
For this reason, instruments which employ col-
leetion voltages in the tube in the saturation
region ind which use one or the other methods
described above for the current measurement, are
called integrating ionization chambers. The ac-
tual voltage which is used in a given type of de-
tector depends on the geometrical construction of
the tube, the type of gas in the chamber and its

BACKGROUND RADIATION. One of the ever-pres-
ent difficulties in the field of radiation meas-
urement is the so-called "background." Back-
ground is the effect of any natural radiation
passing through the detector and must be con-
sidered before any additional radiation effects
are interpreted. It is caused by (1) the effects
of secondary electrons formed by the interaction
of cosmic radiation with the detector walls, and
t2) radiation arising from the contamination of
radium, potassium, and other naturally radioac-
tive elements in the construction materials of
and surrounding the detector. There have been
many arrangements suggested and used for re-
ducing the background of detectors, such as the
use of special paints to shield from alpha rays,
large metal shields, electrostatic shielding de-
vices, and by making the detectors as small as
practicable. However, it has not yet been possi-
ble to eliminate the background effect completely.
In all radioactivity measurements, the back-
ground is measured and subtracted from subse-
quent measurements of activity.

IZATION CHAMBERS. While the principle of
the detector operation is the same for all inte-
grating ionization chambers, there are many
different methods that are used in the laboratory
for making and recording measurements with
such chambers. One of the simplest of these in-
struments is the classical gold leaf electroscope
which is frequently used for demonstration, al-
though it has been used extensively in research.
More recent modifications of the electroscope
principle and those which show considerable
promise for public health work are in the widely
used Lauritsen electroscope (Fig. 2) and the
Landsverk Sample Analyzer. In this type of in-
strument, the gold leaf of the older electroscope
is replaced by a gold plated quartz fiber. A sche-
matic representation of the instrument is shown
in Fig. 3. In this instrument, the fiber is charged
with a battery, a rectifier, or a friction charging
mechanism. Through the eyepiece can be seen an
illuminated scale with a visible cross-hair. After
being charged, the fiber is on the zero mark on
the scale. If a radioactive source is brought near
the instrument or placed in the sample measuring
position, the fiber will move back toward the dis-

Fig. 2.
Typical portable Luritsen Electrosope..
charge position at a rate nearly proportional to
the intensity of the radiation entering the cham-
ber. The reading may then be expressed in scale
divisions per unit time. The background may be
determined by allowing the fiber to drift over the
scale in the same manner with no radioactivity
in the vicinity of the chamber. Since the instru-
ment is not linear over the entire scale, it is usual
to take a reading over a certain part of the scale
and use, for comparison, readings taken over the
same portion.
The apparent activity of the sample is then
proportional to the difference in reciprocal times
required for the measurement of the source and
for the background over a given region of the
A 1 1
twarnule t U. ,,til'k i il
The fiber instrument is quite simple to operate
and is considered to be among the most reliable
and rugged detection instruments available for
laboratory or field use It has the distinct ad-
vantage of being able to measure a wide range of
apparent activities in various sample, but is
somewhat tedious to use for extended periods of
time, since it is necessary to watch the fiber
through the telescope ocular.
The direct reading electroscope is re.isonably
seinsiive but considerable; greater sensitivity may
be acquired by using al electrometer to mrieaiurc
the ion current from the ionization chamber A
number of very satisfactory electrometers have
been i1n she for -everal years Included in this
category are those of the Lindemantn type. the
string eilettrineter, varibnls modificraliuis n the

1I0Cu Ua-p ovn lll

Eig. 3.
Schematic diagram of Laurtsen Electroscope.
quadrant electrometer and various types of
vacuum tube electrometers.
The .atter type has been used in man'y aborsa
ies bause of i relative ~impcity of opera

tion, and because the measurements may be made
either by a visual determination of the rate of
drift of a galvanometer needle, by the deflection
of a needle if the resistor method is used, or by
some other type of recording device. The basic
iof a neT i"f" Tth r to d tlto thod is u ,or

Shematic dity ram of Lreiotr n elietrboaop si

circuits of these electrometers employ one of
several tubes such as the General
Electric FP 54, the Victoreen VX 32, or the
Raytheon bCK 571 AX. These are circuits com-
monly used with portable ionization chamber
monitoring devices.
The resistances that are utilized in this type of
circuit a fre fquently selected in powers of 10
ranging from 10 to 0L-va ohms, to give satisfac-
tory readings on common voltmeters. These are
usually quite satisfactory instruments for labora-
tory or field us, although they usually are not as
sensitive as some other types of instruments.
The statistical fluctuations at very small currents
are quite troublesome.
aUCLEAR COUNTERS. Nothing has been said so
far about the length of time which is in-
volved in the measurement of the ionization cur-
rent produced in the detector. Theoretically, with
sensitive enough detectors and current measure-
ment circuits, the effect of any radiation passing
through the detective device could be measured.
However, in practice, that radiation with a low
specific ionization in the detector would not give
rise to a current which can be measured by the
circuit ci a reasonable length of time,
It is frequently desirable to determine the rate
at which particles are entering the detector. This
is particularly true of work with radioactive
tracers in which the rate of emission of particles
is used as an indication of the amount of radio-
active material present. The basic difference be-
twenli the integrating ionization chamber instru-
ments described above and particle counting cir-
cuits lies In the length of time required to col
lect all of the ions which were formed by the
passage of a Ningie radiation particle In other
words, if the detector is to be used as a particle
counter, the time in which the measurement of
the voltage thallng produced by the ionization
Iurli is made. must he shorter than the time

Fig. 4.
Typical personnel monitoring instruments.

required for all of the ions formed by the pas-
sage of a single particle to be collected on the
A measure of the time required for this in
the various circuits is called the time constant
of the circuit.
The time constant of a given circuit is de-
termined by the resistance and electrical capaci-
tance of the entire circuit and is the time re-
quired for the charge in the system to be reduced
by a certain fraction (I/e) of its original value.
In other words, if a long time constant is em-
ployed in a given instrument, individual ioniza-
tion bursts will not be registered but will con-
tribute only to an averaging or integrating of
the measurement. On the other hand, if a short
time constant is employed, individual ionization
bursts will be measured by the instrument and
it will then operate as a counter. Ambiguity
sometimes arises over the use of the term "count-
ers." In some laboratories, the counter refers
only to the detector or counter tube. In others,
the detector and associated measuring and rec-
ording equipment is called the counter. In still
others, the term is used interchangeably. Possibly
the best suggestion is to use the term counter to
include the entire instrument and use the term
detector or counter tube for the ion collection

ionization chamber region may be done in
principle in the same manner as was discussed
for integrating measurement in the ionization
chamber region with a modification of the ex-
ternal circuit to introduce the short time constant
required for the counting operation. They can
be used only for alpha, neutron, or fission frag-
ment counting. In practice, ionization chamber
design for counting is fairly difficult and has no

Fig. 5.
Portable ionization chamber radiation det.ction insiru-
very satisfactory theory on which to depend At
the present time. no great amount of work is be-
ing done in this field, since much of the counting
can be done more satisfactorily with proportional
counters. Although the parallel plate alpha count-
er was widely used for some time, other types of
detection devices are supplanting these instru-

PROPORTIONAL COUNTERS. The proportional region
is rapidly becoming one of the most used and
important regions for counting measurements.
There are two reasons for this development. One
of these lies in the fact that with proper voltage
adjustment, it is possible to distinguish Ietween
various types of radiation. For example, if a
sample containing two radioisotopes, one en'it-
ting alpha radiation and the other beta radiation,
is measured, it is possible to adjust the voltage
to a value which will permit the alpha particle
ionization bursts to be measured and recorded,
but not the beta particle bursts, since they pro-
duce much less ionization in the tube. By rais-
ing the voltage to attain a gas amplification fac-
tor which will permit the recording of the beta
particles, the total counting rate due to the alpha
and beta particles may be obtained. The beta
counting rate is then determined by the differ-
ence in counting rates.
The other advantage in the use of proportional
counters lies in the speed with which the collec-
tion of ions takes place. Mention was made
of the avalanche characteristic of the Geiger re-
gion, which occurs when the discharge or the
collection takes place. This extends along the
length of the collecting electrode and occupies the
whole volume of the tube. In the proportional re-
gion, the discharge is localized to a limited re-
gion along the wire. As a result, the time re-
quired for the collection of these ions is quite
short compared to the time required to co'lcet all
of the ions in the tube after a Geiger discharge.
This may be of the order of 10 microseconds
per count in the proportional region compared
to 300 microseconds in the Geiger region.
Proportional counters are usually operated at
atmospheric pressure using some kind of a flow-

--. �
Fig. 6.
Portable Geaigr-MuIlll radiation delection instru-
ing gas system or gas purging system. There
are several difficulties involved in proportional
counting, such as the high voltage supplies that
are frequently necessary and the necessity of
good amplifying circuits. Probably the most im-
portant single feature which is necessary for
good proportional counting is that of the stability
or regulation of the collecting voltage. Because
of this feature and because of the necessity for a
gas supply, these instruments have been used
relatively little for field work. There are some
portable units being used for laboratory moni
touring, but there are no commercial units avail-
able for actual field use.

Mueller counters (frequently shortened to
GM counters) have been the type of detector
most often employed during the last several
years for much of the radiochemical work. They
are not particularly stable or long-lived, but have
probably been used because of the ease with
which the results are recorded, and because of
the fait that only moderately good amplifiers
have been needed in their auxiliary equipment.
They are much lI e tediou, to use than electro-
scopes .nd give direct counting rates which many
workers prefer to the i-ate of drift or potentiome-
ter readings.
As has been pointed out before, the Geiger
counter is characterized by the fact that a single
lonization event inside the tube is sufMiCient to
bring about the ava;ilcrhe f lons. The Geiger
tube Ihen mIe.i.sures tie inumner of pules of ra-
diation of whalcver energy or iype, either than

the total effect of this radiationi Tle Geiger
counter must then be equipped with a device
which measures the number of pulses and a timer
to record the length of time over which the
measurement is made Two methods of determin-
ing the counting rate will be described later.

GEIGER TUBE QUENCHING. One of the points
mentioned earlier in the collection of ioniza-
tion from a detector comes into prominence in
connection with the Geiger tube mechanism It
was pointed out that the electrons, or negative
ions, are collected very rapidly by the center wire
of a detector, which leaves an atmosphere of
positive ions remaining in the tube. These posi-
tive ions are attracted then to the wall of the
counter tube, they finally are neutralized, and
the tube is ready for another burst of ionization.
If the voltage is high enough to be in the Geiger
region, this impact of the positive ions with the
wall may be quite hard. It may, indeed, be hard
enough to cause the ejection of electrons from
the wall. Likewise, it may give off some of its
energy in the form of radiation which is able to
produce photoelectrons in the tube. If these ex-
traneous electrons are formed, they are sufficiently
energetic to cause another discharge in the tube
and, give rise to spurious count in the instrument.
If this cycle is repeated, it is possible to obtain
many counts which are entirely independent of
the radiation source which one used initially, and
the results would be worthless. To avoid this diffi-
culty, the tube must be stopped in its operation
after each pulse so that subsequent electrons
caused by the discharge mechanism will not trip
the counter.
This stopping of the action is referred to as
"quenching" the tube. It may be done either by
the addition of an electrical circuit which lowers
the voltage below the Geiger region momentarily,
or it may be done by the addition of a gas to the
tube-filling mixture which will not permit the
formation of these extra electrons to come about.
Most of the present-day tubes employ an inert
gas, such as argon, for the main counting gas
with the addition of some organic vapor as the
quenching gas. A typical filling might consist of
8 cm pressure of argon and 2 cm of ethyl alcohol.
This length of time the counter tube is out
of operation is referred to as the "dead time"
of the tube. Other terms used in this connection
are "resolving time" and "coincidence loss." The
resolving time is the length of time between
pulses that the counter can register, whdle the
coincidence losses arn those pulses lost when
measuring a sample having such a high rate of
enls registered by the counter, since some will arrive
in the tube during its "dead time,"

OPERATIONAL PLATEAUS. When it is intended
to make measurements of radiation with a
Lypical Geiger ijisli iument, sevciral utheli iceitfts
must be kept inl mind. While it is theoretically
ronceivable that a given detector tube could op-

prate in several of the voltage regions, in practice
the detectors are used either as ionization cham-
bers or as proportional or Geiger counters.
Because of the structural limitations imposed
by the restrictions of the electrostatic fields in
high voltage counters, and because of the limita-
tions imposed by the amplifiers that are necessary
to record counts on a mechanical register, there is
a voltage minimum below which most proportional
and Geiger counters will not operate. This voltage
which is necessary to obtain a large enough pulse
to record the impulse is called the threshold volt-
age and is a characteristic of a particular type of
Geiger tube and filling. The same phenomenon
is observed with proportional counters unless an
extremely wide band amplifier is used. The first
step in operating a counter, then, is to determine
this threshold voltage by bringing an active sam-
ple into the vicinity of the detector and turning the
voltage up until the impulses start registering in
the counter.
If the operator then continues to raise the volt-
age while the sample is in the same position rela-
tive to the detector, and while it is giving off
particles at a constant rate, it is observed that a
voltage is reached at which the counting rate be-
gins to level off after rising rather sharply just
above the threshold. This plateau may continue
for several hundred volts as the voltage is raised
higher. The plateau terminates with an abrupt
rise in counting rate when the counter goes into
discharge and counts in a "continuous" fashion.
The detector should not be left at this voltage, but
should be immediately turned down into the pla-
teau region to avoid ruining the tube. The Geiger
region is commonly in the voltage range of 1000
to 2000 volts, although this varies markedly with
the tube and its filling. The nature and length of
the plateau is one of the most important character-
istics of a detector. For laboratory and tracer
work a tube is considered satisfactory if it has a
plateau with a variation in counting rate (slope of
the curve) of not greater than 5% per hundred
volts. For portable or field instruments, this is
probably not necessary and 10% per hundred volts
is not uncommon in these commercial models.
While many investigators are familiar with the
plateau of a Geiger tube, it should be pointed out
that proportional counters also have plateaus
which extend over a thousand or more volts. In
other words, with given type of radiation, a point
is reached at which all of the radiation particles
are detected and no increase in voltage causes a
change in the number of impulses registered. If
there are two types of particles being emitted from
the sample (such as alpha and beta radiation),
there will be one plateau observed for the highly
ionizing particles, and then another plateau cor-
responding to the voltage is observed which will
cause both the highly ionizing and less highly
ionizing particles to be registered. Thiseharacter-
istic of "discrimination" between types of radia-
tion. together with the increased counting rates
which are acceptable, are the factors which make

proportional counting highly desirable for many
problems met in the public health field when desir-
able to determine the type of radiation present.

SCINTILLATION COUNTERS. A somewhat different
type of counter has come into use within the
last two years which has several distinct advan-
tages over both the Geiger counter and the pro-
portional counter. This is the "new" scintillation
counter which has been in use for something over
50 years for the detection of radiation. It is essen-
tially the same as the old spinthariscope, with the
difference being in the use of the photomultiplier
tubes to detect the light flashes rather than count-
ing them visually, as was done in Rutherford's
day. This detector is based on the principle that
ionizing radiation, when passed through a certain
type of crystal or other medium, causes excitation
in the crystal which is followed by the emission of
light as the electrons are replaced in their original
position. This light is allowed to impinge on the
photoelectric cell and the current thus obtained is
multiplied with a photomultiplier tube. Consider-
able study is being made now of the best types of
crystals and photomultiplier tubes. It appears
that there will be a distinct advantage in the count-
ing of alpha particles and gamma radiation with
these devices. Since beta radiation (that enters
the tube) is counted essentially with 100% effi-
ciency in the Geiger tube, there is less need for
improvement unless otherspecial phenomena, such
as the energy spectrum of the radiation, are un-
der investigation. The commercial models of these
instruments will undoubtedly be improved rapidly
within the next few years, and undoubtedly there
will be many applications where this type of de-
tection will be used considerably.

have discussed something of the problems asso-
ciated with the current measurement for the in-
tegrating type ionization chambers. This meas-
urement consisted either of following the rate of
drift of a fiber or needle, or of using an appro-
priate resistor to determine a voltage proportional
to a given ionization current. In using a counter,
it is only desired to detect the number of pulses
per unit time after making the assumption that
one is measuring all or a certain proportion of the
ionization bursts taking place in the detector tube.
In addition to an amplifying circuit which will am-
plify the impulses enough to excite a neon bulb
or actuate a register, it is usually necessary to
have one other component in the circuit. Since
mechanical registers cannot operate much faster
than five to eight per second, some kind of auxil-
iary component is needed to increase the number
of counts that can be accepted by the tube. To do
this, most instruments use an electronic "sealer"
which divides the number of pulses by some con-
stant factor, such as 2, 8, 64, or possibly 100 or
1000, or using an integrating type of circuit called
a counting rate meter which reads directly in
counts per unit time.

." UMs BP
:V '

rq. 7
Typical Lboratory equipment for alday Of redia-

For most laboratory or assay purposes, it is usu-
ally considered somewhat better to use the sealer.
On the other hand, most portable Geiger counters
and soum laboratory n mlde s employ the counting
rate meter directly. Most scalers employ a system
which uses a neon bulb to indicate the acceptance
of a pulse by the circuit. These neon lamp, are
then actuated in a series, either by steps of twol
or by a more complicated system in which a decade
series is indicated on the instrument. When the
lamp scaling reaches the end of the series, the
next pulse actuates a mechanical register. To de-
termine the number of total counts which have
been accepted in a given time, the investigator
multiplies the number showing on the register b.
the appropriate scaling factor (such as 64 or 1000)
and adds the total determined from the lamp-
which are left burning at the end of the counting
Most of the portable counting rate meters do not
give an indication in counts per minute, but. in-
stead, are frequently calibrated in "mr/hr." This
is rather unfortunate in that this implies that the
ionization caused by radiation of various types is
independent of energy or that one pulse corre-
?ponds to a given portion of an mr hr. The de-
fence of the manufacturers is that the instruments
are calibrated with radium so that if they are
used to monitor radium gamma radiation, the
readings do come out in these units. For work
with artificial radioisotopes this independence does
not hold. Readings must be interpreted with care.

While counting rate meters have manii advan-
tLi es lvr- coniventioln[ii scalers, it it imponrtallt to
ie I'iw hiat an instrument whros indicator nredrl
is ings ifmmedlately to give the counting rate wll)
hive blrg, flucltuations in its ieadrlig. As a matter
of fact. a counting rate meter should proper
have a time constant which makes the instrument
lake as long to give a reading as tihn measurement
would take with a sealer, if proper statistical r'-
liability is to he assured.

FILM. It is well known that phitograph]i film
is affected by nuclear radiations. Film is fre
quently used for twoi purposes and in reality is .
type if nuclear instrumentationn." It may be noted
either as a film ladge for monitoring purpose,, or
as a ineans of taking autoradiograms showing the
location of radiaurlive material in a sample. The
density of the blackness produced may he meas-
ureed on a densitometer. For personal monitoring.
thel( dlsity readings may be compared with those
from a ediliratvd film which has undergone the
,sme deverloppmilt treatment as the unknown
monitor film, The films are not of high sensitiv-
ity for monitoring, so it is usual for the wearer
to retain the same badge for a period of a week
or so unless the pocket ionization chamber indi-
ratls that an overexposure may have occurred.

amples of some of the types of equipment
which are used by public health personnel engaged
in radiation detection are shown in the illustra-
tions, Figs. 4, 5, and 6. There are four general
types: electroscopes and pocket chambers, porta-
ble ionization chamber instruments, portable
Geiger counters, and film badges. There are
other types of instruments which are used for
laboratory detection and assaying procedures.
One ih shown in Fig. 7.

I ,p . .. n I, h.L s..I l.' I : u.
('n*r. nhU11ter 1
r 'l 11 ihIIt i* t l K.it .N I Ch''aptt,
JI -Fl. A H.. K' llMAN. T. - nd f r. ..,. i, A. "A KI;
oI ell M--a firrlanl "f I -lilmliwlie." Vs.SA.lI'. Kill":
IKAI lW,. f'hn iltr I
St u r, A . . . r,. ., . null n a y....*.. Ip .. .. II V v . sri l.
New y'"'k, I ll)
tL," niil ANrd "I.r C l,'ttr> ',p. |i.
r'H.IA:lP un.I I O)AV iir.\s, . ChhIee tr 1.
SKApuI.. 1i B 'An Intr~l!ti.n 1t, Nulc ir Ch.rn'l i . I-rcoe
u ae l .. l., U.S.A-:,C. M111.ll", ll Pit6
S I.. W.. llainl ,n nidn'i',lilir nrvf T rm lrsllt4 lnlh i
Snt.tpi.. rhinfl, r , 7

Reprinted from ithe Mannal of the Lectures prreenltd at
The Insiet ri Training Course in Radioalogal Health.
University of Michigan, School of Pnblic Health. February 5-8. 1s51.

Part 2: kadioPical ,ealt



A. A. Bless

Professor of Physics
University of Florida

The methods of radiation detection described to
you by Dr. Overman are by far the easiest and most
convenient, as well as most sensitive. However, these
methods can be used only when an observer is present,
as is the case when an area is tested for safety from
radioactivity or when testing samples, or in case of
atomic explosions expected or planned. Naturally these
methods cannot be used if the area is too "hot" for
an observer, or in the case of an unexpected explosion,
far from a competent observer. In cases of this kind
biophysical methods come in handy. These methods are
not nearly as sensitive or as accurate as the ordinary
ones, but they do give a great deal of valuable informa-
tion concerning the amount of radiation to which a given
area was subjected.

Penetrating radiations affect all living matter.
In many cases these effects are a function of the radia-
tion dose. In cases of this kind the effect may serve
as an estimate of the amount of radiation incident on a
given body. This is essentially the biophysical method
of measuring radiation. The total radiation incident in
the case of atomic explosions, may be measured in that
fashion. Two biophysical methods of radiation detection
will be discussed. The first is the detection of radiation
by means of bioelectric potentials. For a great many
years it was known that some animals, especially eels,
are capable of generating very high voltages, some spe-
cies generating as much as 600 volts. However, most
living things are able to generate only very small poten-
tals which are difficult to measure. Only in recent
years has the technique of measuring these small volt-
ages been developed sufficiently well to enable one to
study these phenomena.

Human bioelectric potentials are known to most of
you. When a physician is obtaining a cardiogram in the
case of heart disorders, he is really getting a record of
the potential difference between the heart and some
neutral member of the human anatomy, such as the leg.
In case of brain disorders a brain specialist may ob-
tain an electroencephalogram, which is a record of
potentials generated by portions of the brain. In the
last analysis all matter, living or dead, consists of

atoms which in turn consist of positive and negative
charges. No change may take place in any system unless
there is a force which causes these changes. No chemi-
cal reaction, no biological event can occur unless some
force creates the conditions necessary for that reaction
to take place. It is reasonably well established that
these forces are electrical in nature.

When a portion of the skin is cut or bruised, that
portion is electro-negative with respect to the uninjured
part. In fact any injury or any change in the normal func-
tion of an organism is bound to change the distribution
of charges in the affected portions of the organism.
Whenever a given portion of the plant or organism is
more active than another, differences of potential arise
which in general are a measure of the extra activity.
Thus there is a difference of potential between the
tip of a growing small plant and its base. There is a
difference of potential between the growing embryo of
a chick and the albumen of the egg.

Now a very interesting question arises. Since the
potential of a plant or an animal reflects the activity
of that organism, and since radiation affects all plants
and animals, will radiation affect the potential of an
organism? Dr. A. L. Romanoff of Cornell University and
the writer approached this problem. Using the embryo
of the chick as the biological material, batches of eggs
were exposed to the action of different doses of X-rays
and the diameter of the developing embryo was measured
as a function of dosage. The potential between the
embryo and the albumen was also measured for different
doses of radiation. The curves obtained for the two
parameters are shown in Fig. 1. It is evident that the
diameter of the blastoderm is stimulated by small doses
of radiation, but large doses inhibit the growth. The
interesting point is that the curve for the potentials
shows similar features. The potentials are stimulated
by small doses of X-rays; however, large doses inhibit
the potentials.

It is recognized that the size of a developing embryo
or plant is a good criterion of the health of a specimen,
and chat the diameter of the chick embryo is a good


~'^>:::':S =-- - -- 0








measure of radiation injury to the specimen. Since
the bioelectric potential shows the same general features
of variation with dose as the diameter of the embryo, it
follows that the bioelectric potential can serve as a
very good measure of radiation injury. More recently
some work has been done on the variation of the poten-
tial of germinating seeds with X-ray dosage and the
same pattern was found as with the variation of the
potential of the embryo with dosage. For most of the ex-
periments the seeds were irradiated 24 hours after the
start of germination because at this age the seedlings
were found to be more sensitive to radiation that at
any other stage of growth. Series of curves were ob-
rained showing the effect on the potential of a given
dose when the potential was measured at different ages
of the seedlings. Fig. 2 shows three such curves from
which it is evident that at the age of 120 hours the
effects of radiation on the potential are considerable,
and that the potentials at that age could serve as a
measure of radiation injury.

Measurements are now being extended to dry seeds,

0 1000 2000 3000 4000 5000


and the effects of various doses on seeds when dry and The experiments with the seeds exposed at Bikini

dormant. Very recently the results of planting seeds
which were subject to radiations at the Bikini explosion
were made public. A number of batches of dry corn
seeds were left on 22 ships stationed around the center
of explosion just outside the zone of destruction. At the
same time dry seeds were irradiated at Comell with
various doses of X-rays. The seeds were later recovered
from the ships and planted in California side by side
with those irradiated at Cornell and the results compared.
The results ndicared rhar the largest dose to which the
seeds were subjected at the atomic explosion was
equivalent to 15,000 units. This huge dose, which
when given to 30 human beings would have caused the
death of at least 15 of them within a short time, was
not enough to kill the seeds. All of them germinated
and reached maturity. However, they were all stunted
and showed various defects both in the fruit as well as
in the chromosomes.

The effects of radiation on dry seeds are extremely
important because they will tell us to what extent the
delay of germination aids the recovery of the seeds from
the radiation effects.

illustrates very well the advantages of the bioelectric
method of measuring radiation injury over the one used
by the Cornell and California scientists. In that ex-
periment a great many seeds had to be planted and the
growth watched for months with all the possibilities
of variation in soil content, humidity, and accidents
that such plantings entail. Of course, if genetic changes
are sought, seeds have to be grown to maturity. However,
if it is merely a question of determination of radiation
injury to which the seeds were subjected, the bioelec-
tric potential method is by far easier, quicker and more
reliable. In this method seeds are placed in a controlled
germinator and the potentials measured 100 hours or so
later. Fifty or sixty seeds of each kind are sufficient
to give good statistical results. It was found that if
several readings of the potential of the same seed are
taken, twenty seeds or less will give satisfactory re-

A more convenient though not as sensitive method
for measuring radiation injury, may be determined by the
oxygen consumption of seedlings, or by their energy
intake. Most living matter, plants or animals need a








certain amount of energy to maintain life processes -
in order to keep alive. We get the energy in two ways -
from the food we take in and from the oxygen we get
from the air. By far the largest fraction of the energy
comes from the food, but in the case of plants and sim-
pler animals, a greater fraction probably comes from
the intake of oxygen by the specimen. The important
thing is the fact that the oxygen intake by the plants
subjected to radiations is a fairly sensitive function of
the dose. If we plot the rate of intake of oxygen against
the radiation dose, we get a curve shown in Fig. 3
which shows the same characteristics as that for bio-
electric potentials; the consumption of oxygen is great-
ly reduced by heavy doses of X-rays. We can estimate
to a very close degree the radiation injury suffered by
the seedling from the number of cc of oxygen taken in
by the specimen each minute. The seeds germinated in
special containers are introduced into flasks of a
Warburg apparatus and the oxygen intake measured for
a time interval of some 30 minutes or so.

The similarity of the curves - potential vs dose
and oxygen intake per minute vs dose is not accidental.
Each of these, the potential as well as oxygen intake
is a measure of the activity of the organism; each
measures a certain vital property of the specimen, and
each shows that the vital processes are profoundly
affected by radiation. Moreover, there is a great deal
of evidence that the potentials depend on oxygen in-

The question naturally arises: can radiation injury
in higher animals such as mice or rats be detected by
these means? At Yale Dr. Burr found chat the potentials
of mice which devclupcd cancer differ from the controls.
The work was repeated in England, and after some ex-
periments the investigators reported negative results.
At Florida some mice were subjected to a dose of 500 r
units - enough to kill half of them inside a month, and
another batch of mice was subjected to a small dose -
150 r units. The comparison of the potentials of the
two batches of mice shows no significant difference
over a period of 30 days. The potential was measured
from the base of the tail to its tip, the two points being
most promising, since the base of the tail is a seat of
considerable cell activity, while the tip is relatively
inactive. The potentials are gratifyingly high, some
twenty millivolts, but these points are evidently not
revealing so far as the state of the animal is concerned.
The fact that the potential between these two points
fails to show radiation effects does not mean that two
other points may not be more revealing. In the case of
seedlings of corn the obvious two points are the ger-
minal and micropilar end; in the case of wheat seedlings
the rip of the colenptile and its base furnished the refer-
ence points, since che germinal end of the corn and the
coleoptile tip of the wheat seedlings are obviously
the points of highest cellular activity. The question
is whether an animal has a point of comparable activity.
In view of the great complexity of its potential picture
and cellular activity, an animal may not have such a
single point.



George K. Davis

Professor of Animal Nutrition
University of Florida

In discussing with this group some of the quanti-
tative aspects of naturally occurring radioactivity, the
questions which you will want answered revolve around
considerations of cosmic rays which are constantly im-
pinging upon us; upon the radiations which are due to
such radioactive isotopes as potassium-40, the con-
tamination of minute amomrs of the transuranium ele-
ments - uranium, radium, thorium, radon, and thallium,
and that due to carbon-14, with perhaps a bit of concern
for radioactivity associated with the disposal of radio-
active isotopes which are waste products from medical
therapy or associated with nuclear explosions such as
those in New Mexico.

Since so many popular articles have been circulated
about the effects of cosmic radiation and their influence
upon life on this earth, it may be well to give some
attention to cosmic rays; the so-called hard and soft
components, and to the energy which cosmic rays must
require to penetrate our atmosphere.

We are concerned with cosmic rays in a considera-
tion of natural radioactivity because they are a part
of the background count of instruments such as the
Geiger-Mueller tubes which are used to measure radio-
activity, because of the ionization which is caused by
these rays, and because the formation of carbon-14
found in nature presumably results from the transmuta-
tion of nitrogen due to cosmic ray bombardment.

Since their discovery in 1911 by Hess, much has
been learned about cosmic rays. But as is so often the
case in new fields of knowledge, as more insight has
been gained into the fundamental nature of cosmic rays,
the more incomplete our present knowledge appears.

We do not know where cosmic rays come from,
but their very name resulted from early demonstrations
that they apparently originate outside of our solar sys-
tem. The information which we have has been developed
by means of the ionization chamber, Wilson Cloud
Chamber, Geiger-Mueller Counters, and photographic
plates. All of these instruments detect ionization pro-
duced by fast charged particles or by gamma rays. The

electrically neutral components of the radiation pre-
sent much more difficulty in measurement.

One of the first observations of cosmic ray intensity
was the rapid increase which occurs with altitude.
Subsequent studies have demonstrated that at the geo-
magnetic equator at sea level, it has an average value
of ionization that is about two ion pairs per cubic cen-
timeter per second and at an altitude o 40,000 ft., the
incidence of ion pairs is about 40 times that of the
sea-level reading.

