• TABLE OF CONTENTS
HIDE
 Front Cover
 Credits
 Table of Contents
 Introduction
 Pharmacological action of phosphatic...
 Symptoms of parathion poisonin...
 Use of parathion on citrus...
 Precautions for handling parat...
 Treatment of parathion poisoni...
 Summary
 Literature cited














Group Title: Bulletin - University of Florida Agricultural Experiment Station ; 479
Title: Toxicology of parathion and other phosphatic insecticides and precautions for their use on citrus
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Permanent Link: http://ufdc.ufl.edu/UF00027592/00001
 Material Information
Title: Toxicology of parathion and other phosphatic insecticides and precautions for their use on citrus
Series Title: Bulletin - University of Florida Agricultural Experiment Station ; 479
Physical Description: Book
Language: English
Creator: Griffiths, James T.
Williams, John W.
Thompson, W. L.
Stearsn, C. R. Jr.
Publisher: University of Florida Agricultural Experiment Station
Publication Date: 1951
 Record Information
Bibliographic ID: UF00027592
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.

Table of Contents
    Front Cover
        Page 1
    Credits
        Page 2
        Page 3
    Table of Contents
        Page 4
    Introduction
        Page 5
        Page 6
        Page 7
    Pharmacological action of phosphatic insecticides
        Page 8
        Page 9
        Page 10
        Page 11
    Symptoms of parathion poisoning
        Page 12
        Page 13
        Page 14
        Page 15
    Use of parathion on citrus in Florida
        Page 16
    Precautions for handling parathion
        Page 16
        Page 17
        Page 18
        Page 19
        Page 20
        Page 21
        Page 22
    Treatment of parathion poisoning
        Page 23
    Summary
        Page 23
    Literature cited
        Page 23
        Page 24
Full Text


Bulletin 479


June, 1951


UNIVERSITY OF FLORIDA
AGRICULTURAL EXPERIMENT STATIONS
WILLARD M. FIFIELD, Director
GAINESVILLE, FLORIDA
(A Contribution From the Citrus Experiment Station)


Toxicology of Parathion and Other

Phosphatic Insecticides and Precautions

For Their Use on Citrus

JAMES T. GRIFFITHS, JOHN W. WILLIAMS, W. L. THOMPSON, AND
C. R. STEARNS, JR.


K^V*!eW Jiak.










BOARD OF CONTROL
Frank M. Harris, Chairman, St. Peters-
burg
N. B. Jordan, Quincy
Hollis Rinehart, Miami
Eli H. Fink, Jacksonville
George J. White, Sr., Mount Dora
W. F. Powers, Secretary, Tallahassee

EXECUTIVE STAFF
J. Hills Miller, Ph.D., President"
J. Wayne Reitz, Ph.D., Provost for Agr.a
Willard M. Fifield, M.S., Director
J. R. Beckenbach, Ph.D., Asso. Director
L. 0. Gratz, Ph.D., Asst. Dir., Research
Geo. F. Baughman, M.S., Business Mgr.'
Rogers L. Bartley, B.S., Admin. Mgr.'
Claranelle Alderman, Accountants

MAIN STATION, GAINESVILLE

AGRICULTURAL ECONOMICS
H. G. Hamilton, Ph.D., Agr. Econo-
mist' 8
R. E. L. Greene, Ph.D., Agr. Economist
Zach Savage, M.S.A., Associate
A H. Spurlock, M.S.A., Associate
D. E. Alleger, M.S., Associate
D. L. Brooke, M.S.A., Associate
M R. Godwin, Ph.D., Associate
H. W. Little, M.S., Assistant'
Tallmadge Bergen, B.S., Assistant
D. C. Kimmel, Ph.D., Assistant
A. L. Larson, Ph.D., Agr. Economist

Orlando, Florida (Cooperative USDA)
G. Norman Rose, B.S., Asso. Agr.
Economist
J. C. Townsend, Jr., B.S.A., Agr.
Statistician2
J. B. Owens, B.S.A., Agr. Statistician
AGRICULTURAL ENGINEERING
Frazier Rogers, M S.A., Agr. Engineer' 3
J. M. Johnson, B.S.A.E., Asso. Agr. Eng.'
J. M. Myers, B S., Asso. Agr. Engineer
_.. E. Choate, B.S.A.E., Asst. Agr. Engr '
A. M. Pettis, B.S.A.E., Asst. Agr. Eng.- s

AGRONOMY
Fred H. Hull, Ph.D., Agronomist'
G. B. Killinger, Ph.D., Agronomist3
H. C. Harris, Ph.D., Agronomist
R. W. Bledsoe, Ph.D., Agronomist
W. A. Carver, Ph.D., Associate
Darrel D. Morey, Ph.D., Associate
Fred A. Clark, B.S., Assistant
Myron C. Grennell, B.S.A.E., Assistant
E. S. Horner, Ph.D., Assistant
A. T. Wallace, Ph.D., Assistant
D. E. McCloud, Ph.D., Assistant

ANIMAL HUSB. AND NUTRITION
T, J. Cunha, Ph.D., An. Hush.'1
R. S. Glasscock, Ph.D., An. Husb.'
G. Davis, Ph.D., Animal Nutritionists
R. L. Shirley, Ph.D., Biochemist'
J. E. Pace, M.S., Asst. An. Hush '
S. John Folks, B.S.A., Asst. An. Husb."
Katherine Boney, B.S., Asst. Chem.
James M. Wing, M.S., Asst. Dairy Husb.
A. M. Pearson, Ph.D., Asst. An. Husb.S
John D. Feaster, Ph.D., An. Nutritionist
H. D. Wallace, Ph.D., Asst. An Husb.

DAIRY SCIENCE
E. L. Fouts, Ph.D.. Dairy Tech.' '
R. B. Becker, Ph.D., Dairy Husb.'
S. P. Marshall, Ph.D., Asso. Dairy
Husb.'
W. A. Krienke, M.S., Asso. in Dairy Mfs.'
P. T. Dix Arnold, M.S.A., Asst. Dairy
Husb.2
Leon Mull, Ph.D., Asst. Dairy Tech.
H. Wilkowske, Ph.D., Asst. Dairy Tech.


