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United States Department of Agriculture
Agricultural Research Administration
Bureau of Entomology and Plant Quarantine
DETERMINING THE EFFICIENCY OF RESP"RA"AT ORY CARTRIDGES
AND GAS-MASK CANISTERS AGAINST DUS I S AND SPRAYS
By R. A. Fulton and M. S. Konecky, Division of Insecticide Investigations,
and Floyd F. Smith, Division of Truck Crop and Garden Insect Investi-
Concern over the inhalation hazard to operators applying dusts, sprays,
and aerosols of parathion and other organic-phosphorus insecticides led to
a conference, in September 1949, by representatives of several govern-
ment agencies, and to subsequent meetings with producers of these in-
secticides and of respiratory protective devices. A cooperative program
was set up, under the auspices of the Interdepartmental Committee on
Pest Controlfor the development of respirators and gas masks for the
protection of operators while handling these materials. Experimental
models of respirators, respirator cartridges, and gas-mask canisters
were supplied by the manufacturers. Testing procedures to determine
their efficiency were developed and applied by chemists of the Bureau of
Entomology and Plant Quarantine, and the results were evaluated jointly
by the Department of the Army, Food and Drug Administration, Public
Health Service, Bureau of Mines, Production and Marketing Administra-
tion, and Bureau of Entomology and Plant Quarantine. Various types of
cartridges and canisters were tested against parathion and other organic-
phosphorus insecticides and also against dieldrin, aldrin, and chlordane.
As a result of this investigation respirator cartridges that contain
a special dust filter have been developed and are now being sold for
protection against parathion dusts and sprays (Fulton 1). More recently
the same units have also been found effective against dieldrin, aldrin,
and chlordane. They are not effective against tetraethyl pyrophosphate,
but other units have been developed for that purpose (Fulton, Nelson,
and Smith 2).
On May 4, 1950, the Interdepartmental Committee on Pest Control
issued a statement concerning these respirators, and listed several
commercial respirators that have been found to give such protection.
A similar statement concer-ii;.' devices that will give protetion. ,.i-,'.I.t
dieldrin, aldrin, and chlordane was is-. '.:. by 'h.e L-rea-2 of >ntomo 0o-,
and Plant Quarantine on August 24, 1951. The method' s:.P fsor '-PY ..-.-d
nicotine are similar to those described for parathion and tetraethyl
MI 0 Qn
The chrysanthemum aphid (Macrosiphoniella sanborni (Gill.)), the
foxglove aphid (Myzus convolvuli (Kltb.)), and parathion-resistant and
nonresistant strains of the two-spotted spider mite (Tetranychus
bimaculatus Harvey) were used as test insects.
The chrysanthemum aphid was reared on young chrysanthemum plants
in active growth, and the foxglove aphid was reared on potato leaves.
The tip of each shoot was removed, and the upper part of the stem was
coated with paraffin to force the aphids to feed on the lower expanded
leaves. The two strains of the two-spotted spider mite were reared on
potted lima bean plants in separate sections of a greenhouse. The
varieties Carolina Sieva and Henderson Bush were used, because they
are highly resistant to mildew and have relatively small leaves.
Tests of Respirator Cartridges
Apparatus. --The apparatus for testing respirator cartridges is shown
in iLgure 1. It consists essentially of a dusting or spraying chamber (A),
a cartridge holder (D), a chamber for exposing the test insects (E), a
flowmeter (TF) to regulate the flow of air through the apparatus, a mano-
meter (G) to determine the resistance of the cartridge to the air flow, and
a unit for sampling the air for chemical analyses. For the tests with
parathion the unit shown in H with flowmeter J is used, but for the
chlorinated hydrocarbons the air is drawn through a heated quartz tube
containing platinum foil to a glass absorption tower (not shown). Chamber
A is a gir- jar 16 inches in diameter and 30 inches high inverted on a
small table in which two holes have been drilled. Into one hole (C) is
inserted a tube for injecting the dust or spray into the chamber, and in
the other hole is a piece of 1/2-inch pipe(C') for connecting the cartridge
holder. At the other outlet of the cartridge holder is another piece of
1/2-inch pipe, which is connected by means of a street elbow and 21-mm.
(i.d.) glass tubing to the exposure chamber E, which is a 10-inch vacuum
desi ocator. From the top outlet of the exposure chamber extends glass
tubing to the vacuum pump and the sampling unit, with the flowmeters
,and mnanorreter inserted in series.
