Study Book
For the Training Course:
SAFETY
and PESTICIDE USAGE
1971
ENVIRONMENTAL PROTECTION AGENCY
PESTICIDES PROGRAMS
Division of Pesticide Community Studies
4770 Buford Highway
Chamblee, Georgia 30341
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PEOTIiCTlON AGEHCt
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ENVIRONMENTAL PROTECTION AGENCY
William D. Ruckelshaus, Administrator
PESTICIDES PROGRAMS
William M. Upholt, Ph.D., Deputy Assistant Administrator
Division of Pesticide Community Studies
Samuel W. Simmons, Ph.D., Director
State Services Branch
Anne R. Yobs, M.D., Acting Chief
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FOREWORD
This studybook is made available to students enrolled in the
"Safety and Pesticide Usage" course to serve as a training aid and
guide. We hope you will find the material presented here useful in
your everyday work. Continued requests for more in-depth information
about pesticides, both for general knowledge and for use in specific
areas, prompted us to develop this course to touch on specific areas
of interest and practical application of previously presented theory.
Although, for the most part, the studybook contains papers pre-
pared especially for this course, it should not be considered a citable
source. Any original research data contained in these papers will be
published by the authors in another form in referenced scientific journals,
Should you be unable to locate the appropriate citable reference for these
data in the future, we ask that you contact the author directly.
We take this opportunity to express our appreciation to the authors
for their participation in this training course and to wish you the stu-
dents rapid progress toward our common goal of adequate protection of
human health and the environment.
fc. (Avte -
Anne R. Yobs, M.D^
Acting Chief, State Services Branch
Division of Pesticide Community Studies
Environmental Protection Agency
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TABLE OF CONTENTS
Page
Foreword iii
Table of Contents iv
Faculty vi
Putting Pesticides and Pollution in Perspective 1
A. R. Yobs
Toxicology of Pesticides 9
T. B. Gaines
Hazards to and Protection of Individuals Who Mix and Apply
Pesticides 15
H. R. Wolfe
Selection of the Proper Pesticide 25
D. A. Eliason
The Mathematics of Mixing and Applying Agricultural Chemicals 97
J. M. Wise *•'
Hazards Associated with Different Methods of Application *
W. E. Yates and N. A. Akesson
Safe Use of Pesticides on the Farm ~-
J. I. Freeman •"
Pesticides and Institutional Environments «•,
H. G. Scott
Safe Use of Pesticides in Vector Control .7
H. D. Pratt
Safe Use of Pesticides in Structural Pest Control *
P. Spear
Diagnosis and Treatment in Pesticide Intoxication cc
G. A. Reich 55
Evaluation of Application from Various Viewpoints *
N. A. Akesson and W. E. Yates
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TABLE OF CONTENTS
Page
Household Use of Pesticides t-7
F. S. Lisella
Disposal of Waste Pesticides: Problems and Suggested Solutions ,,
H. C. Johnson and L. P. Wallace
Industrial Hygiene Practice in the Manufacture, Formulation fi7
and Packaging of Pesticides
C. M. Berry
Herbicides - What We Know, What We Need to Know and Where We ^
Are Going
V. Freed
Minimizing Fish and Wildlife Losses from Pesticides
W. E. Martin 75
Future Trends in Chemical and Nonchemical Methods of
Pest Control 79
L. A. Richardson
Why Some Chemicals Fail to Control g7
A. A. Badiei
Federal Legislation - Its Impact on Pesticides Safety 93
E. R. Baker
Pesticide Poisoning - A Medical Examiner's View 97
J. Davis
Safety in Transport and Storage of Pesticides ,nl
J. F. Byrne ILM
Calibration of Equipment 105
R. D. Black
See ADDENDUM
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FACULTY
Norman A. Akesson. Professor
Department of Agricultural
Engineering
University of California
Davis, California 95616
Amir Badiei, Ph.D.
Plant Biology Laboratory
Pesticide Research, EPA
3320 Orchard Street
Corvallis, Oregon 97331
Emerson R. Baker, J.D.
Consultant
Division of Pesticide Community
Studies, EPA
4770 Buford Highway
Chamblee, Ga. 30341
Clyde M. Berry, Ph.D.
Department of Preventive Medicine
and Environmental Health
University of Iowa
Iowa City, Iowa 52240
Robert D. Black
Assistant Sales Manager
Stephenson Chemical Company
P.O. Box 87188
College Park, Ga. 30337
James F. Byrne
Shell Chemical Company
P.O. Box 813
Princeton, New Jersey 08540
Joseph H. Davis, M.D.
Dade County Medical Examiner
Jackson Memorial Hospital
1700 N.W. 10th Ave.
Miami, Florida 33125
Donald A. Eliason, M.P.H., Dr.P.H.
Acting Chief, Biology Section
Technical Development Laboratory
Center for Disease Control
Savannah, Ga. 31402
Virgil Freed, Ph.D.
Head, Department of Agricultural
Chemistry
Oregon State University
Corvallis, Oregon
John I. Freeman, D.V.M., M.P.H.
Chief, Veterinary Public Health
North Carolina State Board of Health
255 N. McDowell St.
Raleigh, N. C. 27602
Thomas B. Gaines
Supervisory Research Pharmacologist
Toxicology Branch, EPA
4770 Buford Highway
Chamblee, Ga. 30341
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FACULTY
Frank S. Lisella, Ph.D.
Assistant Director
Division of Pesticide Community
Studies, EPA
4770 Buford Highway
Chamblee, Ga. 30341
William E. Martin
Chief, Pesticide Appraisal & Moni-
toring Branch
Bureau of Sport Fisheries and Wildlife
Washington, D. C. 20240
Harry D. Pratt, Ph.D.
Chief, Insect and Rodent Control Branch
Bureau of Community Environmental
Management
Public Health Service - DHEW
3384 Peachtree Rd., Room 313
Atlanta, Ga. 30326
George A. Reich, M.D., M.P.H.
Assistant Chief, Community Studies
Branch
Division of Pesticide Community
Studies, EPA
4770 Buford Highway
Chamblee, Ga. 30341
L. A. Richardson, Ph.D.
Leader, Training Unit
Perrine Primate Research Laboratory, EPA
P.O. Box 490
Perrine, Florida 33157
Harold G. Scott, Ph.D.
Department of Tropical Medicine
and Parasito!ogy
Tulane University School of Public
Health and Tropical Medicine
New Orleans, La. 70112
S. W. Simmons, Ph.D., Chief
Division of Pesticide Community
Studies, EPA
4770 Buford Highway
Chamblee, Ga. 30341
Phillip Spear, Ph.D.
National Pest Control Association
250 W. Jersey St.
Elizabeth, New Jersey
Lynn P. Wallace, Ph.D., Chief
Ultimate Disposal Branch
Toxic Materials, Waste Management
Office, EPA
5555 Ridge Ave.
Cincinnati, Ohio 45213
John M. Wise
Quality Control Manager
Stephenson Chemical Company
P.O. Box 87188
College Park, Ga. 30337
Homer R. Wolfe, Chief
Western Pesticide Research
Laboratory, EPA
P.O. Box 73
Wenatchee, Washington 98801
Wesley E. Yates, Professor
Department of Agricultural
Engineering
University of California
Davis, California 95616
Anne R. Yobs, M.D., Chief
State Services Branch
Division of Pesticide Community
Studies, EPA
4770 Buford Highway
Chamblee, Ga. 30341
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PUTTING PESTICIDES AND POLLUTION IN PERSPECTIVE
Anne R. Yobs, M.D.