The discovery of latitude effects upon cosmic ray
intensity led to the knowledge that primary cosmic
rays are mostly high energy protons which are acted
upon by the earth magnetic field.

These primary cosmic rays are not able to traverse
the atmosphere very far before they interact in a mul-
tiple production process that gives rise to secondary
particles. The primary cosmic rays produce mezons or
mezotrons of high or low energy. The decay of the low
energy mezons gives rise to electrons that form the
soft components of cosmic radiation, while the high
energy mezons constitute the bulk of the so-called hard
components which have great penetrating power. Arbi-
trarily defined, the hard component is the radiation which
penetrates 12 centimeters of lead. The soft component
is that which is absorbed by the 12 centimeters of lead.

At sea level, the soft component is about 23 per cent
of the total intensity. In the lower atmosphere, the soft
component is almost entirely protons, electrons, and
positions. On the other hand, the hard component con-
stitutes primarily mezotrons which are particles of
positive and negative charges and a mass of about 200
times the electron mass. The energy of the cosmic rays
is immense and it can be demonstrated that while the
average energy of the primary cosmic ray is about 6
billion electron volts, a considerable portion have high-
er energies and a few have exceedingly high energies
of about 1015 electron volts. In an effort to bring this
consideration into terms of natural radiation, it may be
well to mention that although the cosmic rays are

possessed of tremendous energy, the incidence and mass for much of the natural radioactivity in and around us.

are such that the total energy from this source reaching
the earth is of the same order as that from starlight
and accounts for about 10 per cent of the total ioniza-
tion on the ground level due to natural radioactive

Put in another way, 30 counts per minute correspond
to 0.2 milliroentgens of cosmic ray intensity per day.
For comparison, it may be pointed out here that the
permissible dose is at present stated to be 0.10 roent-
gen equivalent-physical per day per gram of tissue or
ten counts per second with a Geiger-Mueller Counter.

About 1018 particles strike the upper atmosphere
of the earth per second. If all of these particles were
of one charge, they would constitute a current flow to
the earth of about 0.1 amp. About two particles per
square centimeter per minute reach die carth's surface
and constitute about four millionths of a roentgen per
hour per cubic centimeter at sea level.

If 10 per cent of the ionization due to radiation at
ground level is due to cosmic rays, the other sources
of naturally occurring radioactivity are of practical
interest to us. I should like to devote most of the re-
mainder of my discussion tothe occurrence of potassium-
40 which, because of the natural abundance of potassium,
provides so much of the natural radioactivity of the
earth, with only brief mention of the transuranium ele-
ments. While it was work with uranium and radium salts
that led to the discovery of radioactivity, except for
the localized concentration of the transuranium elements,
the radioactivity to which we are exposed from natural
sources is most likely to arise from radioactive potas-
sium-40 and to carbon-14. The existence of radioactive
potassium-40 has given rise to some highly theoretical
speculations and it is possible to find in the literature
speculations to the effect that our earth must be at
least fourteen hundred times 106 years old since the
heat from potassium-40 radioactivity would have pre-
vented solidifikation before that time. But the same
author also calculates that the earth might be at least
twenty-one times 106 hour years old if it is assumed
that granite, on which these calculations are based,
lost no argon-40 from potassium-40 disintegrations.

It is also possible to find authors who would have
you believe that evolution may well have been due to
the high intensity of radioactivity of many years ago
closely associated with porassium-40 activity. However,
porassium-40 is present to the extent of approximately
0.012 per cent of all the potassium in nature and be-
cause of the wide distribution of potassium accounts

It is interesting to speculate on the amount of
potassium-40 present in sea water, for instance, and
to calculate the radioactivity due to this source. This
may have practical significance in consideration of
waste disposal into the ocean.
Potassium-40 disintegrates by emitting beta rays
yielding 28 beta rays per gram of potassium per second
and by electron capture, it yields 3.6 gamma rays per gram
of potassium per second for combined half-life of 12.7
times 108 years. By beta emission, potassium-40 yields
calcium-40 and by electron capture porassium-40 yields
argon-40. It is on the basis of the occurrence of argon-40
that many of the calculations on the age of the earth are
Calculations of the potassium-40 in sea water gives
values of about 42 micrograms per kilogram which yields
perhaps 12 disintegrations per kilogram per second.
This compares with values from the transuranium ele-
ments of 0.02 disintegrations per second per kilogram
or approximately 1/600 of the radioactivity due to po-
tassium-40. As has been emphasized by many others,
there is a lot of water in the ocean and the total of
potassium-40 in sea water becomes sizeable in terms
of radioactivity.

A cubic kilometer of sea water contains 330 curies
of potassium-40 and since the total sea water is esti-
mated at 1.37 times 109 cubic kilometers, this may be
calculated to contain five times 1011 cries of po-
tassium-40. This has an interesting aspect from a dis-
posal problem point of view because it means that some
1010 curies of long-lived isotopes would have to be
disposed of in sea water to raise the radioactivity 10
per cent.

This would be equivalent to the radioactivity of the
sea water 200 million years ago, if we assume that the
same concentration of potassium existed. There is reason
to believe that the concentration of potassium 200 mil-
lion years ago was less than that at the present time and
the values of radioactivity of sea water are still far be-
low what we have accepted as the permissible exposure
dose. We are interested in potassium-40 because potas-
sium is one of the essential elements of living materials
and is present in all biological entities.

Because of the 0.012 per cent of the natural potas-
sium, that is potassium-40, there is a constant exposure
of plants and animals to the radioactivity from this
source. If we assume that in an average man there are
approximately 262 grams of potassium, then there is

about 0.031 gram of potassium-40. This level of potas-
sium-40 would result in 5.2 times 105 beta particles
per minute. For every 100 beta particles there are 12.7
gamma rays. In that same man there will be radiation
from carbon-14. At the present, best estimates are that
an average man will be subjected to about 1.2 times 105
beta particles per minute from carbon-14, occurring
naturally in his body. This level is about one-fourth
that which results from potassium-40 disintegration,

In Florida, we are interested in some other sources
of natural radioactivity which occur because of the so-
called black sands and to some extent in the phosphate
deposits. In these natural deposits there are present
thorium salts which yield measurable radiation. The
amount of activity is appreciable in the locality of
these deposits but with concentration of the minerals
which are present, the levels of radiation which occur
are concentrated a great deal.

There are occasionally short time increases in
radioactivity which in certain localities are due to the
deposition or concentration of radioactivity associated
with nuclear explosions. Almost everyone has heard
of the experience of the Eastman Kodak Co. whose
film fogged subsequent to the first Almagordo explosion.
Because of contamination from water used in its manu-

facture, scrawboard packaging was found to contain
sufficient radioactive material to cause film fogging.
Eventually this was traced to the presence of cerium-141
with a 30-day half-life. The occurrence was about two
weeks following the Almagordo explosion and was many
hundreds of miles from the scene of the explosion.
Despite the practical economical loss in this case, the
active level of radiation was not high. In a considera-
tion of the problems of radiological health facing this
conference, the question of natural radioactivity which
requires consideration an a quantitative way may be
summed up in a consideration of cosmic rays which
provide approximately 10 per cent of the ionization
occurring at sea level. Less than one per cent of the
exposure is associated with contamination from traces
of radium, thorium, uranium, and heavy radioactive ele-
ments. The remainder of the exposure comes from potas-
sium-40 and carbon-14 which make up the bulk of ex-
posure. Still with all the natural occurring radioactivity
the exposure of humans amounts to several thousandths
ofthe permissible daily dosage of 100 milliroentgens per
day. In other words, less than 0.6 milliroentgens daily
is the exposure from natural radioactivity. Important
as is a consideration of the exposure to natural radio-
activity, the luminous dial of your wrist watch subjects
you to more radioactivity than do natural occurring
isotopes, but it is far below the level that need provide

Quantitative Limits of Permissible Exposure of Personnel
(External and Internal)

Director, Health Physics Division
Oak Ridge National Laboratory
Oak Ridge, Tennessee

T HERE are two general classifications of ioniz-
ing radiation exposure-external and in-
ternal. An external exposure is defined as one in
which the radiation source remains outside the
body and the radiation is of sufficient energy or
range to penetrate all or a portion of the body. For
example, it may result from an x-ray tube, a high
voltage accelerator or from some radioisotope
such as Ra or Co". An internal exposure is one
that results from a source deposited in one or
more of the body organs. Such a source may
confine its radiation to a small volume of body
tissue such as is the case when I"" is deposited
in the thyroid, or the source may be rather uni-
formly distributed throughout the body such as
is the case with Nan4.

Factors Determining Radiation Damage to Man
THERE are many factors that determine the
radiation damage to man Some of these are:
(a) Radiation damage to man increases with
the total accunadation of exposure. There is con-
siderable variation in radiosensitivity among
animals and even a wide variation among indi-
vidual animals of the same type. Therefore, one
cannot state with certainty what the results
would be if a given person were exposed to a
measured dose of ionizing radiation. However,
if enough experimental data were available, it
would be possible to state what damage on the
average would result if a large number of indi-
viduals were subjected to a given dose of ionizing
radiation. Sufficient data are not available to
indicate what the results would be for various
exposures to man of ionizing radiation, but we
have a great variety of datl on exposures of
several species of animals to ionizing radiation,
and a few instances of large doses of ionizing
radiation to man in which some estimates of the
exposure can be made. An examination of these
data might lead one to estimate the results of
exposure of a large number of persons to ionizing
radiation to be somewhat as indicated in Table I.
(b) Radiation damage to lan in increased if
the area and/or volume of tissue irradiated is
increased It is not uncommon to give very high
exposures to limited portions of the body. Such
exposures may result in considerable biological
damage to the irradiated areas. but may not
result in severe or permanent damage to the
entire body. For example, 400 rontg'no' of hard
gamma radiation to I sq. cm. of most areas of
the body would not result in Nevere damage, but
if this dose were delivered to the entire body

Total Body Exposure to
Gamma Rays in Roentgens Result
0--0 No readily detectable damage
50-100 Detectable damage
200 Probably kill 10'%; of persons
400 Probably kill 50', of persons
600 Probably kill 754/; of persons
800 Probably kill 90'% of persons
1000 Probably kill 95r, of persons
there would be about a 50-50 chance of survival.
It is for this same reason that beta rays or low
voltage x-rays must be administered as external
sources of radiation in larger doses than indicated
in Table I to obtain corresponding results. Owing
to the limited range of beta radiation, it would
require about 10 times the dose of beta rays with
the maximum energy of 1 mev to produce damage
of the same order of magnitude as indicated in
Table I.
(c) There is a considerable variation in the
radiosensitivlty of body tissue. The lymphocytes,
gonads, bone marrow and gastro-intestinal canal
are among the more radiosensitive tissues. Nerve,
muscle, heart tissue, etc., are less subject to
detectable radiation damage. If 400 roentgens
are applied in a single dose to most of the bone
marrow and the spleen, severe damage can be
expected, but 400 roentgens can be applied to the
hands without serious results.
(d) In most cases greater damage results if
the radiation dose is delivered in a short period
of liie. For example, it would probably be dif-
ficult to detect the damage resulting from the
accumulation of 400 roentgens of hard gamma
radiation delivered to the total body in small
increments over a period of 40 years Definite
biological changes could be detected if this dose
were delivered uniformly over a period of a
month, but no fatalities would be anticipated. If
this dose were delivered in one minute, 50% of
the exposed personnel probably would not survive.
The damage would be slightly less if the dose
were delivered uniformly over a period of a
single day, but there probably would not be any
appreciable increase in damage if the dose were
delivered over one second or a microsecond. Prob-
ably if the period over which the radiation dose
is delivered is comparable with the time required
for the body to repair a considerable fraction of
the damage, the resulting damage is not as severe

as if the rate of exposure were much higher.
(e) The greater the specific ionization of the
ionizing radiation the greater the local tissue
damage in general. Specific ionization is usually
defined in terms of the number of ion pairs pro-
duced in the medium per centimeter path of the
ionizing particle. For example, the specific ioniza-
tion of an alpha particle of 1 mev energy is
about 6 X 104 ion pairs per centimeter, and it
is about 45 ion pairs per centimeter for a beta
particle of 1 mev energy. It is because of the
variation in specific ionization primarily that the
relative biological effectiveness of x, gamma and
beta radiation is given as one, whereas the
relative biological effectiveness of fast neutrons
is taken as 10, and that of alpha particles as 20.
It should be pointed out, however, that these
values of biological effectiveness apply only when
the ionizing radiation penetrates the critical body
tissues. Alpha radiation has a relative biological
effectiveness of zero when the source of the alpha
particles is outside the body and the energy of
the alpha radiation is less than 7.5 mev. The
body is surrounded by a protective layer of skin
which ranges in thickness from 0.07 to 0.12 mm,
and alpha rays with energy less than 7.5 mev will
just penetrate the minimum epidermal thickness
of 0.07 mm. Similarly, beta rays must have an
energy of 0.07 mev in order to barely penetrate
0.07 mm of skin. None of the natural radioiso-
topes or pile produced radioisotopes have a ener-
gies greater than 7.5 mev with the exception of
ThC', RaC' and At'21, which are available in neg-
ligible quantities. However, many radioisotopes
produce beta radiation with a maximum energy
greater than 0.07 mev and a number of the high-
voltage accelerators produce beams of protons
and alpha particles of sufficient energy to pene-
trate the epidermal layer. The result is that 1
rep of alpha radiation inside the body is more
hazardous-possibly by a factor of 20-than the
same dose of 1 rep of gamma radiation to that
part of the body.
(f) The radiation hazard resulting from a
radioisotope deposited in the body is proportional
to the average energy of disintegration weighted
for the biological effectiveness of the radiation.
For example, the effective energy per disintegra-
tion of Ha is 0.006 mev and the effective energy
per disintegration of NaL is 2.7 mev. Since both
of these radioisotopes are beta emitters and both
are deposited rather uniformly throughout the
body, this energy difference is the principal fac-
tor which determines that the maximum permis-
sible concentration of H" in the body is about 450
times that of Na2'.

Calculation of External Exposure
THE external exposure may result from a point
source such as a radium needle or an x-ray
target, or it may result from an extended source
such as a large area on the floor of a laboratory
which is badly contaminated or from a big tank
of solution that is radioactive Also the external
exposure may be the result of the irradiated body

------- ---- -----


Fig. I.
Diutance, r in fast from source in air.

submerged in a large volume of radioactive ma-
terial. Examples of this type of exposure are
clouds of radioactive gas completely surrounding
the point of measurement or fish swimming in a
pond of water that is uniformly contaminated
with radioactive material.
(a) In the case of a simple point source that
emits gamma radiation, the dose, D, in r/hr deliv-
ered at the point of measurement is given by the
e-. a
D=Nzni R ---- (1)
in which N is the number of millicuries (1 me =
3.7 x 10J dis/sec); n, is the fraction of disinte-
grations that are accompanied by gamma emis-
son of energy Ei; R, is the r/hr at 1 centimeter
from a 1 millicurie point source of energy E1;
, is the effective absorption coefficient of the
radiation of energy E,; x is the thickness of the
absorbing medium and r is the distance of the
source from the point of measurement. Ri is
given by the equation:
R,= 1.56 , E1 10 (2)
The problem has been somewhat oversimplified
because in practice one does not know what values
to take for a,. If one assumes that all the scat-
tered radiation between the source and the point
of measurement is lost, the results are obtained
as indicated by curve C in Fig. 1 for a LatU0
source in air. If on the other hand one assumes
that all the radiation scattered from the direct
line of sight from the source to the point of
measurement is on the average eventually scat-
tered to the point of measurement, a curve indi-
cated by B in Fig- 1 is obtained for the gamma
radiation from La"4. Curve A is the experimen-
tal curve obtained by J. H. Roberson.* It is to
be observed from Fig. I that the slope of curve
C is more nearly equal to the experimental slope
of curve A, but the average values of dose rep-
resented by curve B more nearly approximate
the experimental values. This figure is given to
illustrate the importance of scattering when one
is measuring the radiation penetrating a thick
absorbing medium. If the distances in air from
Clna-fieul men rmndum CF No i.-7-S[i), ,ii SS, 2I49. Thi�
I in lLrnnillt ierfrormed b) J. aII Koa ~n., frnmrerly of alr
H.tilth Physic Division of Oak Rfdge Natimonl I- oratory.

Fig. 2.
the point source are small (up to lI meters),
equation (1) can be considerably simplified by
placing the term e-, - I and by neglecting
the scattering correction.
(b) The problem becomes somewhat more in-
volved when one wishes to calculate the radiation
nfrm a large extended source. In the simple case
in which we have a disc-shaped area uniformly
cnt.iminated with a gamma emitting radio-
isotope, such as indicated in Pig. 2, and in which
the adiattiun is attenuated by an absorbing
medium of thickness, t, the dose. I), in r/hr is
given by the equation:
I), 2�rNX. n.R.

.-. . +.. l+ ( . 1_| -- 'a i


S9' 11

in which the functions F, are first order exponen-
tial equations. Values of F, and ., are given in
standard numerical tables. Fig. 3 is a plot of
equation 3, indicating the dose in r/hr at various
distances above the center of disc-shaped sources
with energy per disintegration of 0.1 mev, 1 mev
and 3 mev, and for the case when the area of the
contaminated disc is 0.1 sq. mi., 1.0 sq. mi. and
infinite square miles. In this case N is equal to
1,08 ie/cm2 (=1 me/ft2). If one knows the
average radioactive contamination per square
foot and the effective euerugy uf the radiation,
Fig. 3 can be used to estimate the radiation dose
at various distances above the contaminated area
due to n uniformly distributed gamma emitting
source. If one assumes that the average gamma
energy is I mev or less, it is observed in Fig. 3
that the dose delivered at various distances above
the source is practically the same whether the
-ource extends over a disc-shaped area of 0.1 sq.
mi. or infinite square miles."
(c) A volume source Time will not permit a
discussion of the general problem of extended
sources. However, if one makes the proper cor-
rections for multiple scattering, it is possible
theoretically possible, at least) to calculate the
dl�e delivered at any point in space from a source
of*any shape and volume. In this discussion we
r1T O-- I d
.I itin y d uthI .. il m.fn. ltir .i fte- r n i thi- -e0d |U I If. "d
land iti **if al u rgi lua a isn l i 11- , r,( K lli.rii' r t n diu Attri' 'n ohr
Ithr an t r P eI ni1 1 tuf di- . ..our.. ....ihin l. tUII l I.rI - 1- f 11l
-..'lt i i i nulL i tl Ir l P. i L ,r lict I -n1f i I ll, ill j l .1 . I rahLi� i-
S- 1LMil til . to .h I I ... l i.1. oi ...t r i il r 4 .l . .lken

. . . . - -.

OSE Irhri
F,. 3.

will only consider the case in which the dose de-
livered to a small object submerged in a large
mass of radioactive material is calculated. In
this case one can assume that we have equilibrium
conditions and that the energy emerging from
each unit volume is equal to the energy absorbed
per unit volume. The dose. W. in reps/wk is
given by the equation:
W 380(MPC),s(bE)P, (4
_=_ --- (4d
in which (MPC),, is the concentration in the me-
dium in terms of ye cc and becomes equal to the
maximum permissible concentration when W is
equal to 0.3 reps/wk for beta or gamma radiation.
The term F (bE) is the effective energy per dis-
integration, P,,, is the density of the radioactive
medium and P,, and P, are the stopping powers
of the medium and tissue, respectively, relative
to air.

Maximum Permissible Levels of Erternal EXposure
THE levels of maximum permissible exposure
used on the U.S. Atomic Energy Projects
until 1950 are given in Table II. Recently values
have been adopted that are slightly more con-
servative, as indicated in Table Ill.
Table IV indicates the values recently agreed
upon at the Chalk River Conference, a meeting of
members of the Radiation Protection Committees
of the United States, Great Britain and Canada.
This meeting was held September 29 and 30,
1949. It should be noted that these presently-
accepted values of maximum permissible expl-
sure are somewhat more conservative than those
used up until 1950. The principal change is a
permissible exposure of 0.5 rems/wk to the epi-
dermal layer of the body or 1.5 rems/wk to the
epidermal layer of the hands and forearms.
Originally the maximum permissible exposure
level to all parts of the body was set at 0.1
rems/day. It should be noted also that the rela-
tive biological effectiveness of fast neutrons has
been increased from 5 to 10 and the value for
alpha rays has been increased from 10 to 20. It
is important to note also that the time over which
the permissible exposure is ineasured has been
increased from one day to one week. This sim-
plifies considerably the monitoring procedures
and makes it possible for persons doing high
level radioactive work to receive in a single day
all of their exposure for a week.

Establishing Maximum Permissible Levels
THERE are various methods of estimating maxi-
mum permissible levels of radiation exposure.
Some of these methods are:
(a) Comparison with x-ray or y-ray damage.
We have had considerable experience for more
than 50 years with these radiations and the Sub-
committee on External Dose of the U. S. Radia-
tion Protection Committee has made comparisons
of the relative damage to be expected from x-rays
and other types of radiation. It has set the rela-
tive biological effectiveness (RBE) of various
t pes of radiation as shown in Table V.

mr7 mrep/ mnrem Approximate Frux ftor
Type of Radiation day day day 24 Hour ExpoIsur
X or gamma rayn 100 10 100 2200 photons or Met/cm*
HBel ma ay no 0o 47 lctran'i of 1 Mevi/em
Thernal neutrons So* 100 150. neutrons of 0.02
ev/cm' see
ast neutrons 20 100 5 e nulrou i a Mevn/em
Alpha ray 10 100 O005 Raphul
Mev/tm' yao
'This value reduce to about 25 for a etn be ys with he normal energ
datributlon ranging from zero to a maximum energy of I Mv bheause
th% mpeic iRamonizon II lctlroni inenn as the snorty deresa.,
iThe specific ionitwUon of eleclnoi hs approidnRae valued of 41, 10'
and 104 ion pmirs per em path or lcron energy' of I Mov. 10 Kev
and 10too v. rpesiely. The renftlv# value for be.t rays a s ion
pairs per m path if the nnimum enem er I Men.)
"The relative biologicl effeetivenes (R"E) and roten en crtuivlaent
physl (rp) value ueed lor thon.l noutor. in Tables It, III. Rnd
IV are only approximate and have questionable meaning. The-flux
values are more preie n that they are detteinied by trelaing sep-
raly the protons and -raw that reul trom thermal neurons, and
adding the contributions of onah alter weighing their properly.

mrep/ mrem/ Approximte Plux for a
Type of Radiation mr/wk wk wk 24 Hoar Expoure"
X or gamma ray 300 300 1300 phots or I
Ret rays 00 300 a electlronr of i
Mev/cm' ev
Thermal neutru 60so* 60e0 nlt ar 0.0
ev/em seec
Fast neutrons 30 00 2 nal of Meov/c se
Alpha rays I5 100 0.0016 alph. o 5
Mev/em' s
'See note') under Table JI. Tht value bemes IT? bes/cmn ee iU the
maxiamn energy is I Mev.
"See note (") under Table II.
"*Values of Bau corresponding to W mrem/day tor an iposui of fie
work day per week.

(This does not guarantee no damage. The values are
based on experience in lack of readily detectable damage
from 200 KV X-Rays)
At Any Point Inthe sB d LLyerEotfthEidermi
Type of Within the ItRE Exposure of Expoasur of
Radiation Body EnUir Body Hands Only
X-Rays and 0.3 I 0.6 1.5
Gamma Rays
Beta Rays .s I 0.3 1.5
Proton. 0.03 10 0.05 0.15
Alphs ayn 0.Q11 S 2 0.025 0.076
Fast Neurons 0.03 10 0.06 0.15
Neutrons 0a Os r* 0.1"* 0.3"
*RBE = Ielave Bioloulic ElITeclivi nFl
"See note under Table 1i.
General Stateomont of the Chalk River Conference
SForpurpni t health monitnrng, whole body exposure should be
aumred when radiation is rervived to any portion of the body other
than hnnds or rearm
2 in the eight of present knlwlndgr no mrniTfet permanent injury is
to be expected trom a single epoiaure of persons to 2i r or les with the
possble exceprnn of pregnant women

Man. Permianlble Epo�auru
JntLlir lanul iLayr of
IHnli llurn lIUl i illilrrmlB (oip/wkL
-fays no tnotgy 0.I In I:.U Mr" 1 o.a
-VRyt oi RI. flltrrcn bly lIi mnm Itl ] U.,
arayi 1 0
protonK il} l, :l
Pfat nulrima o if uenergny ino leauL r l
Lhan 20 Mov IU0 U0.
--ray0 20 U.UII

The values in Table V were accepted by the
Chalk River, Canada, Conference (September 29
and 30, 1949) and the International Commission
on Radiological Protection Meeting in London,
England (July. 1950). The maximum permissi-
ble rates of exposure in column 3 of Table V ap-
ply to readings marid ii free air or to readings
inside the body organs. For convenience, it may
be considered-in theory, at least-that the
measurements are made with a thin-walled cavity
chamber containing a tissue equivalent gas.
(b) Comparison with radium damage. The
damaging effects of radium were observed shortly
after the discovery of radium-just as was the
case with x-rays-so that we have had over 50
years of experience in which to observe and study
the damaging effects of various amounts of ra-
dium fixed in the body, The radium content of
the body can be obtained by measurement of the
gamma radiation from the body, by measurement
of the radon exhaled from the body and by au-
topsy measurements. The U. S. Radiation Pro-
tection Committee has set the maximum permis-
sible amount of radium in the body as 0.1 pic.
The U. S. Subcommittee on Internal Dose and
the International Commission on Radiological
Protection have made the estimate that the dam
age of Pu ." relative to Ra,'"~ is 2 5, and the dam-
age of Po2u- relative to Ra""' is 20. (This value
of 20 is based on acute doses of Pos'0. When
chronic experiments are completed a few years
hence, this value may require revision.) Great
care must be taken when making comparisons
with radium in order to make comparisons only
with those elements that behave similarly in the
(c) Comparison with background concentra-
tions of naturally occurring radioisotopes in our
bodies, in the air we breathe and in the water and
food we take into our bodies. For example, if a
large group of people in one part of the world has
10 times the average content of radium in the
body as the rest of the people in the world, and
if this group of people has shown no detectable
disadvantages, the conclusions might be that
these higher concentrations would be safe as
maximum permissible values.
(d) Animal experiments (on mice, rats, dogs,
pigs, etc.) are being conducted by many labor
stories in order to determine the initial retention,
the concentration in the various body organs and
the biological half life. Careful observatiuiio are
made on both the living ad sacriedelhe animals in
order to detect damage to the various body or

gains. Studies are made of blood changes, tumor
production, sperm counts, reduction of life span,
etc. These results are extrapolated to man by
giving more weight to the dati from species that
,are closest to man.
(e) Experiments on man give the only com-
pletely reliable data, and even here the statistical
variation is so great that data should be obtained
for a large number of cases in order to secure
reliable results. For ethical reasons there is a
limit to the data one can obtain by direct obser-
vations on man. However, very useful data have
been obtained from observations on man follow-
ing the accidental ingestion and inhalation of
radioisotopes. For example, urnalyses of per-
sons who have inhaled Pue"" and Sr9o due to
carelessness or accidents have furnished some of
the best estimates of the biological half life of
these radioisotopes in man. Small tracer doses of
some of the radioisotopes with short effective
half lives can be administered to man to obtain
valuable information about the initial retention
and biological half life. In some cases short lived
radioisotopes can be substituted to obtain essen-
tial data concerning the behavior of the more
dangerous long lived radioisotopes. For example,
5.8-day Cai7 can be used il place of the 152-day
Ca1' or the 9-day Po'"O can be used in place of
the 138-day Po-'i. If harmless doses are admin-
istered to terminal cases, autopsy studies will
reveal the radioisotope distribution in the vari-
uus body organs Care must be exercised in inter-
preting such results because the radioisotope dis-
tribution in the body of a sick person may be

Internal Exposure More Difficult
RADIOISOTOPES, when contained inside the body,
present greater hazards than when they are
limited to external sources, for the following
(a) They irradiate one eon tinuously until they
are eliminated.
(b) The biological half life is very long for
some radioisotopes and in most cases it is
difficult if not impossible-to increase
Appreciably the elimination rate from the
(u) Sources inside the body are in intimate
contact with the body tissue. This enables
alpha and low-energy beta radiations
(which, because of their limited range,
do not present an external hazard) to
reach radiosensitive tissue inside the
body and to dissipate all their energy in
a'small volume of tissue inside a critical
body organ.
(d) It is very difficult to measure the amount
and distribution of a radioisotope in the
body so that it is usually impossible to
assess the hazard accurately. Methods of
urinalysis have been developed for some
radioisotopes but most of these analyses
are tedious, time-consiming, and expen-

Methods of Intake of Radioisotopes
THE principal methods by which radioisotopes
enter the body are as follows: (a) inhalation;
tb) ingestion: (e) through skin; (d) through
The method of entry of the radioisotopes in the
body determines many of the current radiation
protection measures, Because some of the radio-
isotopes become air-borne, elaborate precautions
must be taken in some of the laboratories to pro-
vide hoods, filters, air washing devices, tall stacks,
etc., to minimize the inhalation hazard. Because
of the possibility of ingestion of radioisotopes,
persons are forbidden to eat food or smoke ciga-
rettes while working with radioactive materials.
They are forbidden to pipette solutions by mouth,
or to use ordinary techniques of glass blowing.
Protective clothing and masks are required for
some of the work with radioisotopes, and this
protective clothing should be removed and the
hands and face thoroughly washed before enter-
ing lunch rooms. Because some of the solvents
and washing compounds increase the permeability
of the skin, great care has been taken in the
choice of suitable agents for the removal of radio-
active materials from the body. Experiments have
indicated that when some of the radioisotopes
enter the body through wounds a large fraction of
the radioactive material remains in the body
unless it is removed within a matter of minutes.
Therefore, when cuts and puncture wounds are
caused by objects contaminated with radioisotopes,
it is general practice to flush out the wound with
copious quantities of water immediately, and re-
port the incident to the medical department for
further assistance. Following some such accidents
it may be necessary to excise some of the con-
taminated tissue, and urinalyses and blood counts
are sometimes made for a period of a few days in
order to assess the hazard. It is for this same
reason that persons with open cuts and skin
abrasions are not permitted to work with radio-
Factors that Determine Damage
THE factors that determine damage from radio-
isotopes deposited inside the body are:
(a)Fraetion initially retained. There is a great
variation in the initial retention of radioisotopes
in the body. A large fraction of some soluble
compounds is retained regardless of method of
intake-whether ingestion, inhalation or through
open wounds. For example, under certain condi-
tions, elements like iodine have an initial reten-
tion of 100%, strontium of about 60%, and
uranium of about 0.05%
(b) Concentration in a single organ. Elements
like sodium are rather uniformly distributed
throughout the entire body, whereas most of the
iodine is concentrated in the thyroid and most of
the strontium goes to the bone. In general, a radio-
isotope that is concentrated in a small organ of
the body presents a greater hazard than a radio-
isotope that is distributed throughout a large
mass of body tissue. For example, one millicurie

of iodine in the body is deposited mostly in the
thyroid, which has a mass of 20 grams. If this
iodine were rather uniformly deposited through-
out the body (as is the case with sodium), the
dose per gram of tissue would be reduced by a
factor of about 350.
(c) Coneentration within small volume of an
organ. Concentration of the elements does not
approach a uniform distribution in some of the
organs of the body. Plutonium is considered to be
more hazardous than radium on the basis of reps,
primarily because it is localized in portions of the
bone (endosteum and periosteum) where greater
damage is done to the blood-producing organs
than is the case with radium, which is more uni-
formly distributed throughout the bone.
(d) Radiosensitivity and vital importance of
tissue. 1'3. is not as hazardous as Sr0O on the basis
of ionizing energy delivered to body tissue, be-
cause radiation to thyroid tissue does not result
in as much gross body damage as the same radia-
tion to the blood-forming organs.
(e)Alpha rather than beta or gamma radiation.
Alpha emitters, such as Po21' and Pu'", are con-
sidered to be 20 times more hazardous on the
basis of energy delivered to tissue than a beta or
gamma emitting isotope like strontium. This
factor of 20 is not well established by biological
experiments (it is probably somewhat conser-
vative), but experimental evidence seems to indi-
cate that the more dense ion tracks along the paths
of alpha particles in most cases result in greater
damage than the sparsely scattered ion tracks
along the paths of beta or gamma radiation.
(f) High energy radiation. The importance of
the energy of the radiation has already been
(g) Physical half life of intermediate value.
The half life and atomic weight of a radioisotope
determine its specific activity. The specific ac-
tivity is given by the equation:
gm/curie = 7.5 x 10- A T, (5)
in which A is the atomic number, and T, is the
radioactive half life in days. Radioisotopes like
natural uranium (U28 + Us34 + U235) do not
constitute a great radiation hazard because the
controlling half life of U2* is 4.5 x 100 years and
the specific activity is 1.5 x 100 gm/curie. The
permissible amount of natural uranium in the
body is 0.07 ec and this corresponds to about 0.1
gm. It is unlikely that a person would get this
much uranium into his body, and if he did it
would probably result in a chemical hazard before
radiation damage would be observed. Very short
lived radioisotopes, such as N" with a half life of
7.35 seconds (10-" gm/curie), do not present an
internal radiation hazard because if they are
taken into the body they very rapidly decay to
insignificant levels. A convenient rule of thumb
to remember is that the activity is reduced to less
than 1% after seven half lives (2-7 = 0.8%). An
element like P32 with a half life of 14.3 days
(3.4 x 10- gm/curie) presents a much greater
hazard than N'1, but when it is deposited in the
body the natural decay processes reduce it to a

$- I
*^\ ~'~ 1-- -- '-,--- -----
D m . . * . ' . i .

a : I -

Fig. 4.
level of insignificant activity in a few months.
Therefore, the radioisntopes of intermediate half
life present the greatest biological hazards. In
general, radioisotopes with half lives of about five
to 20 years present the greatest hazards-other
factors being equal. The most important period
of exposure to laboratory personnel is from the
age of 20 to 45 because very few younger persons
are employed by laboratories that handle radio
isotopes and many of the chronic effects of radia-
tion do not manifest Llihenelves until 15 to 25
years after the radiation insult (45 +'25 = 70
years, the average life span). From the stand-
point of half life, Sr", with a half life of 25 years
(6.1 X 10-3 gm/curie), is one of the more danger-
ous radioactive materials commonly available.
(h) Long biological half life. The biological
half life is the time required by the body to
eliminate half of the radioactive product. Some
radioisotopes like C", with a half life of only 35
days, are eliminated very rapidly from the body,
whereas radioisotopes like Sr" and Sr'I, with a
half life of 3.9 h 10* days, ful all plactical pui-
poses are fixed permanently in the body where
they continue to produce damage indefinitely.

