\- its absorption

‘ irreversible

| which are not common

cause distu symptoms, the danger to those
who handle ck nore Patera is
apparent. Applicator pilots are- less likely to
experience toxic exposure. than. ground-crew

personnel, but many factors must be taken. into -

account. For instance: the application desired.
may be heavy and the dilution factar low; the
Spray equipment may ‘produce’ a fine aerosol
under atriespheric conditions which cause it
to settle slowly; the aireraft may pull, large

_ Volumes of such contaminated afr into the cock-
it; the pilot may assist with the mixing and
Teading: may fly for a longer period than is

usual. Under any or all of these conditions he

may be in danger of toxic exposure from. both. -

inhalation and surface contamination. It should
be remembered that inhalation of a drug’ or
chemical is roughly equivalent to intravenous

injection with respect to the completeness. of
i and the speed of onset of its
fects.

The chlorinated compounds owe their insecti-

cidal activity. and their inimediate or acute
toxicity to an action on the nervous”

human aa pr
system. Symptoms and signs take the f
rausea, dizziness, headache, trethor and weake
ness, proceeding in the case of tagge doses, to
convulsions, dyspnea, evanosis and circulat.
collapse. The exact mephanism by which these
effects are produced is unknown, and there i

no specific treatment. Convulsiéns can be con-

trolled by medium or long-acting barbitura
other measures are symptomatic and suppor.
tive. There is a possibility of long-lasting or
damage to liver or kidnevs from
chronic , but there are no diagnostic
tests which will reveal whether damage which
a physician may detect upon examination has
in fact resulted from contact with these agents.
Cettain members of the group possess actions
to a Lindane, for
example, may cause cardiac arrhythmias, and
chlordane may. cause depression of the bone
marrow, witha resultant reduction in the num-

than’ one

ber of red and white blood cel. These fects

are reversible if the individual is protected for

_ a reasonabile petiod, from further absorption ef
response.

group’ of chemivals. More'than twenty com-
pounds of this type-are currently in use. Chem.
ically, they are esters. or thie estes of an
organic base with or t iophosphorie
acid. Like the chldrinated compounds, the in-
dividual -members of this vary widely ia.
toxicity, and most of them are absorbed throngh .
the skin. They cwe.their insecticidal effective-"
ness_and their -human ity primarily to
more properly,

inhibiton of the cholinesterase
acetylcholine-esterase) enzyme.

significance and consequences of this
action become clear from a consideration. of
the physiological importance of Icholine.
aati is the chemical agent. which is
responsible for the transfer of impulses at most
of the points, in man or lower animals, where

‘one nerve fiber connects with another or with

an organ or tissue. This is comparable to the
use of a relay in an electrical system to supply
current to the final load, When a nerve im-
pulse, which is electrical in nature, arrives at
such a transfer point, acetylcholine is released
from the terminal branches of the nerve almost
instantaneously, and in high concentration, It
excites the muscle, gland or nerve
fiber into activity, and then mast be as quickly
destroved, just as a relay or contact must re-
lease quickly in an electrical system desi

for repetitive action. Otherwise, the
would vontinue to secrete, involuntary (smooth)
muscle would continue to be affected, and vol-
untary (skeletal) muscle, after a preliminary
stimulation, would, become paralysed. Also,
acetylcholine would diffuse into neighboring
areas, ‘and selective, localized actions of single

. Muscles or other’ tissttes would be impossible.