The uses of chemical substances become more numerous each day, leading
to the formulation of new substances and the development of new commercial
applications.
Man's physical environment is now exposed to a myriad of substances which
are potentially toxic to man himself or to constituents of his environment.
Such substances are found in nearly everything that man uses. In trace
amounts in the human body, some substances may be essential to life or
have no demonstrable effect, but in larger amounts, these same substances
may be toxic. It has been estimated that some 2 million chemical compounds
are now known and that several thousand new chemicals'are discovered each
year. Most new compounds remain laboratory curiosities which are never
produced commercially; however, several hundred new chemicals do enter
commercial markets annually. The metals, metallic compounds and synthetic
organic compounds -- among these pesticides -- cause particular concern
because of their rapidly increasing number and use.
United States consumption of metals with known toxic effects has increased
greatly in the last 20 years. Use data tend to underestimate their
increasing pervasiveness in our environment due to the many new metallic
compounds being formulated and used in ever-widening varieties of new
products. The use of synthetic organic chemicals is growing in a similar
manner. More than 9,000 synthetic compounds are now in commercial use
in amounts exceeding 1,000 pounds a year. In 1968, synthetics totaled
nearly 120 billion pounds — 60 million tons. This represented a 15 percent
increase over 1967 and a 161$ increase over the 10 years since 1961 .-I/
Admittedly many of these substances are not toxic, but their sheer numbers,
increasing diversity and use and the environmental problems already
encountered from some indicate the existence of a problem of potential
significance. These substances enter man's environment—and man himself--
through complex and interrelated pathways. Present in air, water, soil,
consumer products and food, they pervade our environment. Some become
concentrated through the food chain—with minute quantities being magnified
thousands of times as they are consumed by higher forms of life. Increasingly,
all forms of life are being exposed to potentially toxic chemical materials.
The environmental effects of most of these substances are not well understood.
Testing has largely been confined to determining their acute effects and
knowledge of the chronic or long-term effects, such as genetic mutation,
is inadequate. Available data, while still incomplete, indicates potential
or actual hazard from a number of these substances.
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Many serious effects, including such things as cancer production
(carcinogenicity), genetic mutation (mutagenicity) which is the production
of permanent changes in genes and is transmissible from parent to child,
as well as the production of physical or biochemical defects in an offspring
(teratogenecity) can occur as a result of exposure to certain of these
compounds. In general, we do not know which substances cause such effects
or the level(s) of a given chemical which must be reached before the
effect(s) occurs. The problem is complicated by the changes which chemicals
may undergo once they enter the environment becoming more or less toxic
through modification or as a result of interaction with other substances.
Existing Federal controls over the introduction of toxic substances into
the environment are of two types. The first is control over initial
production of a substance and its distribution. For example, under the
Federal Insecticide, Fungicide and Rodenticide Act (FIFRA), a manufacturer
must register a pesticide with the Environmental Protection Agency before
it can be introduced in interstate commerce. EPA can prohibit distribution
of a pesticide or require labeling of acceptable uses. This type of
control, exercised at the point of manufacture, is also applied to drugs
and food additives by FDA. Although this control technique can be very
effective, current authorities cover only a small part of the total
number of potentially toxic substances and do not deal with all of the
uses of a substance which may produce toxic effects. The second type of
control is media-oriented, that is directed at air and water pollution
from various sources. Federal authority derives primarily from the Clean
Air Act and the Federal Water Pollution Control Act. Under the latter,
the Federal Government, in cooperation with the states, sets standards
for the amounts of particular substances allowable in water. Under the
Clean Air Act, the Federal Government sets national air quality standards,
allowing the states to set more stringent standards. Enforcement of
standards depends on limiting the emission of a substance from a given
source.
In theory, this type of authority can be used to control all substances,
but there are several limitations to the effective application of such
controls. These media-based authorities are mainly concerned with pollutants
which occur in large quantities. It is difficult to control minute amounts
of toxic materials with this type authority partly because of the difficulty
in detecting their presence in air or water and partly because many
substances enter the environment through disposal of consumer products.
If a product is disposed of through the municipal sewer line or by burning
at an incinerator, it is almost impossible for the media-oriented controls
to deal effectively with minute amounts of decomposition products. To do
so requires their effective removal by the municipal waste treatment plant
or incinerator stack scrubbers.
Most toxic substances are not exclusively air and water pollutants, but
can be found in varying quantities in air, water, soil, food and
industrial and consumer products. The multiplicity of ways by which man
can be exposed to these substances makes it difficult for the media-oriented
authorities to consider the total exposure of an individual to a given
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substance, a consideration necessary for the establishment of adequate
standards.
Since the worst aspects of pesticides are usually the ones which make the
most news, it sometimes seems that pesticides are credited with more than
their share of the overall pollution problem. Pesticides properly used
are tools, however when they move off target or are misused, they become
pollutants. Pesticides might not be much of a problem if they stayed
where applied, but in fact they do not remain where applied and do
remain in the environment for relatively long periods of time as shown
by the widespread distribution of DDT and some other chlorinated
hydrocarbons.
Pesticides are deliberately introduced into the environment in order to
improve the quality of the environment for man himself and for his
domesticated animals and plants. These chemicals are used in agriculture
to improve the farmer's cost/benefit ratio and for the ultimate benefit
of the consumer. The technology of the use of modern pesticides is one
important component of the agricultural revolution of the last 100 years,
other components include farm mechanization and the development of
chemical fertilizers. This revolution has made it possible for the United
States farmer to increase his production from an amount sufficient to
support 4 people in 1850 to that sufficient for an estimated 46 people
today. In our present system of monoculture, farm mechanization, and
complex systems of food harvesting, processing, distribution and storage,
the use of pesticides often means the difference between crop production
and crop failure and between economic profit and loss. In developing
countries where food supplies are marginal, pesticide use may represent
the margin between survival and starvation.
Food losses attributable to all forms of pests, including pathogens, weeds
and arthropods, are very difficult to estimate, and to some extent the
estimates are subjective in nature—it is not easy to say with certainty
what the yield of a crop might have been in some hypothetical, disease-
free circumstance.
The losses which can be attributed to pests are of several kinds. Sometimes,
losses occur as a result of direct reduction of growth with concomitant
reduction of yield; such reduction results both from competition of weeds
and from damage caused by insects and pathogens. Frequently, a loss
of quality is also evident; deformed, discoloured or small-sized produce
often carries small market value. A third type of loss relates to costs
incurred by the farmer in attempts to reduce damage caused by pests; in
addition to the cost of chemicals and their application, there may be
costs arising from additional cultivations or from the need to purchase
more expensive, resistant varieties of crop seed. Furthermore, resistant
varieties are sometimes less productive than susceptible ones, and indirect
costs are incurred this way, as they may be when the farmer resorts to crop
rotation for the purpose of crop hygiene.
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As has been mentioned, it is difficult to quantify losses although figures
of the order of 10 to 20% loss of useful crop are, frequently quoted both
in the United States of America and in Britain.-^
Problems of environmental quality inevitably result from conflicts of interest,
and the use of pesticides has been attacked by conservationists and ecologists
as a focal point of concern for the preservation of environmental quality.