Classification of Radioisotopes
THE Subcommittee on Safe Handling of Radio-
active Isotopes of the U.S. X-Ray and Radium
Protection Committee, has divided the mourt
common radioisotopes that are beta-gamma emit-
ters into three groups: slightly hazardous, mod-
erately dangerous and very dangerous.* The chart
indicates, as shown in Fig. 4, what are considered
to be low, intermediate and high levels of activity
of radioisotopes of these three groups when
handled in the laboratory Caution should be ob-
served in placing too literal interpretation on some
of the data given in Fig. 4, because the maxi-
mum permissible concentrations of some of these
radioisotopes are not well established and in many
cases little better than educated guesses."*

Maximum Permissible Concentration
THE U.S. Subcommittee on Internal Dose of
the U. S. Radiation Protection Committee has
*Handhbook *12, '"Su.r. llu lnrli, n "t I1]ld .1~ Isotr ' ..II "[ issued hIn
Ilte Nauin] .l i 1-o�'.i i Sltaumlinar
"For i**nx p'lll there Jl �oa *.\irlrn thLli might loud one tm pl...I
Call ntaj F.�l LrI n la II lnt.iind 1I th I 1li Ind lIiqtuqpcI I I' ind
S" in dia I im mln i f rinv itI


Medum in which

0, nr Ebmittr
in )

a Emiitto
rx n-oi

set values of maximum permissible concentration
of general radioactive contaminants beyond areas
that are under the control of institutions, as
given in Table VI.
These values may be used to great advantage
when the gross activity only is known, and may
be continued in use for several weeks until the
identities of the radioisotopes are established.
They do not refer to natural backgrounds but
additions to the natural background caused by
man. These values are safe for indefinite use for
all radioisotopes, with the exception of a few
radioisotopes such as Ra'1". Pu-' and Sren. In
such cases the values in Table VI should be re-
duced by a factor of 10 to be oni the safe side.
In routine water analyses the problem is greatly
simplified if the general level of gross aefivity is
always less than the values given in Table VI. II
may mean that no complicated, expensive and
time consuming radionnalyses are necessary, and
the only requirement may he to evaporate down
a water sample and determine the gross count
with a Geiger counter,

Equations for Calculating
(a) Maximum permissible aliluuIL of a radioiso-
tope in the body.
2.6 x10- m W m in total body to give W
q= . rep'wk exposure to the criti-
zLbE) f cal organ of mass, m. (6)
Ib) Maximum permissible concentration in air.
3 x 10-8 q fIn ' ec of air to give W
(MPC).'= ,,(-e t rep wk exposure to
T ,,(I-e-o r the critical organ after
the exclusive use of
contaminated air for
time, t. (7)
lc) Maximum permissible concentration in water.
PC) 3 x 104 q f, e cc of water to give
MPC). 1 n T) W rep wk exposure to
T [.(l-e " T) the critical organ af-
ter the exclusive use of
contaminated water
Nomenclature: for time, 1. (8)
RBE rep wk
RBE=1 for S and , and 20 for , as indicated
in Table IV.
m =mass of critical organ in grams.
z(bE)=effective energy of radiation per dis-
integration in Mev.
f =-fraction in critical organ of that in total
Z1 2\ / 2
b =0.33(l- -) (1 +-- -)
for a radiation
E =maximum energy

Z = atomic number of radioisotope
b =(1- -(Pf-*)-)for , radiation
b =1 for a radiation
I -o.)=total coefficient of absorption minus
the Compton scattering coefficient of
absorption in tissue ecm I)
x =effective diameter of organ (cm,
T, =radioactive half life
TL =biological half life. When T. is not
known as a result of direct measure-
ments, one may be able to calculate it
by equation:
0.693 me
I f.
' =effective half life in days
'T _=T T,
1 T,+T ,
S = time of exposure (taken as 10'1 days)
1. = fraction deposited in critical organ from
ft = fraction deposited in critical organ from
References of Committees Giving Values Listed
in Table VII:
1. U.S. X-Ray and Radium Piotection Cmmnittee.
2. Subcommittee on Intrnal Dose of the U.S. Ra-
diation Protection Committee.
3. Washington Conference on Waste Disposal,
called by the Isotopes Division of the Atomic Energy
Commission, meeting in Washington, D.C., Septem-
ber 20, 1948,
4. Chalk River Confeiene--a meeting of reprciesen
Latives of the radiation protection committees of the
United States, Great Blitain and Canada, meeting
in Chalk River, Canada, September 29 and 30, 1949.

5, Values used by some of the Atomce Energy
Commission Laboratories,
i6, Meeting in Rochester, New York, September
27, 1949, called by the University of Rochester
Atomic Energy Project to discuss the toxicity of
7, International Commission on Radiological Pro-
teetion at the Sixth International Congress of Ra-
diology, meeting in London, England, July, 1950.
8. American Standards Association, Subcommit-
tee on Radium Dust, Radon Gas and Gamma Ray

Use of Atomic Weapons
BECAUSE of the imminent possibility of the use
of atomic weapons, it should be pointed out
that much higher values of maximum permissible
exposure can and should be permitted under war
emergency conditions. It should be emphasized
that the usually quoted values of maximum per-
missible exposure and, in fact, the values given
above are values that are considered safe and
satisfactory for indefinite periods of exposure
during peacetime conditions. They should not
under any circumstances to applied to wartime
conditions. Under emergency conditions of atomic
war, no one should hesitate to take 25 roentgens
of gamma radiation (or the equivalent of other
types of radiation), and in special emergencies a
person should be willing to receive 100 or more
roentgens of exposure if it is necessary to save a
life or perform some function essential for na-
tional defense. Exposures up to 300 roentgens
may be accumulated over a period of a month
(provided not more than about 150 roentgens are
received in a period of a week) without any great
probability of serious consequences and in the

U-natural (


PuL (sol.)


_t Organ (gm) q c/ce Water eC/cc Air
sol.) Bone 7 X 10 0.07 (E-6) 6 X 10- (E-8) 2 X 10"' (4, 7,O G
--- I X 10 (E-7)
nsol ) Lungs 10" 0.009 (E-6 --2 X 10-'" (4,6E-7)
3 X 101' (5)
Bone 7 X 10 0.04 (7) iX 10- (7) X 10 f (4)
0.07 (E-6) 6 X 10 (E-8) 8 X 10 (7)
0.006 (4) 2 X 10 (4) 1 x 10 i (E-7)
Lungs 10' 0,008 (7, E-6) - X 10TI (7, E-7)
3 X 10-11 5)
Bone 7 X 10 0.1 (1,2 47)8) 4 14 X 1"4,7) (4 -7)
0.02 (E-) 7 X l (-8) 8 X 10 1 (7)
Lungs JO 0.002 (E-M) 2 X m16 (E-4) 2 X 10 i(E-4
Body 7 X 104 0.1 (E-6) 10-i (1,8)
2 X 10 7 (E-4)
Bone 7 x 10 004 (7) 1 X 10- (7) 2 X 10-p i (7,E-7)
0.03(2) 2 X 10-x (4) 3 x 10-1 (4.5)

0.07 (E-6)
0.006 (4) 3 X 5 0S (E-8)
Put' (inuol.) Lungs 10 0.008 (E-6) --- 2 X0' (7,4)
8 X 10 (5)-
6 X 10-i2 (E-71
Po'o (sol.) Spleen 150 0.02 (E-6 X 10 X E( )E--) 2 X 100 (E-7\
PoI0i (insol.) Lungs 10S 7 X 10s (E-6) 7 X 10 i (E-7)
*E-4 refers to equation 4 on page 70. E-6, E-7 and E-8 refer to equations 6, 7 and 8, respectively. Other
references are given on page 73. All values are rounded off to one significant figure. These data are taken
from an unpublished report of the author to the Subommiittee on Internal Dose of the U.S. Radiation
Protectiun Committee.


interest of saving life. For certain military op-
erations such calculated risks may be necessary.
Considerable concern has been given to the
problem of radioactively contaminated water sup-
plies following the use of atomic weapons. In
fact, one of the major problems of the Health
Physics Division of Oak Ridge National Labora-
tory is to determine the effectiveness of conven-
tional systems of water purification in removing
radioisotopes and what modifications should be
made to increase the effectiveness of such sys-
tems. Also. work is being done on testing and
developing portable water purification plants that

will be of use to the military when it is required
that water contaminated with radioisotopes be
used for human consumption. Recently A. H.
Emmons and R. A. Lauderdale, of our Labora-
tory, have developed a simple system with a series
of adsorbents that proves to be a very effective
means of purifying small quantities of water for
potable use. They have taken mixtures of radio-
isotopes, simulating those that would be present
at various intervals following an atomic blast,
placed them in the appropriate concentrations in
water, and passed the mixture through the sys-
tem of adsorbents, obtaining an over-all reduc-

Element and

% in Body * Organ (gm)
CII (CO) 18% Fat 10'

FP 10%
(HTO or TO)

Cal 1.5%< _
P" 1.0i"

Total Body
7 X 10'

Bone 7 X 10
Bone 7 x I10

K" 0.35, - Muscle 3 X 104
S" 0.25;, Skin 2 X LO'

q __e/c Water .c/ce Air
250 (E-6) 3 X 10i (E-8) 10 � (7,4)*
30 (4) _10- (3)
10I (7,E-6) 0.2 (E-8) 5 X 10- (7)
10 (4) 0.4 (7) 10- (4)
0.01 (4) 2 X 10i (E-7)
65 (E-6) 5 X 10-4 (E-8) 4 X 10"- (E-7)
10 (2,7,4,E-6) 2 X 10- (7,4) 2 X 10- (4)
10-' (E-8), 10 (3) 1 x 10i (E-7)
20 (E-6) 1 X 10 C (E-8) 2 X 10-- (E-7)
100 (7) 10 (4) 10-' (4)
150 (E-6) 6 x 10' (E-8) 7 x 10 (E-7)

Na" 0.15';

Ci" 0.15'

Total Body
7 X 10*

Total Body
7 X 10

Fe - Blood 5 X 1

200 (2.4)
15 (7,4)
20 (E-6)

200 (E-6)

T X 10 (E-6)

8 10 (7) 2 x 10te (E-7.4)
10- (E-8)
5 X 10-I (4)
2 X 10 (E-8) 4 X 10 (E-7)
4 X< 10-s (E-) 6 X 10 (E-7)

Fei Blood 5 X 10T 10 (E-6) 1 X 10 (E-8) I X 10- (E-7)
Mne 3 X 10-". Kidneys 300 2 (E-6) 0.2 (E-8) 3 X 10-- (E-7)
Cun* 2 X -~t 9 Eyes 30 4 X 10' (E-6) 0.1 (E-B) 7 x 10- (E-7)
Liver 1.7 x 10 10 (E-6) 8 X 10-' (E-8) 6 X 10"- (E-7)
1'l 4 X 10 , Thyroid 20 0.1 (2.4) 3 X 10 (7) 3 x 10-9 (7)
0.3 (7,E-6) 1 X 10- (E-8,4) 10- (4)
5XI0-4 (3) 2 X 10- (E-7)
*Per cents of stable element by weight comprising total body. The other principal body elements, oxygen (657),
nitrogen (%)) and magnesium (4X 10 '",), are omitted because all their radioactive isotopes have very short half-
*Calculated from concentration of CO, in alveolar air.

Element Organ (gim) q_ c/cc
Srt Bone 7 X 10o 2 (2,7). 1 (4) 2 X 10
15 (E-6)

Srou+Yu Bone 7 X t10

A" Total Body
7 X 100
Xe'l Total Body
7 X 104
Xei" ' Total Body
7 x lot
Liver 1.7 x 10l
Spleen 150
Au 19" Kidneys 300
Aul ' Kidneys 300
Cro' Kidneys 300
Ni" Liver 1.7 X 10"
MoUW Bone 7 X 10~

Water ec/ce Air
FT(E-8) 3 x 10- (F-7)

i (2,7): 0.5 (4) 8 X 10 (7)
8 (E-6) 2X 10- (4) 10- 1 (4)
3 X 10 (E-8) 3 X 10-o (E-7)
30 (E-6) 5 X 10-' (E-4) 10- (4)
5 X 10- (E-4)
300 (E-6) 4 X 10* (E-4) 10- (4)
5 X 0-6 (E-4)
100 (E-61 1 1 0a (E-4) 3 x 10- (4)
2 X 10-' (E-4)
1 (4,7) 10 (4,7) 2 X 10- (4)
3 (E-6) 2 X 10- (E-) 1 X 106 (E-7)
1 (E-6) 0.2 (E-8) I X 10-i (E-7)
10 (E-6) 3 X 10 (E-8) I X 10-' (E-7)
30 (E-"6 7 x I10 (E-8) 3 X 10 I (E-7)
390 (E-6) 5 X 10 I (E-8) 8 X 10 - (E-7)
70 (E-6) 7 X 10 ' (r-8) 4 X 10- (E-71
50 (E-6) -10 (E-8) 2 X 10-3 (E 7)

tion in activity of 103 to 10'. This system of
adsorbents can be made up into small portable
units, which will process about one gallon of
water per hour, at a cost of a few dollars, or
larger units can be constructed and added as the
final stage to conventional portable water purifi-
cation systems at correspondingly higher cost. It
is not anticipated that there will ordinarily be a
great necessity for such equipment following the
use of atomic weapons, but it is reassuring to
know that a simple, inexpensive and easily port-
able unit can be made available which will furnish
all the water decontamination that is likely to be
required under the most adverse circumstances.
Preliminary measurements indicate that such a
unit could be made effective both for water con-
taminated from an atomic bomb or radioactive
contaminants used in radiological warfare.
Much higher levels of concentration of radio-
isotopes in water and air can be permitted during
the period immediately following an atomic ex-
plosion because the conditions are much different
from those during peacetime operation. I have
made some estimates that indicate that a level
of maximum permissible concentration of gross
activity of approximately 10-s gc cc of alpha,
beta or gamma emitting radioisotopes in the
water would be an acceptable and relatively safe
value for adoption during the early period follow-
ing an atomic explosion (an increase by a factor
of 10'). Corresponding maximum permissible air
concentrations would be about 10-" 1c/cc for beta
and gamma activity and 10-'0 .eCcc for alpha ac-
tivity (the increase is considerably less for air
due to the possible initial accumulation in the
upper respiratory tract). During such emergency
conditions these higher values are acceptable for
three reasons: (1) the radioactive half lives are
short (approximately equal to the time since the
atomic explosion), (2) the percent of the more
hazardous radioisotopes present is small, and (3)
certain hazards can be assumed under emergency
conditions that are not permissible for peacetime
and continuous conditions of exposure.
Radiation monitoring can be made quite simple
in the case of an atomic explosion because the
permissible levels of radiation exposure are very
high during the short periods of emergency. By
this I mean to say that the areas of high contami-
nation can be readily detected at considerable
distance-perhaps a few hundred yards in some
cases-and the instruments need not be as sensi-
tive. Rugged instruments like fiber electroscopes
which maintain their calibration indefinitely
should be made available at low cost and in large
quantities as soon as possible. The instruments
should have thin windows so that they are capable
of reading alpha, beta and gamma radiation, be-
cause under certain conditions of selective absorp-
tion the beta activity may become several hundred
times that of the gamma and, In case of a "fizzle"
.bomb, alpha activity may present the principal
hazard. In general, the alpha activity will follow
along with the gamma activity so if there is no
hazard from gamma, there is no problem of seri-

ous alpha contamination for periods of a few
weeks following the atomic explosion. The alpha
activity may present problems of contamination
in certain localized areas many months following
the explosion, but experts can be called in later
to deal with this problem in most cases. In case
of the "fizzle" bomb, there is little destructive-
ness but a considerable amount of plutonium may
be present. Let us hope that all of the enemy
bombs will have a great amount of alpha contami-
nation present! Under emergency conditions fol-
lowing an atomic explosion there would be no
difficulty in determining whether the water
supply was safe. The levels of maximum permis-
sible exposure of radioisotopes in water would be
so high under these conditions that there wquld
be no difficult problems of radiochemical analysis
of water supplies. A large tank of water (10 feet
or more in diameter) would be safe as drinking
water if a thin-walled electroscope or Geiger
counter, held just above its surface, gave a read-
ing of less than 10 mrep per hour. Likewise the
air contaminated with beta and gamma emitting
radioisotopes would be safe to breathe (without
a mask) during the emergency conditions follow-
ing an atomic explosion if the reading of a thin-
walled electroscope or Geiger counter held up in
the contaminated air (and away from other con-
taminated objects) did not read more than 1 mrep
per hour. There are many instruments now avail-
able for making these simplified measurements.
When an atomic bomb explodes in an area (or
nearby), radiation measurements should be made
as soon as possible. The chances are favorable
that none of the areas will be seriously contami-
nated but nothing is more reassuring than meas-
urements made by an experienced monitor using
a proper and reliable instrument. The first step
is to mark off areas of red, yellow and green (dan-
ger, caution and safe). The flow of traffic must
be toward the green zones and not a mad scramble
for everyone to get away from the city at once.
If an essential production plant is in or near the
bombed area, the radiation measurements should
be begun as soon as the fire fighting equipment is
brought in to fight the fires-and there is a good
chance that many fires will spring up as a result
of the terrific heat of the explosion. At Oak
Ridge National Laboratory when there is a fire
in a contaminated area, the health physics moni-
tor usually gets to the fire as soon as the fire
trucks, but in case he does not, the firemen always
take a carload of radiation detection instruments
with them to each fire anyway and they are
trained to make the necessary radiation detection
measurements if required. However, we cannot
depend on the firemen to make these measure-
ments because they will have their hands full
fighting fires. They will want to know how long
the men can fight fires in each area without re-
ceiving serious radiation (greater than 100 roent-
gens), and because of the high levels of maximum
permissible exposure under these conditions, the
necessary measurement nan be made quickly
and with a minimum of difficulty.

Reprinted from the Manual of the Lectures presented at
The Inservice Training Course in Radiological Health,
University of Michigan, School of Public Health, February 5-8, 1951.



Eldo E. Anderson, Director

Health Physics Training
Oak Ridge National Laboratory

In the summer of 1942 when plans were being made
for the construction of the first nuclear reactor, it was
recognized that if this reactor operated successfully
a new and powerful source of radiation was available.
Recalling the early years when many people had been
killed and injured in using X-rays and by the small
amounts of radium then available, deep concern was
felt over this potential radiation hazard, one which
would be equivalent to millions of pounds of radium.
Unless extreme precautions were taken the sad experi-
ences of the radium industry would be repeated, but on
a greatly magnified scale.

Now after 8 years of reactor operation, we can look
with satisfaction on an excellent safety record. In
spite of the fact that no warning body sensation or
pain accompanies exposure to radiation, we have shown
that we can safely live with radiation. The fact that
in the reactor projects there has not been a known case
of serious radiation damage attests to the safety of such
work if proper precautions are taken. Existence of
hazards is not a legitimate barrier to advancement in
any field-the answer is to minimize the hazards, and
it has been amply demonstrated that it is possible to
minimize and in some cases eliminate radiation hazards.

Information regarding fundamental principles of
radiological safety, applies to every day working with
radiation and may be extrapolated to an atomic disaster.
The sources of radiation hazards may be X-ray machines,
high energy particle accelerators (the cyclotron, the
Van de Graaff, betatron, etc.) reactors, natural radio-
active elements, or some of the many radioactiv- iso-
topes that have been produced in recent years-some
the products of fission (in the case of an atomic bomb),
others the product of nuclear bombardment. The radia-
tions from which we must protect are primarily gammas,
alphas, betas, X-rays, and neutrons. To establish and
follow safe procedures requires thorough understanding
of the radiation hazards associated with a given pro-
cedure or environment, a thorough knowledge of the
maximum permissible levels of exposure and of contami-
nation, followed by careful planning to reduce the haz-
ards to a minimum. Radiation dose rates from sources

external to the body can be reduced to a safe value.
Hazards due to radiation sources within the body can
be prevented by control of radioactive contamination.
Each of these in turn will be considered.

We will discuss first the external hazard; that is,
where the source of radiation is outside of the body.
Here we are concerned largely with X-rays, gammas,
and neutrons. The alpha particle, which is the nucleus
of a helium atom, with its larger mass, slower velocity,
and greater electrical charge, is capable of traveling
only a few centimeters in air and rarely penetrates the
horny layer of the skin. Thus, in general, we can ignore
alphas as an external hazard since the horny layer of
the skin affords us good protection, but we will give
them full consideration when we discuss internal haz-
ards. Beta particles (electrons) are not as serious an
external hazard as gammas for they again have a rela-
tivity short range in air, although, greater than alphas.
They may reach the germinal layer of the skin and can
cause severe damage upon contact with the skin. Since
X-rays, gammas, and neutrons can penetrate deep into
the body to affect radiosensitive tissue, it is with them
that we are concerned primarily in discussing external

Shielding isone of our most important safety devices
and should be designed keeping three factors in mind:
(1) That the primary beam is to be attenuated to a
safe value.
(2) That the emission of hazardous secondary ra-
diation may result from the interaction of the
primary radiation with the shielding material.
(3) That some radiation may be scattered.

Shields of adequate thickness will eliminate or
reduce to safe intensities the primary and secondary
radiation; while if scattered radiation is present it can
be detected by monitoring and eliminated by proper
design of the shielding. Let us consider for a moment
the specific shielding materials for these various radia-
tions and the approximate thicknesses that might be
required. As gammas interact with matter they lose
energy through three processes: the photoelectric ef-

feet, the Compton effect, and pair production; which will not escape from the water. One should note that

effect predominates oris most responsible for the energy
loss of the gammas depends on the energy of the photons
and the atomic number of the absorber. As the gamma rays
or photons travel through an absorber or shield they de-
crease in number exponentially with increase in absorber
thickness. Thus, we can calculate the loss in photons for
a given absorber thickness by means of the well-known
equation: I - Ioe'1t where I is the intensity of the beam
after it has traversed a thickness t of the material, I, is
the original intensity of the beam andi the linear absorp-
tioncoefficient; the greater g the greater the reduction in
intensity for a given thickness of material.

Another convenient concept is that of half-value
thickness; by that is meant the thickness of material
which will reduce the intensity of radiation passing
through it by one-half of its incident value. Thus for a
1.5 Mev gamma one-half inch of lead will reduce the
original intensity 50%, another one-half inch of lead
will reduce it 50% again, or the intensity after going
through two one-half inch thicknesses or one inch
will be one-quarter the original value, another half-
inch will reduce it to one-eighth, and another half-
inch to one-sixteenth of the original value. Gamma radia-
tion is never reduced to zero by shielding, but it can
be reduced to safe levels.

Let us look for a moment at the thicknesses of
various materials required to give equivalent absorption
of various energy gammas. For 0.2 Mev gammas, if one
inch of lead reduces the beam a given amount, it re-
quires 4.7 inches of iron, 15 inches of aluminum and 36
inches of water to give the same absorption. For 1 Mev
gammas, the relative thicknesses are lead 1, iron 1.75,
aluminum 4.8, water 11.5; or for 5 Mev lead 1,iron 2.0,
aluminum 6.5, water 16.0. Thus we see that the degree
of shielding offered by a given material depends on the
energy of the gammas, and for a given energy different
materials require different thickness to give equal

The problem of shielding against neutrons is not the
same type of problem as shielding against gammas.
Fast neutrons are very poorly absorbed by most materi-
als, hence it is necessary to slow them down to speeds
at which they can be absorbed efficiently. For this
reason a neutron shield usually consists of a mixture of
material containing hydrogen to slow down the neutrons
and a material to absorb the slow neutrons. Atypical
neutron shield is water containing boron. The hydrogen
atoms of the water slow down the neutrons, and the
boron atoms absorb the slow neutrons and give off alpha
particles. The alpha particles having very short ranges

when some materials, such as cadmium which is an
excellent slow neutron absorber, absorb neutrons,
gamma rays are emitted, and one will need to shield
against these gammas with lead or a similar good gamma

While betas are not as serious an external hazard
as gammas and neutrons, beta radiation may penetrate
several meters of air and even an inch of wood may not
stop high energy betas. Beta radiation is attenuated by
shielding, and since it takes but little to stop it com-
pletely, the general practice is to use enough shielding
for complete absorption. For solution of low energy beta
emitters, the glass container may give complete pro-
tection. In many cases close plastic shielding is ef-
fective and convenient. When shielding against great
intensities of beta radiation another factor must be con-
sidered. The high velocity electrons (beta particles)
striking an absorber are rapidly decelerated and the
resulting electromagnetic radiation, called 'brems-
strahlung" is more penetrating than the beta radiation
which produced it. "Bremsstrahlung" can be detected
emerging from the shielding where it was produced and
while it is only a small fraction of the incident beta,
when we are dealing with high orders of radioactivity,
"bremsstrahlung" may be a serious hazard and must
not be overlooked in beta shielding.

Tables are available to permit a computation of the
shielding thicknesses of various materials required to
reduce a given radiation to a desired intensity when
the energy, intensity, and type of the incident radiation
is known. Shields may be of a permanent type, portable
or flexible shielding, or close shielding. Permanent
shielding against gammas and neutrons usually takes
the form of thick walls of concrete to which other sub-
stances may be added to increase its efficiency. Port-
able shielding in the form of specially designed con-
tainers of heavy metal is used for transferring and for
storing sources. By flexible shielding, we mean tem-
porary shielding of lead bricks which may be erected
around hot samples. Alphas and betas seldom require
permanent or portable shields, for plastic of the re-
quired thickness around the source vessel will normally
eliminate the hazard more conveniently and also facili-
tate the handling of the material.

In shielding there are a few facts to keep in mind:
(1) That persons outside the shadow cast by the
shield are not protected.
(2) That a wall, a partition, or a table top is not
necessarily a safe shield for persons on the
other side.

(3) That in effect radiation can "bounce around
corners;" that is, it can be scattered.

Thus, the vicinity of a shielded source should be
checked for scattered radiation as well as for radiation
which may leak through gaps and cracks in the shield.
When a shield has been assembled, the shield surface
and working area should be carefully monitored before
personnel are permitted to work.

To protect personnel, we limit the exposure to
gamma radiation to 0.3 rep per week (60 mrep/day).
As we have just seen, we can reduce the dosage rate
(rep/hr) by proper shielding, but limiting the time of
exposure and controlling the distance between personnel
and source are equally effective in preventing over-
exposure. For example, if due to a gamma source, the
dosage rate at a point in a contaminated area is 50
mr/hr, limiting the exposure time to less than 2 hours
will keep the dose under the average maximum permis-
sible value for a day based on the maximum permissible
dose of 0.3 r/week. It may be more convenient to double
the distance from the source rather than to limit the
working time to 2 hours. If the source is essentially a
point source, doubling the distance will reduce the
dosage rate to one-quarter, and thus permit four times
as many working hours. It is well to remember that the
inverse square law applies only to point sources or
sources sufficiently far removed to act as point sources.
It cannot with safety be applied to radiation close to an
extended source, such as a contaminated area, for here
the relation may approach more nearly an inverse first
power relation. It would be well to point out that direct
contact with a radioactive source should be avoided for
the inverse square law intensity increases with amazing
rapidity as the distance approaches zero.

While considering external hazards, gammas and
neutrons have been of primary concern; with internal
hazards, alphas and betas become important as well.
Here we are concerned with radiation sources within
the body. Radioactive materials may gain access to the
body by ingestion, by inhaling air containing radio-
active materials, by absorbing radioactive material into
the blood stream through a cut or break in the skin. In
general, the danger of ingesting radioactive material is
not that of a large amount swallowed at one time, but
rather the accumulation of small amounts on the hands,
on cigarettes, on food stuffs and other objects, and
thus bringing the material into the mouth. Radioactive
particles may also get into the gastro-intesrinal tract
by way of the lungs. After ingestion, the damage is due
to the chronic irradiation of the organs in which the
particular material localizes or concentrates. How great

the damage will be depends on the radiosensitivity of
the organ, the radioactive half-life of the material, how
long it is retained in the body, and the energy and type
of its radiations. Exposure to radioactive dust or spray
is particularly hazardous since a large fraction of such
contamination may be retained by the lungs. Radioactive
materials in solution may be absorbed through the skin,
particularly if the use of organic solvents has made the
skin more permeable to the penetration and absorption
of the materials. In addition, radioactive materials
may quickly enter the blood stream through breaks and
cuts in the skin.