The rapid: destruction of acetylcholine is pro-
vided for by the presence of cholinesterase at
the nerve endings, The enzyme splits acetyl-
choline into two inactive fragments, choline
and acetic acid. The organophosphates form
a tight union with cholinesterase, and it cannot
unite with, and destroy, acetylcholine, As a
result, some degree of malfunction occurs in
almost every organ and system in the body,

-4-


armed. It has been

bud in ean of liquid id comotntrate
wilich has heen exposed 0 the fan When sisch

raté of absorption the skin, but this
factor has not been adi tested.
No specific mention has been inade in’ this
dusts Tt should go thou sag tar te
dusts. It should go without’saying, that
can be as dangetous as liquid. peeparation

. simpler to protect against them: reqiiire
less preliminary handling than Teuide e are
more easil blocked from contact with the oy
by cov. irators; they provide
70 obvious evidence of their preence on

Operator and equipment than do liquid

materials,

Admittedly, this is a rather discoutaging pic-
ture of the hazards involved in h: ling ua
control chemicals. It is not intended to frighten

pilots and other personnel, but to alert them to”

the fact that constant vigilance is the price of

safety; that to be forewamed is to be fore-

that safety ig ppos-
sible, by the ly good record of many
who have handled the organophasphates and
chlorinated compounds in large quantities for
the past several years. Better equipment, such,
as bottom-loading systems for ;spray pla

- newly-designed helmets with integral visors wi
masks for pilots, can be of help. For’ ground
personnel, the fundamental principle of safety
is miore basic and simple; it consists of think-.
ing in ddvance about each move, and making
it deliberately. All members of an aerial-
application team should observe each other for

- signs of toxicity; these are sometimes’ more
| obvjous ‘to others than to the victim himself.

It should always be remembered that repeated,

.- ‘small exposures may constitute a greater danger

than the large, single dose.
Two specific recommendations should be
“made to handling organophosphates:

a

1) Smoking is not advisable during or imme
diately after work periods, Nicotine in small.

doses can produce toms very similar in
siature 40 these of the org : . Even
in the person who is habituated and somewhat

tolerant to nicotine, there is a chance that the
effects of the two agents might be additive,
2) The practice of attempting to suppress mild
atropine to avoid less of time is ext a
dangerous and should be discontinued. It has
been pointed out that atropine does nothing
to the voluntary muscle impairment, and it is
possible to over-correct other symptoms such
as constriction of the pupil. :

With ‘respect. to protective measures and
equipment, the following generalizations ap-
pear to be justified: ‘

Each person’ connécted with aerial applica-

‘ton operations, whether “swamper” (mixer-

loader), flagman or pilot, should have gog-

gles, respirator and at least one spare coverall.
available at all times, and should have access.
to a shower or an adequate supply of soap and
water. A quart or more of i 1 or
denatured eth 1 alcohol should be kept avail-
able for scrubbing areas of known, heavy |
contamination. .Ground personnel should
have, in addition, rubber or plastic boots and
gloves, Wearing. protective gear should be
ational with ground crew and pilots if they
are handling compounds no more toxic than

DDT and Malathion, or mixtures of them.

Ground crews should be required to wear

full protective equipment, and to take all

other reasonable precautions, when they
work with compounds as toxic as toxaphene
and parathion. “Pilots should wear goggles
and respirators under these circumstances,

on their wn volition. In certain areas of .
_ the United States, respirators are frequently

considered unnecessary because there is suf-

ficient wind to protect personnel from fumes
and fine spray. For haudling materials such
as Phosdrin spray and TEPP dust, no pre-
caution or protective measure should be

overlooked, °

Both farmers and applicators must accept
some degree of responsibility for protection of
the public from the hazards of chemical toxicity
associated with pest-contro] operations.

-7-—


individual ccfls in the orgzinism, ia which axida-

tive reactions are:amcoupled from the.
energy for | ¢ He end resul
t  Weimeudons hncitoay (as iaash Lieta
in the metabolic rate of the individual, to-no
useful: purpose. .