Considerations in the "pesticide controversy" include a variety of technologica
economic and sociological points. These include overzealous application of
new products and techniques, farm labor shortages, lack of appreciation of
the ecological complexities of crop production, failure to develop pest-
management strategies and newer selective and biodegradable pesticides
and the supermarket approach of many consumers today.-^
There are now some 300 different chemical compounds which are used as
commercial pesticides variously on crops, harvested produce, processed and
stored foods, soil, water, structures and habitations. They serve to
minimize and control the attacks of pests and resultant damage. Pesticides
may be categorized according to the type of pest controlled - insecticides,
fungicides, herbicides, nematocides, molluscacides, rodenticides and acaricides
Numbers of pest species in the United States have been estimated as follows^-'
bacteria
fungi
viruses
weeds
nematodes
molluscs
insects
rodents
birds
10
250
8000
250
500
500
50
000
200
10
species
species
species
species
species
species
species
species
species
The annual loss in the United States from pests in crops, forests, livestock
and other agricultural products has been estimated at $14.3 billiyon with
additional losses of $2.3 billion during storage and marketing r^-' Worldwide,
crop production losses are estimated to be 14% due to plant diseases, 2%
insects, and 9% weeds, for a total loss of $70-90 billions. It has been
estimated that enough food is lost to feed 1 billion people. Modern
pesticides have accounted for astonishing gains in agricultural production
by reducing the damage from pest attack. The average potato yield in
New York State from 1936-45 with good growing practices and arsenical
insecticides was 110 bushels per acre - in 1946-47 with DDT used exclusively,
yield was 172 bushels per acre - up 56%. The use of systemic insecticides
the ye was
to control insect vectors of plant virus diseases increased wheat yields
in the California Imperial Valley by 10%. The use of phenoxy acid heribicides
in small grains to control weeds has been stated to inccaase grain yields
over a 15 year period by more than 800 million bushel ST^-'
"Pesticide Technology has made it possible to increase the efficiency of
farm operations and has led the way to greater productivity through
mechanization of all phases of crop production from planting to harvesting
and storing. . . .
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"Ecologically, the use of pesticides is an almost inevitable consequence
of the development of modern high production agriculture. The pure
monocultures of corn, wheat, cotton or rice, often extending for thousands
of contiguous acres, represent the highest sort of ecosystem specialization.
Compare if you will, a midwestern cornfield with its original predecessor,
the tall grass prarie. The cornfield ideally contains only a single plant
species without any competitors-bacterial, fungal, weed, nematode, insect,
bird or rodent pests; while the prarie consisted of perhaps 100 plant
species and thousands of associated animals. Through the development of
the cornfield, man has aimed to maximize the harvestable energy of the
ecosystem, and this has been achieved at the cost of ecosystem stability.
The extent of the instability of the hybrid cornfield has been dramatically
revealed in the calamitous attack of southern corn leafblight.
"Modern agri-ecosystems require large inputs of energy to maintain them
in a stable state. Pesticides, fertilizers, gasoline for tractors and
electric power for irrigation represent the major energy inputs required
for ecosystem stability. Energy applied as pesticides is Cheaper and far
more efficient than the man with the hoe or fly swatter.lbi^
In the drive toward increased agricultural productivity man has paid
little attention to the broader aspects of the agri-ecosystem and to the
sound principles of crop rotation developed during the past 100 years. These
had very beneficial effects in the control of many agricultural pests, both
plant and animal. Unfortunately, in many areas most of them have been
all but abandoned today. Newer technologies such as the "no-till" concept
depart still further from sound eco-system strategies for agricultural
pest management. However much these Increase crop production, a corresponding
price will be paid in need for more pesticides.
The new hybrid varieties of crops which have brought about the "green
revolution" have also complicated the problems of the agri-ecosystem. These
have been bred largely for high production characteristics and may exhibit
markedly different susceptibilities to various types of pests. Moreover,
their high production characteristics are effective only under very high
levels of fertilization with nitrogen and phosphorus and often with greatly
increased reliance on pesticides.
The agri-ecosystem does not exist in a vacuum, and the future trends and
developments in agriculture must be weighed in terms of the total quality
of the environment.
The value of pesticides to the agricultural industry may also be considered
from the extent to which they are employed. By this measure these materials
have been outstandingly successful. Table 1 shows U. S. sales of
pesticides for the 8-year period 1962-1969.
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Table 1. Pesticide Use in the United States^/
Sales in Millions of Pounds
Year Fungicides Herbicides Insecticides To
1962 97 95 442 6
1963 93 123 435 6
1964 95 152 445 6
1965 106 184 473 7
1966 118 221 502 8
1967 120 288 489 8
1968 124 '2f> 318 198 '•<" 9
1969 127 ' i-- -348 *' 502 ; 9
a/ U. S. Tariff Commission.
Total pesticide use has increased an average of more than 7 percent per year.
For herbicides the increase is substantially higher, their use more than
doubling over a 4-year period. In terms of crop applications the U. S.
Department of Agriculture estimated in 1966 that herbicides were applied
to 27 percent of the 350 million crop acres, insecticides to 12 percent,
and fungicides to 2.6 percent.
The role of these chemicals in pest control and in crop production has
been intensively studied, and their use has become virtually indispensible
to modern agriculture but for the majority of the individual pesticide
chemicals there is only a superficial knowledge of the effects of their
long-term use on the quality of the environment. On a national level we
have developed an impressive array of knowledge relating to pesticide
contamination of crops, foods, soils, animals, and even humans. However,
in relation to the immensity of the total pollution problem, these efforts
leave many end points unresolved. Special attention needs to be given
to the rates of accumulation of pesticides and their breakdown products in
soils and to the extent of contamination of water resources; to the interrelatic
between various combinations of pesticides and the soil microflora; to the
effects of all new compounds on food chains and food-chain organisms,
especially including wildlife; and to the effects of possible mutagenic and
teratogenic compounds and their breakdown products upon man..6-/
The persistence of many pesticides has made possible the development
of new agricultural techniques such as preemergent herbicides, soil
insecticides, and seed treatments and have caused many of the environmental
problems facing the nation today. The values shown in Table 2 give an
indication of the relative persistence in soils of various types of
pesticides.
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Table 2. Persistence of Pesticides in Soils^/
Lead, arsenic, copper, mercury
Dieldrin, BHC, DDT insecticides
Triazine herbicides
Benzoic acid herbicides
Urea herbicides
2,4-D; 2,4,5-T herbicides
Organophosphorus insecticides
Carbamate insecticides
a/ Metcalf and Pitts (13).
Approximate half-life, years
10-30
2-4
1-2
.2-1
.3-.8
.1-.4
.02-.2
.02-.!
Difficulties have been encountered with residues of heavy-metal pesticides
containing lead and arsenic, which were used extensively for 20 to 30 years
in apple orchards and tobacco farms. Compounds of these elements are
intrinsically deleterious to life when solubilized sufficiently to enter
living systems. More than 3,500 pounds of lead arsenate was applied to
a commercial orchard in Washington over a 25-year period and was found to
accumulate in soil at levels which were seriously injurious to cover crops.
Tobacco soils in North Carolina have accumulated arsenic up to 5 ppm.