To reduce the hazards means the prevention and
control of contamination, the use of protective devices,
the establishment of good practices and the prepara-
tron of sound plans. Good housekeeping necessitates
laboratory and equipment designed for handling radio-
active materials. The floors, walls and ceilings should
be finished with a nonporous material so they can be
easily cleaned to remove any accumulation of radioactive
materials. Dry sweeping and bull-dozing an area without
wetting should be avoided as an active dust hazard.
All laboratory operations should be conducted in hoods,
so designed that ventilation is capable of keeping the
activity in the air below the maximum permissible value.
Furthermore, persons outside the laboratory must be
protected; hence, the radioactive material forced out of
the laboratory through hood vents must not be allowed
to become a public hazard. Protective, or a better title
would be expendable, clothing should be wrn whenever
there is the possibility of contaminating the clothing.
The proper care of such clothing will help to prevent
the spread of contamination. Masks and respirators
should always be worn in areas where the concentration
of airborne activity is above maximum permissible
levels. To reduce the ingestion hazard, the wise prac-
tice of not eating or smoking where radioactive materi-
als are handled should be followed, and it is well to
form the habit of washing the hands carefully before
eating, smoking, or leaving work. Contamination con-
trol is needed to preclude general airborne radioactive
contamination as well as to prevent the accumulation
of hazardous sources of penetrating radiation. Immaculate
housekeeping is essential to the control of contamina-
tion. Some maximum permissible levels used at present
for an occupied area are as follows:
Beta and gamma radiation of 7.5 mrep/hr.
Alpha-emitting contamination of 3000 dis/min in
an area of 150 cm2, or the minimum amount of
alpha material which can be detected by use of the
"smear" technique.
Thermal neutron flux of approximately 1750 neu-

Fast neutron flux of approximately 70 neutrons/
cm2/ second, dependent upon energy.

Atmospheric contamination of 10-8 p/cc for beta-
emitting materials and 3 x 10-11 e/cc for alpha-
emitting materials.
If two or more types of radiation are present, the
combination shall not produce an exposure to any part
of the body biologically equivalent to more than 7.2
mrep/hr of beta or gamma radiation. While maximum
permissible doses and levels have been stated, radia-
tion hazards should be tolerated only if unavoidable.

Radiation is a permanent part of modern science
and will become increasingly important in industry,
in medicine and in the day-to-day experiences of men.
Protection from hazards of radiation has been remarkably
successful in the Atomic Energy Commission Instal-
lations where exposures have been kept well below the
maximum permissible dose. However, if protection is
to keep pace with the increased useofradiation sources,
the existing knowledge of radiation protection must
be applied on an ever widening scale; and to reduce
casualties in the event of an atomic bomb, knowledge
and planning are essential.



Cyril L. Comor, Laboratory Director

UT-AEC Agricultural Research Program
Oak Ridge, Tennessee

It is apparent that the future will see an increasing
need for work with radioactive materials, and it is to
be expected that there will be an increase in the ex-
posure of the population to radioactive materials. Thus
it becomes imperative that as much information as pos-
sible be gamed in regard to the amount of a given
isotope that can be tolerated by man.

The development of the nuclear reactor has led to
the production of enormous quantities of radioactive
fission products. The possibility of air and water con-
ramination by pile coolants, the escape of some frac-
tion of radioactive materials in the chemical processing
of the fissionable material and its products, and the
military use of atomic weapons must be reckoned with,
From the constructive point of view, it is recognized
chat the full development of scientific, industrial, agri-
cultural and medical uses of radioactive materials will
depend largely upon having available a reliable esti-
mate of the hazards involved. Responsible authorities
will not allow potentially dangerous civilian usage of
radioactivity, while on the other hand if the safety factors
are unreasonably large the use of these materials will
be retarded by financial considerations.

It is essential to have as a starting point some
standards for the tolerance levels of radioisotopes in
man, however arbitrary and lacking of foundation they
may have to be. It is obvious that determination of these
levels by direct experiment is impossible. There are
other possible indirect methods, all of which have cer-
tain disadvantages: (a) animal experiments, which may
be uncertain in their extrapolation to man, (b) theoretical
comparison of probable effects of internal radiation with
known external radiation effects in man; the dissimilar
mode of action of external and internal radiation makes
this method of questionable value, and (c) comparison
with known effects in man of internally deposited radium;
uncertainties with this method are due to the fact that
each element will have an individual pattern of behavior
in the body. It would seem that detailed animal experi-
ments with different species will represent the most
fruitful approach to this problem.

The critical evaluation of internal radiation hazards
is an extremely complicated chemical, biological and
radiological problem ms which a large number of inter-
related variables must be taken into account.
The following consideration of some of the more
important factors will serve to illustrate the complexity
of this problem and to indicate the difficulties in gen-
eralizing from one isotope to another or.between species
and individuals. A complete discussion of each element
is beyond the scope of this paper; however, specific
illustrations will be given where applicable.
1. Physical hair-life of the Isotope: The greatest
biological hazard is presented by radioisotopes with half-
lives ai the range of 4 to 20 years. The short lived iso-
topes decay away before the body can be exposed to
relatively large amounts of radiation; with the extremely
long lived isotopes it requires very large amounts of the
element to produce radiotoxic effects so that in these
cases chemical hazards may be apparent before radia-
tion damage.
2. Biological half-life: The biological half-life
is defined as the time required by the body to eliminate
half of the radioactive material. This is primarily a
function of the element, but also depends upon such
individual factors as discussed later under "Biological
Variables" and "Localization Within the Body." Table
I presents some data which give an estimate of the or-
ders of magnitude involved.

Estimated Percent of Dose Retained
Six Months after Exposure
Nucleonics 8, 66; 1951
Radioisotope Ingested
Po-210 10
Ra-226 5
Pu-239 0.05
H-3 50-
C-14 1
S-35 1**
Ca-45 15
Sr-90 15
* 70 days after exposure
** week after exposure


3. Energy and kind of radiation: The biological
effect depends upon the energy and kind of radiation.
For instance it is estimated that alpha particles, due
to the ionization density, are about 20 times as biolo-
gically hazardous as are beta or gamma rays. Likewise
it is reasonable to expect that some of the weak beta
emitters such as H-3, C-14 and S-35 may be more bio-
logically effective than the higher energy emitters.

4. Route of entry into body: When foreign material
is inhaled, the degree to which particles reach and
penetrate the lungs will be largely dependent upon
particle size. The nose will filter out almost all parti-
cles greater than 10 microns in diameter, while parti-
cles smaller than 5 microns will be exhaled to a con-
siderable extent. Solubility is also an important factor;
soluble substances will be dissolved and rapidly elimi-
nated from the lung by passage into the blood stream.

When radioisotopes are ingested, the important
factor is the degree to which they are absorbed from the
G.. tract. This depends first of all upon the way in
which the particular element is handled by the body; for
instance, in general one would expect uranium to be
very poorly absorbed, calcium and strontium to be
absorbed to a somewhat greater extent, and iodine to
be readily taken up. This problem of absorption is in
itself quite complicated. The presence of precipitating
ions in the gut may interfere as illustrated by the case
of high oxalate levels reducing calcium and presumably
strontium absorption. The specific activity of the ele-
ment in question or related elements in the gut will
also be important; for instance the absorption of 1131
can be greatly reduced by administration with large
amounts of stable iodine. The age of the person will
also be a factor; young animals are known to absorb
calcium to a much greater extent than do older ones.

The expected retention of isotopes which enter the
body through the skin or through wounds is difficult to

5. Localization within the body: The distribution
of an isotope in the body is again mainly dependent
upon the metabolism of the element. Thus sodium is
uniformly distributed throughout the body, calcium and
strontium go almost entirely to the bone, while iodine
Lcocentrates in the thyroid gland. It is obvious that the
net harmful effect on the organism will be a summation
of the following factors: (a) the size of the volume of the
tissue in which the isotope is concentrated; the smaller
the volume, the greater the radiation effect, (b) the
radiosensitivity of the tissue, and (c) the importance
of the particular tissue to the well-being of the organism.

The over-all biological half-life as previously dis-
cussed is not very meaningful when it is recognized
that the rate of removal of elements varies from organ
to organ and may even vary in different parts of an
organ. For instance, it can be demonstrated that radio-
calcium appears first in the epiphyseal and periosteal
parts of the bone, but that which enters the epiphyseal
region is readily and rapidly removed, whereas that
which is incorporated in the shaft of the bone is firmly
fixed. Depending upon the relative amount of osteo-
clastic and osteoblastic activity, the radiocalcium may
eventually be found in the endosteal region, where it
could irradiate the bone marrow. This will be determined
by the age of the animal and rate of bone growth.

6. Biological Variables: Many of the biological
variables have already been discussed briefly. The age
factor may be a very important one. It has been shown
that such elements as calcium are far more readily
laid down in the bones of younger than in those of older
individuals; there is as yet no definite evidence as to
whether removal from the bones of younger animals is
significantly greater. This is an important considera-
tion since with the hazardous radioisotopes the greater
the life expectancy of the individual, the greater the
possibility of harmful effects; also, younger animals are
generally more radiosensitive.

Radiostrontium and radiocalcium, for instance, have
been shown to cross the placental barrier with ease and
to accumulate to a much higher concentration in the
bones of the fetus than in the bones of the mother.
Adding to this the probable increased radiosensitivity
of the younger organism we may have a potentially
hazardous situation in the case of exposure of pregnant
women. It is well established that calcium deficient
or ricketic animals will tend to absorb and lay down
more of this element in the bones. This means that the
state of nutrition of an individual may have a direct
bearing upon the magnitude of absorption of some of the
bone-seeking radioisotopes.

In summary, then, are some of the biological vari-
ables which govern the extent of incorporation and
retention of materials in the body: factors which increase
or decrease absorption and utilization of elements and
compounds, factors which affect excretion and destruc-
tion, detoxification processes, growth, physical exertion,
fever, drugs, toxins, abnormal environmental conditions,
pregnancy, lactation and any related conditions that
result in a changed metabolic requirement on the part
of the tissue cell.

7. Mechanisms of bone accumulation: The ncor-

portion of radioisotopes in the bone constitutes per-
haps the greatest hazard. For this reason particular
attention has been paid to the means by which elements
get into the bone.

Certain radioelements including calcium, strontium,
radium, phosphorus, uranium and molybdenum are known
to accumulate in bone primarily by means of an ionex-
change reaction. The main features of this mechanism
are as follows: (a) the younger the animal the greater
the uptake by the skeleton, (b) bone uptake is affected
by changes in calcium metabolism or calcium nutri-
tional status of the animal, (c) rate of elimination may
be significant depending upon bone growth, and (d) the
element may shift its position within the bone.

Other radioelements such as plutonium, yttrium,
actinium, thorium, polonium and zirconium are known
to accumulate in bone by means of colloidal absorption
uptake. In this case the following is generally true:
(a) the uptake is independent of the age of the animal,
(b) bone uptake is not affected by changes in calcium
metabolism or the nutritional status of the animal, (c)
there is no significant elimination of the element once
it has been fixed in the bone, and (d) there is no shift
from the initial site of deposit which is mainly the
periosteum, the endosteum, and the covering of the

8. Removal of bone-seekers from the body: It would
be of practical importance to be able to increase the
rate of excretion of the hazardous bone-seeking radio-
isotopes, or at least to cause them to be relocated in
less radiosensitive areas. Actually there has been little
success in accomplishing this especially when treatment

is delayed until such time as the radioelements have
become fixed in the skeleton.

Rats which had received plutonium were placed on
a diet designed to produce bone resorption and then
changed to an optimum diet which allowed bone produc-
tion. Autoradiograms shows that the plutonium was
then located deep in the shaft with the consequence
that the short range alpha particles were less likely
to reach the more sensitive tissue. This method has
not yet been studied by actual toxicity trials.

Complex-forming agents such as citrates which will
combine with radium and calcium, have been studied
from this point of view. Although the administration of
these completing agents may increase the excretion of
the complex ion there is some evidence that they may
also increase the amount of the element deposited in
the skeleton, so that caution must be exercised in their

When zirconium salts are administered to an animal
containing plutonium or yttrium in the blood stream the
latter will tend to be absorbed on the colloidal aggre-
gates formed from the zirconium. The subsequent behavior
of the radioelement is determined by the distribution
of the colloid carrier. Deposition of the radioelement in
the bone can thus be prevented. Although this method
will remove some of the plutonium or yttrium already in
the skeleton, the treatment is more efficient the sooner
it is started. In animal experiments the deposition of
plutonium in the skeleton has been minimized by in-
jection of the zirconium several days before the plu-
tonium exposure.



Gould A. Andrews, Chief Clinician

O.R.I.N.S. Hospital
Oak Ridge, Tennessee

In this brief discussion an effort is made to sum-
marize the current status of medical uses of radioiso-
topes. The use of isotopes to deliver radiation to tis-
sues is relatively familiar, and radium, a naturally oc-
curring radioisotope, has been used in this way for
almost 50 years. The recent availability of many other
isotopes, some of which are suitable for internal admin-
istration, has led to the development of techniques for
their application in tracer studies and diagnostic tests
as well as therapeutic radiation.

The amount of publicity given to current uses of
isotopes has not been entirely appropriate to the pres-
ent importance of these uses. The impressive basic
research in physiology and metabolism which has been
made possible by radioactive tracers has received rela-
tively little attention in the lay press while therapeutic
attempts have been publicized widely, in spite of their
present limited value.

Almost every phase of biological research has
benefitted from isotope research upon fundamental
metabolic phenomena. In these studies, the remarkable
detectability of the isotopes is exploited and the doses
are kept low enough to avoid gross radiation effects
on tissues. One of the great general contributions of
these studies has been an emphasis on the extreme
liability of the chemical compounds within the body.
Much of this work has been done with stable as well as
radioactive isotopes.

An example of a more specific phase of metabolism
in which radioisotopes have been of value is the absorp-
tion and utilization of iron. By introduction of small
quantities of radioactive iron into the body it is pos-
sible to study very precisely the rate at which the iron
is absorbed from the gastro-intestinal tract and subse-
quently removed from the plasma and taken up by the
developing red cells in the bone marrow. Studies of
survival of the red cells can also be made and the fate
of transfused cells can be accurately determined. Radio-
active isotopes have similarly been used effectively
in the study of electrolytes and other aspects of mineral
metabolism. It would be a mistake to assume, however,

that isotope techniques have replaced chemical studies.
As a matter of fact, in most laboratories where research
utilizing isotopes is being done, the most precise
stable chemical determinations are being used in con-
junction with the isotope work. The isotopes have
greatly expanded the horizons in biological research
but they have not simplified the procedures or replaced
other techniques.

Another medical use, which is essentially an ap-
plication of tracer techniques, is in diagnostic tests.
These have become gradually more important during
the last five years and most large medical centers
are now utilizing isotopes in this way. The most famil-
iar example is the use of radioactive iodine to deter-
mine thyroid function. For this test, a small dose of
radioactive iodine is given to the patient by mouth or
intravenously and at suitable intervals the amount of
the iodine taken up by the thyroid gland is measured
by means of a Geiger tube held near the neck at a pre-
determined distance from the thyroid gland. Information
can also be obtained by determining urinary excretion
of radioactive iodine. Patients with an increased activity
of the thyroid gland will take up a larger amount of the
radioactive material and excrete less than the normal.
On the other hand patients with myxedema or extreme
hypothyroidism will retain a very small amount of the
material in the thyroid gland. This test gives information
similar to that obtained from a basal metabolic rate but
is not a measurement of the same phenomena. It has
some very distinct advantages over the basal metabolic
rate in many patients. In this type of rest the amount of
radioactive iodine given is extremely small, so small
that the actual radiation delivered co the thyroid gland
does not cause any detectable effect upon the gland or
its function.

Another group of diagnostic tests are those which
utilize radioactive compounds in localizing brain tumors.
The substance most commonly used is radioactive
diiodofluorescein. In this instance radioactive iodine
is added to the fluorescein molecule, and remains fixed,
serving no purpose except as a means of labeling the
compound. Because of the peculiar vascular behavior

of certain brain tumors, the radioactive material con-
centrates there is sufficient quantity to allow detection
by means of a Geiger tube or scintillation counter placed
at certain positions over the outside of the head. This
procedure is a supplement to standard means of examina-
tion and does nor replace any of the established methods
of studying patients with possible brain tumors. Other
radioisotope diagnostic tests are in use and still more
are being developed. It appears probable that these
techniques will become important in evaluating many
types of metabolic disorders.

The third large group of medical uses of isotopes
is that in which they are used as a means of delivering
therapeutic amounts of radiation to tissues. Here the
doses are obviously much larger than needed for tracer
and diagnostic work. Most of the interest is directed
toward the treatment of malignant tumors. There has
been a period of excessive enthusiasm for the intriguing
possibilities of this form of treatment and a tendency to
expect remarkable results. Possibly this tendency to
exaggerate the importance of these possibilities is a
result of the secrecy and aura of drama which has sur-
rounded the military use of aromic energy plus the fact
that the public is always prone to pounce upon a treat-
ment for cancer. In some instances the discovery that
isotopes are of really very limited value has led phy-
sicians to an excessive disillusionment and a failure
to exploit the very definite though limited possibilities.
In one group of diseases treated by isotopes, there is
little need for localization of the radioactive material
and the result obtained is essentially total body irradia-
tion. Radioactive phosphorus has been used extensively
in treating polycythemia vera and chronic leukemia. This
isotope does show some tendency to concentrate in
rapidly growing tissues including the spleen and bone
marrow and also in the hard crystalline par of bones.
Thus, it can be said to some extent to have a favorable
localization. However, the results obtained with radio-
active phosphorus can almost be duplicated by total
body X-ray irradiation and it seems doubtful that the
specific localization of the isotope is important in its
therapeutic effect. The diseases for which it is used
can also be treated approximately equally as well by
other means and thus the introduction of the isotope
has added only slightly to the ability of the physician
to benefit his patients. Nevertheless, in certain situa-
tions, radioactive phosphorus is quite valuable and it
seems to have obtained a permanent place in therapy.

A second general group of therapeutic uses takes
advantage of a highly specific metabolic localization
of the radioisotope. This is the group in which the
most intriguing possibilities have existed. Unfortunately,

it appears that at the present stage of our knowledge
there are very few situations in which the metabolic
localization can be utilized effectively. Radioactive
iodine, of course, has a remarkable tendency to localize
in the thyroid gland and in certain rumors originating
in the thyroid gland and is of distinct clinical value
in these cases. It has been popular to say that radio-
active iodine is an example of metabolic localization.
Actually, it is erroneous to imply that there are many
other equally simple specific metabolic pathways. Iodine
appears to be a remarkable exception rather than an
example, and there is no other element which is handled
by the body in any comparable manner. Nevertheless
there are possibilities of developing compounds which,
by means of more complicated techniques, can be made
to concentrate in tumor tissues in sufficient degree to
have therapeutic effect. At Oak Ridge we have been
working on radioactive gallium, a material which is
given intravenously and which localizes quite strikingly
in areas of bone growth and areas of bone-formation in
tumors. The concentration is not nearly as specific
as that of radioactive iodine in thyroid tissue but it
may be sufficient to be of some therapeutic value in
certain cases.

A third type of therapeutic application of isotopes
depends upon mechanical means of directing the radia-
tion or depositing the radioactive material. Radium is,
of course, the classic example; more recently radioactive
cobalt has been found effective when used in a manner
similar to radium. Cobalt appears to have certain def-
inite advantages over radium and is much less expensive.
Another mechanically localized isotope which is of
great current interest is radioactive colloidal gold,
which can be used in the treatment of tumors which
cause collections of fluid in body cavities. It has
been found that by injecting the gold directly into the
cavity in many instances it is possible to decrease or
stop the fluid formation. This does not result in a cure
of the rumor but may greatly improve the patient's com-
fort and prolong life. Other types of mechanical local-
ization include the direct injection of tumors with radio-
active material and the use of certain isotopes with
short range radiations by direct application on the skin.

The increasing medical use of radioactive isotopes
has created a new type of health hazard which is re-
ceiving a good deal of attention at the present time.
The unfortunate early experiences with X-ray and radium
have led to a very determined effort to prevent a recur-
rence of these disasters in the handling of radioactive
isotopes. Since the hazard is invisible and somewhat
mysterious to those who are not familiar with isotopes,
there is a tendency for excessive fear and unwillingness

to utilize the material in some individuals, while in
others there may be carelessness and too little appre-
ciation of the dangers. The fact that there is uncertainty
about the amount of radiation which can be tolerated
safely by the normal individual adds to this confused
situation in the field of health protection. Fortunately,
for most radioisotopes now used, there are instruments
which will detect and measure fairly accurately the
radiation hazard. There are two general types of haz-
ards. One is exposure to penetrating radiation from the
isotope either before or after it is given to the patient.
This type of exposure exists even when there is no
direct contact with radioactive material and even when
the material is completely under control at all times.
It can be avoided only by means of arranging to keep a
sufficient distance away from the radioactive material
or by interposing adequate shielding material.

The other type of exposure is that which occurs
when there is lack of control of the radioactive material
so that it is spilled on tables or floors or is spread
in volatile form in the air. With this type of dissemina-
tion of the material, in addition to the exposure to the
radiation from outside there is the possibility of picking
up the material on the hands or even breathing it or
ingesting it internally. This form of exposure can be
avoided by controlling meticulously the radioactive
material and by taking adequate precautions to avoid

In a hospital situation there is possible danger
from both exposure and contamination. The initial hand-
ling of the isotope must be done with suitable equip-
ment so that the operators do not receive too much radia-
tion in preparing the material for the patient. The actual
administration of the isotope likewise must be done
without excessive danger to the hospital, personnel.
This is relatively simple when the patient drinks the
material as in the case of radioactive iodine but may
become difficult when certain isotopes are given by
injection. However, special equipment has been devised
to greatly simplify this problem.

Other problems involved in hospital management

include the radiation hazard from the patient himself.
At first at was thought that it would never be possible
to give a patient enough radioactive material to make
him a radiation hazard; it has been found that this is not
true, chat an individual patient can be a serious radia-
tian hazard. An even more difficult problem is the hand-
ling of the urine and stools from these patients. In most
hospitals it has been the practice to simply add these
radioactive excretory products to the sewage system and
not to worry about what happens from there on. This is
reasonably satisfactory when a small isotope program
is under way but when many patients are being treated
the plumbing system may become contaminated with
radioactive material and be a health hazard. Further-
more the sewage may be dangerous and in certain in-
stances it is necessary to store the radioactive waste
products or to deposit them in specially designated
areas where they cannot become a source of contamina-

One very good result has come of the interest in
radioisotopes-a renewed consciousness of the general
dangers of radiation injury to hospital personnel. This
has influenced the practice in many X-ray departments
which were formerly relatively careless about this
problem. There has been a new interest in making ac-
curate measurements of personnel hazards and in many
instances it is found that the X-ray department which
has been functioning for years is of greater danger to
hospital personnel than is the new isotope laboratory.
There is ample evidence that various forms of radiation
can be used extensively in hospitals without any real
danger to nurses, doctors, or other hospital workers
provided that sensible precautions are taken.

Radioactive isotopes are being utilized increasing-
ly in research, diagnostic, and therapeutic phases of
medicine. Increasing clinical and laboratory experience
is indicating the peculiar advantages and limitations
of present isotope techniques, and these newer proce-
dures are finding their proper place in relation to older
methods. Meanwhile there remain many possibilities
for further extension of the fields of usefulness of radio-
isotopes in medicine.



George G. Monov, Chief

Advisory Field Service Branch
Isotopes Division, AEC
Oak Ridge, Tennessee

During the past year the number of industrial appli-
cations of radioactive materials has increased at a slow
but steady rate. Thus far their usage has been confined
to laboratory-scale investigations by consulting labora-
tories or by companies that carry on active research
programs. At present approximately ninety industrial
andcommercial resting laboratories are using radioactive

Radioisotopes may be advantageously employed in
several circumstances: first, where the extreme sensiti-
vity of detection required clearly dictates their use;
second, where they can be used to provide a faster or a
more specific method of detection or measurement; and,
third, where conventional methods of detection inherent-
ly fail to provide the information desired. The unique-
nessof radioisotopes willbe pointed our in the examples
that follow, and mention will be made of the degree of
hazard associated with the industrial use of radio-

Broadly speaking, industrial uses of radioisotopes
can be divided into two categories: (a) those in which
they are used simply as sources of radiation, and (b)
those in which they are used for tracing some particular
process. In neither case is the intensity of radiation so
high as to induce radioactivity in the material under

The application of radioisotopes as sources of
radiation gives rise to devices such as thickness gages,
liquid-level indicators, etc. The use of radioisotopes
as tracers permits studies of reaction mechanisms,
wear testing, and other problems. Radioisotopes are
frequently used to obtain specific information, as for
example, determining the best method of carrying out
a particular process. In such cases, once the answer has
been obtained, further experimentation using radioactive
materials is generally not required. On the other hand,
some applications require continuous use of atomic
radiation, for example, to measure some property, such
as thickness or density.

From the standpoint of the quantity of active mate-

rials involved, radioisotopes in the form of sealed
sources of radiation account for the majority of the
industrial uses of these man-made substances. With
sealed sources there is no problem of waste disposal.
Other industrial uses of radioisotopes involve such
small quantities of materials that the disposal problem
is not at present considered significant. A brief sum-
mary of the industrial uses of radioisotopes according
to the principle involved is given in Table L


Uses or Radoiasolopes In Industry

Fixed Source (Measure Change
in Radiation
Intensity) . . .

Movable Source (Locate or
Follow Marked
Object) .....

Tracer (Physical Transfer) . .

Trcer (Physical - Chemical
Transfer) ........

Tracer (Mechanism of
Reaction) ........

(Thickness Gage
(Liquid Level Gage
(Density Meter

(Liquid Flow Through Pipe
(Location of "Go Devil"

(Friction Wear
(Solid Diffusion

. (Mineral Flotation
(Movement of Preservative

(Role of Catalysts
. (Fischer-Tropsch Synrhesis
(Source of Coke Sulfur

Radiographic Testing

Pile-produced Cobalt-60 can sometimes be used as
a substitute for radium or X-rays. The problems of pro-
tection against the radiations from the two sources
are similar in many respects except that (for equal
quantities of material) the radiation from Cobalt-60 is
about 50 percent more penetrating than the latter. The
quantities used may range from 100 or 200 me up to as
high perhaps as I curie in some cases.

Interest is being manifested in the use of radiocobalt
because of its lower cost per millicurie and the higher

specific activity (from two to six times that of radium) I

that can be obtained. The latter advantage can some-
times be important, particularly where very intense
point-sources of radiation are needed. The comparative
economics of radiographic testing with cobalt, X-rays
and radium has been explored by Schwinn (1).

Details of making radiographs of castings with
radiocobalt have been published by several authors,
notably Morrison (2), and a typical arrangement for
radiographic testing is shown in Figure 1 Other radio-
isotopes have also been used. McCutcheon (3) has





Figure 1: Radiographic Tesmng Using Cobalt 60.

investigated Seleniumn-75, and a group of workers at
Los Alamos Scientific Laboratory (4) has studied the
comparative values of radium, Tantalum-182 and Cobalt-
60 in industrial radiography. The large variety and
quantity of man-made isotopes which are becoming
available will undoubtedly serve to stimulate further
research in this field.

Liquid-Level Gages

Liquid-level gages now on the market that use
conventional sensing devices involving changes of
hydrostatic pressure, current, etc., perform adequately
in many respects and are satisfactory in a great majority
of cases. Where extremes of pressure, temperature,
corrosivity, or other very unusual conditions are in-
volved, liquid-level gages using radioisotopes may pro-
vide a unique solution to a difficult problem. One type
of a liquid-level device is shown in Figure 2- Both the



EiGHr waters Bu




Figure 2: Liquid-level Gage.

source and the detector are placed outside of the cham-
ber and operate at room temperature and pressure. When
the level of the liquid rises (or falls) so that it causes
the intensity of the radiation reaching the detector to
diminish (or to increase), the device becomes actuated
and sets off an appropriate type of alarm. Such an ap-
paratus, in use by the Ford Motor Company to determine
the level of liquid steel in a cupola, has been described
by McCutcheon (3). This simple device could be trans-
formed into a liquid-level recorder and controller by
automatically raising or lowering the source and the
detector with a suitable follow-up mechanism. From the
standpoint of radiological safety, the only requirement
is that the stray radiation be reduced to a permissible

Thickness Gages

Perhaps one of the most interesting uses of radio-
isotopes as sources of radiation is their application
in measuring the thickness of various materials. Sim-
ple types of transmission gages (in which the material
whose thickness is to be measured is moved between
a fixed source and a detector) have found application
in paper, plastic and rubber industries as shown in
Figure 3.

Occasionally it is desired to measure the thickness
of a material plated on the surface of a base component.
For example, one may wish to determine the thickness
of a plastic coating on a base metal. An appropriate
type of instrument, known as a backscatter gage (see



ne e riE OK - --



wso-I.snc Jou


Figure 3: Transmission-type Thickness Gage.

Figure 4), operates by measuring the intensity of radia-
tion reflected from the surface of the material whose
thickness is to be measured.

Because the quantity of radiation back-scattered
from a surface depends upon the atomic number of the
reflecting material, these gages become increasingly
practicable the larger the difference between the atomic
numbers of the plated and the base materials. If a
number of conditions are fulfilled, the intensity of the
reflected radiation will be proportional to the thickness



Figure 4: Reflection-type Thickness Gage.

of the coating. Backscarter thickness gages usually use
a few millicuriesofa hard beta emitter, such as Sr90 as a
sealed source, and an ionization-chamber detecting
instrument (5).

One of the advantages of using radioactive thickness
gages of the type shown in Figures 3 and 4 is that one
can make measurements without mechanical contacting,
stopping, or cutting the material. These gages can be
operated by non-technical personnel.

From the standpoint of radiological safety it is nec-
cessary that the source be sealed so that there is no pos-
sibiltry for escape of the radioisotope into the atmos-
phere, and that the housing be so designed as to shield
personnel from direct or scattered radiation. These prob-
lems have recently been solved with a satisfactory de-
gree of success, and the increase in the number of in-
stallations of radioactive thickness gages is a measure
of the degree of satisfaction that is being experienced
as a result of their use. Radioactive thickness gages are
now being made by at least two companies for commer-
cial distribution to approved users.

Radioactive atoms can be used to "tag" or label se-
lected atoms in compounds so that the fate of these com-
pounds or portions thereof can be traced through complex
reactions involving other kinds of atoms or molecules.
Tagging these particular atoms often permits acquiring
information that can be obtained in no other way.

Let us review how experiments should be planned
if radioisotopes are to be used as tracers only. First,
the maximum concentration of the radioisotope to be
used should be just enough to detect its presence with
ease. Second, the compound containing the radioactivity
should have the same chemical or physical structure
as that of the non-radioactive material being traced. Be-
cause it is comparatively easy to plan an experiment
that will meet these requirements, tracers have been
widely applied to the study of many problems.

One of the most outstanding features of the use of
tracers is that in the majority of the experiments only
very small quantities of radioactivity are required /.