EDITORIAL
J. Francis Cooper, M.S.A., Editor'
Clyde Beale, A.B.J., Associate Editor'
L. Odell Griffith, B.A.J., Asst. Editor'
J. N. Joiner, B.S.A., Assistant Editor' *

ENTOMOLOGY
A. N. Tissot, Ph.D., Entomologist'
L. C. Kuitert, Ph.D., Associate
H. E. Bratley, M.S.A., Assistant
F. A. Robinson, M.S., Asst. Apiculturist

HOME ECONOMICS
Ouida D. Abbott, Ph.D., Home Econ.'
R. B. French, Ph.D., Biochemist
HORTICULTURE
G. H. Blackmon, M.S.A., Horticulturist'
F. S. Jamison, Ph.D., Horticulturist'
Albert P Lorz, Ph.D., Horticulturist
R. K. Showalter, M.S., Asso. Hort.
R. A. Dennison, Ph.D., Asso. Hort.
R. H. Sharpe, M.S., Asso. Horticulturist
F. S. Lagasse, Ph.D., Asso. Hort.2
R. D. Dickey, M.S.A., Asst. Hort.
V. F. Nettles, Ph.D., Asst. Hort.
L. H. Halsey, M.S.A., Asst. Hort.
C. D. Hall, Ph.D., Asst. Horticulturist
S. E. McFadden, Ph.D., Asst. Hort.
Austin Griffiths, Jr., B.S., Asst. Hort.
LIBRARY
Ida Keeling Cresap, Librarian
PLANT PATHOLOGY
W. B. Tisdale, Ph.D., Plant Patholo-
gist' I
Phares Decker, Ph.D., Plant Pathologist
Erdman West, M.S., Mycologist and
Botanist
Robert W. Earhart, Ph.D., Plant Path.2
Howard N. Miller, Ph.D., Asso. Plant
Path.
Lillian E. Arnold, M.S., Asst. Botanist
C. W. Anderson, Ph.D., Asst. Plant Path.

POULTRY HUSBANDRY
N. R. Mehrhof, M.Agr., Poultry Husb.' '
J. C.' Driggers, Ph.D., Asso. Poultry
Husbh.
SOILS
F. B. Smith, Ph.D., Microbiologist1
Gaylord M. Volk, Ph.D., Soils Chemist

J. R. Henderson, M.S.A., Soil Technolo-
gists
J. R. Neller, Ph.D., Soils Chemist
Nathan Gammon, Jr., Ph.D., Soils
Chemist
R. A. Carrigan, Ph.D., Biochemist'
Ralph G. Leighty, B.S., Asso. Soil
Surveyor'
G. D. Thornton, Ph.D., Asso.4
Microbiologist'
Charles F. Eno, Ph.D., Asst. Soils
Microbiologist
H. W. Winsor, B.S.A., Assistant Chemist
R. E. Caldwell, M.S.A., Asst. Chemist'
V. W. Carlisle, B.S., Asst. Soil Surveyor
.ames H. Walker, M.S.A., Asst. Soil
Surveyor
S N. Edson, M.S., Asst. Microbiologist
William K. Robertson, Ph.D., Asst.
Chemist
0. E. Cruz, B.S.A., Asst. Soil Surveyor
W. G. Blue, Ph.D., Asst. Biochemist
VETERINARY SCIENCE
D. A. Sanders, D.V.M., Veterinarian'
M. W. Emmel, D.V.M., Veterinarian'
C. F. Simpson, D.V.M., Asso.
Veterinarian
L. E. Swanson, D.V.M., Parasitologist
Glenn Van Ness, D.V.M., Asso. Poultry
Pathologist
G. E. Batte, D.V.M., Asso. Parasitologist









BRANCH STATIONS

NORTH FLORIDA STATION, QUINCY
J. D. Warner, M.S., Vice-Director in
Charge
R. R. Kincaid, Ph.D., Plant Pathologist
L. G. Thompson, Ph.D., Soils Chemist
W. C. Rhoads, M.S., Entomologist
W. H. Chapman, M.S., Asso. Agronomist
Frank S Baker, Jr., B.S,, Asst. An.
Husb.
Mobile Unit, Monticello
R. W. Wallace, B.S., Associate
Agronomist
Mobile Unit, Marianna
R. W. Lipscomb, M.S., Associate
Agronomist
Mobile Unit, Pensacola
R. L. Smith, M.S., Associate Agronomist

Mobile Unit, Chipley
J. B. White, B.S.A., Associate
Agronomist

CITRUS STATION, LAKE ALFRED
A. F. Camp, Ph.D., Vice-Director in
Charge
W. L. Thompson, B.S., Entomologist
J. T. Griffiths, Ph.D., Asso.
Entomologist
R. F. Suit, Ph.D., Plant Pathologist
E. P. Ducharme, Ph.D., Asso. Plant
Path.4
R. K. Voorhees, Ph.D., Asso.
Horticulturist
C. R. Stearns, Jr., B.S.A., Asso. Chemist
T. W. Sites. M.S.A., Horticulturist
H. 0. Sterling, B.S., Asst. Horticulturist
H. J. Reitz, Ph.D., Asso. Horticulturist
Francine Fisher, M.S., Asst. Plant Path.
I. W. Wander, Ph.D., Soils Chemist
J. W. Kesterson, M.S., Asso. Chemist
R. N. Hendrickson, B.S., Asst. Chemist
J. C. Bowers, M.S., Asst. Chemist
D. S. Prosser, Jr., B.S., Asst.
Horticulturist
R. W. Olsen, B.S., Biochemist
F. W. Wenzel, Jr., Ph.D., Supervisory
Chem.
Alvin H. Rouse, M.S., Asso. Chemist
H. W. Ford, Ph.D., Asst. Horticulturist
L W. Faville, Ph.D., Asst. Chemist
L. C. Knorr, Ph.D., Asso. Histologist4
R. M. Pratt, B.S., Asso. Ent.-Pathologist
W. A. Simanton, Ph.D., Entomologist
E. J. Desyck, Ph.D., Asso. Horticulturist
C. D. Leonard, Ph.D., Asso. Horticul-
turist

EVERGLADES STATION,
BELLE GLADE
R. V. Allison, Ph.D., Vice-Director in
Charge
Thomas Bregger, Ph.D., Sugar
Physiologist
J. W. Randolph, M.S., Agricultural Egr.
W. T. Forsee, Jr., Ph.D., Chemist
R. W. Kidder, M.S., Asso. Animal Hush.
T. C. Erwin, Assistant Chemist
C. C. Seale, Asso. Agronomist
N. C. Hayslip, B.S.A., Asso. Entomolo-
gist
E. A. Wolf, M.S., Asst. Horticulturist
W. H. Thames. M.S., Asst. Entomologist
W. N. Stoner, Ph.D., Asst. Plant Path.
W. A. Hills, M.S., Asso. Horticulturist
W. G. Genung, B.S.A., Asst. Entomologist
D. W. Smith, B.S., Asst. Chemist
Frank V. Stevenson, M.S., Asso. Plant
Pathologist
Raymond H. Webster, Ph.D., Asst.
Agronomist
Robert J. Allen, M.S., Asst. Agronomist


SUB-TROPICAL STATION,
HOMESTEAD
Geo. D. Ruehle, Ph.D., Vice-Dir. in
Charge
D. O. Wolfenbarger, Ph.D., Entomologist
Francis B. Lincoln, Ph.D., Horticulturist
Milton Cobin, B.S., Asso. Horticulturist
Robert A. Conover, Ph.D., Plant Path.
John A. Malcolm, Ph.D., Asso. Soils
Chemist
R. W. Harkness, Ph.D., Asst. Chemist

W. CENT. FLA. STATION,
BROOKSVILLE
William Jackson, B.S.A., Animal
Husbandman in Charge2
RANGE CATTLE STATION, ONA
W. G. Kirk, Ph.D., Vice-Director in
Charge
E. M. Hodges, Ph.D., Agronomist
D. W. Jones, M.S., Asst. Soil
Technologist

CENTRAL FLORIDA STATION,
SANFORD
R. W. Ruprecht, Ph.D., Vice-Dir. in
Charge
J. W. Wilson, Sc.D., Entomologist
P. J. Westgate, Ph.D., Asso. Hort.
Ben F. Whitner, Jr., B.S.A., Asst. Hort.
Geo. Swank, Jr., Ph.D., Asst. Plant Path.