Many years are required for the levels of lead and arsenic in such soils
to return to normal values. The persistent herbicides sometimes show
disconcerting tendencies to render soils sterile to plant growth long
after their usefulness was expended. This is particularly true where
use patterns are abruptly changed.
Pesticides will be used for the foreseeable future. This is the collective
judgment of the Jensen Committee on Persistent Pesticides, National Academy
of Sciences^/, which stated "For most purposes, nonchemical methods of
control are not expected to supplant'the use of chemicals in the forseeable
future"; and/of the Mark Commission of the Secretary of Health, Education,
and Welfare^, which said, "Our need to use pesticides and other pest
control chemicals will continue to increase for the foreseeable future."
This does not, however, give license to utilize pesticides on an infinitely
increasing scope or to use them irresponsibly with regard to the quality
of the environment. Changes must be made in pest-control practices and
in some cases in the nature of pesticide chemicals themselves if the
agricultural industry is to maintain public confidence in its practices
and to observe an appropriate and responsible regard for public health
and environmental quality.
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REFERENCES
1. Council on Environmental Quality: Toxic Substances.
U.S. Government Printing Office, Washington, D.C., April 1971.
2. HassaH, K.A.: World Crop Protection, Vol. 2: Pesticides.
CRC Press, Chemical Rubber Co., Cleveland, Ohio,1969.
3. Metcalf, R.L.: Putting Pesticides and Pollution in Perspective -
from the Summaries of Presentations - Twenty-third Illinois Custom
Spray Operators Training School, Urbana, Illinois, Jan. 1971.
4. Metcalf, R. L.: Poisons, Economic. In: Vol. 15 of "Encyclopedia
of Chemical Technology", Wiley-Interscience, New York, N.Y., p. 908,
1968.
5. Moseman, A. H.: Pest Control -- Its Role in the United States
Economy and in the World. In: "Scientific Aspects of Pest Control,"
National Academy of Sciences - National Research Council Pub!. No. 1402,
Washington, D.C., p. 26, 1966.
6. Mrak, E. (Chairman): Report of the Secretary's Commission on
Pesticides and Their Relationship to Environmental Health. U.S. Government
Printing Office, Washington, D.C. 1969.
7. Metcalf, R.L.: Methods of estimating effects. In: Research in
Pesticides," edited by C. 0. Chicester, Academic Press, New York,
pp. 17-29, 1969.
8. Jensen, J.H. (Chairman): Report of the Committee on Persistent Pesticides,
Division of Biology and Agriculture, National Research Council, Washington,
D.C., May 1969.
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TOXICOLOGY OF PESTICIDES
Thomas B, Gaines
Toxicology may be defined as a science that deals with the action of
poisonous materials on living cells and tissues, the response of the
living structures, and the detection, identification, and evaluation
of safety of these poisonous materials. Of course, many chemical
compounds are quite beneficial for use in man at certain levels. On
the other hand, these same materials can be quite harmful if used
without regard for their potential toxicity. Drug therapy in man
must be practiced with care to prevent the development of toxic
manifestations. Even table salt, a common part of our diet, is as
toxic in a single oral dose as some of our pesticides. Although
pesticides may be quite hazardous to man, at least one of them, the
organic phosphorus Dipterex, has been used experimentally for control
of intestinal parasites in man. This and some other organic phos-
phorus compounds are used for control of intestinal parasites of live-
stock.
Factors Influencing Toxicity
The toxicity of pesticides in mammals is influenced by compound, dos-
age level, schedule of dosage, duration of dosage, route of exposure,
species and strain differences, sex, age, interaction of compounds,
nutrition, disease, and temperature and other environmental factors.
Among 100 pesticides tested for their acute oral toxicity in male
rats the organophosphorus Abate was the least toxic with an U^Q
of 8600 mg/kg and the carbamate Temik the most toxic with an LDcQ
of 0.8 mg/kg. The toxicity of any one pesticide in mammals corres-
ponds to the dosage level in accordance with the dosage-response con-
cept. This implies that there is a dosage level great enough to kill
all of the poisoned organisma and, at the other end of the scale, a
dose small enough to be a "no effect" level. It should be emphasized
that a "no effect" level may actually represent our inability to detect
an effect. It is doubtful that there is any level of a foreign sub-
stance that fails to exert some effect when introduced into a living
organism.
A schedule of dosage that involves continuous exposure to a pesticide
is generally more hazardous than intermittent exposure at the same
level. The degree of difference depends to a great extent on the rate
at which the organism is able to excrete the poison or convert it to
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a non-toxic substance. The single dose oral LDcn for carbofuran in
rats is about 8.0 mg/kg. However, if the compound is fed in the diet
so that the total dose is consumed each day over a period of several
hours, the rats will survive 40 mg/kg/day for 90 days. Thus inter-
mittent exposure will prolong the time required for a toxic effect to
develop even for those compounds known to be cumulative in their effect.
The development of some manifestations of toxicity are dependent on
duration of dosage. This is the reasoning behind the requirement for
90-day and 2-year exposure studies in animals. Effect of long-term
exposure is especially important in consideration of carcinogenicity
(development of malignant tumors) of pesticides.
The three most common routes of exposure to pesticides are oral, dermal,
and inhalation. The oral route is the dominant route of exposure from
pesticide residues in food. Formulators and applicators of pesticides
are subject to considerable exposure by dermal absorption and inhala-
tion. In laboratory tests with pesticides in rats most compounds tested
were more toxic by the oral route than by the dermal route. Only five
of 90 pesticides tested by both routes were more toxic by the dermal
route. Three of these were organophosphorus compounds; one was a car-
bamate; and the other was a sulfite compound.
The question of species difference in susceptibility of animals to
pesticides is, of course, of only academic interest to those concerned
with human health, but it may vary by a factor of 10 or more for some
compounds in mammalian species.
Pesticides in a single oral dose are usually more toxic to female than
male rats. Although toxicity is influenced by sex, this may vary for
different animal species. Compounds also vary as to their toxicity
in different age animals. In 1965, Lu and his co-workers reported that
in rats givena single oral dose malathion was more toxic in newborn rats
than in adults. DDT and dieldrin in a single dose were more toxic to
adults than to newborn rats. In acute oral toxicity studies conducted
by the author the herbicides atrazine, simazine, and paraquat were more
toxic to adults than to v/eanlingrats. On the other hand, the synergist
sulfoxide and the insecticide famphur were more toxic in weanling rats
than in adults.
The interaction of pesticides may be of practical as well as theoretical
significance. Two compounds may (1) be simply additive (2) antagonistic
or (3) potentiate one another. The effect is usually additive. Antago-
nism between two compounds has been demonstrated between some chlori-
nated hydrocarbon and organophosphorus pesticides and between some
chlorinated hydrocarbons and drugs. >•* This antagonism is associated
with liver microsomal enzyme induction. When the combined effect of
two compounds is greater than additive they are said to potentiate
each other. EPN and malathion have been shown to produce a 50-fold
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potentiation in oral toxicity of these two compounds in dogs. Dioxa-
thion and trichlorfon will also do this with malathion. Potentiation
between compounds has to be considered in establishing food tolerances
and labeling restrictions for pesticides.