Early signs and symptomis of DNOC poison-
ing are excessive sweating, thirst, an. exag-
Etiowed by fatigue, If thes signa and syiup
i in hot weather, they may be misinterpreted
and. i . This adds to their i
| ax ry rn cr at

lure may rise to
| heights ‘ind. complete collapse follow.” The
| course of acute poisoning from a snassive, single

exposure quite
‘signalled by nauses and gastric pains, Rest-
lessness, a feeling of intense heat, flushed skin,
rapid breathing, fever and Oanosis follow, and
death may occur within a few hours (3) (4).
The dose necessary to produce such an acute
death is estimated to. be approximately 2
grams (4). This is probably in error on the

high side”, and disturbing ymptoms will re-
sult from a few hundred milfigems There is

fatigue and ay
! i ined loss of weight, he si
'__bé watched carefully and protected from fur-
ther exposure for several days, If a concentrate
| of DNOC or other nitrophenol should come in
| contactywith the skin, decontamination with
| soap and water should be immediate — not only
; to prevent absorption, but because these sub-
| stances can cause painful skin invitation,

The use of the carbamates ‘as pesticides is
a fairly recent development. The group in- *

cludes such familiar compounds as dimetan,
Isolan, pyrolan and Sevin, Their basic chemical
structure is ROC=ONHCH,. are. there.

closely related, both chemically and phar-

rapid. ‘The. onset is :

Physostigmine and neostigmine. Like the
phosphates, they derive their insccticidal
from inhibition of the -cholinesterase

aie as Because of this action, they are
dangerous for man, a wil be exe

later. Acute te studies on
approximate! as toxic as parathion.
Sevin crpoat to be somewhat less toxic than
other members of this group. Their action on
erase is not persistent, as is the case
with the or; phates, and their toxic
effects are therefore not equally cumulative.
Tn case of exposure, however, the onset of
action is , similar to the effects of such
organoph tes as Phosdrin or TEPP.

The same safety precautions which apply to
the organophosphates should be observed when
these compounds are used. Should poisoning
occur, the treatment consists of administration
of atropine, artificial respiration if. necessary,
and of course, decontamination and removal
from further exposure until is com-
plete. The duration of this isolation period
must be left to the judgment of a physician,
but should be no less than 24 hours if the symp-
toms have been mild, or several days if severe.
Cholinesterase tests are of little practical value

_in carbamate toxicity. We still have much to

Jeam about .hese compounds with respect to
such factors as toxie dosage levels, the extent
of absorption through the skin, and the rate of
recovery from toxic effects,

The chlorinated, cyclic Pydrocarbons com-
prise a‘large and heterogeneous com-
pounds, ‘They have now been Ete longer,
and their properties.are generally better known,
than is the case with any other class of insecti-
cides. The names of several of them have in
fact, become household words; DDT, lindane,
‘chi ._ They yary widely in toxicity. The
estimated fatal dose of DDT for an adult
human male is 95 to 30 grams, taken orally.

' DDT is not appreciably absorbed through the

skin. On the other hand, the estimated lethal
dose -of lindane, dieldrin or toxaphene is 2 to
7 grams, These compounds are readily absorbed
through the skin, and the lethal dose by the
percutaneous route is estimated to be from 3
to 5 times greater than the oral lethal dose.

These figures may seem large, and the possi-

-3-

nt


constriction, slov
blood pressure, anal and
muscle twitching followed by brief convulsions,
coma, pulmonary edema, muscular
respiratory faihire and death. Certain of th
symptoms may be deceptive. For instance, the

pil of the eye usually constricts, and the
eart rate usually decreases. In early stages
of poisoning, however, the pupil may dilate
and the heart beat faster.

Unlike the carbamates’ and other cholin-
esterase inhibitors which have a short period
of action, the effects of these agents are either
persistent or irreversible. Recovery depends
upon a combined process of slow reactivation
and synthesis of new enzyme, and ma: require
from one to three weels, Their effects are,

therefore, cumulative. An especially insidious. -

feature of certain of these compounds, such as
parathion, is that the onset of symptoms follow.
ing a single cutaneous exposure may be delayed
as long as 24 to 48 hours. Also, symptoms may
appear on a day when exposure has been slight,
because of residual effects from Previows

a aay t i
Malathion, the O, O-Dimethy! thiophosphate
of Diethyl mercaptosuccinate, is’ considered to