W. FLA. STATION, JAY
C. E. Hutton, Ph.D., Vice-Director in
Charge
H. W. Lundy, B.S.A., Associate
Agronomist

SUWANEE VALLEY STA., LIVE OAK
G. E. Ritchey, M.S., Agronomist in
Charge
GULF COAST STA., BRADENTON
E. L. Spencer, Ph.D., Soils Chemist in
Charge
E. G. Kelsheimer, Ph.D., Entomologist
David G. Kelbert, Asso. Horticulturist
Robert 0. Magie, Ph.D., Gladioli Hort.
J. M. Walter, Ph.D., Plant Pathologist
Donald S. Burgis, M.S.A., Asst. Hort.
C. M. Geraldson, Ph.D., Asst. Hort.

FIELD LABORATORIES

Watermelon, Grape, Pasture-Leesbnrg
G. K. Parris, Ph.D., Plant Path. in
Charge
C. C. Helms, Jr., B.S., Asst. Agronomist
Strawberry-Plant City
A. N. Brooks, Ph.D.. Plant Pathologist

Vegetables-Hastings
A. H. Eddins, Ph.D., Plant Path. in
Charge
E. N. McCubbin, Ph.D., Horticulturist

Pecans-Monticello
A. M. Phillips, B.S., Asso. Entomologist2
John R. Large, M.S., Asso. Plant Path.

Frost Forecasting-Lakeland
Warren 0. Johnson, B.S., Meteorologist2

1 Head of Department
2 In cooperation with U. S.
I Cooperative, other division, U. of F.
SOn leave.







CONTENTS


INTRODUCTION ...---- __ _-------------_.------------ 5
PHARMACOLOGICAL ACTION OF PHOSPHATIC INSECTICIDES ---..... -------... 8
A CANOPY FOR A TRACTOR --...... -------------------------- 11
SYMPTOMS OF PARATHION POISONING ........----------------------------- 12
USE OF PARATHION ON CITRUS IN FLORIDA ----------- ] 6(
PRECAUTIONS FOR HANDLING PARATHION------------------- 16
Protective Clothing .------------ ---------- ---- 17
Personal Cleanliness ......... ............................. ......... 17
Tractor Canopies or Raincoats ----------------------..... 18
Danger in Groves After Spraying.--- -------- 20
Mixing Operations --. ------... -------------. ------ 21
Warning Signs After Spraying. --------- ---- 22
Cleaning Spray Equipment -...------. .-..---. -------- 22
Working After Sickness... ... ---------.. ... ------.-..-. 22
TREATMENT OF PARATHION POISONING ... .. -------------------- 23
SUMMARY ..--......-------.--- .... ----------.-- --- 23
LITERATURE CITED ..-..--. ----------------. --- 23


Fig. 1.-Cut the bag open with a knife. Do not tear it open. Wear
natural rubber gloves, mask and hat. Keep sleeve? rolled down.

Opening a Parathion Bag

DO THIS NOT THIS







Toxicology of Parathion and Other

Phosphatic Insecticides and Precautions
For Their Use on Citrus

JAMES T. GRIFFITHS, JOHN W. WILLIAMS, W. L. THOMPSON, AND
C. R. STEARNS, JR.'


Introduction
In 1947 early trials with the insecticide parathion (22)2 indi-
cated that this material offered promise of satisfactorily replac-
ing oil as a scalicide for citrus. It was known that parathion
was a poisonous substance and it remained to be determined
whether it could be safely used in commercial spraying opera-
tions. Since that time much research has been completed, con-
cerned not only with the action of parathion and other organic
phosphatic insecticides on human beings but also with ways and
means to handle these insecticides safely.
This bulletin is intended to explain the action of phosphatic
insecticides upon the human body, to clarify some of the mis-
information that has existed concerning phosphatic insecticides,
and finally to suggest specific precautions for the use of parathion
so that it can be handled safely by grove labor under field con-
ditions.
It is realized that parathion may be an insecticide of only
transitory importance, used for a few years and then discarded
in favor of a still better material. However, it is probable that
the replacement for parathion will be another phosphatic insecti-
cide with similar pharmacological characteristics. Thus, the in-
formation that has been gathered concerning parathion may also
be applicable to other newly developed insecticides.
Shortly after the close of World War II a new material known
as HETP (hexaethyl tetraphosphate) appeared on the market
for use as a replacement for nicotine. It proved to be the fore-
runner of a number of new insecticidal compounds, all related
as esters of phosphoric acid and all with similar pharmacological
effects in their toxicity to warm-blooded animals. HETP was
shortly replaced by TEPP tetraethyll pyrophosphate), which was
1 Asso. Entomologist, Citrus Experiment Station; Pathologist (M.D.),
Morrell Memorial Hospital, Lakeland; Entomologist, Citrus Experiment
Station; and Associate Chemist, Citrus Experiment Station, respectively.
2 Italic figures in parentheses refer to Literature Cited in thz back of
this bulletin.






Florida Agricultural Experiment Stations


found to be the active ingredient in HETP. The structural
formula of TEPP was believed to be the following (2) :

SC2\ 0 /OC2H5
P-0 p

H5C20 OC2H5
Parathion is a member of the phosphatic group of insecticides.
Parathion is the approved common name for the chemical
O,0-diethyl O-p-nitrophenyl thiophosphate. Its structural for-
mula is (20):
0C2H5
S.P 0 \NO2

0
C2H5
On citrus it proved to be an excellent scalicide. It not only
was a replacement for oil in the control of Florida red scale and
purple scale but also was effective against citrus mealybugs and
cottony cushion scale. Thus, for the first time adequate chemical
control measures of these latter two pests were assured. It fol-
lowed naturally that parathion would be used in large quantities
on citrus in Florida. Since the introduction of parathion upon
the insecticide market numerous other phosphatic compounds
have been made available for testing. One is a combination of
parathion with the dimethyl derivative of parathion, being mar-
keted under the trade name Metacide.
Another material, available for use on some crops but not
recommended for use on citrus, is known as EPN (ethyl p-nitro-
phenyl thionobenzenephosphonate). Current advertising material
for this compound lists essentially the same precautions for its
use as have been laid down for parathion. Its structural formula
is:
S

O- p-- N
0 C2H5






Toxicology of Parathion


Spraying Parathion with a Speed Sprayer


DO THIS


t INOT TH


Fig. 2.-The tractor driver should wear a mask, hat, natural rubber
gloves and long sleeves. A poncho or a rain coat can be used to throw
over his head and shoulders if spray drift is a problem.