Measurement of Toxicity
In evaluating the toxicity of pesticides in man it is, of course, im-
portant to have as much data as possible from studies in humans. How-
ever, since it is practical to do only limited studies in man with pesti-
cides, most toxicological information must be obtained from investi-
gations in laboratory animals. In establishing dose-response relation-
ships, types of toxicity tests include determination of the 1-dose LDcQ
(acute), 90-day exposure (subacute), and chronic exposure. The LDcn is
a statistically calculated value which represents the best estimation
of the dose required to produce death in 50 percent of the test animals.
It is, therefore, always accompanied by some means of estimation of the
error of the value, such as the probability range of the value. If
the 11)50 ^or comPound B is greater than that of compound A, compound B
may be said to be less potent than compound A. The slope of the dose
response curve is most significant when comparing two or more compounds.
The LD5Q for compound A may be greater than for B and the LD,. for
compound B be greater than that for compound A. Each LD,-n determination
usually involves about four or more dosage levels of the test material
selected at a certain geometric or logarithmic interval with each dos-
age level being given to several animals. The most commonly used mfithods
for calculating LDcn values are those of Litchfield and Wilcoxon , Miller
and Tainter, and Weil. The author uses the method of Litchfield and
Wilcoxon^ which employs the use of logarithmic probit graph paper with
the dosage levels in logarithms plotted against percent mortality in
probits. A straight line is fitted to the plotted data so that the LD^ •
or LDiQ> etc., as well as the 11)50 value can be read from the line. The
£050 (effective dose for 50 percent of test animals), ECrQ (effective
concentration in air or water for 50 percent of the test animals) and
the LCcn (lethal concentration for 50 percent of the test animals) can
be calculated in the same was as the I-Dcrr ^e ^RD or ^SO
required to produce an effect or death in 50 percent of the test animals)
can be calculated according to the method of Litchfield. ^
Ninety-day studies may involve daily dosing, or in the case of oral
exposure the pesticide may be fed as a component of the diet. Hayes
described the application of a 90-day feeding study with an acute
oral toxicity study to arrive at a chronicity factor for a compound.
The factor is calculated by dividing the 1-dose oral LDrQ in mg/kg by
the 90-dose 11)50 value in mg/kg/day. The chronicity factor is useful
for comparing the cumulative toxicity of various pesticides in labora-
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tory animals. Of the pesticides evaluated in this way some of the
chlorinated hydrocarbons show the greatest degree of cumulative toxi-
city. The organophosphorus pesticides show little cumulative toxicity
and some of the carbamate insecticides have chronicity factors of less
than one. Ninet3r-day studies are also useful for evaluating the effect
of continuous pesticide exposure upon growth, symptomatology, hematology,
and pathology in laboratory animals.
Chronic exposure studies (usually up to two years in rats and longer in
animals with longer life spans) are used to evaluate the effect of long-
term exposure to pesticides such as the possible development of car-
cinogenesis. There are also special tests for evaluating the sensi-
tization, eye irritation, neurotoxic, teratogenic (including effect on
reproduction) and mutagenic effects of pesticides in animals.
Selective Toxicity
13
Albert defines selective toxicity as the injury of one kind of living
matter without harming some other kind with which the first is in inti-
mate contact. The living matter to be injured may be referred to as
the uneconomic species, and the matter which is to be unaltered as the
economic species. This characteristic of certain compounds is signifi-
cant in the field of chemotherapy in man in that it allows the elimi-
nation of certain organisms without injury to the host. Selective
toxicity of pesticides makes it possible to use many of them effectively
without injury to man. Diazinon, an effective pesticide againse roaches,
has an ID50 °f only 2 mg/kg for roaches compared with 40 mg/kg for mice. ^
The LDsp f°r malathion in mice is 815 mg/kg but only 30 mg/kg in house
flies.**
Pesticides may be more toxic to insects than mammals because of species
differences in rate of absorption, metabolism, or excretion. Mammals
generally have a much better enzyme system for degrading pesticides
than do insects. This may be illustrated by studying malathion, a
relatively inactive compound. It is rapidly oxidized to the active
malaoxon in both insects and mammals. However, the toxic tnalaoxon is
hydrolyzed slowly in the insect and rapidly in the mammal to non-toxic
products. The hydrolysis and binding of malathion itself is slow in
insects but rapid in mammals.
Factors Affecting Absorption
Some of the factors affecting the absorption of poisons by the oral
route are the type of solvent used for the compound, the dilution of
the dose, and the fasting state of the animal. Some solvents are more
readily absorbed from the gastrointestinal tract than are others. Fer-
guson reported that the death rates from 12 different drugs given
orally to mice and rats were higher the greater the dilution of the dose
in water. The absorption rate of a compound is generally considered to
be greater in a fasted than in a non-fasted animal.
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Dermal absorption is influenced by compound, type of solvent or
physical state of the material, size of area of application, and con-
dition of the treated skin. O'Brien and Dannelley16 studied the rate
of penetration through rat skin of DDT, famphur, carbaryl, malathion,
and dieldrin end found that the penetration rates of the compounds in-
creased in the order given. The vehicle in which the compounds were
given also influenced the penetration rate which increased in the order
corn oil, benzene, acetone. Fredriksson demonstrated in guinea pigs
dosed dermally with sarin that the time from dosing to respiratory arrest
in the animals decreased as the area of application of the poison was
increased. The dermal toxicity of parathion in rats was significantly
increased when the skin was abraded by stripping with cellophane tape
to remove the stratum corneum just prior to dosing.
The respiratory toxicity of a compound is affected by the physical
state of the material. The efficiency of respiratory absorption of
compounds increases in the order of sprays, dusts, and gases. Particle
size is of great importance. Particles in excess of 20 u in diameter
are seldom inhaled. The upper respiratory tract tends to capture
particles between 5 and 10 u size. The alveoli are most efficient in
capturing particles of 0.1 to 3 u. in size.
References
1. Talaat, S.M. : Dipterex: an oral therapeutic agent in the treat-
ment of schistosomiasis and other parasites. J. Egypt. Med. Assoc.
47: 589-593, 1964.
2. Gaines, T.B.: Acute toxicity of Pesticides. Toxicol. Appl. Pharma-
col. 14: 515-534, 1969.
3. Lu, F.C., Jessup, D.C., and Lavallee, A.: Toxicity of pesticides
in young versus adult rats. Fd Cosmet. Toxicol. 3_: 591-596, 1965.
4. Ball, W.L., Sinclair, J.W., Crevier, M., and Kay, K.: Modification
of parathion toxicity for rats by pretreatment with chlorinated
hydrocarbon insecticides. Canad. J. Biochem. Physiol. 32: 440-445,
1954.
5. Burns, J.J. and Parkhurst, A.S.: Biochemical effects of drugs.
Ann. Rev. Pharmacol. I: 79-104, 1961.
6. Frawley, J.P., Fuyat, H.N., Hagan, E.G., Blake, J.R., and Fitz-
hugh, O.G.: Marked potentiation in mammalian toxicity from
simultaneous administration of two anti-cholinesterase compounds.
J. Pharmacol. Exper. Therap. 121 (1): 96-106, 1957.
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14
7. Loomis, T.A. : Essentials of Toxicology. Lea and Febiger, Phila-
delphia, 1968.
8. Litchfield, J.T. Jr. and Wilcoxon, F. : A simplified method of
evaluating dose-effect experiments. J. Pharmacol. Exper. Therap.