“be one of the least toxic of tHe organophos-

phates. It is considered to be;even less

than DDT, and to this date there has

no authenticated report of a humay: fatdlity
due to accidental occupational contac
with it. Chlorthion and Dipterex are other
exaniples of organophosphates with low toxicity
for man. In contrast to these, the estimated
lethal, oral dose of gompounds ‘such as tetra-
ethyl pyrophosphate (TEPP ), Phosdrin, Systox

"(demeton) and parathion is from 20 to 100

milligrams (5). The fatal dose by percutaneous
absorption is estimated to be from 2 to 3 times
greater. ~A parathion concentrate containing 2
Ibs. per gallon, contains about 250 milligrams
per cubic centimeter, This amounts te two or

® three oral, lethal doses according to the most

urinary incontinence, |

conservative estimate, and isa potentially lethal
percutaneous route, assuming com--
plete soernton Since 1 cc is about 20 drops,

A recent report indicates that a surprisingly

waked, i that com.
fend ch te we dangers 5 after

7. amount of a chemical may collect on body

faces or be inhaled from a dilute solution
during a in ration (6). The chem-
ical fevolved was 2.4dinitre-6-soe-butyl
(DNOSBP), used in the a fe ilution
in an orchard application. Operators of ground
equipment, under the conditions existing at the
time of the test, collected the chemical on their
body surfaces at the rate of 88.7 mg. per hour,
and on respirator filter pads at the rate of 0.47
mg. per hour. Only one airplane was involved
in the study, since it was primarily concemed
with ground application, and only that material
which collected on the hands’ of the pilot and
flagman was measured. On this small area, the
pilot collected DNOSBP at the rate of 0.2
mg, per hour. The corresponding rate for the
flagman was 0.9 mg. per hour.

is aspect of aerial application deserves

further study. Had the above study involved
an agent as toxic as Phosdrin for instance, the
implications are obvious.

The first, crucial step after known or sus-
pected contamination oft the skin, is a thorough
cleansing with soap and water. Alcohol is a
better decontaminating agent, particularly if
the area of cuntz:tination is limited, In any
event, speed is essential. It has been found
that 30 minutes after a test application of
parathion to the skin, vigorous scrubbing with
soap and water’ will remove 80% or more of
the material, and: alcohol will remove most of
the remainder. After 5 hours, however, 40%
of a test dose will resist removal with soap and

"water, and 10 will persist after scrubbing with

alcohot (7). \Decontamination is
important for the pilot who may be unconscious
from accidental injury when found, if the pos-
sibility of, chemical contsinition exists,
First aid, in nophasphate intoxication
consists of the adiministration of atropine; by
mouth if the symptoms are early and mild,
subcutaneously or intravenously if the symp-
toms are prominent and .yrettes or hypodermic
equipment available, Treatment in the field

-5-

a


. be taken to preven ‘persons from

. Fealized, and should Be mua:

. thal eee os eee found, for instance,
thee omnes thi hick
had contained 58 percent ‘emulsifiable con-

f The problem of drift thas Niels pe ;
ofgiied’ and all recrnle pesceatene toe

being taken to avoid it. Precautions should also
entering fields

toxic compounds, either by posting warning

signs or by other means. . .
Discarded insecticide containers may cénsti-
tute more of a menace than has previously been
carefully prior

centrate may contain as much as ‘10 gm of ac-
tive parathion after months of exposure to the
weather (9). This amounts of course. to many
lethal doses for an adult human or a farm ani
mal of equal size. Procedures designed to de-
contaminate such containers to a fe condition
for Hiandling and storage were tested. The

"most practicable method consisted of several

rinses (2 or more) with plain water, but this
did not make the drums safe for any secondary.
‘we. It is suggested, therefore, that containers
should be rinsed if possible, and that in addi-
should be or crushed to
tender useless before impgundment for
final disposition. °

"5. Hendbook of Poi
Edition

TEXT REFERENCES;
4. Nesiba, T., and K. Hiski JAMA, 168, 1834, 1958,
2 seencck of, Tascdlny, Vel. I National Acadeary
of Sciences, National Research Council. W. 0. Negher
hon, Ed. Philadelphia, 1999, W. B. Saunders Co.
3. Bidstrup, P. L. Proc. Royal Soc. of hied., 45, 574, 1952,

4. Clinteal Memoranda én Economic Poisotie. U. S. Dept.
Health, Education and Welfare, Public Health Service,
Publication No. 476, Washington, D.C., 1958.