Florida Agricultural Experiment Stations


The most recent group of phosphatic materials to gain inter-
est in the entomological world have been materials known as
systemic poisons. These can be absorbed through either roots
or foliage and taken into the tissues of the plant. There they
serve as an insecticidal material against mites and other insects
which feed upon the plants. One of these, known as OMPA
(octamethyl pyrophosphoramide), has been described by Ripper
et al. (19). Its structural formula is as follows:

(CH3)2N 0 0 N(CH3)2

P --0 -P
/ \

(CH3)2N N(CH3)2
Other closely related materials are in the experimental stage
and some will undoubtedly soon be commercially available.

Pharmacological Action of Phosphatic Insecticides
All of the materials mentioned above have the same general
physiological action upon warm-blooded animals. All may be
classed as anti-cholinesterase agents. These chemicals destroy
a material in the body which is known as cholinesterase. Ac-
tually, cholinesterase is an enzyme which has to do with the nor-
mal functioning of the nervous system (3). Cholinesterase is
present not only in all warm-blooded animals but also in insects,
and it is the destruction of cholinesterase in insects by the phos-
phatic insecticides which gives these materials their insecticidal
value. When cholinesterase is destroyed the nervous system no
longer can function properly, symptoms occur and, if extreme,
death ultimately may result. The actual function of cholines-
terase is to destroy a substance called acetylcholine. In the
presence of the enzyme cholinesterase, acetylcholine is broken
down into choline and acetic acid:
acetylcholine cholinesterase acetic acid + choline
When a muscle contracts, the actual sequence of events is due
to an impulse being sent from the brain or nerve center along
a nerve to that muscle. At the point where the nerve ending
joins the muscle fibers the nerve impulse causes the liberation of
acetylcholine, and it is the presence of acetylcholine which causes
the muscle to contract. Normally there is cholinesterase present







Toxicology of Parathion


at the point where the acetylcholine is formed, and acetic acid
and choline are formed immediately. As soon as the acetyl-
choline is destroyed the muscle stops its contraction. If cholines-
terase is not present acetylcholine accumulates and this causes
a continuous twitching of the muscle. Muscular twitching is a
symptom of parathion or other phosphatic insecticide poisoning.
Thus, the loss of cholinesterase due to the absorption of a phos-
phatic insecticide results in an accumulation of acetylcholine.
Not only are acetylcholine and cholinesterase necessary
for the proper functioning of muscles, they are also necessary
and are present at nerve endings in glands and in the vital organs
of the body such as the liver, the pancreas, the stomach, the
brain, etc. The presence of cholinesterase is necessary in all
tissues of the body. When a phosphatic insecticide has been
absorbed into the body the end result is the destruction of or a
reduction in the amount of cholinesterase present. A person may
be able to tolerate temporarily a fairly large cholinesterase re-
duction, but if too much is destroyed, symptoms result.
Phosphatic insecticide poisoning may occur as the result of
a very large dose of the insecticide. However, in most cases
under field conditions poisoning is the end product of prolonged
exposures to small amounts of parathion or other similar insecti-
cides. There is good evidence to show that parathion is not
stored in the organs of the body (4, 13) and thus it is not cumu-
lative in the sense that lead or arsenic poisoning is cumulative.
In lead poisoning, for example, quantities of lead actually ac-
cumulate in the tissues of the body. In the case of parathion the
action may be cumulative. If it be assumed that the body is
capable of producing 50 units of cholinesterase per day and the
parathion exposure is such that only 45 units are destroyed per
day the body is capable of replacing cholinesterase as rapidly as
it is destroyed. Thus, there will be no lowering of the cholines-
terase levels in the tissues of the body and no symptoms of
poisoning will occur. However, if the exposure to parathion
results in the destruction of 60 units of cholinesterase per day,
this represents a loss of 10 units per day and at the end of each
day there will be 10 less units of cholinesterase in the body than
when the day started. If this process be continued, ultimately
the individual will have such a severe lowering of his cholines-
terase reserves that symptoms of poisoning will appear and he
may be seriously ill.
A complicating factor in the cumulative effect of parathion






Florida Agricultural Experiment Stations


Spraying with Hand Machine

DO THIS NOT THIS


Fig. 3.-Spray so as to avoid as much spray drift as possible. Always
wear a hat, respirator, long sleeves and natural rubber gloves. Wear
boots. The trousers may be tucked inside or worn on the outside of boots
as in the left picture.







Toxicology of Parathion


upon cholinesterase levels of the body is due to the fact that a
person ordinarily will not show symptoms of poisoning until the
cholinesterase levels have been markedly reduced. However,
there was some evidence during the 1950 spray season, when
studies of cholinesterase were made on a number of poisoned
individuals, to indicate that there is not always a severe lowering
of the blood levels of cholinesterase before symptoms occur (25).


A Canopy for a Tractor


Fig. 4.-A removable canopy will minimize the spray drift hazard. This can
be used in most groves. (See Prosser et al., A Protective Canopy for Tractor
Drivers, Fla. Ag. Expt. Sta. Cir. S-29.)

Cholinesterase is normally present in both red blood cells and
the plasma or the fluid fraction of the blood. Experimental work
has indicated that the amount of cholinesterase in the red blood
cells is relatively commensurate with that in other tissues in the
body (6, 11). Thus, if the amount of cholinesterase in the red
blood cells is decreased due to parathion absorption, it may be
assumed that cholinesterase has been lowered in other tissues in
the body, but this effect will vary somewhat from one tissue to
another.