9j>: 99-113, 1949.
9. Miller, L.C. and Tainter, M.L.: Estimation of ED5Q and its error
by means of logarithmic-probit graph paper. Proc. Soc. Exper. Biol,
52: 261-264, 1944.
10. Weil, C.S.: Tables for convenient calculation of median-effective
dose (LCt-... or ED n) and instructions in their use. Biometrics J5:
t-... n
249-263, 1952.
11. Litchfield, J.T., Jr.: A method for rapid graphic solution of time-
percent effect curves. J. Pharmacol. Exper. Therap. 97; 399-406,
1949.
12. Hayes, W.J., Jr.: The 90-dose LD,-n and a chronicity factor as
measures of toxicity. Toxicol. Appl. Pharmacol. II (2): 327-335,
1967..
13. Albert, A.: Selective toxicity. John Wiley and Sons, Inc., New
York, 1965.
14. Dauterman, W.C.: Personal communication.
15. Ferguson, H.C.: Dilution of dose and acute oral toxicity. Toxi-
col. Appl. Pharmacol. 4 (6): 759-762, 1962.
16. O'Brien, R.D. and Dannelley, C.F. : Penetration of insecticides
through rat skin. J. Agr. Fd Chem. 13 (3): 245-247, 1965.
17. Fredriksson, T. : Influence of solvents and surface active agents
on the barrier function of the skin towards sarin. Acta. Derm.
43 (2): 91-101, 1963.
18. Gaines, T.B. : Unpublished data.
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1J
HAZARDS TO AND PROTECTION OF INDIVIDUALS
WHO MIX OR APPLY PESTICIDES
Homer R. Wolfe
Man is often subjected to relatively high levels of pesticide compounds
when he is actively engaged in pest control operations or working
directly with the compounds in formulating plants. Experience has shown
that if proper precautionary measures and directions are followed, even
the more toxic compounds can be handled safely. Although illnesses and
even deaths from pesticides occur each year in the United States, it
should be pointed out that most of these cases are caused by carelessness
or by accident.
The more extensively used modern synthetic insecticides are the organo-
phosphorus, chlorinated hydrocarbon, and carbamate compounds. Generally,
the acute toxicity of the organophosphorus group is somewhat greater than
that of the chlorinated hydrocarbon or the carbamate compounds. However,
the chlorinated hydrocarbon compounds, due to their greater stability,
present more of a residue problem. The estimation of hazard to workers
who come in contact with pesticides is based primarily on the observed
acute dermal, and to a less extent oral, toxicity of these compounds
to experimental animals. Where it is available, use experience is con-
sidered. The estimated relative acute toxic hazard to spraymen for a
number of pesticides can be seen in the table. The classification into
toxicity groups is both approximate and relative. It should be noted
that these toxicity categories are not related to specific categories
spelled out for label requirements.
Much of the safety in relation to pesticides rests on the user or appli-
cator of the compounds. If he is knowledgeable concerning pesticides
and understands the importance of taking proper precautions, he can do
much to insure the safety of himself and others. This also applies to
workers involved in the manufacture and formulation of toxic compounds.
Their contact is usually with the more concentrated forms of pesticides;
therefore, they should be especially aware of the need for protecting
themselves from exposure. Thus, an important adjunct to safety in
relation to pesticides is education, not only of supervisory personnel
but also of those individuals who actually handle the materials.
There are several very important indirect ways of protecting the worker
such as providing education and medical supervision, stressing the
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16
importance of personal hygiene and cleanliness, the importance of not
being careless, and pointing out the need for reading and following
directions on the pesticide label. However, these topics will be covered
by other presentations on this program. The main purpose of this pres-
entation is to discuss the more direct protection of the various routes
of entry of pesticide into the body. Protection of these routes means
prevention of exposure and prevention of exposure is undoubtedly the best
insurance against poisoning.
ROUTES OF ENTRY
There are four routes of entry of pesticide compounds into the body: (1)
dermal, (2) respiratory, (3) oral, and (4) through cuts or abrasions in
the skin.
DERMAL ROUTE
The dermal route is considered to be the most important route of entry
into the body during most exposure situations in the field and probably
plays an important part in exposure of workers in formulating plants.
This route is one that has undoubtedly been responsible for a great many
poisonings of workers, especially from the more toxic organophosphorus
compounds.
In research studies we have measured the potential exposure of several
hundred pesticide applicators, and the results indicate that over 91%
of the pesticide to which the body is subjected during most exposure
situations, and especially to applicators of liquid sprays, is deposited
on the skin. It should be understood that any given amount of pesticide
is more rapidly and more completely absorbed by the oral or respiratory
routes. However, absorption of pesticides by these two routes is probably
too small a fraction of the total potential exposure to be considered
the main factor in most poisoning cases of workers in the field.
The importance of protecting specific body areas has not been clearly
defined in the past. This is because the rate of absorption of different
compounds through human skin is difficult to measure with any degree of
accuracy. The most useful and probably most accurate estimations or
measurements on the percutaneous penetration of pesticides in man which
have been accomplished thus far have been made by Maibach and Feldman.
Using radioactive labeled pesticides they were able to determine approxi-
mately what fraction of an applied dose would be absorbed through the skin.
In this way they not only compared the degree of dermal absorption for
certain pesticides but also compared absorption of a single pesticide
for different parts of the human body. The results obtained indicate
that sufficient importance may not have been attached to protection of
certain body areas. In checking dermal penetration of parathion at
different body areas these researchers found that the area of greatest
absorption on man is the scrotum where approximately 100% of an applied
dose was absorbed. The possibility of pesticide on this body area being
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completely absorbed is a very important point and emphasizes the need for
increased concern about protection of the area. Of utmost importance
would be the need for extreme caution in order to avoid spillage of
highly toxic liquid pesticide onto the scrotum.
Although cloth coveralls or trousers provide a reasonable amount of pro-
tection where contamination does not easily penetrate clothing, the
wearing of waterproof trousers provides the best protection for the lower
trunk and leg areas and is especially recommended in work situations
where there is a chance of liquid spillage, soaking by continued contact
with more dilute liquid sprays, or penetration of clothing through ex-
cessive contact with dry pesticides. In formulating plants where the
main outer protective garment is usually cotton coveralls, workers should
be required to wear waterproof aprons, especially if they are on duty at
bagging or mixing stations where there is often considerable contamination
down the front of the clothing with relatively concentrated wettable
powder formulations. Fortunately, many plants require the use of aprons.
Even when the waterproof apron is used it is very important that the
worker change to freshly laundered clothing each day in order to prevent
contamination of the scrotum or other skin areas. Needless to say, use
of clean clothing and daily bathing in an effort to avoid excess dermal
absorption are essential in any type of exposure situation.
Protection of the upper trunk and arms from contamination by toxic pesti-
cides is important, especially under conditions where heavy spray drift
may thoroughly wet cloth shirts, coveralls, and underclothing or where
concentrated dry pesticides come in contact with clothing and skin in
formulating plants. Our studies have shown that the greatest potential
contamination of spraymen in this general body area is the upper back,
shoulders, and forearms of workers operating equipment which propels
spray up into the air where it is more subject to drift. Under these
conditions a waterproof jacket or raincoat provides the best protection
for this general body area. This gear is usually worn during cooler
conditions, but as the temperature rises and the clothing becomes un-
bearably hot to wear, workers tend to discard them and work with much
less protection--perhaps only a short-sleeved T-shirt-type undershirt
on the upper trunk area. Under such conditions workers should be
encouraged to at least wear a long-sleeved cloth jacket that will not
be easily penetrated by pesticide, and preferably one that can be
properly washed.