Diagnosie and Treatment. 3rd
. . H., Los Altos, Calif, 1961,
Lange Medical Publications.

6. Wolfe, H.R. W. F. Dusham and G. S, Batchelor,
Arch. Env. Health, 3, 104, 1961.

‘1. Fredriksson, T., Arch. Env. Health, 3, 67, 1961.

8. Witson, I. B, Neurology (supp. 1), 8, 41, 1958,

9. Wolfe, H.R, W. F. Durham, K. C. Walker and J. F.
Armstrong, Arch. Env. Health, 3 194, 1961. ,

GENERAL REFERENCES:

Textbook of Toxicology, DuBots,K, P. and EM-K. Getting
New York, 1959, Oxford Univ. Press.

Poisoning. von Oettingen, W. F. Philad ia, 1958, W. B.
"Saunders Oo, -

Holmstedt, B. Pharmacology of the Oj anophosphorus
Cholinesterase Inhibitors. Pharmacol. fev 11, 567,
1959. :


lam Ga-8 "TOXIC HAZARDS

AERIAL APPLICATION

Paul W. Smith, Ph. D.
Pharmacology-Biochemistry Branch ..

FEDERAL AVIATION ACENCY

AERONAUTICAL CENTER
OKLAHOMA CITY, OKLAHOMA
Apail i962

we


” nota

should never o beyond a few such doses of
atropine, in ion to such other igehe
measures as may be indicated — artific
Peched "to phys, Sood ery
‘rushed to a physician or a hospital for ‘aft.
further treatment. ; :
of
‘Ss

Tes-

Treatment has. traditionally consisted -
atropine in amounts. In severe cases, §
to 30 m vw te ar le Qe intravenonily
within the first 24 hours, usually ia the form
of 2 mg. individual doses, Atropine however, is
antidote. It can control hyper.
motility of the gastrointestinal tract, dilate the
bronchioles, correct most of the visual disturb-
ances, and suppress the excessive secrction of
saliva, mucus and sweat. It will not, however,
correct all of the cardiovascular-pulmonary dis-
turbances, and it cannot relieve the paralysis
cf the respiratory muscles and. the central

effects ‘which together are responsible for

respiratory failure. Artificial respiration with
oxygen under slight positive pressure should be

maintained until breathing resumes or other _

measures taken. At no time during treatment
should a drug which. respiration
(morphine, barbiturates, etc.) be used,

It was discovered comparativel “:récently
that certain drugs as aldoximes or

~-Rotroso compounds (8), are able to disrupt the

organophosphate-cholinesterase complex and
reactivate ti

2-pyridine aldoxime methiodide (2-PAM) has
proved to be highly effective ( 1), It is avail-
able for use only under the direction of a phy-
sician, One gram of this drug is given in

~ hours, in individual doses of 0.3 grarh, by slow,
' intravenous administration. The initial doses
"may be spaced closely
: lengthened, at the discretion of tle physician, /

Treatment may be continued into t

day if necessary, but should not extend beyond

48 hours, and no patient should receive more
| than 2 grams. If the physician intends at the
| outset to fise 2-PAM at some stage of the treat-
| ment, the amount of a¥ropine should be re-
| duced to avoid the late appearance of atropine
| toxicity if and when 2-PAM relieves the
patient's symptoms,