Florida Agricultural Experiment Stations


A test for the amount of cholinesterase present in the blood
thus affords a rough means of determining the extent of para-
thion absorption. The test is not infallible, but it is an excellent
tool to be used in the diagnosis of parathion poisoning, to be
used in pre-employment examinations to determine whether a
man might be particularly susceptible to parathion, or to be used
to indicate whether a man has recovered from a previous illness
and is again fit for a job where parathion exposure will be in-
volved. All of the phosphates which have been investigated do
not have the same identical effects upon the reduction of blood
cholinesterase and upon its return to normal levels after exposure
to the insecticide has been stopped, but the pattern is similar.
Plasma cholinesterase is rapidly destroyed in the presence of
a phosphatic insecticide such as parathion, but return to normal
levels is also rapid. If plasma cholinesterase be reduced 75
percent it may return to normal within a matter of 7 to 10 days.
Red blood cell cholinesterase will be destroyed more slowly than
the plasma fraction and similarly it is replaced more slowly. It
is replaced at the rate at which new red cells are formed, and
thus it returns toward normality at the rate of about 1 percent
per day (6, 9, 10). The cholinesterase of the brain and muscles
is also replaced slowly and three months may be required after
inactivation by di-isopropyl fluorophosphate before normal ac-
tivity returns. This curve of regeneration for these tissues is
parabolic. Thus, the rate during the first few weeks is rapid,
but it slows considerably after that time. Generally, there will
be a 50 percent recovery in the first few weeks (5, 14, 18) and it
may take six to eight weeks for the other 50 percent.
Cholinesterase is apparently manufactured by the liver and
the production of plasma cholinesterase is greatly diminished by
liver damage (10, 23). Thus, any disease which results in im-
proper liver function could result in a failure to maintain high
cholinesterase levels. This suggests the rather obvious con-
clusion that a person suffering from liver malfunction should
not be exposed to the hazards of handling parathion or similar
phosphatic materials. At least one case of parathion poisoning
has been reported (25) where the man was suffering with liver
disease.

Symptoms of Parathion Poisoning
When parathion poisoning occurs, rather well defined symp-
toms are present. These may be divided into three separate







Toxicology of Parathion


categories -(11, 15, 24). One group of symptoms, which closely
resembles stimulation of the parasympathetic nervous system,
includes nausea, diarrhea and increased secretion of saliva, tears
and sweat. Another common symptom is the constriction of the
pupils of the eye. Faulty vision may accompany this condition.
Respiratory difficulty with a feeling of tightness in the chest is
another manifestation. This group of symptoms is known as the
muscarinic effects of phosphatic insecticide poisoning.
A second set of symptoms is known as the nicotinic symp-
toms. These include twitching of the muscles in the eyelids and
the tongue which may be followed by generalized jerking of the
muscles of the entire body. At the same time, overall muscular
weakness develops. Muscular weakness may become so severe
that the muscles involved in breathing fail to respond normally
and artificial respiration is necessary.
A third set of symptoms, known as the central nervous
system effects, includes most commonly a headache, which may
be accompanied by dizziness and a general feeling of uneasiness
and restlessness.
If poisoning is severe, coma and death may result. Grob (9)
has reported that the average time between the last exposure
to parathion and death varies between 1 and 211/2 hours, with an
average of 101/2 hours. There is a lapse of from 1 to 131/2 hours
between the time of last exposure to parathion and the onset
of poisoning symptoms, the average time being approximately
9 hours. In general, it appears that symptoms follow exposure
to parathion somewhat more slowly than in the case of some of
the other organic phosphates.
Parathion has caused the death of three people in the field
during the course of spray operations, but only one of these was
in Florida (1). Several other individuals have died in chemical
plants while handling technical grade material. During the 1950
spray season, in which over 1,000 tons of parathion were applied
to Florida citrus groves, records were obtained on a number
of cases of supposed parathion poisoning (7). Forty-eight cases
were reported to the Citrus Experiment Station. Of these, 11
were definitely not parathion poisoning, 12 were doubtful and
25 could be considered to be relatively definite cases of parathion
illness. Most cases occurred among men who were using hand
spray guns. The next most hazardous job seemed to be mixing
the spray material in the spray tank. Information was obtained
which showed that Speed Sprayer drivers had a relatively high







Florida Agricultural Experiment Stations


exposure to spray drift; nevertheless, parathion poisoning among
them was a rarity. It was noted that many spray operators were
so afraid of handling parathion that they often thought they
were sick. Such psychosomatic cases emphasize the fact that
some test such as one for blood cholinesterase is necessary to
make positive diagnoses of parathion poisoning. Mild poisoning
cases could exhibit nausea and headache, and these same symp-
toms would be shown by individuals who were working in fear
of the material. This study indicated that parathion, if handled
properly, can be used with a minimum hazard to the spray oper-
ator.
The amount of parathion necessary to produce poisoning
symptoms for man has not been definitely determined, but some
information concerning its toxicity is available. Parathion has
been estimated to be as much as 70 times more toxic to man
than DDT (16). Results from different sources vary, but in
general the oral LD,,, dosage for experimental animals varied
between as little as 3 and as high as 30 mg. per kg. (12, 13, 16).
LD.,o means the amount of parathion at which 50 percent of the
animals received lethal dosages. In terms of parts per million in
the diet over a period of two years, animals fed as high as 50 parts
per million showed no symptoms and no evidence of parathion
storage. At 100 parts per million in the diet, occasional symp-
toms were manifested (8). Based on data similar to these,
Lehman (17) stated that 2 to 5 parts per million of parathion
in the diet would not represent a health hazard. Even on a whole
fruit weight basis the amount of parathion found in the fruit
has always been lower than 1 part per million (21). Thus,
there appear to be no health hazards associated with parathion
residues in citrus fruit.
It is of major importance to determine the way in which citrus
grove labor may be poisoned. When parathion work was first
begun, emphasis was placed upon the wearing of respirators
with organic vapor cartridges. This is of considerable import-
ance, but data collected during the 1950 spray season indicated
that other factors were of even greater importance (7, 25). Most
of the cases of authentic parathion poisoning reported were in
spite of the wearing of respirators. Parathion vapors in a grove
are probably not particularly hazardous. Animals which were
exposed in a grove for 10 days following an extremely heavy
application of parathion showed no effect on blood cholinesterase
and no parathion poisoning symptoms (7). However, respira-






Toxicology of Parathion


tors are essential as a means of minimizing the hazard of para-
thion vapors and also as a means of preventing the inhalation
of spray or dust particles upon which parathion is impregnated.
In view of the data on oral toxicity already presented, it appears
likely that the contamination of food will be of only minor con-
sideration as a possible source of poisoning. Skin absorption is
probably a major route of entry for parathion into the body.
Because of this the precautions which have to do with lessening
skin contact with either wettable powder or spray drift should
be rigorously enforced.


Fig. 5.-Have tank almost full of water and agitator going. Introduce
parathion onto surface of water and let the agitation pull the material out
of the bag. Always wear a respirator, natural rubber gloves, long sleeves
and hat.
Adding Wettable Parathion to Tank


DO THIS


NOT THIS


'~Ih
3Qif







Florida Agricultural Experiment Stations


Use of Parathion on Citrus in Florida
Parathion is used primarily for the control of scale insects
but it may be used as an aphicide and it may be used also in
the control of such insects as grasshoppers and pumpkin bugs.
However, most parathion is used as a replacement for oil sprays
in the control of purple scale and Florida red scale. Two basic
recommendations have been made for parathion applications. If
a single parathion application is to control scales for an entire
12-month period, it is recommended that 1%/ to 2 pounds of
a 15 percent wettable material be used per 100 gallons of spray,
and that this spray be applied during June, July or August.
If it is desired to split the parathion application into two
parts, one should be applied at post-bloom time and the second
during the period from June through August. Each spray
should contain only 1 pound of a 15 percent wettable material
per 100 gallons of spray. Both spray programs were followed
during 1950 and gave results generally as satisfactory as oil
spraying.