The wearing of long-sleeved heavy grade "GI" cotton shirts or coveralls
as outer clothing during hot weather, often with no underclothing, is
popular with many applicators even though this is not a recommended
practice. Fortunately, these items of outer clothing provide a reason-
able amount of protection where spray drift is light with very fine
droplets that do not wet through to the skin. Under such conditions the
clothing should be changed and laundered daily. If clothing used during
spraying such as shirts, jackets, or coveralls are merely hung up to dry
after work and used repeatedly, as is often the practice, it doesn't take
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18
long for the pesticide material to work through where it will make
contact with underclothes or skin.
In selecting protective clothing for workers it is important to take into
consideration the comfort of the individual when he wears such items.
The conventional black or dark green rubberized or plastic waterproof
jackets in common use during past years are considered by many applicators
to be uncomfortable to wear not only because of greater heat absorption
but also because they may be of heavy grade material and not very flex-
ible. During recent years, however, several jackets and jacket-trouser
combinations that are lighter in color and weight have been available.
Although less durable, they are less costly to replace. Nevertheless,
there is still considerable discomfort in wearing any waterproof clothing
during hot weather because of the trapping of body heat.
Observations of pesticide applicators have indicated that although water-
proof clothing items, and especially jackets, are usually carried by the
workers, or readily available to them, they usually will not don the
clothing until drift of pesticide increases to the point where they feel
protection is necessary. Unfortunately, by this time there is often con-
siderable contamination of skin and clothing. The covering of contami-
nated skin areas by waterproof clothing may create conditions under which
dermal absorption may be increased. This may be more important during hot
weather where high temperatures and perspiration are involved. Whether or
not there would be less absorption under these conditions than if the
clothing were left off entirely depends upon the potential exposure which
might occur after the worker puts on the clothing. Maibach and Feldman-'-
found that covering up (occlusion) of contaminated skin with thin plastic
wrap material caused approximately a four-fold increase in absorption of
parathion. Although the increase of absorption of pesticide by covering
contaminated skin with various items of protective clothing is not known,
the above occlusion test results are cause to emphasize the need to put on
protective gear before the skin has been contaminated to any great degree.
The use of waterproof jackets in pesticide formulating plants is not
common and generally not considered a requirement if, as stated earlier,
rubber aprons are worn and coveralls are kept clean. It should be noted,
however, that in a plant there is more ready access to showers and other
means of decontamination, should excess exposure occur, than in the field
where applicators work.
Results of the dermal absorption studies noted above indicate that the
head-neck area should be given more attention. In this area absorption
of parathion was found to be from 32 to 477» of an applied dose, much
more than we would have anticipated and more than at other areas of the
body studied with the exception of the armpit and scrotum. When observing
either pesticide applicators or workers in formulating plants it is easy
to conclude that the face-neck area is less protected than most other
parts of the body. Head coverings or caps used in formulating plants are
often made of material that allows easy penetration of pesticide onto the
scalp. The headgear may have no bill or brim which would provide some
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added protection to the face-neck area, especially from pesticide material
which drifts downward.
Protection from downward drift is especially important during application
of liquid sprays. The headgear most commonly used by pesticide appli-
cators is the billed cap which provides some protection for the face but
very little for the remainder of the head-neck area other than the scalp.
The conventional "Sou'wester" rain hat, often used when heavy downward
drift occurs, does not provide exceptionally good protection for the face
and sides of the neck. This is because of the narrow brim in all areas
except at the back of the neck. Metal or fiber "hard hats" are also used
to some extent; however, most have too narrow a brim to provide adequate
protection. "Hard hats" which allow circulation of air over the head
under the hat should not be used where exposure is to toxic dusts.
Our studies have shown that the greatest protection from downward drift
of pesticides is afforded by some type of wide-brimmed hat, preferably
made of water-repellent material. Waterproof hats, other than the
"Sou'wester," were not readily available at that time. However, one is
now available which is waterproof and also has a wide brim that affords
good protection of the face-neck area. This type of hat should be
recommended for use by all applicators who may be subjected to downward
drift of pesticides.
Of particular interest in relation to exposure of the head-neck area is
the finding by Maibach and Feldman-'- that absorption of parathion is
relatively efficient (47% of applied dose) in the ear canal. Exposure in
this area could occur through drift of fine pesticide mists or dusts or
by digging in the ear with the tip of a contaminated finger. Of particu-
lar importance is the potential for drift into the ear of concentrated
dry formulations of toxic compounds in the formulating plant.
It is of importance to note that wearing goggles and respirators pro-
vides considerable protection to the face.
Although a statement suggesting the use of goggles can be found on certain
pesticide labels, they are rarely worn except by pilots who apply pesti-
cides by aircraft. Questioning of pilots has revealed that they wear
goggles not only to prevent poisoning and to keep wind out of the eyes
but also to prevent certain organophosphorus pesticides that are direct
inhibitors of cholinesterase from causing miosis. This is understandable
because it has been shown that unilateral contamination of the eye with
TEPP may cause pilots to inadequately judge distance. The incoordi-
nation which may accompany this could be a serious threat to safety.
The hands are often the body area having the highest exposure to pesti-
cides and they have a greater chance of coming in contact with the more
concentrate formulations. They are also more subject to cuts or
abrasions, which will be discussed later.
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High potential exposure to the hands brings attention to the need for
wearing gloves. Some people who have worked with pesticides feel it
is better not to wear gloves than to wear gloves that are contaminated
on the inside; something which invariably occurs to some degree. Our
research concerning the use of protective gloves indicates that, unless
there is gross contamination of the inside of the gloves, the potential
exposure is less when wearing gloves than when not wearing them. If
gloves are kept clean on the inside there is very little doubt concerning
the value of their use when handling pesticides. Unlined rubber gauntlet
gloves provide the best protection because the gauntlet covers the wrist
area not normally covered by the jacket sleeve and they can be turned
wrong side out for proper cleansing of the unlined inside surface.
Waterproof shoes or boots should be worn when handling or applying pesti-
cides on a large scale. During liquid spray operations the ground cover
of weeds, grasses, or other plants invariably becomes wet with dilute
pesticide regardless of whether or not it is the target of the application.
Shoes quickly become contaminated when walking through such plant growth.
When leather shoes become wet with spray material they have a tendency
to become cracked and dried out to the extent that pesticide easily pene-
trates through to the sock or foot. Both leather and canvas shoes absorb
chemicals and may hold them in contact with the wearer. Boots should be
washed and dried thoroughly, inside and out, as frequently as needed to
remove any pesticide contaminant.
Workers in pesticide formulating plants should wear waterproof boots.
Coverall pant legs should be worn outside the boot tops to prevent sift-
ing of dry concentrated pesticide into the footwear.