Because of a fortunate physiological circum-
stance, the presence of cholinesterase in blood,
it is possible to confirm the existence of organo-
phosphate intoxication and to follow its course,

a

” hloo ‘One of these, in the j

enzyme quickly: One of these, ‘

atid the infervals then }

i laboratory test.. Two

peso Sat ery tt, Teo
(or serum),
and is termed

eel wk Balt nn ae Miparently iden.
tical with that in nerve ‘tissue, rape
is determined by one
three metteds, Our af hen eee a colori-
metrie precedure, The other two take advant-
age of the fact that one of the products of
aeetvichcline hydrolysis is an acid, which can
be made to relez:2 CO, from sodium bicarbon-
ate, or change the pH of the reaction mix-
ture. Either of these can be accurately
measured

The value of blood cholinesterase tests de-
pends upon how and when are made.
Whole-blood or red-cell Tee, more val-
uable than those of plasma or serum. It is
advisable for each person connected with an
aerial application team to have a test made at
the begin ing of the season, prior to any con-
tact with organophosphates, to establish his
normal level, since there is considerable varia-
tion between individuals. There is no direct
correlation between the cholinesterase level

“and the severity of symptoms, but no person

can have a normal value if he ites absorbed
appreciable amounts of an or: te
any route. Therefore, if tess ‘ne made 4
some regularity during the spraying season,
they will reveal whether personel are taking
adequate precautions, wil indicate i
whether the individual i in danger of
experiencing symptoms from further, slight ex-
posure. If a test is made at the time of an
accident, it could suppgrt symptomatic findings
in establishing whether or not chemical toxicity
might have*been contributory. Since the test
itself is relativel simple, local laboratories
should be persuaded to equip themselves for it,
becazise of the difficulties involved in sending
blood samples by mail to a central location.
The fact that our most effective pest-control
chemicals are relatively insoluble in water, con-
tributes te the Vcaarde involved in preparing
and applying them. The non-aqueous solvents
used in liquid formulations (benzene, xylene,
naphtha, kerosene, ete.) are flammable, and

constitute a definite fire hazard, Certain ones
of them are sufficiently volatile that pressure


! y
An analysis of the hazards
chemieals is presented. The nature of t

The introduction of the chlorinated, ‘cyclic

| hydrocarbons for large-scale use as agricultural
insecticides somewhat ‘less than two decades
ago, marked the beginning of a new era in agri-
cultural pest con! . In the intervening years,
new chemicals; many of them engineered for
 specifie agricul tural purposes, have appeared in
prepa he number and wide

y itor eu and their new and
Vatoty of cee ix "and their new ay
infarilar chenbal aod toacater de

bties, have brought a ‘host of medical problems.
The insecticides which were the farmer's first
line of defense prior to the 1940's, presented no

when inhaled or taken by mouth, and these/are
routes of entry into the body which are rel-
atively easy to protect. Mixtures of sulfur and
lime are comparatively innocuous. Nicotine,
derris tthe ins and mercurials were never
sed for large-scale: aricultural purposes as we
understand the term. There were no effec-
‘five defotiants or weed-control chemicals,
_aTherefore, when the chlorinated compounds
ippe in the 1940's and the organophos-
hates shortly thereafter in the 1950's, neither
nor pest control operators were  pre-
for the higher intrinsic toxicity of these

“ pubstances, Nor were they prepared for the

TOXIC HAZARDS IN AERIAL APPLICATON

“Paul W. Smith, Ph. D.

the aerial application of toxic pest-control

themicals, the symptoms of toxicity, recommended
treatment, and megrtins for efchnding. we dich ( ° icy

appearance of symptoms without waming, due
toa strange new hazard, absorption of the toxic
agent through the skin.

It is not surprising therefore, that a familiar
pattern has emerged. Many poisonings have
occurred in the first months or years
the introduction of the more potent pesticides

into a region where they were previously un-
known. Tus i the patton ahi eed
“= Japanese scientists to accumulate the histories
»- QF 6000 cases «of

rathion poisoning within
the figst 5 vears following the introduction of
this chemical into Japan for use in the rice
fields (1). Ultimately, instruction, training, and
experience reducé” the incidence of such
poisonings.