The ca t idrge holder is shown in detail in figure 2. It was constructed
from two floor flanges 4 1/4 inches in diameter made for 1 1,2-inch pipe
(A and A'), ard provided with gaskets (E and E'). The diameter of the
outlets was reduced to fit 1/2-inch pipe by means of two 1 1/2- to 3,4-inch
bushings (B and B') and a 3/4- to 1/2-inch bushing (C). The cartridge (D)
to be tested is placed between the pipe flanges, and the holder made air-
tight with 1/4-inch bolts (F).
Tests with Parathion. --For the tests with parathion dusts a wettable
powder containing 15 percent of parathion in attapulgite clay was used,
and for the test with sprays an emulsion containing 0.16 percent of
parathion prepared from a 16-percent emulsion concentrate.
On the evening before a test was to be made portions of mite-infested
leaves from the stock mite colonies were pinned to primary leaves on
clean young lima bean plants with the upper surfaces together, and the
tips and lobes of the bean leaves were cut off. The lima bean plants were
placed under 200-watt lamps. During the night the light and mild heat
from the lamps stimulated the mites to move from the source leaf to the
test leaf. Aphids were taken directly from the stock colony.
In the morning, after the testing apparatus had been assembled, the
test leaves infested with aphids and mites were removed from the plants,
placed in vials containing water, and set in the exposure chamber (E).
A petri dish was used under each vial to catch any insects that might fall
from the leaves. Either 0.2 gram of the parathion dust or 1.4 grams of
the emulsion was introduced into the chamber A every 5 minutes for
15 minutes or 1 hour. For introducing the spray a hydraulic sprayer
that produced a mist with an average particle size of 55-58 microns was
used. These particles were found to settle at about the same rate as the
Air was drawn through the apparatus by means of a vacuum pump, at
the rate of 16 liters per minute for cartridges for dual-type respirators
and 32 liters for cartridges for single-type respirators.
For chemical determinations samples of air were drawn through the
sampling unit, which contained 5 ml. of absolute alcohol, at 1 liter per
minute. At the end of the sampling time the alcohol from each unit was
transferred to a volumetric flask, rinsed twice with 2 to 3 ml. of alcohol,
and made up to 10-ml. with alcohol. The optical density was determined
with a quartz spectrophotometer at a wave length of 274 millimicrons and
compared with a previously prepared optical density-concentration curve
For the biological tests, after the exposure each leaf bearing aphids
or mites was transferred to a vial standing in a beaker. A layer of
paraffin in the beaker supported the vial and provided a light-colored
surface on which fallen aphids or mites were readily observed, and a
coating of lanolin on the rim prevented the survivors from escaping.
Mortality counts of aphids were made after 4 to 6 hours. Affected
individuals were shriveled, and a yellow exudate was usually present at
the opening of the cornicles. Mites were usually examined at the same
time, but always within 24 to 30 hours after they had been transferred to
test leaves, to reduce the occurrence of newly hatched nymphs or new
adults. Any that did appear were usually recognized by their lack of
pigmentation. Aphids and mites that survived these tests were never
returned to the stock colonies.
T-.'ical results obtained with parathion dusts are presented in table 1.
i iree types of cartridges were exposed to the dust-laden air in conjunction
with the filters with which they would be used under practical conditions.
Ti,.e air was drawn through the apparatus at the rate of 16 liters per
minute and the exposure period was 1 hour.
Table 1. --Results of tests of three respirator cartridges against 15-percent
Weight of cartridge to Parathion passing Mortality of
Cartridge dust on air flow through cartridge aphids after--
Cye artridge ---- ----on---air- --flow--
type cartridge First Last First Last
filter Initial Final 10 min. 10 min. 15 min. 15 min.
.. .. .. .. .... .
Milligrams Inches of water
Tests with Tetraethyl Pyrophosphate. --No chemical analysis was made
to evaluate the amount of tetraethyl pyrophosphate passing through the
cartridges, but only biological tests with aphids. The procedure was the
same as for parathion, and the tests were made with a spray prepared
by diluting 3 to 40 percent emulsion concentrate (or wettable powder)
to contain part of tetraethyl pyrophosphate in 200 parts of water.