Precautions for Handling Parathion
The precautions suggested below are designed to minimize
the hazards which may exist during parathion spray operations
or after a grove has been sprayed. All are designed to reduce
possible parathion exposure and all should be rigidly adhered
to. Brief exposures to parathion are not particularly hazardous,
but the more prolonged the exposure the more dangerous it is.
Where men are to be exposed to parathion sprays for more than
-a week medical examinations should be given prior to employ-
ment (7, 25). This examination should include a general physical
check-up as well as specific tests for liver function (serum
protein), blood cholinesterase and anemia. A history of liver
disease, low serum protein, low blood cholinesterase or anemia
could predispose an individual to parathion poisoning. Psycho-
logical instability could easily result in cases of simulated para-
thion poisoning.
It is important that red blood cell cholinesterase be deter-
mined for all individuals who are to spray with parathion. This
test would serve several purposes. It would indicate whether
normal levels of red blood cell cholinesterase are present before
the man starts using it. His own norm would thus be established
and cholinesterase tests at a later date would be more readily







Florida Agricultural Experiment Stations


Use of Parathion on Citrus in Florida
Parathion is used primarily for the control of scale insects
but it may be used as an aphicide and it may be used also in
the control of such insects as grasshoppers and pumpkin bugs.
However, most parathion is used as a replacement for oil sprays
in the control of purple scale and Florida red scale. Two basic
recommendations have been made for parathion applications. If
a single parathion application is to control scales for an entire
12-month period, it is recommended that 1%/ to 2 pounds of
a 15 percent wettable material be used per 100 gallons of spray,
and that this spray be applied during June, July or August.
If it is desired to split the parathion application into two
parts, one should be applied at post-bloom time and the second
during the period from June through August. Each spray
should contain only 1 pound of a 15 percent wettable material
per 100 gallons of spray. Both spray programs were followed
during 1950 and gave results generally as satisfactory as oil
spraying.

Precautions for Handling Parathion
The precautions suggested below are designed to minimize
the hazards which may exist during parathion spray operations
or after a grove has been sprayed. All are designed to reduce
possible parathion exposure and all should be rigidly adhered
to. Brief exposures to parathion are not particularly hazardous,
but the more prolonged the exposure the more dangerous it is.
Where men are to be exposed to parathion sprays for more than
-a week medical examinations should be given prior to employ-
ment (7, 25). This examination should include a general physical
check-up as well as specific tests for liver function (serum
protein), blood cholinesterase and anemia. A history of liver
disease, low serum protein, low blood cholinesterase or anemia
could predispose an individual to parathion poisoning. Psycho-
logical instability could easily result in cases of simulated para-
thion poisoning.
It is important that red blood cell cholinesterase be deter-
mined for all individuals who are to spray with parathion. This
test would serve several purposes. It would indicate whether
normal levels of red blood cell cholinesterase are present before
the man starts using it. His own norm would thus be established
and cholinesterase tests at a later date would be more readily







Toxicology of Parathion


interpreted. Thus, periodic cholinesterase determinations could
be used to tell if he was being affected by parathion absorption.
This might prevent a case of poisoning. Similarly, should the
man become ill, a blood test would enable a more reliable
diagnosis if the man's own normal level were known.

Protective Clothing
Masks.-Some type of respirator should be worn whenever
an individual is exposed to parathion. It may be one which covers
only the nose and mouth, but it must have a cartridge or
chamber which will remove organic vapors, as well as a paper
filter disc3. In wearing such a mask, care should be taken to in-
sure that the mask does not leak about the nose or cheeks. Paper
filters should be changed daily and the organic vapor cartridges
changed every few days. Once a week is probably often enough,
but complete information is not available. The operator should
keep the mask clean and under no circumstances should spray
residues be allowed on the inside of the mask. It is desirable
that the mask be washed at the end of each work day.
Coveralls.-Coveralls are the best type of clothing for spray
labor to wear. These should be worn no longer than one day
without washing and should be changed at half-day intervals
if extreme spray drift is encountered. The sleeves should be
long in order to minimize skin exposure (see Fig. 2).
Rubber Boots and Gloves.-All men handling parathion, fill-
ing tanks or exposed to spray drifts should wear natural rubber
gloves. Since parathion can accumulate in leather or canvas
shoes, rubber boots should be worn by spray hands operating
pressure guns and walking in the grove (see Fig. 3).

Personal Cleanliness
A thorough bath should be taken as soon as the work day is
finished. Particular emphasis should be placed on washing ex-
posed skin or those parts of the body where clothing has been
contaminated. It is possible that this daily bath is more im-
portant than any other single precaution.
Hands should be washed before eating or smoking.

3 There are several approved types, but two have been in general use
in Florida. One is the Willson Agrisol Chemical Cartridge Respirator
and the other is the Mine Safety Appliance Chemical Cartridge Respirator
(CR-49290).






Florida Agricultural Experiment Stations


During spray operations it is desirable to work into the
wind as in dusting. This will minimize parathion exposure.

Tractor Canopies or Raincoats
Except in very close planted groves, a canopy over the tractor
driver is desirable. Such a canopy can be easily attached and it
will afford a great measure of protection to the Speed Sprayer
operator or a driver pulling a pressure sprayer (see Fig. 4).
Where canopies are not practical a raincoat or poncho can be
thrown over the tractor driver's head and shoulders during the
time he is driving in the spray drift.

Fig. 6.-Have wind blowing across in front of the operator. This cre-
ates less air turbulence. Keep bucket and paddle handle clean. Avoid
spilling parathion on ground. Always wear a respirator, natural rubber
gloves, hat and long sleeves.

Mixing Parathion Slurry

DO THIS NOT THIS
____ IHII_________ IjjljfIljf lllfll/lflifiii





Toxicology of Parathion
Pouring Slurry into Tank


DO THIS


NOT THIS

,~J~q! %/


I -


Fig. 7.-Always wear a respirator, natural rubber gloves, hat and long
sleeves. Do not smoke. Avoid spilling contents of bucket.






Florida Agricultural Experiment Stations


Danger in Groves After Spraying
The hazards involved in working a grove after spraying have
not been fully ascertained. Until more information is available
the following suggestions are made:
Entering Grove after Spraying.-There is little, if any,
danger in walking in or through a grove that has just been
sprayed with parathion. Some danger does exist in handling
contaminated foliage or fruit and it is recommended that people
stay out of a grove at least four days after spraying.
Cultivation or Irrigation.-This type of operation may be
carried out seven days after spraying.