/ The sensitivity of radiochemical detection far surpasses
that of conventional physical or chemical methods of analy-
sis. For example, a conventional chemical balance will weigh
to approximately 0.1 mg and a good grade of microchemical
balance will weigh to about 0.001 mg. A spectrographic
method of analysis may detect 106 to 109 mgs of material.
However, the sensitivity of radiochemical detection far sur-
passes these figures, and it is frequently possible to detect
quantities from 10"12 to 10-14 . If a short-lived radio-
isotope is used, for example Na2 , it is possible to detect
the disioregrations of as little as 10,000 atoms per second.
This figure corresponds to 1019 grams of Sodium-24.

For example, quantities of the order of a few micro-
curies (1 uc = 40,000 disintegrations per second) can
be used to study many industrial problems involving the
mechanism of physical and chemical processes. Con-
siderabl) larger quantities (perhaps several millicuries)
are needed to determine the rate of flow in pipelines,
the mechanism of engine wear, and other investigations
of considerable importance.

Detection of Transfer of Material

(a) Pipeline flow.

Radioisotopes can be used as tracers to detect trans-
fer of materials from one location to another, for example
to determine the position of the interface between two
different kinds of materials. The California Research
Corporation has found that radioisotopes make excellent
markers for locating the boundary or interface between
two types of oil flowing through the same pipeline, as
shown in Figure 5. Initial experiments involved approx-





qqq� trof

Figure 5: Determination of Rate of Flow of Oil in Pipelines.
imately 1 to 4 millicuries of a mixture of Barium-140
and its daughter, Lanthanum-140 /, and the length of

- Barium-140 has a half-life of 13 days, emits a beta-ry
of 1.05 Mev, and a weak gamma-ray of 0.5 Mev. Barimm-140
decays to Lanthanum-140 with a half-life of 40 hours. Lan-
thanum-140 emits a mixture of beta-rays ranging from 0.9 to
1.4 Mev, and a gamma radiation of 1.6 Mev. It is the garnma
radiation from Lanthanum-140 that is detected as the inter-
face travels through the length of the pipe.

the pipeline was approximately 5 miles 1-. Locating
the interface between the two oils proved to be a very
simple matter, and the rate at which it traveled through
the pipeline could be followed either by moving a Geiger
counter along the outside of the pipe or by strapping
several counters along the length of the pipe and noting
the time interval between the maximum response of suc-
cessive counters.

This use of radioisotopes has proved to be quite
beneficial, both from the standpoint of economy and
from the standpoint of obtaining considerable information
regarding the flow of fluids. This, in turn, may lead to
better design of piping to reduce friction losses and
perhaps to better types of pumps.

From the point of view of public health, it is of
interest to examine in detail the method by which health
problems have been minimized with respect to person-
nel within the refinery and eliminated with respect to
the public that uses the finished product. With the use
of suitable shielding and safe-handling equipment, the
exposure to men performing this test was reduced to
approximately 10 mr. At the terminal end of the pipeline,
the oil containing the radioactive interface was diverted
and several barrels of material collected before the sec-
ond oil with negligible radioactivity was sent to its
proper storage tank. The average activity of the bar-
rels containing the interface mixture was approximately
0.02 mr/hr which was only about four times the normal
background. The radioactive material contained in the
interface was allowed to decay to a safe value and the
oil then returned to the refinery. (Since the half-life
of the Barium-140 is only 13 days, either a storage
period of about one month or dilution of the interface
material with at least three times its volume of inert
oil suffices to reduce the radioactivity to that approx-
imating background.) The quantity of radioactivity pres-
ent in the oil eventually delivered to the customer is
completely negligible.

(b) Friction and wear.

Because of the increased sensitivity of detection
which is possible and the ability to measure the wear
from any specific surface, the use of radioisotopes has
opened new lines of research in fundamental studies of

- Routine applications with distances up to 180 miles, from
Rangeley. Colo.. to Salt Lake City, Utah, have recently been
reported and tests over a distance of 566 miles (Salt Lake
City. Utah, to Pasco, Wash.) are projected. Radioactive anti-
mony is now being used in place of the mixture of barium and

friction. By conventional methods it would be well-nigh
impossible to determine the transfer, for example, of
10-"0 grams of material from one surface of the contact
points of a relay to another, particularly if the composi-
tion of the two contacts were identical. With the use
of radioisotopes these limitations disappear; one con-
tact is being made radioactive, the second left un-
changed. The relay is allowed to operate for a short
time and the second contact is tested for radioactivity.
Knowing the number of disintegrations per second per
unit weight of material in the first contact, it is a com-
paratively simple matter to calculate the number of
micromicrograms of material which has been transferred
by the operation of the relay. Such applications of radio-
isotopes open up new opportunities in the field of ac-
celerated testing.

The California Research Corporation and the At-
lantic Refining Company have had a number of piston
rings irradiated at Oak Ridge, the activity of these
rings being such that one atom in approximately one
billion atoms of iron is radioactive. The isotope used
was mainly Fe59 (half-life 46 days, 0.2-0.5 Mev beta,
1.1-1.3 Mev gamma) containing some Fe55 (half-life
4 years, very weak K capture). These piston rings were
assembled in various internal combustion engines for
the purpose of studying engine wear (see Figure 6) as




Figure 6: Use of Radioisotopes in Studies of Friction and Wear.
affected both by conditions of operation of the engine
and the kinds of lubricating oils used (6). The engine
was started and the radioactivity of the lubricating oil
measured as a function of time. Continuous measurement
of the rate of wear could be made without disassembling

the engine, and it was possible to make measurements
as a function of the speed of the engine, the load, the
water-jacket temperature, the kind of lubricating oil
being used, etc. The effects of adding various com-
pounds to the base oil to improve its "oiliness," the
relative merits of different refining processes for pro-
ducing lubricants, etc., could also be investigated un-
der test conditions.

One of these oil companies has equipped a test
car to determine the rate of engine wear under service
or highway conditions. The results have indicated that
an engine driven all day in a desert wears less than
one driven a much shorter distance through stop-and-go
city traffic. The practical application of these tests
has resulted in the tailormaking of an improved lubri-
cating oil, and may lead to new knowledge concerning
high-pressure gear lubricants, cup greases, and other
petroleum products. Radioisotopes may also point the
way to the design of engines with better wearing sur-

Detection of Transfer of Materials by Phystco-Chemical

Radioisotopes are also being used in mining prob-
lems to determine the mechanism of flotation of minerals
(7). The flotation process involves use of various ad-
sorbates (usually selected organic compounds) whose
concentration may be as low as 10S or 10-10 moles/ml.
Because of the sensitivity and the specificity of radio-
isotopes, new lines of research may be made possible.
Similarly, the textile industry may profit from the use
of radioisotopes for obtaining information regarding
many still-unsolved problems in dyeing fabrics.

In addition, the field of detergents may benefit fur-
ther from the application of radioactive tracer tech-
niques. Radioactive Calcium-45 has been used by the
General Aniline and Film Corporation and by the Atlantic
Refining Company to study the efficiency of various
detergents in hard water. Work performed at the School
of Public Health, University of Michigan, has shown
how the efficiency of washing processes can be tested
using cloches that have been soiled with dirt or bacteria
containing Phosphorus-32. It should also be possible to
use radioisotopes to study the efficiency of various
commercial methods for softening waters.

Use of Radioisotopes to Study Mechanisms of Chemical

(a) Synthetic gasoline.

Radioisotopes have been applied (8) to the stu
of catalytic reactions in the Fischer-Tropsch synthes
of gasoline. This process, first developed in German
utilizes a mixture of carbon monoxide and hydrog
which is passed at high temperature and pressure ov
a suitably prepared catalyst. The actual reaction mec
anism has been in doubt for some time. One theory po
tulated the formation of iron carbide as an intermedia
in the reaction; according to a second theory, the cat
lyst offered a suitable surface at which the reacti
could take place but did not of itself assume any oth
role; other theories offered other explanations. T
use of radiocarbon provided a unique method of test
the validity of the first theory. Carbon monoxide, tagg
with radioactive carbon, was prepared and passed ov
an inert mixture of iron and iron carbide as shown
Figure 7. If the reaction proceeded by way of format


rtM anofl SiuauSS w- CJmau Eirn


. ,rn-u an uu

Iu Ima UM NM S lnu s uuW - B r doc a uTow
1 I- CAU B M1 A P*WTU IUSCATE &F - 5fli-W

Figure 7: Use of Radiocarbon in Studies of Catalysis.

of the carbide, the radioactivity in the hydrocarbons
initially synthesized should have been lower than that
corresponding to the initial radioactivity in the active
carbon monoxide. Experimentally, very little dimunition
in the activity was found. To check this finding, radio-
active iron carbide was synthesized in situ and inert
carbon monoxide and hydrogen were passed over it.
The synthetic hydrocarbons produced showed very little
radioactivity. These two observations were in agree-
ment and showed that the greater par of the synthesis
reaction proceeded by some process other than by re-
duction of carbide as an intermediate. It is interesting
to note that the quantity ol radiocarbon used in these
experiments totaled only 1 millicurie.

Very recently (9) results of experiments have been
reported in which labeled ethyl alcohol (one of the
intermediates in the Fischer-Tropsch synthesis of hy-
drocarbons) was passed over an iron catalyst. The re-
sults suggest that either ethyl alcohol or some surface
complex formed by the adsorption of ethyl alcohol be-
haves like an intermediate in hydrocarbon synthesis
over iron Fischer-Tropsch catalysts and that at least
the first of the added carbon atoms attaches itself prin-
cipally to the alpha-carbon atom of the surface complex.

(b) Metallurgy.

ed Radioactive calcium has been used by research
mer workers at the Carnegie Institute of Technology (10) to
in study iron-slag reactions and to measure the solubility
on of calcium in molten iron. The data showed that the
solubility of calcium was of the order of a few pans per
million. Other workers have applied radioactive tracer
techniques to various metallurgical problems such as
surface oxidation (11) and the distribution of phosphorus
in steelmaking (12). Many other studies have been made
using artificially produced radioactive materials.

One might list many other industrial applications
of radioactivity. However, those cited above indicate
the general principles along which these materials may
be used in technology. Radioisotopes offer to industry
an important tool in carrying out many investigations.
They can aid the industrial research worker in studying
the basic principles underlying the chemical and physi-
cal reactions of his processes. They can assist the
engineer in developing production methods to meet more
rigid specifications and therefore to manufacture better
articles of commerce. Radioisotopes have entered the
industrial field as newcomers but they have already
recorded many important accomplishments.


*adY��I.Uo. 4v
set. o�I^s

Tfl'rknss geges

Oil pip.ljn flow
Oi ,piphne flhew
Engine W*


a) Sarvi. Irrodilrn n pilr, may cal ctomn oIwer rodl oi.arIou ofr iilret
S lentel'


1. W. L. Sclwinn, "Economic Comparison of X-Ray,
Radium and Cobalt 60 in Inspection of Steel Weld-
ments,' presented before the American Society for
Testing Materials, Atlantic City, New Jersey, June
25-30, 1950.

2. A. Morrlson. "Radiography with Cobalt 60," Nucleo-
nics 5, 19 (1949).

3. D. M. McCutcheon. "Radioactive isotopes of Cobalt
and Selenium . . . In Industry," Steel 123, 61 (1948).

4. J. W. Dtlil, G. II. Tenney and J. E. Withrow, "Ra-
dium,Tantalum 182 and Cobalt 60 in Industrial Radio-
graphy," Los Alamos Laboratory Report LADC-712
(AECD-2719, October 10, 1949); available from Office
of Technical Services, U. S. Dept. of Commerce,
Washington, D. C. Price 10 cents-

5. 0. J. M. Smith, "Beta-Ray Thickness Gage for Sheet
Sreel," Electronics 20, 106 (1947).

6. P. L. Pinotti. D. E. Bull and E. S. McLaughlin.
"Radioactive Tracers Used in Research on Engine
Wear," Petroleum Engineer 20, June (1949).

7. R. II. Ramsey, "Research and Development Open
New Phase in Milling," Engineering and Mining
journal 149, 104 (1948).

8. J. T. Kummer. T. W. DeWitt and P. II. Emmett,
"Some Mechanism Studies on the Fischer-Tropsch
Synthesis Using C-14," 1. Am. Chem. Soc. 70.
3632 (1948).

9. J. T. Kummer, II. H. Podgarski, W. B. Spencer and
P. II. Emmett, "Mechanism Studies of the Fischer-
Tropsch Synthesis. The Addition of Radioactive
Alcohol," i. Am. Chem. Soc. 73, 564(1951).

10. E. S. Kopecki. "Radioactive Tracers in Metallurgi-
cal Research," Iron Age 160, 60 (1947); also see
J. . Harwood, "Tracers in Metallurgy," Nucleonics
2, No. 1, 57 (1948); and J. K. Stanley. "Tracer
Isotopes in Metallurgy," Nucleonics 1, No. 2, 70

11. M. S. Maier, II. R. Nelson, American institute of
Mining Engineers 147. 39 (1942).

12. T. B. Winkler. I. Chipman, Metals Technology 13,
No. 3 (1946).



C. C. Ruchhoft, Chief

Physics and Chemistry Section, Research and Development Branch
Environmental Health Center, U.S.P.H.S.
Cincinnati, Ohio

In considering the disposition of radioactive sources,
it is necessary to have a knowledge of radiation haz-
ards and safety. This subject has been covered in an
excellent manner by previous speakers, and, consequent-
ly we shall consider here the sources of radioactivity
and the disposition of radioactive wastes as indicated
by the half-lives, toxicity, and tolerance values.

The principal sources of radioactivity may be listed
as follows:
(1) Mining, refining and purifying of radium and
uranium ores, i.e., naturally occurring radio-
(2) Pile reactors.
(a) For plutonium production
(b) For power development
(c) For production of radioactive isotopes
(3) Atomic weapons.
(4) Radium therapy and radium dial industry.
(5) lonitrons (static eliminators).
(6) Wastes from hospitals using radioactive iso-
(7) Wastes from chemical and biological research
laboratories using radioactive isotopes.

The artificial production of radioactive isotopes
for use by industry, research laboratories, and hospitals
has grown tremendously in the last few years. The bulk
of the isotopes are being produced in reactors or sepa-
rated from fission products under the control and dis-
tribution of the Atomic Energy Commission. During the
period of shipment and application these materials
undergo a continuous radioactive decay. Finally, appli-
cation produces wastes containing residual radioactive
material, and these wastes present a disposal problem.

Radioactive wastes produced in the industry or in
off-commission laboratories may be gaseous, liquid, or
solid. The handling or treatment of liquid and solid
wastes frequently results in additional problems in the
disposal of gaseous or aerosol wastes. For instance,
incineration of contaminated refuse from radiation labora-
tories may produce aerosols and gases that are radio-
active. Similarly, decontamination of gaseous wastes

by fluid scrubbing produces liquid wastes that are radio-
active and may require additional treatment.

Alpha, beta and gamma aerosols may be expected
from pile reactors, atomic weapons, and the radium
industry. Gaseous radioactive materials (iodine and
argon) may be expected from pile reactors and also from
the atom bomb by either an air or underwater burst.
Gaseous compounds of uranium and plutonium, as well
as radon, may be expected from the refining and puri-
fying of radium and uranium ores.

Liquid wastes containing radioactive materials in
solution or suspension may be expected from reactors
and the atom bomb. Liquid wastes containing uranium
and plutonium may result from the refining and purifying
of radium and uranium ores and from the operation of the
reactors. Liquid wastes may also be obtained from the
scrubbing of gaseous aerosols and incinerator gases in
refining operations, and from the operation of incinera-
tors used for the disposal of rubbish and animals by
research and medical laboratories.

Liquid wastes also result from decontamination
procedures and from laundry operations. Smaller volumes
of contaminated liquid wastes are produced in the re-
search and medical laboratories.

Solid sources of radioactive wastes include con-
taminated equipment, laboratory apparatus, rubber gloves,
glassware, sacrificed laboratory animals, paper, and
clothing. One laboratory installation uses 6,000 dozen
pairs of rubber gloves each month. These are expendable,
but because of contamination special care must be taken
in their disposal. In addition to the above sources,
there are small volumes of solids resulting from evapora-
tion or chemical and biological treatment of radioactive
liquid waste which present troublesome problems.

Treatment of radioactive gases and aerosols is
ordinarily necessary only at Atomic Energy Commission
installations. However, purification of flue gases from
the incineration of solid contaminated laboratory wastes,
consisting of small animal carcasses, rubbish, rubber

gloves, etc., may present problems and should be con-
sidered for large off-site laboratories and hospitals
using isotopes.

The degree of treatment required by gases or aero-
sols depends upon the amount and characteristics of
the radioactive contaminants, the volume of gas or
aerosols, the meteorology of the area, and the location
of the laboratory. Conmmon procedures ur equipment used
in carrying out the disposal of aerosols or gases include:
(1) Dilution by discharge from a high stack.
(2) Electrostatic precipitators.
(3) Liquid scrubbing devices such as the Pease
Anthony scrubbers, capillary air washers, etc.
(4) Filtration using packed metal, glass, mineral
fiber, or carbon filters.
(5) Filtration through high resistance filters such
as Atomic Energy Commission or Chemical
Warfare Filters.

In commenting upon the operation, it should be
pointed out that acute problems frequently require the
application of two or more of the above processes ap*
plied in series. Some of the characteristics of different
processes may be noted briefly. Electrostatic precipi-
tarors have nor proven satisfactory for the treatment of
gases containing very fine radioactive particulate mate-
rial. The liquid scrubbing devices have proved most
effective for removing relatively coarse particulate
material, When filters are used, the filter unit may be
expected to become contaminated and will wind up as
waste to be disposed of by incineration or burial.

Methods suitable for the treatment of disposal of
liquid wastes are determined by (l)the chemical nature,
(2) the level of contamination of the wastes, (3) the
volume of waste to be handled, (4) the radiation charac-
teristics andthe half life of the radioactive constituents,
and (5) the flow characteristics and uses of the receiv-
ing stream.

In the case of wastes contaminated with very small
amounts of certain short half-life materials, the dis-
position may be made by direct discharge to sewer or
stream. Such disposition by hospitals of 1131 and P32
is permissible with proper dilution. The proper disposi-
tion of these particular materials is described in a hand-
book currently being prepared by the Subcommittee on
Waste Disposal of the National Committee on Radiation
Protection under the sponsorship of the National Bureau
of Standards. A maximum concentration in sewage of
400 microcuries per liter of either isotope is reasonable
for a period of no more than 30 seconds. To allow for an
additional margin of safety, the values for maximum con-

lamination permitted to occur in sewage are 100 micro-
curies per liter. The conditions necessary to prevent
exceeding this standard during the disposal of hospital
wastes are very carefully prescribed in the recommenda-
tions of the forthcoming handbook.

The table below shows some data on shipments of 1131
and P32 from selected large cities in the United States
between January 1, 1950 and June 30, 1950. thesee data
were obtained from the Isotopes Division of the Atomic
Energy Commission at Oak Ridge, Tennessee. It will be
noted that the total quantity of 1131 received during
this period varied from 1,148 millicuries for New Orleans
to 24,099 millicuries for New York City. During the same
period, St. Louis received theminimum of 46 millicuries
of p32 and New York City received the maximum of
4,393. The total quantity of both isotopes obtained in
these large cities represent 70,010 millicuries or about
70 curies. The records of the Isotopes Division show
that the shipments during the last half of the year were
very similar to those shown here. Consequently, it may
be assumed that the total shipments of these two iso-
ropes for the year 1950 were of the order of 150 curies.
It is interesting to compare this value of 150 curies of
isotopes shipped to these cities in one year with the
value of 15,000,000 curies of radioactivity that will be
obtained in the second following the explosion of one
"A" bomb .

fJaugjto 1. 0BS L JuE M . l-S)
I-YeI 00 lle o1
Amcm M-ltlr.a. WatI to I llir
It*ll RB eved 1o

N. o, g 7 24,I09 ri T 4,011

p32 7 33 s49 1,30
!t; LP., l. 11 1 Iti 1 .e,

p3 IS a 2 5 4

In 75 ma

La Anae. ...s ,,..
" Prow�oa~l itm porr by Feltelga Qal~y I h� Natc l Com t a 3ad9 ,0

Column 4 in the above table shows the millicurie
of activity which would be disposed as wastes weekly
as the result of the isotope shipments in the six cities
listed. The last column shows the number of gallons of
water that is required to dilute the weekly wastes of

these isotopes to the 100 microcuries per liter standard by sedimentation, the supernatant is further deconram-

which has been adopted in the forthcoming National
Bureau of Standards Manual.

The estimated domestic water consumption in mil-
lions of gallons per day for the cities listed in the table
is as follows:

New York City
St. Louis
Los Angeles
New Orleans
San Francisco

It will be seen from these data that the discharge
of 1131 and p32 wastes from hospitals will be very
amply diluted to values very much below the standards
desired when this waste becomes mixed with the daily
flow of water from each of these cities. In fact the
diluted values for 1131 and p32 should be of the order
of 10 microcuries per cc. after dilution at each of
these cities.

The second method of disposal which may some-
times be required by installations not under the Atomic
Energy Commission consists of storing the wastes to
take advantage of the decay of short lived isotopes, and
evaporation or concentration to reduce the volume,
followed by shipment of the material to the Atomic Ener-
gy Commission Isotopes Division for final disposition.

The third and perhaps most obvious method for the
treatment of liquid wastes is the evaporation of the
liquids followed by storage of the resulting contaminated
solids. This method is expensive for large volumes of
waste but costs may be reduced in some areas by solar
evaporation. An excellent paper describing the evapora-
tion of the wastes at the Knolls Atomic Power Labora-
tory was presented by McCullough (2). The evaporation
process used at Oak Ridge has been described by
Browder 3'.

Where long lived radioactive materials are to be
disposed of at an Atomic Energy Commission installa-
tion, the wastes are treated to reduce the level of radio-
active contaminant in the waste below the tolerance
level for drinking water. One method in use at Atomic
Energy Commission installations for accomplishing this
type of decontamination has been described by Christen-
son et al (4). This method consists of chemical coagu-
lation or co-precipitation of such material by means of
chemical coagulants. After the solids resulting from pH
adjustment and addition of coagulant have been removed

inated by filtration through conventional sand filters.
The coagulation may be carried out in conventional
mixing and sedimentation tanks or in accelators or
clariflocculators. Iron or aluminum salts in doses con-
siderably higher than are used in municipal water treat-
ment are required for effective coagulation because of
the completing agents citratess, polyphosphares, etc.)
which are frequently contained in the wastes. Variations
in the characteristics of the wastes make it necessary
to determine experimentally the best kind and quantity
of coagulant and coagulation aides that are required
and the optimum pH for coagulation.

Another method used at Atomic Energy Commission
installations involves precipitation from neutralized
wastes combined with storage to permit decay of soluble
short half-life radioisotopes before discharge into sur-
face waters. A system for such treatment, which also
includes evaporation, is in operation at Oak Ridge (3)
The decay and dilution of the waste is such that the
radioactivity found in the Clinch Rivet below the plant
effluent has only a fraction of the drinking water toler-
ance concentration.

Biological and physical treatment may also be used
for some wastes at Atomic Energy Commission installa-
tions. These methods of treatment are indicated for
laundry wastes containing relatively low level long
life isotopes. Evaporation of these dilute wastes may be
too expensive for the relatively large volume involved
(10,000 to 15,000 gallons per day). Newell et al (5)
state that the biological treatment is favored in this
instance because the wastes contain completing agents
and detergents which make chemical treatment unsatis-
factory. Trickling filter treatment applied to laundry
wastes containing plutonium and oomplexing agents,
such as citric acid, soap, Igepal and other detergents,
is effective. In these cases the waste is applied to
trickling filters at low rates with high recirculation ra-
ties. The completing agents are destroyed in this treat-
ment and the radioactive isotopes are cnncenrated
in the sludge.

The possibility of the use of ion exchange columns
for treatment of liquid radioactive wastes should be
mentioned.Studies on the use of such columns have been
reported by Ayers (6). Regeneration of these columns
does not appear to be coo promising, and, consequently,
the cost of this method may be excessive. However,
ion exchange and absorption columns may be considered
for emergency water decontamination in time of disaster.
A small unit of this kind has recently been developed
by Emmons and Lauderdale at the Oak Ridge National


Finally, liquid or semi-solid wastes may be converted
to solids by mixing with concrete and the concrete
blocks can then be treated as solid wastes.

Incineration of combustible and other, materials to
produce a relatively small volume of ash is an important
method for handling contaminated wastes. The precau-
tions mentioned with respect to air and aerosol containm-
ination from incineration must be taken into considera-
tion in using this method of disposal Residual ash will
usually contain radioactivity and must be disposed of
by storage, burial or sea disposal.

Burial in the ground appears to have certain ad-
vantages for disposal of solid materials. This method
should be used principally on solid wastes or equipment
contaminated with long-life isotopes. There should be
a minimum number of burial sites carefully selected,
Factors that must be considered in the selection of
such sites include topography and drainage, climate,
soil composition, vegetation, ground water movement,
and bed rock formation. Sedimentary bed rocks, such
as limestone and sandstone, should be avoided. Com-
pact argillaceous shale, or other soils in which there
is little or no leaching may be favorably considered.
Abandoned mines in isolated areas may also be con-
sidered. In all cases complete records should be kept
on ground burial, markers should be used on burial
locations, and such areas should be fenced and re-

The problem of the return of radioactive isotope
wastes to the Commission for burial or storage has been
studied by Woodruff and Morgan (7). Their report pre-
sented a list of the radioactive isotopes to be returned
as wastes, the forms and quantities of these that were
returnable, and the packaging and shipping regulations
governing the materials returned.

Radioactive isotopes presenting sufficient hazard
for return to the Commission were selected on the basis
of the following factors:
(1) Degree of radioroxicity.
(2) Availability and suitability of stable isotopes
of the same element to serve as diluents.
(3) Length of half life.

Accordingly, wastes from three groups of radioiso-
ropes were suggested for return to the Atomic Energy

Commission. The first group has high radiotoxicity and
is listed as very dangerous in Handbook No. 42 (8)
The second group includes only the radioisotopes of
elements whose stable isotopes are not available in the
laboratory or do not exist in nature in quantities which
would permit sufficient isotopic dilution. The third
group contains the radioisotopes having half life of
over 100 days.

This report suggests that 100 microcuries is the
minimum quantity of waste that will be accepted for
one shipment. The maximum quantities shipped will
be governed by the Interstate Commerce Commission
regulations. To transfer waste materials to the Atomic
Energy Commission, the applicant should request as-
sistance in the disposal of material at the time of the
formal application for the isotopes.

Sea disposal of solid wastes is an important and
satisfactory method. However, a number of factors
must be taken into consideration. These include inter-
national clearances, avoidance of shipping lanes,
oceanography, including currents, depth, animal and
plant life, and proximity to land masses. The solubility
and dispersibility of the wastes must also be considered.
Preference is naturally for encasement of the material
in concrete and disposal in canyons or deeps of the sea.
The question of disposal into inland lakes, such as
the Great Lakes, naturally arises. Because of the fact
that these are international boundary waters and are the
source of drinking water for all cities on their shores,
disposal of long life materials is not recommended.
Discharge of the quantities of 1131 and P32 with sewage
in the manner to be prescribed by the National Bureau
of Standards Handbook may be permitted in the Great
Lakes. Certainly no mass dumping of radioactive wastes
should be permitted therein.

Before concluding, the subject of decontamination
must be mentioned briefly. Decontamination is a broad
subject in itself and has been discussed by Hoffman (9).
Decontamination in the case of radioactive materials is
the process of removing the activity to a safe level.
This may be done by allowing the material (1) to decay
to a safe level, (2) to cover or shield the material to
reduce intensities, and (3) to remove the contaminants
by physical or chemical means. The removal of con-
tamination may be by a non-destructive washing and
scrubbing with effective detergents or solvents, or a
destructive removal of the surface.


(1) U.S. Department of Defense and U.S. Atomic Energy
Commission. "The Effects of Atomic Weapons."
September 1950. U. S. Government Printing Office,
Washington, D. C.

(2) McCullough, G. E.. "Concentration of Radioactive
Liquid Wastes by Evaporation." Industrial and
Engineering Chemistry. In Press (1951).

(3) Browder, F. N., "Liquid Waste Disposal at Oak
Ridge National Laboratory.' Chemical Technology
Division,Oak Ridge National Laboratory, Oak Ridge,
Tennessee. Industrial and Engineering Chemistry.
In Press (1951).

(4) Christenson, C.W.. EtUnger, M.B.. Robeck. G.G.,
Hermann, E.R., Kohr, K.C., and Newell, J.F.. "The
Removal of Pluronium from Laboratory Wastes."
Industrial and Engineering Chemistry. In Press (1951).

(5) Newell, J.F., Christenson, C.W.. Krieger, H.L.,

Moeller, D.W., Mathews, E.R., and Ruchhoft. C.C.,
"Laboratory Studies on the Removal of Plutonium
from Laundry Wastes." Industrial and Engineering
Chemistry. In Press (1951).

(6) Ayers, J.A., "Radioactive Waste Disposal." Indus-
trial and Engineering Chemistry. In Press (1951).

(7) Woodruff, N.H., and Morgan, G.W.. C"onsiderations
for the Return of Radioactive sotopes to Commission
Facilities for Disposal." Mimeographed Report,
U.S. Atomic Energy Commission, Isotopes Division,
Oak Ridge, Tennessee (1950).

(8) "Safe Handling of Radioactive Isotopes," Handbook
42, U. S. Department of Commerce, National Bureau
of Standards, Washington, D. C.

(9) loffman. E.J.. "Radioactive Decontamination Prob-
lems." Radiological Defense, Vol. 3, Armed Forces
Special Weapons Project.



Edwin G. Williams, Chief

Radiological Health Branch
Division of Engineering Resources, U.S.P.H.S.
Washington, D. C.

The development of atomic energy is unique in
public health experience. Perhaps never before in the
history of the profession has there been a prolonged
"pilot-plant-type" study of hazards related to an indus-
try before its birth. During the half century prior to the
creation of the Manhattan District the numbers of people
potentially exposed to radiation were so small and so
highly skilled that there was little reason for the aver-
age public health worker to concern himself with radio-

Even the radium poisoning disasters of the 1920's
in the luminous dial painting industry caused only a
ripple on this placid sea of widespread iguuranie.
Yet when scientists, statesmen and militarists joined
hands in the tremendous program for harnessing nuclear
energy a remarkably effective health protection program
proved possible. Despite widespread potential exposure
to unheralded amounts of radiation, our more than 50
years of experience in use of penetrating rays provided
a fund of knowledge sufficient to prevent all but two
radiation deaths and less than a score of known radia-
tion injuries over the first seven years of the atomic
energy program. Compare this record of application of
health procedures in an activity employing hundreds of
thousands of people with that of any other industry
involving specific hazards!

But before allowing yourselves to be lulled into
a state of complacency by the mere fact of the splendid
health achievement of this new industry let me point
out its cost in manpower and scientific skill. For ex-
ample, some 2� percent of the total manpower at Han-
ford is needed for the close control of intrinsically
dangerous radiation conditions and in this number are
to be found some of our most capable scientists.

As a result of the fact that man has deliberately
increased the available amount of high energy radia-
tion in the world, public health authorities have found
themselves with the moral responsibility of helping
people live with radiation without compromising their
health. The term "Radiological Health" has crept
increasingly into the vocabulary of health workers.