In typical tsts this spray was used on activated-charcoal cartridges
in conjunction with two types of filters. Aphid mortalities determined
after 30 irirnutes' exposure were as follows:
Foni, filter without cartridge
100, 99.2, 99.3
14.0, 10.4, 4.5
'These results indicate that the dust filter in conjunction with an
activated-clarcoal cartridge will not remove tetraethyl pyrophosphate
but that th, fumre filter is effective even without the cartridge. The
fume filter is made to stop particles as small as 0.01 micron diameter.
Tests with Chlorinated Hydrocarbon Insecticides. --Dieldrin was; used
both as a dust and as a spray, but aldrin and chlordane only as dusts.
The concentration was 5 percent in all cases. The dieldrin and aldrin
dusts were prepared by grinding the technical material with synthetic
magnesium silicate, and the chlordane dust contained attapulgite clay as
the diluent. The sprays were prepared from 25-percent emulsifiable con-
centrates. The effectiveness of the cartridges was tested only by chemical
analyses; no insect-mortality tests were made for these materials.
Samples of air that had passed through the cartridges were drawn through
the quartz tube containing platinum foil heated to a bright red to the absorp-
tion tower containing glass beads that had been wet with a chlorine-free
solution of sodium carbonate containing arsenic trioxide (1 gram of arsenic
trioxide to 80 ml. of saturated sodium carbonate solution and 20 ml. of
distilled water). At the end of the sampling period the beads were washed
with distilled water. The washings were transferred to a Nessler tube,
acidified with nitric acid, treated with an excess of silver nitrate, made
up to volume, and the chlorine determined by the turbidimetric method.
The results of typical tests with several respirator cartridges in
conjunction with dust filters are shown in table 2.
Table 2. --Results of tests of respirator cartridges with dust filters and
of a fume filter alone against aldrin, dieldrin, and chlordane
Insecticide passing through cartridge
(micrograms per liter)
Type of cartridge
Dieldrin Aldrin Chlordane
________________ Dust Spray dust dust
A 0.4 0.6 0.4 0.3
.6 .4 -
B .4 .8 .8 .3
C .2 .3
.3 .6 .3 .3
D 1.1- -
Fume filter only 2.9 3.6
1/ In each of 3 replications.
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Tests of Gas-Mask Canisters
The apparatus for producing vapors for the testing of gas-mask
canisters is shown in figure 4. Air is passed at the rate of 1/2 liter per
minute through a fritted-glass bubbling unit (A) and then through a column
of glass beads (B) to remove small particles that might be carried in the
air stream. The insecticide is allowed to drip into B from the separatory
funnel (D) throughout the test period to keep the beads covered at all times.
A small drying tube (C) removes the moisture from the air entering the
funnel. The excess liquid is trapped in a flask (E). The outlet (F) of the
column is connected directly to the canister holder. The sampling unit
and the insect-exposure chamber are the same as for the cartridge tests
(fig. 1). To maintain a uniform temperature the entire apparatus is
placed in a large constant-temperature box. All the tests reported were
made at 85 F.
Technical parathion, a product containing 38 to 40 percent of tetraethyl
pyrophosphate, and technical tetraethyl dithiopyrophosphate were used to
produce the vapors.
The efficiency of the canisters was determined only by biological tests.
The test insects were the same as for the tests of respirator cartridge.
In tests of three commercial brands of canisters designed to remove
organic vapors, acid gases, fumes, and dusts, an air stream containing
60 micrograms of parathion vapor per liter gave 2, 1.7, and 0 percent
mortality after 60 minutes' exposure as compared with 100 percent
mortality of aphids after 10 minutes' exposure to vapors that had not
passed through a canister.
Tests of similar canisters against tetraethyl pyrophosphate and
tetraethyl dithiopyrophosphate vapors gave similar results.
Procedures have been developed for evaluating the efficiency of
respirator cartridges in protecting against dusts and sprays of agricul-
tural insecticides and of gas-mask canisters against vapors of these
materials. These methods have been used to test cartridges and
canisters for their effectiveness against parathion, tetraethyl pyro-
phosphate, tetraethyl dithiopyrophosphate, aldrin, dieldrin, and
chlordane. Results of some typical tests are presented.
(1) Fulton, R. A.
1950. How to select and use a respirator. Amer. Fruit Grower
70(6): 17, 29.
(2)_____ Nelson, R. H. and Smith, F. F.
1M5'5. The toxicity of lindane vapor to insects. Jour. Econ. Ent.
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Figure 4. --Apparatus used for saturating air
with organic phosphorus compounds.
UNtIVERSTY OF FLOR DA
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