There are so many insecticides, acaricides,

‘ herbicides, defoliants and. other

chemicals which present toxicological problems,
that it would be impossible to describe the
properties of each of them in a brief discussion.
For instance, Volume [I (“Insecticides”) of

the “Handbook of Toxicology” (2) contains al-

most 200 entries. Many of these are not adapt-
able to aerial application, and others present
no serious toxiculogical problems, However,
fifty or more of them are of sufficient com-
mercial and toxicological importance to warrant

-l-


.

Geet Sete to ase:

“If the magiittude of the probilem ‘scars Linge ~

at this time, the futare promises further cota

‘piéations The ‘organ nirere t cial : :
miidify existing compounds of known effect on ak ‘tsiial .

"tress to produce’ an almost’ infinite variety of ing the “LD.” = the dose per unit of body -
potentially valuable insecticides. While the ..-welight which will kill 50 percent of a group of

number of individual agents can thus become fest animals. It is not possible to this —

quite Tange, itis fortunate, perhaps, that only 2 figure directly to man, but it can be the basis -*

few types or classes of chemicals possess wee for an estimate. Hf, for instance, the LD. of -

must, wracti , upt or m {al . |, we
alter onk or more of thethane te poten i aie fay covet at 300 mg. would be

: rt
which are common to all animal organisms: dangerous for a 150 fb. man. Actually, we find
Emsfrmation of energy by nan of nace that much less than this can

lar enzymes or catalysts; synt essential Occasionally an accidental poisoning occurs in
cell conztituents, inckoding those for . a human subject, under circumstances in which
growth and reproduction; transport of vital ma- the dose, the time, the manner of taking the —
terials across cell membranes; co.amunteation compound, and other essential facts. are known.
by means of excitable tissues; ot the biophysical Sueh an accident is the only ineans we have of
phenomena involved in locomotion and cireu-. establishing the true relationship between the
lation of body fluids. ‘2. * "actual toxicity for man and the estimate derived
‘The toxicological threat to man, from chem- from animal experiments,
icals which are capable of altering ‘these Probably 90 percent of all the compounds
. functions in lower animal forms, is obvious, ‘It - which possess uefa pesticidal or icidal

is also obvious that the hazards are exception-__ actions can be classified, on the basis of chem-
ally great to workers who manufacture and ical composition and structure, into no more
formulate these compounds, and to those who’. than a dozen major classes, Four of these con-
handle them in concentrated form in the field. tain the which are. responsible for
- Certain. ones of these chemicals are so almost all of the aerial applicator's toxicological
» 4a their effects on tan, that they are definitely problems; the ni the carbamates,
dangerous, even after ditution for final applita-°- the chlorinated, cyclic hyrocarbons and the
tion, whether by aircraft or other means. “This organo)
foot ts of particular importance to the applicator The ovicidal, acaricidal and insecticidal
pilot, and ‘to those concerned with his safety. properties of the nitrophenols have been rec-
As will be pointed out lifer, even mild exposure, ‘ognized for many years. Concentrations which

to certain insecticides can sym are effective for these , however, are
which would make it impossible for Mw strongly phytotoxie, ially when applied in
fly the precise patterns necessary in 4 oil, and in recent years they lave been used

|. application, h de primarily as defoliants or perce. Typical of
as been made in recent years, compounds is 4, 6-Dinitro-2-

in producing chemicals which possess relatively (les orthocresol), which is perhaps more
greater toxicity for insegts than for man. There familiar under its trade names, Sinox. Antin-
is no, reason for believing, however, that the nonin or DNOC, These compounds niust be
time will ever come when those whe handle classified as dangerous, since the toxic dose for
agricultural pesticides can afford to ignore the caperimental animals an¢ man is contained in a
basic safety practices. which they must now relatively small volume of a commercial con-
follow. ~ ‘ centrate, and the effects are cumulative, DNOC
It should be pointed out, in connection with is absorbed to an appreciable extent through
the discussion which follows, that it is not. the intact human skin. The toxic manifesta-
ible to make a direct determination of the tions are similar to those produced by

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