It was coined to designate the public health aspects of
ionizing radiations, and, in addition to the prevention
of undue exposure, embraces the application of knowl-
edge derived from radiation research which may be of
value in the improvement of health standards. One of the
best known examples of this is the mass X-ray survey
method for detection of early chest pathology, a pro-
cedure which may lead to the eventual control or eradi-
cation of tuberculosis as a public health problem.

A partial list of applications of ionizing radiations
which have public health implications includes:

1. Clinical Radiology
2. Industrial
3. Research
4. Military

Taking these uses as a composite, it is obvious that
the scope of radiological health includes interests in
all fields of public health endeavor. On the assumption
that your interests and-responsibilities relating to mili-
tary uses will be covered by civil defense authorities
these- aspects will not be dealt with in this discussion.

Radiological health activities do not imply a re-
striction of proper uses of radiation, but are intended
to provide that radiation be used in a manner that will
assure the safety of all persons concerned. From the
environmental health viewpoint one of the most com-
Dlex-and important considerations is that to be given to
the treatment and disposition of wastes containing
radioactive substances. This matter requires an under-
standing of the method of handling the substance in the
laboratory, the hospital or the industrial plant which
is the source of the waste. Up to now environmental
conramination has been held to a safe minimum. There
is still time to ensure that radioactive waste materials
are not spread unacceptably in our waters, land or
atmosphere. You have had recalled to you the research
and development efforts under way in this field. The
ultimate and widespread application of the fruits of
this work will require the enlightened cooperation and
guidance of the public health worker in order that

acceptable radiological health standards may be main- arduous conditions must often be arbitrary. It follows


Practically all institutions - educational, indus-
trial or other - using artificially produced radioactive
substances, whether obtained from the Atomic Energy
Commission or not, have formed radiation protection
committees. This practice should be extended to all
users of ionizing radiations. In each such committee
there should be some one individual (preferably having
no primary interest in the application of the radiation)
responsible for the safe handling of the machine or
substance and the proper disposition of waste radio-
active materials.

Scientists themselves working with high energy
radiations are not logical candidates to establish per-
missible dose figures nor to exercise control, since
they are apt to ignore personnel hazards in their inter-
est to achieve experimental results. This was demon-
strated time and again in early experiences with radia-
tion injury among radiologists and other radiation work-
ers and was recognized in the organization of the Man-
hattan District. It is the responsibility of the public
health authority to work with these groups - to urge
continued consideration of control procedures. He can
learn much in this way and at the same time give the
scientist, or industrialist an opportunity to understand
the philosophies, interests and duties of the health

If we accept the statement, and I think we may,
that the immediate effects in tissue of all ionizing ra-
diation are harmful, the only tenable philosophy is
"Avoid All Avoidable Ionizing Radiation." Any amount
of radiation can be worked with safely if proper pre-
cautions are taken. No amount of radiation can be
worked with safely if proper precautions are not taken.
Maximum permissible doses are not licenses but are
ceilings. They must be reasonable or they cannot be
enforced. In light of our present knowledge we think
the maximum permissible doses now in effect are rea-

It has been amply shown in many places -govern-
mental and non-governmental - that it is feasible to
keep actual exposures down to a small fraction of the
maximum permissible level. And since our goal is to
hold radiation exposure as close tonatural background
as possible, the standards should not have to be en-
forced on the basis of measurable excesses or demon-
strable harm but rather on principle.

Differentiation between hazardous and non-haz

that if we must err the error should be on the side of
safety. Our knowledge about the public health aspects
of high energy radiation is developing so rapidly that
detailed laws passed at this time might prove inoper-
able or soon seem foolishly naive. It would seem wiser
to write necessary legislation in terms of responsibili-
ties and powers and to rely on expert technical advice,
statements of guiding principles and readily changeable
codes for detailed operations.

In planning a radiological health program a few
facts must be constantly borne in mind:

1. Man will continue to develop atomic energy.
2. Generally speaking, the public has not been
exposed to radiation hazard.
3. We cannot afford the luxury of widespread con-
tamination or radiation injury as a stimulus to
bestir ourselves to activity.
4. sufficient knowledge is at hand to allow us
to develop a radiological health program more
adequate for safe living than was true in the
beginning of many if not most other public
health endeavours.

What then is the specific challenge to each health
department? No standard pattern can be applied. Some
communities will be primarily concerned with the pub-
lic health aspects of medical and dental uses of radia-
tion, some with radioactive wastes from large labora-
tories or plants, some with the industrial environment
of the worker.

In addition to these differences of primary or ini-
tial interest there are organizational differences from
State to Stare and in some States certain matters per-
taining to the health of specific segments of the popu-
lation under certain circumstances is not the legal
responsibility of the health department. At first the
radiological health activity will not be large and most
probably will be placed in the organizational or pro-
fessional category showing the keenest interest or hav-
ing what at the moment seems to be the primary re-
sponsibility. Great care must be exercised to insure
chat this specific assignment carries with it no im-
plication that other parts of the health department or
other departments dealing with health matters are with-
our radiological health problems or are relieved of
responsibilities concerning them. Sooner or later thought
will have to be given to the question as to whether
it is better to have each category carry its own radio-
logical health program or to have the activity as an
entity operating an over-all program and rendering serv-

ices in the other specific categories. There are good
arguments for either decision and in many locations a
combination of the systems will be advantageous. It is
important however that these matters be given thorough
consideration and that there be a constant readiness at
the directing level to make readjustments as changing
circumstances may dictate.

Protective measures, monitoring methods and in-
strumentation will vary with the installation or proce-
dure under consideration. Each unit dealing with radia-
tion must assume responsibility for the protection of
its staff and of all other people who may be or may be-
come exposed as a result of the activities of the unit.
It is the responsibility of the public health worker to
provide advice and guidance in these matters and to
assure himself and the public that good practices are
constantly in force.

A community-wide program designed to acquaint
the public with facts relating to the health aspecLt of
radiation so as to allow the development of a true per-
spective and a respect for, rather than a fear of, ra-
diation is certainly, in part at least, the responsibility
of the health department.

Recommended immediate steps:
1. Each health officer who has not done so should
acquaint himself with radiological health at
least on a conceptual basis.
2. Each health officer should provide himself with
assistants with some degree of technical pro-
ficiency in radiological health - either by hir-
ing new employees or training present ones.
3. Encourage industry, the larger laboratories,
hospitals, etc., to employ specially trained peo--
pie for health physics or radiological health
work. Such people are currently being trained
by several universities and by the A.E.C.
4. Start with a modest program such as monitoring
of X-ray and radium operations rather than low.
level counting or attempting to measure natural
5. Develop programs around specific needs.

There has evolved a serious lack of perspective
with regard to radiation hazards and with regard to the
amount of knowledge available concerning radiobiology.
The first is probably due to the dramatic way in which
we were introduced to the fact that radiation accompanies
our present method of transforming mass into energy.
The second is due to the difficulty which the scientist
experiences in stepping from the laboratory to the pub-
lic platform. If you ask a pharmacologist who is spe-

cializing in the field of anesthesia how ether puts you
to sleep he will probably start out by saying he does
not know, and then proceed to confuse you with a few
facts, some theories, many gaps in our knowledge and
plans for his next ten years of research which he very
hopefully states will fill in a few of the gaps. If you
ask a practicing anethetist how ether puts you to sleep
he will probably tell you that you simply breathe deeply
and after the first few breaths you will nor mind the
odor; you then go to sleep and will feel no pain during
the operation: and after the operation, you will wake
up with a good-looking nurse holding your hand. Except
for the absence of the nurse, a parallel situation exists
in the field of atomic energy. We were catapulted into
the atomic era with only a few nuclear scientists and
almost no practitioners of applied radiobiology to under-
take the Herculean task of translating theoretical and
applied physics into understandable "English." I am
sure they too agree that they were unprepared to cope
with this unforeseen assignment. Yet, after this week's
experience I am sure you cannot help but agree they have
mastered the situation with almost unbelievable success.

With a firm conviction that anything which affects
or is likely to affect the health of people either directly
or indirectly is of public health concern, you have
assumed or demanded authority in this field. In so doing
you are fully justified. With this authority, however,
goes a responsibility for which few of us are prepared.
I should like to discuss with you for a few moments
this question of preparation. The university groups with
whom we have discussed this matter have taken the
attitude that such institutions are in a position (1) to
sponsor and conduct short orientation courses, inserv-
ice training courses, symposia, institutes, etc.; (2) to
establish special departments such as has been done
at California, Chicago and elsewhere; (3) to offer spe-
cial courses in the field; and (4) to integrate nuclear
science and radiobiology into their more general cur-
ricula. But that it is not a prime responsibility of uni-
versities to conduct trade school rype of training. With
this philosophy I am in full accord. It leaves, however,
a rather serious temporary need of providing varying de-
grees of technical competence in radiological health
now. A number of attempts have been made to fill this
gap - some being compromises which closely approach
educationn" rather than "training." A partial listing
of these efforts includes:
(1) The Armed Forces Courses offered intheir own es-
tablishments and in conjunction with civilian in-
stitutions extending from one week to three years.
(2) The Atomic Energy Commission one-year fellow-
ships in health physics at Oak Ridge and Ro-

(3) The Oak Ridge Institute of Nuclear Studies one- I would suggest that as a preliminary to drafting

month courses in isotope handling.
(4) The Atomic Energy Commission sponsored one-
year fellowship in the radiological aspects of
industrial medicine.
(5) The Berkeley Division of Tracerlab short course
in the techniques of handling radioactive sub-
(6) The Public Health Service radiological health
training activity located at its Environmental
Health Center in Cincinnati, Ohio.

It is the purpose of this latter activity to explore
with public health workers of all categories and oper-
ational levels the specific needs of the health worker
and to provide training to meet the more immediate and
and urgent of these needs.

legislative suggestions, planning programs or preparing
budgets in this field, public health people seriously
consider taking advantage of these various opportunities
in the radiological health field. I would further suggest
that consideration be given to the employment of some
of the graduates from the longer training courses.

What I have said here may be summarized in three
sentences. The fields of atomic energy and nuclear
physics will continue to modify and enrich our lives.
Advances in these fields are accompanied by serious
threats to our personal health and comfort and to the
healthfulness of our environment. It is unacceptable
that these threats will not be met and controlled by the
combined efforts of science, industry and public health.



Roy J. Morton, Leader

Waste Disposal Research
Oak Ridge National Laboratory

It is well recognizedthat the safe handling and dis-
posal of radioactive wastes constitute a major problem.
Continued improvement in methods for the control of
wastes is essential for the development of nuclear
energy to its fullest extent.

Many of the fundamental considerations in radio-
active waste disposal have been covered by previous
lectures. These have included discussions of the na-
ture of radioisotopes and radiation hazards, methods
of measurement of radioactivity, and maximum permis-
sible exposures to radiation for long term and for brief
emergency periods. An extensive review of the sources
of radioactive wasre and of various methods for treat-
ment and disposal was presented by C. C. Ruchhofr.
His discussion summarized the problems and present
practices with respect to gaseous, liquid, and solid
radioactive wastes.

The potential hazards from radioactive wastes art
concerned almost entirely with internal exposures due
to inhalation or ingestion of radioisotopes from con-
taminated air, water or food. These and other modes of
entry, retention and localization in the body, elimination
from the body, and the principles of radiation protection
have been explained in detail.

The present discussion, therefore, can be rather
specific. It will be based mainly upon the experience
and the results of studies at the Oak Ridge National
Laboratory. Most of the discussion will be concerned
with liquid wastes and the problems of water protection
and water decontamination.

Much progress has been made in the techniques
of radioactive waste disposal but much more information
is needed. The program at the Oak Ridge Narienal
Laboratory emphasizes research as well as control.
Some basic considerations and the scope of information
needed may be summarized in two groups as follows:

I. Fundamental research to obtain detailed knowledge
of the behavior of radioactive materials in air, water,
soil, plants, animals, and man.

A. Meteorological studies
8. Geological studies
C. Research on the gross behavior of radioactive
materials in drainage systems, soil and plant
life, and underground water - under the condi-
tions of discharge from ORNL and from other
atomic energy installations. Studies of water
purification and sewage treatment plants are
D. Specific behavior of individual elements such as
plutonium, polonium, uranium, and numerous beta
and gamma emitters.
E. Effects of radioactive materials on fish and
animal life.

II. Development of methods of preventing radioactive
materials from producing damage to man, animals or

A. Control at the source. At ORNL it is understood
that the technical problems of salvage or hold-
up within operations areas will be attacked
principally by the Chemical Technology Division.
B. Removal of radioactive materials from water
C. Removal of radioactive materials from air by
means of masks, filters and other methods.
D. Decontamination of persons, clothing, equip-
ment and buildings.
E. Methods of survey and detection of radioactive
materials under conditions of warfare.

The ORNL Health Physics research program is
concerned with the fundamental questions in Group I
as a means of specific approach to the developmental
problems outlined in Group II. This outline is broad and
general and a large number of specific study projects
are in progress or planned by the Health Physics and
other divisions at ORNL, in the research programs at
other atomic energy sites and through contract projects
sponsored by the AEC in universities and other research

At the Oak Ridge National Laboratory there are

two Health Physics groups engaged specifically in work The amounts of radioactivity that may be discharged

on radioactive waste disposal: the Area Monitoring
Group which is responsible for routine measurements
and control, and the Radioactive Waste Disposal Re-
search and Development Section.

In the Laboratory area liquid wastes come from
radioisotope production operations, pilot plants, Labora-
tories and a number of other sources. A description
of the types of liquid wastes produced at the Laboratory
and the facilities for their processing and disposal
has been presented by Browder (2). Known radioactive
liquid wastes are collected in a separate system for
treatment and storage. The completeness of separation
and hold-up in the Laboratory area has been constantly
improved, particularly during the past two years.

The discharge of liquid wastes to White Oak Creek
and Lake was mentioned in an earlier lecture. The
waste discharged for disposal includes: (1) radioactive
liquid wastes that are released after treatment and
storage so as to reduce the concentration below pre-
scribed levels; (2) the larger volume of process wastes
containing small amounts of radioactive materials from
miscellaneous sources; and (3) uncontaminated wastes
such as cooling water. Sanitary sewage is collected and
disposed of in a separate system which includes a
sewage treatment plant with final discharge to White
Oak Creek.

The elements of the system for the disposal of
radioactive liquid wastes are: a large settling basin,
White Oak Creek and marshes, White Oak Lake impound-
ed by White Oak Dam, White Oak Embayment below the
dam, and the Clinch River.

The waste flows through the settling basin with a
detention period of about two days, and then into White
Oak Creek. The effluent from the settling basin is dis-
charged through a weir box with constant measurement
and recording of the flow. A Trebler sampler, which
collects a continuous sample proportional to the flow,
provides periodic composite samples for analyses.

Diluted by creek water, the wastes flow through a
marshy area and are retained for varying periods in
White Oak Lake. Considerable portions of the radio-
active materials are removed and deposited in the creek
and marshy areas and in the lake. Discharges from the
lake pass through a controlled gate and spillway at
White Oak Dam, into the embayment, and thence to the
Clinch River. The level of the lake can be controlled
and the race of discharge increased or decreased at the
gate and spillway.

into White Oak Creek and from White Oak Lake are
established by the Health Physics Division. Discharges
from the settling basin are checked several times daily
through sampling and analysis by both the Operations
Division and the Health Physics Division. The Health
Physics Division makes daily checks of the discharges
from White Oak Lake and operates the gate for control
of the outflow from the lake. The concentration of radio-
activity after dilution in the Clinch River is less than
the accepted maximum permissible value for water con-
tamination; namely, an average of not more than 10i7
pc/cc of total alpha and beta-gamma emitters.

The program of waste disposal studies in the Health
Physics Division of the Oak Ridge National Laboratory
was organized in 1948 and has been active since that
time. A basic sanitary engineering approach was adopted
and a broad and cooperative research and development
program was developed. The Public Health Service and
the Tennessee Valley Authority have cooperated with
AEC and the Laboratory by providing qualified sanitary
engineers and research scientists of various special-
ties and experience. In addition to the operation of an
integrated research program with the above agencies,
the Health Physics Division both directly and in a
sponsoring capacity takes part in related studies includ-
ing military, geological, meteorological, and biological
investigative projects.

The general purpose of the program is to conduct
field surveys and experimental investigations which
will better answer the problems of radioactive waste
disposal and aid in the development of control measures
at Oak Ridge or elsewhere. A primary objective is the
development of procedures that will help to appraise
andminimize anyhazards or problems that might develop
in connection with sewage and waste disposal works
or water supply systems. Both laboratory and pilot
plant studies are included in the program.

To provide adequate physical facilities for an ex-
panded program, an especially designed laboratory and
pilot plant building is under construction and will be-
come available about November, 1951. Also the Public
Health Service is increasing its participation in the

Details of the studies and activities included in
this program will not be given here. The program and
related problems have been discussed in several arti-
cles including a summary by Placak and Morton in the
Journal of the American Water Works Association (3)
In experimental laboratory and pilot plant studies, much

work has been done and is continuing. Data are being
obtained or the efficacy of conventional and modified
water treatment procedures in the removal of radioiso-
ropes-singly or in mixtures. Such data are of interest
to those who are responsible for the protection and if
necessary the decontamination of either civilian or mili-
tary water supplies.

The program includes studies of radioactive mate-
rials in sewage and industrial waste treatment process-
es. Data on these processes are of increasing importance
asatomic energy operations and the use of radioisotopes
increase and become more widespread. A comprehensive
ecological study of White Oak Creek and Lake is being
carried on cooperatively with the Tennessee Valley
Authority to determine whether the contamination in
this drainage system over a period of about seven years
has caused significant changes in the plant and animal
life; and also to obtain additional information regard-
ing the behavior of radioisotopes in surface waters.
Difficult problems are encountered and much develop-
mental work is necessary in connection with instrumen-
ration and laboratory techniques for the measurement
of radioactivity in various materials such as water,
sewage, liquid wastes and samples from experimental

The protection of drinking water supplies against
the possibility of contamination with radioactive mate-
rials is a problem that justifies serious consideration.
As pointed out by previous speakers the probability of
the occurrence of dangerous concentrations of radioiso-
topes in water supplies is low compared with other ra-
diation hazards. Under peacetime conditions deliberate
releases of radioactive materials are kept to extremely
low levels and multiple safeguards are maintained
against the possibility of accidental discharges. In the
event of atomic warfare it is considered unlikely that
heavy radioactive contamination of a water supply source
will occur unless the water is obtained from a surface
supply and is affected by an underwater or a nearby
ground burst of an atomic bomb. Nevertheless, since
there are some possibilities that radioactive contamina-
cion of water supplies may occur, there is great interest
in the development and evaluation of methods for the
removal of radioactive materials from water.

The removal of radioactive contaminants fIlm water
is similar in principle to well-known water treatment
processes such as iron and manganese removal or water
softening. The problem is complicated, however, by
numerous factors. These include: (11 the large number
of radioactive isotopes with differing chemical charac-
teristics; (21 the variety of raw water conditions and

of water treatment plants; (3) the minute quantities (in
terms of mass) that must be considered; (4) the uncer-
tainty of the concentrations of contaminants that may
be expected and of the degree of removal that may be
necessary; and (5) the uncertainties of maximum permis-
sible levels for various types and conditions of con-
tamination. Present knowledge of the performance of
water treatment processes in the removal of turbidity,
bacteria, and the common dissolved minerals does not
provide a sound basis for predicting the efficiency of
such processes in the removal of radioisotopes from
water. The efficacy of conventional or modified water
treatment procedures in the removal of radioactive mate-
rials must be determined by experiment or in practice
under the particular conditions for which the data are
to be applied.

At the Oak Ridge National Laboratory during the
past two years workers of the Health Physics Division
have conducted many laboratory and pilot plant experi-
ments in studies of the well-known water treatment pro-
cesses and in investigations of other processes that
might prove useful in water decontamination. Although
still far from adequate these studies are sufficient to
indicate the approximate ranges of removals that maybe
expected andro afford factual data on a number of basic
questions for which answers are urgently needed.

Selected data are presented below with brief dis-
cussions of the conditions and results of the experiments
from which they were obtained. The methods of experi-
mental treatment, although not described in detail, cor-
respond to normal water purification practice. For ex-
ample, the test material used in most cases was raw or
treated Clinch River water modified by the addition of
radioisotopes and in some cases of clay to increase the
turbidity. In flocculation experiments the optimum condi-
tions of coagulation for the particular water were deter-
mined by preliminary tests.

Within the Limits of the data available and under the
conditions of the experiments the following statements
appear to be valid.

I. The efficiency of removal in a normal range of pH
and of chemical dosage is determined by the radio-
elements involved.

Data to illustrate this statement are given in Table
I which shows the approximate removals of single radio-
elements chat maybe expected from alum flocculation fol-
lowed by filtration or centrifuging for clarification.

A mixture of materials may actdifferently than single

effect of pH is illustrated in Table III.


Radioisotope % Removed

1131 0 - 10

P32 96 - 98

Ce144 90 - 98

Sr89 10

Zr95 - Nb95 90

Y91 98

Ru106 10

Cs 10

isotopes. In the case of yttrium it was found that the
type of alkalinity influenced the results. When hydrox-
ides were used the removals of yetrium were less than
half as great as those obtained with carbonate alka-
linity. It was found that activated carbon treatment or
small amounts of copper or silver salts specifically
increased the removal of radioiodine.

2. Under the same conditions of treatment alum and
iron coagulants appear to be equally effective in
removing radioactive materials. This is illustrated
in Table II.

Table II

% Removed
Radioisotopes Alum Iron

1131 0 - 10 0 - 10

Y91 94 - 97 95- 98

Ce144 91 - 97 95 - 97

Sr89 6- 18 10- 20

3- An increase in pH will generally increase the effi-
ciency of removal of mixed fission products. The

Table III


PH % Removed by Filtration

2.5 14.6
6.2 63.1
8.6 80.7
10.5 85.1
12.2 88.6

These data were obtained using mixed fission prod-
ucts without flocculation. The increase in removal by
filtration was due solely to increased pH. The values
shown were selected to illustrate a very low range of
pH values, intermediate values that correspond roughly
to alum, iron and softening ranges and finally a very
high value.

Softening procedures operate in a high pH range.
In one series of experiments using a softening procedure
(similar to excess lime treatment) and mixed fission
products in Clinch River water, removals of 90 to 94.5
per cent were obtained.

4. Increased coagulant dosages, with other conditions
the same, give slight increases in the efficiency
of removal of radioactive materials. This is illus-
trated in Table IV.

Table IV


FeCL3 6 11S0

ppm % Removed

10 77.9
20 80,3
30 81.5
40 82.4
70 83.7
120 85.3
200 87.5
270 88.6

Table I

The coagulant used was ferric chloride, the pH was
maintained at 8.5 and mixed fission products were used
as the radioactive test material.

From the observations and tables given above it is
evident that conventional water treatment processes do
not have very high efficiencies in the removal of most
of the radioisotopes or of mixed fission products. For
example, the removal of a typical mixture of fission
products might be in the range of 60-80 per cent in a
normally operated plant employing alum or iron coagu-
lation, and of the order of 90 per cent in softening plants
or under conditions where high pH values prevail. Con-
ditions which should tend to increase the degree of
removal include high pH values, large coagulant dos-
ages, use of activated carbon, high natural or added
turbidity (such as clay), use of a coagulant that will
operate at a high pH (such as iron), and treatment with
specific precipitating chemicals if the contaminant is
known (as the addition of a few ppm of silver salts to
increase the removal of radioiodine).

The essential question is whether the reduction in
radioactivity afforded by the available treatment is
sufficient to meet the maximum permissible concentra-
tion in the finished water. This can be determined only
by making actual measurements of the radioactivity in
representative samples of the water before and after
treatment. If the required removal to make the water
potable is greater than 90 per cent it should not be ex-
pected that this can be accomplished by a conventional
water treatment process with or without easily-made
modifications in the treatment procedures. It is impor-
tant, however, that the efficiencies of such plants should
be known so chat full advantage may be taken of any
margins of safety provided by these processes and also
that undue reliance will not be placed upon them.

Investigations have been made of certain non-con-
ventional methods of water treatment, some of which
will moderately or greatly increase the efficiency of
removal of radioisotopes as compared with conventional
treatment. These may or may not be adaptable as sup-
plements to community water plants. Studies by Lauder-
dale using phosphate compounds as coagulants have
been reported (4. Monobed units of the newer synthetic
anion and cation exchange materials, together with

other adsorbents, were utilized by Lauderdale and Em-
mons as a column device which appears to be suitable
for the emergency treatment of small volumes of water
contaminated with radioactive materials (5).

It is apparent that the control and disposal of radio-
active wastes present difficult problems similar to the
disposal of chemical wastes but complicated by the
peculiar properties and hazards of the radioisotopes
present. The only adequate approach has been and must
continue to be through a comprehensive program of re-
search and practical studies. Progress is being made,
everyone concerned is very conscious of the problems
involved, and a concerted effort is being made to solve


1. Digest of Proceedings, Seminar on the Disposal of
Radioactive Wastes, sponsored by the U. S. Atomic
Energy Commission, January 24-25, 1949, Washington,
D. C. (Mimeographed).

2. Browder, Frank N. Liquid Waste Disposal at Oak
Ridge National Laboratory. Presented at the 118th
National Meeting, Am. Chem. Soc., Chicago, Illinois.
September 3-8, 1950. In press. Ind. Eng. Chem.
(July, 1951).

3. Placak . R. and Roy J. Morton. Research on the
Disposal of Radioactive Wastes. Journal of American
Water Works Association. Vol. 42, No. 2, February,
1950. Pages 135-142.

4. Lauderdale, R. A. The Removal of Radioactive Iso-
copes from Water by a Phosphate Coagulation and
Flocculation Process. Presented at the 118th Na-
tional Meeting, Am. Chem. Soc., Chicago, Illinois,
September 3-8, 1950. In press. Ind. Eng. Chem. (July,

5. Lauderdale, R. A. and A. H. Emmons. A Method for
Decontaminating Small Volumes of Radioactive
Water. J. Am. Water Works Assn., 43: 5, 327 (May,

Part 3: Cial 2Defense



George A. Hardie, Assistant Chief

Medical Branch for industrial Hygiene, AEC
Washington, D. C.

Because of the developments in this air-atomic age,
the United States can no longer be free from the danger
of a sudden devastating attack. Since there can be no
absolute military defense, an effective civil defense
is vital to the future security of the United States.

The ability of this country to successfully defend
itself against repeated enemy attacks might well depend
in the main on the organization and functional effi-
ciency of the civil defense.

In Hiroshima at a little after 8:00 a.m. on August
6, 1945,one atomic bomb exploded destroying 4.7 square
miles of the heart of that city, killing an estimated
70,000 people and injuring 70,000 others. These are
staggering figures, and the fact that not a single enemy
bomb was dropped on the United States during World
War II makes them all the more impressive to us. How-
ever, approximately five months before the first atomic
bomb was dropped, 1,667 tons of TNT and incendiary
bombs were dropped in one raid on Tokyo destroying
15.8 square miles, killing an estimated 83,000 people
and injuring 102,000 others. To me, this shows that
conventional bombing can also be devastating.

Atomic bombs differ from conventional bombs in
several respects:

First, by the amount of energy released. The largest
conventional bombs used during World War II contained
about 5 or 6 tons of TNT as compared with the 20,000-
ton TNT equivalent for a "nominal" atomic bomb, such
as those used at Hiroshina and Nagasaki.

Second, atomic bombs are accompanied by (a)
nuclear radiation, (b) intense heat which will produce
thermal burns, and (c) a brilliant light flash, in addi-
tion to the blast effects.

Third, atomic bombs exploded under certain condi-
tions will leave a radioactive residual.

What can we expect if an atomic bomb is dropped
on an "average" United States city? For purposes of
discussion we will use a city with a population density

of about 13,000 per square mile, which is the average
for our large cities. The atomic bomb used is what we
call a "nominal" bomb: one with an energy release
equivalent to 20,000 tons of TNT. The bomb will be
exploded approximately 2,000 feet above the ground,
the height at which the maximum damage will be pro-

The United States Civil Defense -. Health Services
and Special Weapons Defense booklet (page 14) esti-
mates that under these conditions a surprise daylight
attack during working hours would produce a total of
about 120,000 casualties, killed or injured. What can
be done about this? If adequate warning of an impending
raid is given to the civilian population, and if adequate
instruction to the public has resulted in good discipline,
it may be assumed that over-all daytime casualties
would be reduced by at least 50%. Thus, the total
hypothetical number of 120,000 killed or injured would
be reduced to about 60,000. This reduction by 50% in
the number of people killed and injured simply by get-
ting adequate warning to a public, which knows what
to do and does not get panicky, means that a great
deal can be done to minimize the medical effects of
atomic weapons. This estimate of the reduction in
number of casualties was not based on the assumptions
that we would have special air raid shelters for the
people or that we would have a several hour warning
to evacuate the city.

If our "nominal" atomic bomb is dropped at night
instead of during the daytime there would be only 60,000
casualties, and this would be reduced with adequate
warning to 40,000 casualties.

Of the 120,000 casualties produced by a surprise
atomic bomb attack 40,000 or 1/3 would be killed out-
right or would die during the first day and 20,000 would
die in the following 5 or 6 weeks.

80,000 or 2/3 of the casualties would survive the
first 24 hours. Of these:
48,000 (or 69%) would be suffering from burns.
40,000 (or 50%) would be suffering from mechanical

injury, and
16 000 (or 20%) would be suffering chiefly from
radiation injury. This same ratio of 60% burns, 50%
traumatic, and 20% radiation injuries would probably
apply regordless of the toral number of casualties.
Thb number of injuries adds up over 100% because
some of the survivors will hove sustained more than
one type of injury.

There are two different types of burns produced by
an atomic bomb explosion, flash burns and flame burns.

Flash Burns

The flash burns from an atomic bomb are distinutly
different from those caused by other typesof explosives,
since they are due to thermal radiation rather than to
hot gases, as is the case of shell bursts and gasoline
explosions. Thermal radiation should not be confused
with nuclear radiation. Any object heated to several
thousand degrees Centigrade will give off thermal rays.
One-third of the total energy of an atomic bomb is re-
leased as thermal energy. Both ultraviolet and infrared
radiation will be given off during the three seconds that
follow the explosion but it is believed that the infrared
radiation play the predominant role in producing flash

Thermal radiation travels in straight lines and pro-
duces "profile" burns. These burns are sharp in out-
line and oriented to the point of explosion. Shadow
effects are prominent. An ear, for example, might be
badly burned yet the skin behind the ear be unharmed.
Very high surface temperatures are produced, upwards
of 1,8000C. at 4,000 feet from the explosion, but due
to the short duration (3 seconds) the burns are not

On a clear day, if you were within 2/3 of a mile of
ground zero (the point on the ground immediately below
where the explosion actually occurred) you would sus-
tain severe flash burns to the exposed areas of your
body that are in direct line with the explosion. Moderate
skin burns would occur out to about 2 miles and slight
skin burns out to about 2 1/4 miles.

It has been estimated that 20-30% of the fatal cas-
ualties at Hiroshima and Nagasaki were due to flash
burns. What can be done to minimize the effects of the
thermal energy given off by an atomic bomb? Flash
burns will be largely confined to the exposed parts of
the body. Almost any objecr between you and the ball
of fire will protect you from flash burns. Light colored
clothing offers more protection than dark colored cloth-

ing, by virture of its greater ability to reflect thermal
rays. Loose fitting clothing offers more protection than
tight clothing. Cotton offers better protection than rayon
and nylon. Ideally the outer layer of clothing should
be flame resistant, but you have to be fairly close to
ground zero before thermal radiation penetrates clothing
and very few flash burns will be produced through more
than one thickness of clothing. The severity of an
individual's injury from a burn depends not only on the
degree of the burn but even more upon the proportion
of the body's total skin area that is affected.