Fig. 8.-Have the tank almost full of water and the agitator going.
Slowly sift mixture onto the surface of the water. Do not hold up sack
and pour. Always wear respirator, natural rubber gloves, hat and long
sleeves.
Adding a Parathion-sulfur Mixture to a Tank

DO THIS NOT THIS
.---/-- A ~-- i-:i







Toxicology of Parathion


Pruning.-Because of intimate contact with the tree, pruning
should not be carried out for 14 days after spraying.
Picking.-Because of close contact with both fruit and tree,
picking should not be undertaken for 14 days after spraying.
Mixing Operations
Form of Parathion to Use.-There are no data to indicate the
safest form in which to use parathion. It may be obtained as a
wettable powder or mixed with sulfur by the manufacturer or
formulator. If a wettable material is used it is desirable to get
packages of such a size that it will necessitate opening only one
package per tank. Some wettable materials have been treated
so as to be more or less dustless. This may give added safety.
Method of Mixing with Wettable Powder.-Several methods
are available, but two are listed here. Cut the bag open with a
knife (see Fig. 1). When the tank is almost full of water and

Fig. 9.-Destroy all containers by burning or burying. If this is not
done they are a menace to the well-being of children and animals.
Destroy All Parathion Containers


Burn Bags


Bury Cans







Florida Agricultural Experiment Stations


the water is circulating, lay the open end of the bag or can on
the surface of the water and let the water carry the powder into
suspension (see Fig. 5). This will result in a minimum amount
of dust. Be sure that the man stands in such a position that
the wind is blowing the dust away from him.
Another method involves the use of a 5-gallon can. Rather
than having the back to the wind, face to one side. This tends
to create less air turbulence. Fill the can half full of water.
Cut the bag open with a knife and add the wettable powder.
Make a slurry by mixing with a paddle (see Fig. 6). This may
then be poured into the tank (see Fig. 7).
The man filling the tank should always wear a mask, gloves,
etc., and take all prescribed personal precautions.
Method of Mixing with Sulfur-Parathion Mix.-Have the
operator stand so that the wind is blowing the dust away from
him. Less dust will be raised if the tank is almost full before
introducing the insecticide. The operator should always wear a
mask, gloves, etc., and take all personal precautions (see Fig. 8).
Destruction of Containers.-All bags, cans, and other con-
tainers should be destroyed (either burned or buried) after they
have been emptied. Otherwise they offer a serious health hazard
to unsuspecting children or animals (see Fig. 9).

Warning Signs After Spraying
Signs stating the date of spraying and warning against en-
tering the groves for four days after spraying or picking fruit
for 14 days after spraying should be posted following all spray
operations.

Cleaning Spray Equipment
All spray equipment should be washed every day after using
parathion. The accumulation of parathion on such equipment
offers a hazard to operators and mechanics.

Working After Sickness
It is suggested that a man should not return to work until a
blood test indicates that his cholinesterase levels are normal.
If a blood test is not made he should stay away from parathion
for at least 60 days after an illness.
If he becomes ill a second time he probably should be placed
in a job where contact with parathion is unlikely to occur.







Toxicology of Parathion


Treatment of Parathion Poisoning
Atropine is a specific drug for the treatment of parathion
poisoning. It has a specific action in correcting the muscarinic
symptoms such as nausea, visual difficulty and excessive sweat-
ing and salivation. It has no effect upon the symptoms of the
central nervous system or the so-called nicotinic effects of para-
thion. If a man becomes sick in the field give two atropine
sulfate tablets (1/100 grain per tablet) by mouth and rush him
to a hospital. A physician should administer treatment. In
cases of severe poisoning the use of oxygen tents and artificial
respiration have been helpful. Morphine is contra-indicated.

Summary
Parathion was first tested in Florida in 1947. Parathion de-
stroys cholinesterase when absorbed into body tissues. The
pharmocology of this phenomenon is described in detail. Symp-
toms of parathion poisoning such as nausea, tightness in the
chest, constricted pupils, etc., as they have been reported in
the literature and as they have been observed in Florida are
discussed. Complete recommendations for handling parathion in
citrus groves include wearing approved respirators; changing
clothes daily; taking a bath at the end of a day's work; wearing
protective clothing such as a hat, rubber boots and rubber gloves;
and taking a pre-employment medical examination. It is sug-
gested that picking and pruning be performed no closer than
14 days to the time of spraying a grove with parathion.

Literature Cited
1. Abrams, H. K., D. O. Hamblin and J. F. Marchand. Pharmacology and
toxicology of certain organic phosphorus insecticides. Clinical Ex-
perience. Jour. Am. Med. Asso. 144: 107-108. 1950.
2. Adrian, E. D., W. Feldberg and B. A. Kilby. Cholinesterase inhibiting
action of fluorophosphates. Brit. Jour. Pharmacol. and Chemo-
therapy 2: 56-58. 1947.
3. Best, C. H., and N. B. Taylor. Physiological basis of medical practice.
Page 1082. The Williams and Wilkins Co. 1950.
4. DuBois, K. P. Pharmacology and toxicology of certain organic phos-
phorus insecticides. Pharmacology. Jour. Am. Med. Asso. 144: 104.
1950.
5. DuBois, K. P., J. Doull, P. R. Salerno and J. M. Coon. Studies on the
toxicity and mechanism of action of p-nitrophenyl diethyl thiono-
phosphate parathionn). Jour. Pharmacol. Exptl. Therap. 95: 79-91.
1950.
6. Freedman, A. M., Alice Willis and H. E. Himwich. Correlation between
signs of toxicity and cholinesterase level of brain and blood during
recovery from di-isopropyl fluorophosphate (DFP) poisoning. Am.
Jour. Physiol. 157: 80-87. 1949.







Toxicology of Parathion


Treatment of Parathion Poisoning
Atropine is a specific drug for the treatment of parathion
poisoning. It has a specific action in correcting the muscarinic
symptoms such as nausea, visual difficulty and excessive sweat-
ing and salivation. It has no effect upon the symptoms of the
central nervous system or the so-called nicotinic effects of para-
thion. If a man becomes sick in the field give two atropine
sulfate tablets (1/100 grain per tablet) by mouth and rush him
to a hospital. A physician should administer treatment. In
cases of severe poisoning the use of oxygen tents and artificial
respiration have been helpful. Morphine is contra-indicated.

Summary
Parathion was first tested in Florida in 1947. Parathion de-
stroys cholinesterase when absorbed into body tissues. The
pharmocology of this phenomenon is described in detail. Symp-
toms of parathion poisoning such as nausea, tightness in the
chest, constricted pupils, etc., as they have been reported in
the literature and as they have been observed in Florida are
discussed. Complete recommendations for handling parathion in
citrus groves include wearing approved respirators; changing
clothes daily; taking a bath at the end of a day's work; wearing
protective clothing such as a hat, rubber boots and rubber gloves;
and taking a pre-employment medical examination. It is sug-
gested that picking and pruning be performed no closer than
14 days to the time of spraying a grove with parathion.