Do not forget that you soak up the thermal radiation
over a three-second period of time. If you do not lose
your head, you should be able to fall flat on the ground,
turn your back, cover your face, or duck behind some
object quick enough to reduce the severity of your
burn at least 50%.

Light Blindness

An extremely bright light is produced by the explo-
sion. At a distance of 5.7 miles from the explosion, the
flash of light, lasting 1:10,000 of a second, will be
100 times as brilliant as the sun. If you were looking
in the direction of the flash you would probably have a
temporary blindness lasting a few seconds.

Flome Burns

The other type of burn produced by atomic bombs
is the flame burn; a burn produced hy contact with
burning or hot objects. About 1/2 of the buns at Hiro-
shima and Nagasaki were of this type and there is no
reason to believe that the incidence will be any lower
in the United States unless we have a well organized
and trained civil defense establishment. Our cities
are just about as susceptible to fires as were the two
cities in Japan. A few fires will be started by the ther-
mal radiation but most of the fires will be secondary,
started by such things as electrical short circuits,
broken gas mains, stoves turning over, etc.

In Hiroshima, 70% of the firefighting equipment was
destroyed, 80% of the firefighting personnel were unable
to report to duty, the streets were blocked, and the
water pressure dropped due to broken mains.

Flame burns may be reduced in several ways:
1. By preventing fires through the use of fire re-
sistant construction, firebreaks, and eliminating fire
hazards where possible.
2. By personnel protection measures such as wear-
ing flame resistant outer clothing.

3. By prompt rescue of the injured before they get
4. By controlling fires and preventing their spread,
5. By good medical management of the burn cas-


Fifty per cent of the surviving casualties will be
suffering from mechanical or traumatic injuries. There
are two types of air-blast effects on people: (1) Those
caused directly by the pressure wave of the blast, and
(2) Those caused indirectly by collapse of buildings,
flying wreckage, and by people being thrown against
solid objects.

Direct Blast Injuries

The blast or shock wave itself is capable of pro-
ducing injury to the ear drums, lungs, intestinal tract,
etc. at over pressures of 35 pounds per square inch
(psi) and above. Since an overpressure of this magnitude
is maintained only for a distance of about 1,000 feet
from ground zero, and most people in this area would
be killed by other types of injuries, there will be few
survivors suffering from direct blast injuries. Only
2-15 psi overpressure is required to damage most man-
made structures.

Indirect Blast Injuries

Indirect or secondary blast injuries are an important
cause of death in an atomic bomb explosion. Since
practically all brick and light masonry buildings with
weight-bearing walls in the blast area will be wrecked,
wooden buildings flattened, and the doors and other
partitions of blast-resistant steel-reinforced concrete
buildings blown out, people in or near these buildings
will he killed or injured by collapse of structures and
by the missile effects of debris. Among such injuries
will be crushing, fracturing of bones, and lacerations
and bruises of various types. Mechanical injuries re-
sulting from atomic bomb damage vary in no way from
those that would be produced by other explosives or

Flying glass contributes a large share of super-
ficial injuries to be expected in any powerful explosion.

The blast damage to be expected from a "nominal"
atomic bomb is:

(a) Up to 0.5 mile. Virtually complete destruction. The
blast pressure would demolish all structures not of re-
inforced concrete or steel construction. Even buildings
of this type would suffer 70% destruction. Persons not
sufficiently protected by shelter able to stand the blast
would undoubtedly be killed by falling buildings or
flying wreckage.
(b) 0.5 to 1 mile. Severe damage to the entire area.
Residential buildings would be almost destroyed. Only
fire and shock-resistant buildings would be immune to
any appreciable extent.
(c) 1 to 1.5 miles. Moderate damage to area. Blast dam-
age would still be extensive to residential structures.
There would be heavy damage to window frames and
(d) 1.5 to 2 miles. Partial damage to structures in the
area. There would be some blast damage to the majority
of homes. Lacerations from flyingglass will be produced
even at this distance.
(e) 2.25 miles. Complete window damage.
(f) 8 miles. Limit of light damage.

It will take approximately three seconds for the
shock wave to travel one mile from ground zero and 10
seconds to travel two miles.

What can you do to protect yourself from the blast?
Of course, if you have warning you will go to the safest
place available. The basement and central portions of
the lower floors of most multistoried buildings will of-
fer good protection.

If the brilliant flash of light is your first warning
of an atomic bomb explosion and you are outside, prob-
ably the best thing that you can do is fall flat on your
face where you are, bury your face in your arms to pre-
vent burns and help protect against flying glass, and
stay there for 12-15 seconds until it is over. If you
are driving an automobile at the time of the flash, stop
and slump to the floor of the car. If you are inside a
building when you see the flash, lie down along an in-
side wall or duck under a bed, desk, or table, but do
not get opposite windows as you are almost sure to be
splattered with glass.


Ofthe three types of injuries resulting from an atomic
bomb explosion, radiation injury is certainly the least
important. It is estimated that 20% of the surviving
casualties will be suffering from radiation injury.

I think many people fear the irradiation effects of an
atomic bomb because nuclear radiation is mysterious;

it is difficult to understand. It is easy to appreciate
why they fear something that they cannot see, hear,
smell, taste, or feel.

There are four types of nuclear radiation connected
with an atomic bomb explosion - alpha particles, beta
particles, gamma rays and neutrons. The lethal range
of neutrons extends only about 1,400 feet from ground
zero and the neutron intensity falls off very rapidly
with increasing distance from the burst. The gamma
rays are, for all practical purposes, the only ones of
importance as casualty producers from an air burst.
These gamma rays are released in about 60 seconds
from the time of the explosion. Fifty percent are re-
leased by the end of one second, 80% by the end of 10
seconds, and 99 plus % by the end of one minute.

With a high air burst, that is an air burst high enough
so that the ball of fire does not touch the ground, it is
perfectly safe as far as radiation is concerned for you
to go to ground zero after the bomb has exploded. Resi-
dual radiation is not a problem with a high air burst
regardless of its size.

Instead of defining a roentgen, the unit of measure
for radiation, I will give you some idea of what different
amounts of nuclear radiation will do to humans. It is
estimated that if you receive 600r of whole body radia-
tion, your chances are about 1 out of 20 in surviving.
With 400r you atand a 50-50 chance of surviving. We
refer to 400r as the mid-lethal dose. With 200r you stand
1 chance out of 20 of not surviving, and with 10Or you
mightbe bothered by some nausea or vomiting, but there
is no danger of your dying from radiation alone.

As the size of the atomic bomb is increased, the
nuclear radiation becomes less and less important as a
casualty producer. For example, with a "nominal" or
IX atomic bomb a mid-lethal dose of 400r will be sus-
tained at a distance 3700 feet (about 0.7 mile) from
ground zero. With a 2X, or double size, bomb the mid-
lethal dosage will extend to 4000 feet, and with an
8X bomb to 4200 feet from ground zero. At the same
rime, however, the limit of severe blast damage of about
1.2 miles for a IX bomb will be extended to about 2.3
miles for an 8X bomb, and the limit at which moderate
skin burns will be produced on a clear day of about 2
miles for a IX bomb will be extended to about 4 miles
for an 8X bomb. Thus, while the radius of mid-lethal
radiation dosage is extended about 12% from ground
zero, the severe blast damage and moderate skin burn
distances are extended about 100%, when going from a
IX to an SX bomb.

Persons receiving certainly fatal doses of nuclear
radiation, doses well above the mid-lethal dose of 400r,
will soon be actively sick with nausea, vomiting, and
prostration and will die in the first few days after ex-
posure. Those receiving in the neighborhood of 400r
units may have transient nausea with or without vomit-
ing the first day and then be relatively symptom free for
a week or ten days. After this latent period they will
begin to exhibit classical symptoms of acute radiation
sickness: fever, prostration, and signs of local ulcers,
especially in the mouth and along the gasoro-intestioal
tract, with or without frank hemorrhage. The symptoms
are largely the result of the great decrease in the white
blood cells which combat infection and the decrease
in blood platelets necessary for normal blood clotting,
plus a failure of normal immunity. Treatment is the
same as in similar situations encountered in the peace-
time practice of medicine. Antibiotics - aureomycin,
penicillin and the like - are useful in controlling in-
fection. Whole blood transfusions are useful in correct-
ing the anemia from blood loss and later to combat the
anemia resulting from the decreased red blood cell for-

Many of the radiation casualties that survive will
not need any treatment because their radiation injury
will have been so mild. Others will have receivedsupra-
lethal doses for which little can be done medically, but
a large group of them will have received doses of radia-
tion for which supportive treatment and reasonably good
medical care will be life saving. At the same time hope
is present that in the not too distant future more speci-
fic and powerful means of combating radiation effects
will be available.

Protection from Gomma Roys

What can you do to minimize the effects of these
gamma rays? How can you protect yourself? Shielding
between you and the bomb is the only certain means of
protection known today. We have no magic pills that
you can take that will protect you. As a very rough
approximation, it may be stated that the ability of a
material to absorb or stop gamma rays is proportional
to its density. The radiation dosage if you were unpro-
rected at ground zero would be 10,000r. To reduce this
dose to a non-disabling dose of 100r would require
about 30 inches of concrete or about 45 inches of tight-
ly packed soil. Underground shelters could thus provide
adequate protection against radiation.

If the flashof light is your first warning of an atomic
bomb attack there is nor very much that you can do.

However, do not forget that this gamma radiation is
given off during 60 seconds and that you have one sec-
ond to reduce your dosage by 50% and 10 seconds to
reduce the dosage by 20% if you can get several feet
of concrete between you and the blast.

If you have sufficient warning to seek shelter, the
central portion of the lower floors and especially the
basements of many of the multistoried buildings will
provide you with sufficient shielding material to reduce
the gamma radiation to a non-disabling level. If you are
at home, the basement is the best place to go. You
would get the maximum shielding from the earth by
stretching out alongside the wall toward the critical
target area, which will usually be the central portion
of the city. To help protect against traumatic injury it
would be desirable to get near one of the supporting

In conclusion, I would like to say that even though
atomic bombs can produce a great deal of damage, much

can be done to reduce the number of casualties and the
severity of their injuries. Good medical care will save
many of the casualties who would otherwise die. The
worst possible thing that the people in this country
could do is to adopt a defeatist attitude.

Editor's Note:

For those interested in
organization, refer to:
1. United States Divil
2. United Stated Civil
and Special Weapons

civil defense planning and

Defense, NSRB Doc. 128
Defense, Health Services
Defense, FCDA Pub. AG-

Both are available from Supt. of Documents, Washing-
con, D.C.



Francis E. Ray, Director

Cancer Research Laboratory
University of Florida

When a nuclear chain reaction was demonstrated in
the West Stands trial at Chicago in December, 1942, it
let loose on the world, potentially at any rate, a whole
host of radioactive materials that were hitherto either
unknown or known only in very minute quantities.

Portable monitoring devices for detecting and sur-
veying radioactivity are of two kinds - the Geiger
counter and the ionization chamber. The Geiger counter
consists of a closed tube filled with a mixed gas under
reduced pressure. The ionization chamber is open to the
air. Both contain electrodes and have an amplifier which
may register on a dial or a loud speaker system. The
Geiger counter is more sensitive to radiation but the
ionization chamber is more rugged. The latter are made
in various sizes ranging from a pocket size about as
big as a fountain pen to somewhat larger than a shoe

Theradioactivity willbe found mostly on the surface
except where a coarse or porous material is involved.
In most cases it will not be worth while to try to de-
contaminate such substances as clothing, bedding, and
other course materials. Clothing will protect the body
from a great deal of radioactivity but it will be heavily
contaminated. It should be removed and either buried
or burned. This should be done in such a way as to pre-
vent the spread of the contamination.

Since the substances like beta particles act only
when in actual contact with the skin, the skin should
be thoroughly cleansed. This can be quite well done
by vigorous rubbing with soap and water. The newer
detergents such as Tide or Vel have been found parti-
cularly effective in removing skin contaminations. Care
should be taken not to scrub the body so vigorously as
to cause abrasions. Isotonic saline slightly acid (pH 2)
or a depilatory such as a mixture of barium sulfide and
starch will lead to the removal of material held more
tenaciously by the skin and also by the hair. A dilute
solution of sodium carbonate is also useful in chis way.

Except for porous materials and a few cases where
neutrons have penetrated and caused a deep-seated

radioactivity, most of the radiation will be on the sur-
face. Probably the first thing to do in decontamination
is to wash everything down with streams of water. Here
the personnel should be protected with rubber boots,
rubber coats and hats, gloves, and because radioactive
spray may fill the air, some sort of respirator should be
furnished. There is no chemical that will destroy radio-
activity. All that any chemical can do is to make the
material more soluble and more easily removed from
the surface.

Afterthe easilyremoved materials have been flushed
away with water the next step should be the use of
soap or detergents as has been mentioned before for
treatment of the skin. These will aid in removing radio-
activity from dirty or greasy surfaces.Small articles,
if highly radioactive, would best be buried unless their
value were sufficient to make it worth while to put them
aside until the activity had decayed to a reasonable and
safe limit. If it were known which radioactive elements
were present it would be possible to apply the particu-
lar solvent that is known to be effective. Since, how-
ever, 200 radioactive forms of 34 different elements
with atomic numbers varying from zinc-30 to europium-63
have been found, the determination of the composition
after a radioactive blast is rather difficult. However,
it is known that most of the radioactivity from one hour
to a year, and possibly longer, is due to the group of
elements known as rare earths, and it is possible to
remove a considerable amount of radioactivity by treat-
ing the material with something that will form a soluble
complex with this rare earth group. For this purpose
the organic acids, such as citric and tartaric are prob-
ably the most effective. A substance like radioactive
iodine is best removed with a slightly alkaline solution
such as trisodium phosphate or strong soap. Substances
-uch as zinc, copper or cadmium form complexes with
ammonia that are very soluble.

If soap and water and the chemicals mentioned are
nor sufficient, live steam may be used. Into the live
steam may be fed a solution of a detergent. This is
particularly effective in treating greasy surfaces. It is
often possible to start the decontamination of buildings

from' within ,lh rt tlhei radioactivitv is low. rather than
trot without whe-re ii is high. After the inside has been
decent minitedl, suiiflcent time lmay have elapsed for
the outside to have decayed to a safer level. In general
it i, better to decontaminate areas of low activity first.
This protects the personnel and allows for the ordinary
mistakes that may be made. Occasionally, however,
certain structures may be so vital that reams working
for short periods of time may have to dash in to try to
decontaminate them in as short time as possible.

Vhen the radioactivity has penetrated into the sur-
face such as into porous stone or has been absorbed
by paint or tar or other material, the surface layer of
the material must be removed. This is a very difficult
task and requires special equipment. Sand blasting is
commonly used. Here, however, the sand blasting should
be of the wet variety for the dry sand blasting would
simply fill the air with the radioactive dust. For small-
er objects such as machinery that would be injured by
sand blasting, scrubbing with fine steel brushes or
steel wool may be sufficient. Dusting or polishing ma-
chines might also be adapted to small articles.

In the decontamination of naval vessels that were
at Bikini it was observed that 00 per cent of the radio-
activity remaining on ship surfaces three years after
being contaminated was removable by vacuum sweeping
or brushing, indicating that most of the activity was on
the surface and was associated with dust, corrosion or
other surface materials. The interior of houses, there-
fore, might first be thoroughly cleaned by vacuum be-
fore the house is gutted with water. One method of
decontaminating surfaces is to spray them with adhesive
materials that can be stripped off. In addition to the
sodium citrate mentioned before, sodium pyrrole phos-
phate has also been used and the sodium salts of ethyl-
enediaminetecraacetic acid and aminotriaceric acid have
also been found useful. Ethanolamines might also be
very useful completing agents. Citric acid to which
hydrochloric or muriatic acid is added proved to be very
useful in decontaminating ships. Probably the acids
dissolved rust and scale that held the radioactivity-

One of the problems in decontamination would he the
roofs of buii.ings. In most cases these ire "asilv con-
taminated and very difficult to decontaminate. Stucco
buildings also represent a considerable problem. A rood
deal of radioactivity would be absorbed bv the soil and
and rhis would produce a real problem. However, the
activity would be in the first few inches so perhaps
removal of the cop soil or deep plowing that would bury
the material beneath a foot of subsoil might be practical.
Food in cans would probably not be injured if the can
survived the blast. This also might be true of food in
dust-proof wrappings. However, most food unprotected
in the stores, homes, or in the field might well become
heavily contaminated. There is no way to decontaminate

The decontamination of water supplies would prob-
ably rake place simply by draining reservoirs and flush-
ing them out. The ordinary methods of purification by
absorption by colloidal matter would probably remove
residual radioactivity. The soil will act as a filter for
most radioactive substances, so that the water from
deep wells should be safe if surface drainage is pre-
vented. In any event the natural dilution and decay of
radioactivity should render the water fit for use within
a week or ten days. The anion and cation water puri-
fication systems, that are now obtainable in all sizes
from a ten gallon a day size up, will effectively remove
the charged particles from water. Distilled water is also
free from radioactivity. One should emphasize that boil-
ing water has absolutely no effect on radioactivity. The
accepted safe tolerant level for water containing radio-
active materials is 4 x 10-6 microcuries per cc. This
activity is lower than that from radioactive mineral wa-
ters which are consumed in quantity without obvious
harm. Probably the best protection is to have surfaces
painted with smooth non-absorbent paint. Concrete es-
pecially should be well sealed and painted.

An attempt has been made in the foregoing pages to
sum up the best available knowledge on the decontami-
nationof radioactive areas. As our knowledge increases
it may well be necessary or desirable to modify or ex-
tend these recommendations.



W. D. Joiner, Chief of Police

Gainesville, Florida

In opening this discussion on the coordination be-
tween Police, Fire, Health, Welfare, and Rescue work-
ers, I would first like to touch on the facilities of my
organization and our ability to handle emergency situa-
tions which might arise throughout Alachua County. It
has been my duty as Director of Police Services of
Alachua County to perfect a county wide organization
which, in addition tothe Gainesville Police Department,
includes the CountySheriff's Department, the University
of Florida Police Department, the Florida Highway Pa-
trol, and all other law enforcement officers throughout
the county. A file is kept at Police Headquarters con-
taining the names, titles, addresses and telephone num-
bers of all law enforcement officers in the county. In
the event of an emergency, these men can be reached
in a short time and assigned to their respective duties.

A Police Reserve Organization has also been acti-
vated with former police officers and auxiliary police
who served during World War II in tlat capacity. This
gives us a nucleus of trained men which simplifies our
rrainingprogram for this group. It is not my idea to have
a large organization of this type, but rather a small,
well trained and highly mobile unit, each man thorough-
ly understanding his duties and having the ability to
carry them out. The men for this unit are being care-
fully chosen. All applicants are screened by the Director
and the Captain in charge with emphasis placed upon
honesty, dependability, physical fitness, emotional
stability and the honest desire to contribute a valuable
service to our community. A training program is being
carried on for this unit, which includes Federal and
State Laws, local ordinances, firearms, First Aid, gen-
eral police duties and responsibilities, discipline,
courtesy and conduct, professional police ethics, powers
anddutiesduring an emergency, arrest technique, search-
ing of prisoners, criminal investigation, observation
and description, report writing and records, evidence
and court procedure, traffic control, accident prevention
and investigation, riot control and prevention of loot-
ing. The Captain in charge of this Reserve Unit is a
well trained former police officer with the qualities of
leadership. Regular meetings of the 'Tnih are held to

discuss changes and improvements in procedure.

We have approximately 85 law enforcement officers
in the county at this time and, with the Police Reserve,
should have a total of 150 men available for emergency
duty. In the event of disaster, police protection to the
area is one of the foremost factors to be considered.
in addition toour routine daily duties,we have numerous
other duties to perform such as paroling the disaster
area, prevention of looting, prevention of panic, identi-
fication of the dead, the detection of unexploded bombs
and isolating the area, and the issuance of passes and

The Police Department has five cars and four motor-
cycles, all radio equipped. For emergency duty we have
riot guns, sub-machine guns, tear gas, riot sticks, safe-
ty helmets and gas masks. The Sheriff's Department
has six radio equipped cars, four of these cars working
out of thie main uffice in Gaiiesville, one car out of
Newberry, and one car out of Archer. The base trans-
mitter for the Sheriff's Department is located in the
County Jail with an operator available around the clock.
The Sheriff's dispatcher also has radio contact with the
Florida Highway Patrol. The Highway Patrol has re-
cently established a patrol station in Gainesville with
a Lieutenant in charge. This unit has a transmitting sta-
tion on a state-wide hookup and is operating four cars
out of Gainesville. The Highway Patrol Station is a
valuable asset to the community. It provides a comple-
ment of men and in times of emergency, additional per-
sonnel and equipment can be brought in without delay.
Information on the movement of traffic in and out of
our area will be furnished by this station.

In coordinating our efforts with the fire, health, wel-
fare, and rescue workers, our communications system
is of primary importance. The efficiency of our operation
depends to a great extent upon this, and we are making
every effort to keep our communications in first class
condition. In the event of power failure, we have an
emergency power unit available. In addition to this, it
is possible to use one of our mobile units temporarily

as a base station, thereby keeping in constant contact Florida Highway Parol or the Sheriff's Department. It

with all mobile units.

Of course, the various law enforcement agencies in
our area are on different radio frequencies. If it is nec-
essary for Police Headquarters to contact one of their
radio cars, this will be done by telephone to their base

During a time of emergency we will be in constant
contactwith the Fire Department bytelephone and radio.
The Fire Department has four mobile units served by
the police base transmitter. This enables us to dispatch
fire-fighting equipment from the scene of one fire to
another without the necessity of this equipment return-
ing to the Fire Station. The Police Department also has
a portable public address system which can be used to
great advantage at the fire scene. This is especially
true where the fire covers a large area, as it enables
the Fire Chief to direct his men and also helps the
Police in the control of traffic. It is very important that
adequate police personnel and equipment be dispatched
to the scene of a fire. Of course, our major problem at
such a time is the control of traffic; but we are also
charged with the prevention of looting, assisting in res-
cue and evacuation, relaying messages, and preventing
unauthorized persons from entering the area. Sightseers
present a serious problem at the scene of a fire. They
not only endanger their own lives but make it difficult
for the police officers, firemen and rescue workers to
carry out their duties.

The Florida Forest and Park Service is rendering
valuable aid in fire control. Their primary duty is the
control of forest fires, but during a time of emergency
their personnel and equipment is available for all types
of fire fighting. The local station of the Forest Service
has a base transmitter and six radio equipped trucks.
The base transmitter is on a state-wide network, which
enables usto call in additional personnel and equipment
if needed during an emergency. The Service has six
observation towers in strategic locations throughout the
county. These towers are equipped with radio and tele-
phone. During a time of emergency, if the Forest Service
sends equipment to the scene of a fire out in the county,
itis our duty to see that police personnel are dispatched
to the scene. This assignment would be handled by the

is desirable that fire-fighting equipment have a police
escort to and from the scene of the fire. Without such
an escort the movement of fire-fighting equipment upon
the streets and highways becomes more hazardous. Our
problem is to get this equipment to the scene as quickly
and safely as possible.

Traffic control is the most important phase of our
work during a time of disaster, and we are placing parti-
cular emphasis upon this part of our training program.
The members four department are being given refresher
courses in traffic control, and all reserves will receive
intensive training in the subject. The training division
of the Highway Patrol is giving us valuable assistance
in conducting these courses in traffic control. Realizing
the absolute necessity of keeping the streets and high-
ways open for the movement of traffic, we have estab-
lished control points throughout the county. In setting
up these control points, the thought has been kept in
mind that country roads connecting with highways shall
be utilized in the event of mass evacuation from a cer-
rain area. Traffic officers will be stationed at these
control points and by telephone and radio will be in
position to advise the control center on the movement
of traffic. Due to bombing or other causes, certain roads
will become impassable at times. The control center
must be advised of this so that traffic may be rerouted.

Our Captain in charge of police reserves owns an
airplane and is a licensed pilot, which is a valuable
asset to us during a time of emergency. This enables
us to make an aerial observation of the county in a few
minutes time, thereby increasing the efficiency of our
entire operation.

Our streets and highways are not adequate to handle
the normal traffic of today and, during a time of disaster,
our problem will increase greatly. Congestion is the
forerunner of panic at such a time, and this must be

In closing my remarks, I might say that the success
ful coordination between Police, Fire, Health, Welfare,
and Rescue Services will depend more upon TRAFFIC
CONTROL than upon any other one element.



H. H. Woeltjon, Director

Office of Civil Defense
Jacksonville, Florida

The great objective of Civil Defense is to save life,
reduce the effects of damage and keep the interruption
of the war effort to a minimum, to prevent panic and pre-
serve morale. Above all, morale must be maintained.
This is viral to the successful conduct of any war. Any
drop of morale at home will have immediate repercus-
sion on the spirit of the fighting services.

All Civil Defense measures in war are therefore
designed to achieve one objective - the maintenance
of morale of the civilian population. Morale is the will
to win, the greatest single factor which brings victory.
The lack of it makes defeat certain. To this end the
people must first learn to help themselves and then
feel assured that everything is being done for cheir
aid and protection.

Self help in a major disaster is limited and we can
readily see that at a time like this all persons involved,
even the local Civil Defense organization, will be so
shocked by the event that even if they are uninjured,
their help for at least several hours will be entirely
inadequate. We must, therefore, look for help and aid,
to the neighboring communities and if necessary to the
State at large.

Mutual aid and mobile support is the answer. Mutual
aid is the voluntary arrangement between organized
communities for the use of each others protective serv-
ices in time of need. This, of course, must be done by
prior planning and agreements. No community can Af-
ford complete self-sufficiency. It would not be practical
since surplus resources, unnecessary in peacetime,
would be vulnerable to destruction in case of an attack.
It is, however, reasonable to assume that most com-
munities can give assistance to each other without un-
reasonably depleting their own Civil Defense or other
protective measures.

Mutual aid is not a new concept. It exists today
between many communities for a variety of purposes;
for instance, in case of big fires, hurricanes or floods.
However, in the Civil Defense plan it is desirable that

every community formalize all existing agreements so
that there will be a complete and full understanding
between all as to their duties and responsibilities to
each other in time of need. If necessary, existing agree-
ments should be extended or new ones negotiated to
cover all of the services of Civil Defense.

Once the plans are adopted they should be tested
in practice to assure that all participants know exactly
what must be done if an emergency should arise. Ad-
vanced planning should be so thorough that in an emer-
gency the mutual aid forces can be dispatched with
speed and precision.

Mutual aid arrangements at this stage may have to
be tentative, pending legislation authorizing definite
agreements. It is advisable, however, that communities
within say a 20 mile or more radius of a large city, that
may be a possible target area, consider mutual aid ar-
rangements for committing up to one-third of their re-
sources as initial reinforcement by pre-arranged plan in
the event ofan attack. This would allow these communi-
ties to initially retain the bulk of their Civil Defense
organizations as a protection for them against a subse-
quent attack and thus greatly help to keep up the morale
of their own people at a time when they are naturally
disturbed. Then when the need arises they no doubt
will be glad to send additional reinforcements. Laws
regarding Civil Defense and mutual agreements will be
considered and no doubt enacted at the meeting of the
State Legislature in April.* P.L. 920 or the Federal
C.D. Act of 1950 has already been enacted by Congress.
Mutual aid agreements between States are covered in
Section 5 of "United States Civil Defense" (Blue Book).

We can well envision that in the event of an atomic
disaster the facilities of even our most populated cities
and States willbe inadequate to cope with such a disas-
ter and outside help will be sorely needed; and while lo-
cal Civil Defense services will be atthe scene of disas-
ter for immediate action, their forces are bound to be in-

*See Chapter 26875, Florida Laws of 1951. - Ed.

sufficient. For this purpose. Mobile groups are being

While mutual aid is usually accomplished through
prior planning and agreements, mobile support is aid
directed by State authorities into a stricken area regard-
less of any such prior agreements. Mobile support is the
extension of the mutual aid system under the direction
of the State Civil Defense authorities.

Colonel Howie, the Scare Director of Civil Defense,
has directed that a number of mobile groups be formed
in each region of the Stare and that the Counties sur-
rounding the principal cities furnish the personnel for
these groups. They are now being organized. Each group
will consist of 513 persons, 65 in headquarters service,
61 in the service command and 387 in the service reams.

The services will parallel those of the County or-
ganizations and each service will contain 3 to 6 reams.
Each team has from 7 to 20 members. The entire group
will be highly trained, fully equipped and ready to move

to a stricken area, both within and without the State on
very short notice. Within the Region they will be under
the direction of the Regional Director, but when thev
are used in other pars of the Scare or outside of the
State, they will be directly under the direction of the
Stace Director of Civil Defense. As they enter the strick-
en area they will report for service to the local Director;
however, the State Civil Defense Director has active
command over all Civil Defense operations within his

These mobile support reams consist of units, with
the manpower and equipment essential for swift and
successful operation, organized to work as special self-
contained services or teams. They are being organized
and trained with one objective, namely to be available
for duty in their own locality, in another community or
in another State. With arrangements made between com-
munities for mutual aid and with the assistance of mo-
bile support everything is being done through Civil
Defense to savelives and reduce damages to a minimum
in the event of a disaster which we all hope may never
strike us.



Richard S. Green

Senior Sanitary Engineer, U.S.P.H.S.
Washington, D. C.

In recent months, several talks have been presented
by highly qualified persons on the subject of biological
warfare. These presentations have all avoided the spec-
tacular and pointed out the basic ideas which we, as
health workers, must understand to carry our share of
the burden if this method of warfare is ever used against
our country. This restraint was not always present, as
was pointed out in the Federal Civil Defense Adminis-
tration's publication, entitled "What You Should Know
About Biological Warfare," released only a few days
ago, and which all public health workers especially
should read without delay. For each of us has a heavy
responsibility, one that can be borne only if we know
something about the potentialities and the limitations
of this weapon.

What is biological warfare? How could it be used>
With what effect? And what are we doing to defend our-
selves against it? This paper will attempt to answer
these questions.

Biological warfare may be described as the "in-
tentional use of living disease agents and their toxic
biological products, or of chemical plant regulators to
produce disease or death in man, animals or crops."
Attacks on animals or crops are of concern chiefly to
professions other than public health and will not be
discussed in this presentation. Biological warfare dif-
fers from our normal struggle against disease, in that
theresulting illnesses are wilfully brought about by man
and hence can conceivably rake on new aspects, man
having gone to the aid not of his fellow man but of the
disease organisms. Some have called this process pub-
lic health in reverse, a term which fits well.

Without getting into the question of moral values in
the use of biological warfare - though you may be sure
thisphase of the problem has received and will continue
to receive much attention - we should understand why
an enemy might wish to use BW instead of some other
weapon. This will help us to foretell how and when an
attack might be made, and enable us better to prepare for

In many respects, the BW weapon is in a class by
itself. It is relatively cheap; capable of being perfected
and produced by any country, large or small, which has
a supply of good biological scientists; and can be fash-
ionedtomeet a very wide variety of circumstances. This
flexibility is one of the most important attributes of the
BWweapon. Microorganisms, or agents, could be chosen
which would produce a high fatality rate in susceptible
individuals. Perhaps, however, an enemy's purposes
would be better served by a debilitating disease, one
that would make people ill for a long while, tie down
medical and nursing care, and take workers away from
production lines. If so, a variety of agents could qualify
for this task. Or, possibly, an enemy would want to make
a selected strategic area difficult to occupy.Widespread
contamination of the area with a resistant disease agent
would do this. Such attacks might be made openly by
disseminating fine sprays or aerosols, or might be car-
tied our entirely by acts of sabotage. Attacks might be
directed at selected groups of persons, either before or
after an open declaration of war, by introducing disease
germs or bacterial toxins into the air, food or water
supplying these groups. If cleverly carried out, it might
be very difficult to tell whether BW had been used or
whether the outbreak was just an unfortunate breakdown
in normal disease controls.

While it is true we have no evidence that any major
use has been made of BW, we know quite positively that
all the previously mentioned applications of BW are
possible and we feel sure if such attacks were made,
they would be at least partially successful. In spite of
all we might do, some people would get sick.

It is important for health workers to realize that be-
cause biological warfare agents are purposely selected,
grown and disseminated byman, we can expect the worst
his ingenuity can bring about. A little thought on the
matter will show any qualified bacteriologist that an
effective BW agent would have to be as highly virulent
as possible, and that its virulence would need to per-
sist through whatever method of dissemination might be
selected. For example, it should be able to withstand

reasonably well such adverse conditions as the drying 1. We should improve our system of reporting com-

effects of air dispersal, or the trip through a public
water supply system. The agent should be capable of
quick production in large amounts and yet have good
storing properties. Furthermore, it should preferably be
an organism for which there exists no effective immuni-
zation and no effective treatment. Special culturing
methods might be used to bring about particularly de-
sired characteristics in the various agents chosen.

Having considered any of several organisms which
might meet these requirements, one might now question
the possible effects of infections distributed through
unusual routes. A disease which normally spreads by
way of the gastro-intestinal tract or the bite of an in-
sect, might be adapted very well to infection spread
artificially through the lungs inthe form of an aerosol or
mist, perhaps with quite different symptoms. Accidental
infections in many of our research laboratories show
that there are possibilities of such an occurrence. The
situation might be further complicated by dispersing a
virus and a bacterial agent simultaneously, thus making
both diagnosis and therapy more difficult.

To a considerable extent, the forces necessary to
counteract an enemy BW attack already exist in the well-
developed health and medical services of our country.
These forces consist of persons well-trained and ex-
perienced in the principles of the medical and sani-
tarv sciences. However, special defensive weapons
still must be fashioned, and we must learn to use them.
We must adapt our arsenal to the stresses of what could
be a more difficult battle than any the public health
profession has yet faced.

Obviously, in order to prevent infection from BW
agents, we must keep them from reaching us and in-
vading our bodies. It might be very difficult, however,
if not impossible, for us to know when a cloud of BW
agents had been loosed in a target area before some-
one becomes ill. The saboteur might succeed in infect-
ing a water supply or the output of a food packing es-
tablishment without being discovered. It should be
clear, therefore, that we should plan our program of de-
fense against BW to include the following major items:
1. Improvement of our system of reporting of com-
municable diseases.
2. Strengthening of our public health and diagnos-
tic laboratories.
3. Development of improved means of detection and
identification of possible BW agents.
4. Establishment of a system of internal security
to aid in preventing BW sabotage activities.

municable diseases to obtain more complete information
more promptly. Early reporting may save many lives.
Remember, the epidemiology of a BW disease might
nor be the same as the occurrence of that disease in
its normalmanner. We might get a sudden and widespread
incidence of an illness which normally would appear
only sporadically or spread only very slowly among any
considerable number of persons. Only prompt and corr
plete reporting will enable us to act effectively in meet-
ing such an outbreak. Necessary as reporting of com-
municable disease is to a public health program in nor-
mal times, it becomes all the more urgent when disease
organisms are intentionally guided to their hosts. The
National Office of Viral Statistics, the Public Health
Service Communicable Disease Center in Atlanta, and
the National Institutes of Health in Bethesda, Mary-
land have already begun a concerted effort to improve
our entire program of disease reporting. In order that
we may be prepared to identify a BW outbreak, physi-
cians and laboratory technicians especially should be
on the alert not only for diseases of an unusual charac-
ter but also for diseases not normally present in an
area. There is a need for specially trained epidemiolo-
gists to help meet this eventuality.

2. Public health laboratories must be prepared to
look for many agents which they may never have handled
before. Obviously, not all public health laboratories
can be staffed and equipped to handle adequately the
gamut of bacteria, viruses, rickettsiae and fungi with
which they might be confronted. However, by careful
advance planning and a well-prepared system of inter-
laboratory cooperation, most areas should be able to
handle this situation. Special training for laboratory
workers should be developed, with guidance given in
the intricate task of planning for mutual assistance. One
badly needed laboratory tool is an identification key es-
pecially suited for use by laboratories which may be
calledupon to identify potential BW agents. No adequate
key is available now. Without one, much valuable time
surely would be lost. There is a good possibility, too,
that as more people become alert to the potentialities
of BW, our laboratories will be receiving varieties of
specimens which have no real significance. Neverthe-
less, many of these will have to be run down in the lab-
oratory if we are to practice vigilance. This work must
be made as efficient as possible.

3. In this discussion so far, no mention has been
made of any special techniques for the detection of BW
agents prior to their appearance in infected persons.
Those of you who are familiar with methods used in the

field of industrial hygiene for sampling air will know
that a wide variety of devices is available for tracking
downthe various pollutants associated with air hygiene,
including some particularly adapted to bacterial sam-
pling. However, you also know that even if these sam-
pling techniques are well developed, the time required
for classical laboratory determination of the bacterial
samples is at least several days. If we were to become
interested in the viruses, it might take our laboratories
much longer to tell us what virus had been collected.
Meanwhile, the outbreaks of human illness from these
agents might have given us the answer before the lab-
oratory staff could.

While several plans are under way to shorten the
time necessary for ordinary identification of biological
samples by the usual processes of culturing, our strong-
est hope for success in this problem seems to lie in a
completely new approach. Physicists and chemists are
working closely with the bacteriologists in an attempt
to apply certain principles from these related sciences
to this very difficult problem. It may be that we can
depend on certain inherent chemical or physical proper-
ties of potential BW agents to bring about rapid identi-
fication in the laboratory. This problem calls for the
application of our best talent.

4. As important as any single action we might take
to protect ourselves from BW attack will be the organiza-
tion ofa system of internal security to guard against the
covert dissemination of BW agents. We must remember
that certain groups of people, such as key administrative
talent and hard-to-get technical and mechanical person-
nel, and public facilities such as waterworks and food-

and milk-processing plants, are attractive to the sabo-
teur. The BW agent is in some ways almost an ideal
weapon in the hands of a clever saboteur, because it
might be entirely possible for him to perform his tasks
and be hundreds of miles away before its results can be

Perhaps of greatest importance in our effort to meet
the threat cf biological warfare to our country is the
need to adopt completely open minds on new develop-
ments in the field of biology and public health. Many of
our everyday methods, though adequate now, are simply
not sufficiently effective to combat the malicious work-
ings of an enemy mind when it sets out to assist what
we might call "the natural development of disease in
the population." We must expect efforts to outguess
us, and we mustwork diligently to prepare for the worst.
There is no reason to become panicky about this threat,
but there is every reason in the world for understanding
it completely and facing it squarely. I cite as an ex-
ample of what hysteria can do to a population the re-
cent excitement raised in one of our major cities when
it was rumored that the water supply had been poisoned.
The mindless behavior oflarge masses of people gripped
in the paralysis of this sort of fear can be as destruc-
tive as any agent of warfare yet devised. BW works
silently. It cannot be seen.Nobody knows where or when
it will strike next. Hence, apprehension, mounting to
fear, and finally reaching the heights of mass hysteria,
is a possible development to be guarded against.

Public health workers must assume their obvious
responsibilities in this part of the over-all problems of
civil defense.



Harry P. Kramer, Sanitary Engineer

Environmental Health Center, U.S.P.H.S.
Cincinnati, Ohio

When the German advance in World War I was stopped,
and both sides became firmly entrenched, the advantage
belonged to the allies since the Germans were surround-
ed. The Germans turned to Chemistry for a solution.
Professors Nernst and Haber, both famous scientists,
produced some poison gases in quantity for offensive
action. The first gas attack was at Ypres on April 22,
1915, using chlorine. Had the Germans pursued the ad-
vantage that this attack afforded them, the course of
history might have been changed. Other gases such as
phosgene, chloropicrin, the arsenicals, and mustard were
soon developed and put to use. Much effort was concen-
trated on the development of protective measures against
these agents. The summation of the results produced by
war gases in World War I shows that with about 17,000
gas troops on both sides, (7) using only 120,000 tons
of chemicals, more than 1,250,000 casualties were pro-
duced, i.e., almost 200 pounds per casualty. Expressing
it in a different way, more than 27 out of every hundred
casualties were produced by gas.

It is taken for granted that our military personnel
receive very adequate training in defense against chem-
ical warfare agents, but the civilian picture is one that
is more complex. Civilian populations are vulnerable
to such attack and all must become informed on courses
of action.

A few common terms 6) used in this discussion are
now defined briefly:
Chemical agent - A substance useful in war which, by
its ordinary and direct chemical ac-
tion, produces a toxic effect, a
screening smoke, or an incendiary
Toaic - A substance which, acting through
its chemical properties and by its
ordinary action, produces a deleteri-
ous physiological reaction when
applied to the body externally, when
breathed, or when taken in moderate
doses internally. All war gases pos-
sess toxicity.

Casualty agent - Produces death or hospital cases.
Harassing agents - Lacrimators or irritant gases caus-
ing irritation of the eyes or nausea
and headache of a few hours duration.
Concentration - The amount of chemical agent pres-
ent in a unit volume of air. May be


Vapor Pressure


expressed as:
(a) Percentage by volume.
(b) Weight of chemical agent per unit
volume of air; ounces per 1,000 cu.
ft. of air; or milligrams per liter.
- Agents which are dissipated rapidly
usually in less than 10 minutes and
require no protection of any kind at
the end ofthat period are termed non-
persistent. Agents whose remaining
concentration atthe end of 10minutes
requireprotection are termed persist-
- The partial pressure exerted by the
vapor under saturation conditions.
Actuallythis propertytells how much
gas canbe present in the atmosphere
at a given temperature.
-The capacity of a liquid to change
into vapor in the open air. The a-
mount of vapor per unit volume of
saturated air is the quantitative ex-
pression of this property.

This discussion shall be limited to those agents
which produce toxic effects. To be effective, a chemical
warfare agent should be verytoxic orvery irritant, should
vaporize readily, should be persistent, and should be
capable of being manufactured and stored without too
much difficulty.

The first gases (7) to be used were lung irritants
such as chlorine, phosgene, and chloropicrin. They are
casualty agents and range from non-persistent to moder-
ately persistent. The lacrimators (tear gases) and ster-
mutators (the arsenicals) are harassing agents. The lat-
ter are very irritant to the nose and cause vomiting and

headache. The vesicants(blister gases)unlike the gases
classified above, require protective clothing as well as
gas masks. These persistent agents, such as mustard,
Lewisite and ethyldichlorarsine are most effective. They
have the property of being absorbed by any part of the
body with which they come in contact, producing severe
blistering. "Mustard" gas was undoubtedly the most
effective of all the gases used in World War I. The odor
ofthe gas is somewhat like that of garlic, or horseradish
and can produce casualties in concentrations below that
which can be smelled. Its effects in water will be de-
scribed later.

There is in addition to the more generally known
chemical warfare agents a new group of substances
known as the "Nerve Gases." These gases have most
unusual properties. To avoid the confusion which may
follow from the name given to these substances, it
should be understood that the term "Nerve Gases" does
not in any way refer to the old group of "blood and
nerve poisons" (systemic poisons) such as cyanogen
chloride and hydrocyanic acid. Rather, it applies to a
new type of chemical agent developed in Germany during
World War II. The nerve gases are both tasteless and
odorless. Not only are they more difficult to detect by
the senses, but they are by far, (2) more toxic than any
previously known war gases.

It would seem logical to assume on this basis alone,
namely very high toxicity coupled with difficulty in
detection, that these gases would be the most likely
to be used against the civilian population. The nerve
gases, like mustard gas, are liquids which may be
sprayed by various means and which result in toxic
vapors. Since taste and odor give no warning of their
presence, letus consider the following feasible methods
of detection. Rapid physical or chemical detection meth-
ods would be required because of the extremely fast
reaction of the gases. For adequate results, sampling
or monitoring stations containing automatic equipment,
capable of detection and interpretation followed by the
relaying of results to some central station would be re-
quired. Such equipment is not economically available.
It seems reasonable to assume that an effective method
of detection would lie in a strategically distributed per-
sonnel trained in the recognition of the physical symp-
toms created by these agents.

Someof these nerve gases are classed as persistent,
others as only moderately so. They may be absorbed
through the skin or mucous membrane by inhalation to
the lungs or through the gastrointestinal tract by swal-
lowing of contaminated saliva, even possibly by con-

taminated food and water. The symptoms appearing di-
rectly after contamination are due largely or entirely to
interference with a vital bodily chemical reaction; the
inhibiting of the enzyme cholinesterase (1) in its neces-
sary function of destroying acetylcholine. The stimula-
tion of nerves produces acetylcholine, which, if not
inactivated by the enzyme at a proper rate, accumulates
in the central and peripheral nervous systems giving
rise to acetylcholine poisoning. These nerve gases are
so toxic that in the presence of a high concentration of
gas, inhalation for a matter of seconds may cause death.
The symptoms of the victim vary with the strength of the
dosage received.

Low doses produce a constriction of the bronchi,
keeping the air from passing rapidly in and out of the
lungs; however, small amounts of the gas are insufficient
to produce severe reactions. These constrictions usual-
ly last only a few days. Man and experimental animals
show the same results when exposed to small amounts
of the vapor. The pupils of the eye contract to pin-point
size within a few moments after exposure. Difficulty in
breathing with shortness of breath results, often accom-
panied by a watery nasal discharge. The resulting head-
ache and the pupil condition do not respond to the treat-
ment which readily overcomes the bronchial constric-
tion. Other procedures are necessary and may require
repeated effort to alleviate the effects of the gases. The
victim may exhibit such mental symptoms as giddiness,
tension, anxiety, insomnia and excessive dreaming.

Intermediate doses, encountered either through the
vapor or the liquid phase, result in violent reactions,
severe bronchial spasm, interfering with inhalation and
exhalation, confusion, cyanosis and severe nausea and
vomiting ending in unconsciousness. The blood pres-
sure of the victim drops to shock levels, the heart beats
more and more slowly and may stop altogether, either as
a temporary or terminal event. When the patient receives
prompt medical attention, the symptoms set down are
reversed. The bronchial tree relaxes, breathing becomes
easier and more oxygen finds its way into the blood.
The heart begins to pick up its normal rhythm and rate;
blood pressure goes back up to normal levels.

In addition to the effects listed above, large doses
of nerve gases may cause several other symptoms. In-
voluntary tremors and shivering, worm-like movements
of the muscles, spasmodic twitchings, even severe epi-
lepsy and convulsions. Tridione has the advantage of
depressing comical activity effectively without depress-
ing respiration. In severely affected cases, especially
where treatment can't be given immediately, the patient

develops profuse salivation, intestinal hypermotiliry,
and spasm and incontinence of bladder and bowel. Mean-
while the acetylcholine level continues to build up in
the nervous system leading to almost continuous convul-
sions until flaccid paralysis results.

The recommended treatment for casualties is the
injection of atropine sulfate. While the use of atropine
is quite effective in the milder cases, its use may be
quite dangerous in the more severe seizures. Such use
may cause the heart to "dry run" - movements of the
heart accompanied by no blood pumpage. This often
results in death to the animals so affected. Thus the
administration of atropine should be delayed until the
lungs have been ventilated and the heart has recovered
somewhat. All such decisions, judgments, and proce-
dures to be followed, can only be made by competent
medical personnel.

Atropine (2) is required in relatively large doses for
the severe case; the danger lying on the side of under-
treatment. The atropine should be given by a route that
reaches the circulation rapidly. From the viewpoint of
rapidity of action and control of dosage, the intravenous
method is the first choice. Intramuscular injection may
be used if the patient is not cold or in shock. For the
initial treatment oral and subcutaneous routes are too
slow. Doses of 2 milligrams (1/30 grain) of atropine
sulfate are repeated every 5 or 10 minutes until three
injections (6 milligrams) have been given or until the
cardiorespiratory symptoms are relieved and some dry-
ness of the mouth appears. Following this, smaller oral
or injected doses should be given every few hours for at
least several days since the poison is more persistent
than the effect of the drug.

The respiratory paralysis (which prevents effective
respiration) is a symptom which should receive immedi-
ate attention. The usual manual methods such as the
Shafer prone pressure method, or the Eve tilt table meth-
od, are ineffective and impractical. The paralysis men-
tioned above does no allow the usual response to com-
pression, that is, expansion.

Emerson's method may yield good results, especial-
ly since it permits a certain amount of drainage from the
respiratory tract. With the victim in a prone position,
grasp the thighs just below the hips and alternately
raise and lower the hips 10 to 12 inches. Ventilation of
the lungs accompanies this practice, for raising of the
hips causes active expiration while lowering the hips
causes passive inspiration. Continue this artificial
respiration until spontaneous or natural breathing is

restored which may take 45 minutes or more.

A mechanical resuscitator provides very practical
means of giving artificial respiration and should be
used if one is available.

A casualty should be made to avoid any physical
exercise. If liquid nerve(l) gas is splashed upon the
skin it should be removed promptly. The safest and most
effective method is by thorough washing with alkaline
solutions such as ammonia water, or a 5 to 10% solu-
tion of sodium carbonate,or a 1 to2% solution of sodium
hydroxide. If these substances are unavailable, use
soap and water or if none of these is available imme-
diately wet any available absorbent material and swab
the infected area with the wet swabs. Great emphasis
must be placed upon avoiding the rubbing and wiping
of the skin since this increases absorption and toxicity
of the agents. When only dry absorbent materials are
available, the excess liquid may be gently blotted from
the skin. Neither the victim nor infected clothing should
be brought into hospitals. Remove the clothing promptly
and leave outdoors. Gas is to be removed from the vic-
tim in the manner outlined above. Without these precau-
tions, the hospitals or other enclosed spaces may be-
come contaminated, thereby endangering others.

While it is clear that atropine sulfate is the prin-
cipal therapeutic agent, it should be made doubly clear
that this substance is a violent poison and is only used
under medical supervision.

The reaction of nerve gases with water hydrolysiss)
proceeds slowly with normal pH ranges, rapidly with
high ranges. The hydrolytic products are less toxic
than the original substances. This suggests a possible
method of decontamination for these materials, namely,
the use of alkaline agents.

Since we are now aware of the serious effects of
exposure to the nerve gases and have a few ideas on
how to treat victims of such attacks, it might be well
to go briefly into some of the known methods for pre-
vention of contamination.

Effective gas masks can protect the wearer against
the effects of nerve gases. The study of the problem
is in progress and just a few days ago a press release
mentioned that an effective mask protecting against both
biological and chemical weapons had been designed and
would be made available.

In the presence of the persistent type of gases, pro-

tective clothing isrequired to prevent absorption through
the skin. Since the non-persistent types would be dis-
persed to non-dangerous levels in the matter of minutes,
protective clothing in such an attack would not be re-

Breathing through a rag which has been soaked in
an alkaline solution offers some measure of protection
against inhalation of the nerve gases. Saturated aqueous
solutions of baking soda, washing soda, or soapy water
may be used to soak the rag.

There are many of us who are vitally interested in
the aspects of water contamination by chemical warfare
agents. The possibility of such contamination is open
to the same arguments that may be used with respect
to gas attack against civilian population. Whatever our
outlook, it is most certain that preparation in advance
to meet such attacks will greatly decrease their effec-
tiveness should they occur.

Group 1 in Table 1 includes substances(5) which are
water-dental agents. Group 2 includes insoluble, stable



eWou I Agents which probaby will prouce Thernl, crud. ol
FS Milur.
non-oxec woter, hough it may be non- HC Mixlur,
Thmniumn rtlrachlornd
potoble. Carb. Monoxide
Group Agents producing a lurbd woter which 1s Adansir.
Diphbnyldcht.ie ina
ncn.loxrc aher r a nal of te turbldity. DOhisnyleyornorln
cr..p 3 Agnts preseinl in faiitly high cnicn- Phoite
trans whch wouldd produce non.

toxic waTer.
etp 4 Agents hikelty t couse trob,. in Chlor.picrmi
wer supply unless exft 0vt.rautlon Nines. Mamards
ar. toake Ethyld'ehlmarlsn
Le i y-id&o.~sin

GrouIp Agen requiring oditional daot for BroainniyLan do
definie clissifletfllgn. CN SolauLo
Gmoup Ciompounds only lkey to be used Areot..es, Asenitnlr
for deit berte contominmion. Hcavy metal sotts
Aflkolids and toxins
Pa~senhe Boctr.*

agents, which are removed in the usual treatment pro-
cesses, coagulation, filtration, etc. Group 3 is self-
explanatory. Group 4 contains the vesicants and chloro-

picrin the presence of which would cause the greatest
difficulty in water supplies. Group 5 agents require more
information on their reactions and effects in water.
Group 6 includes compounds other than chemical war-
fare agents which are likely to be used for deliberate
contamination of water supplies.

Table I(5) attempts to show the basis for the clas-
sification given above. Here, solubility, behavior, hydro-
lytic products, and treatment required for many of the
more important agents are included.

Mustard gas, which is likely to give trouble in water
supplies is soluble to the extent of 800 p.p.m. at 200C.
When discharged into water the mustard gas(4) is dis-
tributed into a surface film and a water soluble fraction
and any excess present settles to the bottom. The un-
dissolved mustard may remain unchanged for several
weeks at the bottom of the water. The soluble fraction
is hydrolyzed according to the following reaction:

(CICH2CH2)2S + 2HOH --> 2HCI + (CHOHCH),S Thlodiglycol

The thiodiglycol formed is soluble in water and is non-
toxic. The rate of hydrolysis depends upon the quantity
of gas present, the temperature and the alkalinity of the
water. Boiling destroys mustard in 15 to 30 minutes but
2 or 3 days are required if storage at ordinary tempera-
ture is used.

The armed services of our country consider water
containing 500 p.p.m. or more of mustard as impossible
to treat for drinking purposes. With less than 500 p.p.m.
the water may be treated if the following procedures
can be employed. Treatment with unusually large doses
of activated carbon followed by coagulation with the
common coagulants and settling. The settled water is
then filtered and chlorinated beyond the break-point.
However, if the filtered water has a 5-minute chlorine
demand of more than 5 p.p.m. the water is still unsatis-
factory and must be retreated. For small doses of mus-
tard (50 p.p.m. or less) the hydrolysis reaction will be
sufficiently complete after one hour to permit use of the
water from intermediate reservoir levels. Where other
sources of water are available,finished water reservoirs
should be pumped to waste if contaminated with mus-
tard gas to any extent.

Water contamination by lewisite, ethyldichlorarsine
or methyldichlorarsine would also give trouble. Lewisite
is the least soluble of these gases but all of them are
rapidly hydrolyzed.

The soluble arsenious oxides are dangerous in a




mg. per liter
at 200C.



Slowly hydrolyzed






Very Soluble


Products of

HCI and thiodiglycol

HCI and toxic products

Sparingly soluble
Toxic, Vesicant

HCI and C H5AsO
toxic, soluble

Treatment Required

Treatment for removal

Treatment for removal

May be used for
period of week or less
if 5 p.p.m. are present
with higher concentra-
tions pump to waste

Some as for Lewisite

Chloropicrin 1700 Stable No hydrolysis Vigorous aeration

Phosgene 1000 Rapidly HCI and CO2 Neutralization if pH
hydrolyzed indicates it, otherwise
no treatment required.

Brombenzylcyanide Insoluble Stable - - - Probably coagulation
and filtration is all
Chloracetophenone 50 Stable - - - that would be required.

Adamsite 15.7 Stable - - - Coagulation and

Diphenylchlorarsine Very Slightly Slowly filtration
soluble hydrolyzed - - -

HC Mixture --- C2Cl6slowly Neutralization with
hydrolyzed CaCO3 or lime, if pH
SO3 in HCISO3 Very soluble Rapid reaction H2S04 & HCI indicates it, otherwise
no treatment required
Titanium Tetrachloride Soluble Hydrolyzed HCI and Ti(OH)4

Hydrocyanic acid

Very soluble

Slowly decomposed

Ammonium format and
brown polymeric products

Ferrous, ferric salt
treatment followed by
coagulation and filtra-

water supply. Furthermore, they are not removed by the
usual water treatment methods. Arsenic levels must be
determined3) and if found not to exceed I to 5p.p.m.,
the water is safe for short periods- 1 to 7 days. Higher
levels of contamination with the arsenicals require pump-
ing to waste. The suggested limits of safety are much
higher than those appearing in the Public Health Serv-
ice Drinking Water Standards; arsenic not to exceed .05
p.p.m. The PublicHealthService limit applies to waters
which are or may be used continuously, while the limits
suggested here apply under emergency conditions to
supplies which use is for one week or less.

The possibility of the introduction of cyanide by
saboteurs or by hydrogen cyanide bombs, should not be
overlooked. Simple tests for cyanide in water are avail-
able and should be made if cyanide contamination is
suspected. Finished waters should be pumped to waste
if cyanide is found. In raw waters the cyanide can be
removed by treatment of the neutral or alkaline water
with ferrous and ferric salts, followed by the standard
water purification processes. This treatment would pre-
cipitate the cyanide as Prussian blue, most of which
would then be removed by coagulation and filtration.
As long as an excess of iron salts were used any blue



Limit beyond which Gases and their detectable
Change required in water is not potable concentrations by these
Drinking Water criterion to suggest and dangerous when criteria. (all values in
Test Used Standard* (p.p.m.) contamination gas contaminated p.p.m.)

Odor No unpleasant odor Any unpleasant odor Any recognizable odor P.S. - 5.0
of vesicant or other MI-500 HS-500
toxic war gas

Turbidity 10 - - - 20 p.p.m. or more Sternutators and CN

pH - - - Decrease 0.3 unit or Lowering of 1.0 pH unit HS - 15, MI - 15
more below normal overage ED - 15, MD, CG, DA
for water slowly

Alkalinity (1) Decrease of 5 p.p.m. If alkalinity is lowered HS, MI, ED, MD, CG,
or more 10 p.p.m. or more or a DA
similar increase in
acidity is noted

Chloride 250 An unusual increase An unusual increase HS, MI, ED, MD, CG,
of 5 p.p.m. of 10 p.p.m. DA

Oxygen - - - Increase of 1. p.p.m. A value of 5.0 p.p.m. HS, MI, ED, MD, DA,
Consumed or more or more CA CN, DM, CDA

Chlorine - - - Increase of 1 p.p.m. A value of 5 p.p.m. HS, MI, ED, MD, DA
Demand or more or more CA, CN, DM, CDA

Arsenic 0.05 Increase above 0.05 A value of 1 to 5 MI, ED, MD, DM, DA,
p.p.m. p.p.m. CDA

AuCI3 -- -- --- HS

(*) U. S. Public Iealth Service, Publc health Reipors Vol. 61 pg 13 (March 15, 1946) Reprint No. 2697.

color coming through the filter would be non-toxic.

Any plan of action suggested for the protection of a
water supply should be made up of criteria which are as
simple as possible to apply so that persons with the
minimum training might carry them out.

A list of simple tests(5) and their use in the detec-
tion of chemical warfare agents is shown in Table III
(preceding page).

The simple criteria in Table nII will provide an
alert observer with some evidence as to whether or not
a gas warfare contaminant is present. Breakpoint chlo-
rination might well be added to this list. Where waters
have a history of fairly constant breakpoint values, a
sudden rise in such values would indicate concamina-

In Tables IV and V,(5) the effects of mustard and
lewisite on the pH and alkalinity, and chloride content
of Cincinnati water is shown. In both cases, the mus-
tard was allowed to react with the water before the test
was made. For pH and alkalinity effect, one hour at
270C. was given, for the chloride determination 24 hours
was allowed for reaction.


Conconlratlon MuMnad (fS) Lwilite (WI-I

P....- p.i. .p.p.,. pOp.m. Pp.D.

0 76 38 -- 7.8 38 -
10 7.2 34 "- 7.3 34
50 5.5 7 -- 6.2 15
o10 3.4 -- 21 3.5 -- to
500 2.4 - - 256 2.8 -- 200

Qunatlt M.Surd (S) Lewisate (a-
4 Gas Added
p,p.m. n.u.m. Chlorlde p.p.m. Chloride

Found Theoretical Found Theoretical

0 18 18 18 18
10 25 22 23 21.4
50 45 40.3 35 35.1
100 67 62.7 49 52.2
500 254 241 168 189

Table VI gives some estimate of dangerous levels
of contamination in water.



Approximate Pounds ao agent required
Approximate Approximate capacity of ele- Pounds of agent required for dangerous contaminnioo
water plart water plant rated tank or for dangerous contam- of contents of elevated
oluput galloa outlpt gallons clear water re- nation of I boers tank or clear water
Population erooai per day. per hour. servolr U used. output. reservoir.
Mustard (1) Lewisite (2) Mustard (1) Lewisite (2)

Family well 50 5 * .002 .0011

100 12,000 500 100,000 .2 .11 41.7 23.1

1,000 120,000 5,000 100,000 2.0 1.16 41.7 23.1

5,000 600,000 25,000 269,000 10.4 5.76 112.1 62.0

10,000 1,200,000 50,000 532,000 20.8 11.55 221.8 122.7

100,000 12,000,000 500,000 22,300,000 208 115.5 9295 4220

500,000 60,000,000 2,500,000 58,800,000 1042 576 24,510 11,127

1,000,000 120,000,000 5,000,000 189,00000000 2084 1155 78,784 35,766

(I) On the basis of a dose of p.p.m. or 416.85 lbs. per million gallons.
(2) On the basis of a dose of 27.7 p.p.m. or 189.24 lbs. per million gallons and results in 10 p.p.m. of As.


1. Address by Colonel John R. Wood,MC, Department of
Defense, Office of Public Information, Washington
25, D. C. (June 1950)

2. "Health Services and Special Weapons Defense".
Federal Civil Defense Administration, U. S. Govern-
ment Printing Office, Washington, D. C. (Dec. 1950)

3. Ruchboft, C. C., et al. "Derection and Analysis of
Arsenic in Water Contaminated by Chemical Warfare
Agents" Public Health Reports 58, 1761-1771, 1943.

4. Santhis, Joseph M. "Chemical Warfare and Water
Supplies" JAWWA 39, 1179-1196, (1946).

5. TechnicalManual for the Senior Gas Officer of Civil-
ian Defense. Prepared under the direction of the
Medical Division of the Office of Civilian Defense,
Washington, D. C., and the National Institutes of
Health, Division of Public Health Methods, Cincin-
nati. Ohio. Prepared by the Faculty of the College
of Medicine, Univ. of Cincinnati and the Staff of
the Office of Stream Pollution Investigations. U.S.
Public Health Service, Cincinnati, Ohio. (July 1942)

6. U. S. War Department Technical Manual TM-3-215
"Military Chemistry and Chemical Agents" (1942)

7. Wiatt, Alden H. 'Gas Warfare" Duell, Sloan and
Pierce, New York (Rev. Ed. 1944)

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