Literature Cited
1. Abrams, H. K., D. O. Hamblin and J. F. Marchand. Pharmacology and
toxicology of certain organic phosphorus insecticides. Clinical Ex-
perience. Jour. Am. Med. Asso. 144: 107-108. 1950.
2. Adrian, E. D., W. Feldberg and B. A. Kilby. Cholinesterase inhibiting
action of fluorophosphates. Brit. Jour. Pharmacol. and Chemo-
therapy 2: 56-58. 1947.
3. Best, C. H., and N. B. Taylor. Physiological basis of medical practice.
Page 1082. The Williams and Wilkins Co. 1950.
4. DuBois, K. P. Pharmacology and toxicology of certain organic phos-
phorus insecticides. Pharmacology. Jour. Am. Med. Asso. 144: 104.
1950.
5. DuBois, K. P., J. Doull, P. R. Salerno and J. M. Coon. Studies on the
toxicity and mechanism of action of p-nitrophenyl diethyl thiono-
phosphate parathionn). Jour. Pharmacol. Exptl. Therap. 95: 79-91.
1950.
6. Freedman, A. M., Alice Willis and H. E. Himwich. Correlation between
signs of toxicity and cholinesterase level of brain and blood during
recovery from di-isopropyl fluorophosphate (DFP) poisoning. Am.
Jour. Physiol. 157: 80-87. 1949.







Toxicology of Parathion


Treatment of Parathion Poisoning
Atropine is a specific drug for the treatment of parathion
poisoning. It has a specific action in correcting the muscarinic
symptoms such as nausea, visual difficulty and excessive sweat-
ing and salivation. It has no effect upon the symptoms of the
central nervous system or the so-called nicotinic effects of para-
thion. If a man becomes sick in the field give two atropine
sulfate tablets (1/100 grain per tablet) by mouth and rush him
to a hospital. A physician should administer treatment. In
cases of severe poisoning the use of oxygen tents and artificial
respiration have been helpful. Morphine is contra-indicated.

Summary
Parathion was first tested in Florida in 1947. Parathion de-
stroys cholinesterase when absorbed into body tissues. The
pharmocology of this phenomenon is described in detail. Symp-
toms of parathion poisoning such as nausea, tightness in the
chest, constricted pupils, etc., as they have been reported in
the literature and as they have been observed in Florida are
discussed. Complete recommendations for handling parathion in
citrus groves include wearing approved respirators; changing
clothes daily; taking a bath at the end of a day's work; wearing
protective clothing such as a hat, rubber boots and rubber gloves;
and taking a pre-employment medical examination. It is sug-
gested that picking and pruning be performed no closer than
14 days to the time of spraying a grove with parathion.

Literature Cited
1. Abrams, H. K., D. O. Hamblin and J. F. Marchand. Pharmacology and
toxicology of certain organic phosphorus insecticides. Clinical Ex-
perience. Jour. Am. Med. Asso. 144: 107-108. 1950.
2. Adrian, E. D., W. Feldberg and B. A. Kilby. Cholinesterase inhibiting
action of fluorophosphates. Brit. Jour. Pharmacol. and Chemo-
therapy 2: 56-58. 1947.
3. Best, C. H., and N. B. Taylor. Physiological basis of medical practice.
Page 1082. The Williams and Wilkins Co. 1950.
4. DuBois, K. P. Pharmacology and toxicology of certain organic phos-
phorus insecticides. Pharmacology. Jour. Am. Med. Asso. 144: 104.
1950.
5. DuBois, K. P., J. Doull, P. R. Salerno and J. M. Coon. Studies on the
toxicity and mechanism of action of p-nitrophenyl diethyl thiono-
phosphate parathionn). Jour. Pharmacol. Exptl. Therap. 95: 79-91.
1950.
6. Freedman, A. M., Alice Willis and H. E. Himwich. Correlation between
signs of toxicity and cholinesterase level of brain and blood during
recovery from di-isopropyl fluorophosphate (DFP) poisoning. Am.
Jour. Physiol. 157: 80-87. 1949.








Florida Agricultural Experiment Stations


7. Griffiths, J. T., and C. R. Stearns. Parathion hazards encountered
spraying citrus in Florida. Jour. of Econ. Entomol. (in press).
1951.
8. Grob, D. Pharmacology and toxicology of certain organic phosphorus
insecticides. Toxicology. Jour. Am. Med. Asso. 144: 105-107. 1950.
9. Grob, D., W. L. Garlick and A. M. Harvey. The toxic effects in man of
the anticholinesterase insecticide parathion (p-nitrophenyl diethyl
thionophosphate). Bul. Johns Hopkins Hosp. 87: 106-129. 1950.
10. Grob, D., J. L. Lilienthal, Jr., A. M. Harvey and B. F. Jones. The admin-
istration of di-isopropyl fluorophosphate (DFP) to man. I. Effect
on cholinesterase and systemic effects. Effect on plasma and
erythrocyte cholinesterase; general systemic effects; use in study
of hepatic function and erythropoiesis; and some properties of
plasma cholinesterase. Bul. Johns Hopkins Hosp. 81: 217-244.
1947.
11. Grob, D., and A. M. Harvey. Observations on the effects of tetraethyl
pyrophosphate (TEPP) in man, and on its use in the treatment of
myasthenia gravis. Bul. Johns Hopkins Hosp. 84: 532-567. 1949.
12. Hagan, E. C., and G. Woodward. Toxicity of O,O-diethyl O-p-nitro-
phenyl thiophosphate parathionn). Federation Proc., Part I., page
224. 1948.
13. Hazelton, L. W., and E. J. Holland. Pharmacology and toxicology of
parathion. Advances in Chem. Series 1: 31. 1950.
14. Koelle, G. B., and A. Gilman. The relationship between cholinesterase
inhibition and the pharmacological action of DFP. Jour. Phar-
macol. Exptl. Therap. 87: 421-434. 1946.
15. Koelle, G. B., and A. Gilman. Anticholinesterase drugs. Jour. Phar-
macol. Exptl. Therap. 95: 166-216. 1949.
16. Lehman, A. J. The toxicology of the newer agricultural chemicals.
Bul. Asso. Food and Drug Officials 12: 82-89. 1948.
17. Lehman, A. J. Some toxicological reasons why certain chemicals may
or may not be permitted as food additives. Bul. Asso. Food and
Drug Officials 14: 82-98. 1950.
18. Mazur, A., and O. Bodansky. Mechanism of in vitro and in vivo inhib-
ition of cholinesterase activity by DFP. Jour. Biol. Chem. 163: 261-
276. 1946.
19. Ripper, W. E., R. M. Greenslade and G. S. Hartley. A new systemic
insecticide bis (bis dimethylamino phosphonous) anhydride. Bul.
Entomol. Research 40: 481-501. 1950.
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