RESPIRATORY ROUTE
Protection of the respiratory route is especially important where toxic
dusts and vapors or very small spray droplets are prevalent, or where
application is in confined spaces. Extremely fine particles and droplets
found in dusts and mists are much more easily drawn into the respiratory
system than the larger droplets formed by most conventional dilute spray
machines. Our tests have shown that when operating an 8X (eight times
the normal dilute concentration) concentrate airblast machine in fruit
orchards the potential respiratory exposure is nearly 3 times greater
than when operating the conventional dilute machine.
Respiratory protection for most types of application can be provided by
use of cartridge-type respirators or, in certain cases, gas masks with
special cannisters which have greater adsorbent capacity than the cartridges.
Applicator pilots who risk the possibility of flying through drift of fine
droplets or dusts should use a face mask equipped with a filter cannister
and attached either to their belt or to the inside of the cockpit. When
fumigating or applying highly toxic pesticides in confined spaces it is
advisable to use a respirator with a special compressed air supply tank
so that none of the contaminated ambient air is inhaled.
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Proper care of respirators is very important to the protection of the
workers. The rubber face-piece becomes hardened and the head straps
lose their elasticity with age and exposure to heat and sunlight. These
conditions lead to poor fit and allow leakage around the face-piece.
Two of the more common offenses in the care of respirators that we have
observed are (1) failing to occasionally wash the face-piece with soap
and water and (2) neglecting to change the filter cartridges or cannisters
regularly. Washing of the face-piece of a cartridge-type respirator
should not be attempted while the cartridges are in place as moisture may
contact the activated charcoal filter material and reduce its effective-
ness in adsorption and absorption of pesticides. Solvents should not be
used as a cleaner for they may damage certain parts of the respirator.
The general recommendation is that cartridges should be changed after
8 hours of continuous exposure. In most application situations this
leaves much up to the individual worker to keep a record of his respirator
exposure time. In a formulating plant where hours of exposure are more
regular this is more easily controlled under the guidance of a foreman.
Under conditions of intense exposure the useful life of the cartridge is
much shorter. Thus, if the breathing seems hampered, or if the odor of
pesticide is detected, the filter cartridges should be changed imme-
diately. If the outer filter pads are separate removable units they
should be changed more frequently than the cartridges.
During discussions of the respiratory route of entry into the body the
question is often raised concerning the hazard of smoking pesticide-
contaminated cigarettes. We have found it difficult to measure such
potential exposure with any great degree of accuracy. The technique we
have utilized thus far involves subjecting the cigarettes to normal
handling through the process of removing them from the pack and placing
them in the mouth, lighting them, and smoking one-half the cigarette.
The remainder of the cigarette is then analyzed for pesticide content.
The values obtained are based on the assumption that pesticide on the
cigarette will be volatilized before being broken down by burning and
that none of the volatile or particulate pesticide would be trapped in
the butt end of the cigarette. In observing smoking by workers it was
noted that the area of greatest contamination of the cigarette was far
enough from the butt end to allow burning of the contaminated area in
most cases.
In studies of cigarette contamination by spraymen applying endrin in
orchards, the potential exposure through smoking during application
operations was calculated to be not more than 0.002 mg per cigarette,
even when the cigarettes were handled with hands wet with the dilute
spray.^ In later studies involving spraymen applying parathion to apple
orchards by airblast machines, from 0.003 to 0.005 mg of parathion per
cigarette could be recovered where they were handled with hands that were
contaminated but dry. When handled with hands that were wet enough with
dilute spray to leave moist spots on the cigarette paper from 0.020 to
0.050 mg could be found. In a controlled study designed to determine
what might be the maximum contamination of cigarettes through such
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22
handling, hands were dipped in 45% emulsifiable concentrate parathion,
the hands wiped off lightly on the trousers, and the cigarettes were
handled to simulate smoking. The highest value found was 0.235 mg per
cigarette.
Even though values for potential respiratory exposure through smoking
contaminated cigarettes may not appear to reflect any great hazard, two
important points must be kept in mind: (1) Pesticide entering by the
respiratory route is practically 100% absorbed, and (2) There is no
assurance that a more toxic breakdown product will not be formed and
inhaled as the high temperature of a burning cigarette reaches the con-
taminated areas rather than complete destruction of the compound by
burning. For example, in the case of parathion the oxidation product,
paraoxon, is estimated to be much more toxic than the parent compound,
possibly 100 to 500 times more toxic. This could be an important factor
as far as hazard is concerned and emphasizes the need for recommending
washing of hands and face before smoking.
ORAL ROUTE
There has been little experimental work conducted to define the magni-
tude of oral exposure. We are studying techniques at the present time.
Analysis of saliva samples of exposed individuals appears to give some
indication of contamination.
The most serious oral exposure may be brought about by splashing of
liquid concentrate into the mouth while pouring and measuring pesticides.
Contamination may also occur through licking the lips, by rubbing the
mouth with contaminated arms or hands, by careless actions such as
attempting to blow out clogged spray nozzles with the mouth, or by eating
or drinking with contaminated hands. Workers should wash hands and face
before eating, drinking, or smoking.
ENTRY TRHOUGH CUTS OR ABRASIONS
This route of entry is one that may not have received enough attention
in the past. Cuts and abrasions occur most frequently on the hands, and
unfortunately the hands are the body area most often in contact with the
more concentrate forms of pesticides.
Any break in the skin may allow a more direct route of entry into the
blood stream. Even if the outer layer of daad cells (strateum cornemn)
of the skin is removed by scratching or scuffing the result may be a
potential for increased absorption at that site as this layer of cells
is considered the main barrier against chemicals. Maibach and Feldman^
found tihat when most of these cells were removed by abrading through
repeated application and removal of sticky tape, the absorption of para-
thion applied to the forearm could be increased more than 8-fold. There
have been poisoning cases suspected as having been a result of entry
through cuts or abrasions. However, there has not been enough evidence
to definitely prove that this route played the major part in the illnesses.
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DISCUSSION
Regardless of how specifically the measures for protection of workers
from exposure to toxic pesticides may be stated for any particular
situation, people who work with such compounds must realize that there
is some element of risk involved. Accidents occur, even among workers
who are careful. In case of accidental gross contamination of skin with
a highly toxic compound every effort must be made to cleanse the contami-
nated area as quickly and as thoroughly as possible. The best recommend-
ation at present is the use of plenty of soap and water. If -pesticide
gets in the eyes they should be thoroughly flushed with water for at least
five minutes. If a person should feel ill while working with pesticides
he should stop work at once and get medical attention. If his illness is
diagnosed as being caused by a pesticide he should not return to work
until a physician advises that it is safe to do so.
References
1. Maibach, H., and Feldman, R.: Manuscript in preparation.
2. Upholt, W.M.; Quinby, G.E.; Batchelor, G.S., and Thompson, J.P.:
Visual Effects Accompanying TEPP-Induced Miosis, AMA. Arch Ophthal
5£:128, 1956.
3. Wolfe, H.R.; Armstrong, J.F., and Durham, W.F.: Pesticide Exposure
from Concentrate Spraying, Arch Environ Health J3:340, 1966.
4. Wolfe, H.R.; Durham, W.F., and Armstrong, J.F.: Health Hazards of
the Pesticides Endrin and Dieldrin, Arch Environ Health
-------
24
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SELECTION OF THE PROPER PESTICIDE
Donald A. Eliason, M.P.H., Dr.P.H.
1. Define the problem
Before attempting to choose the proper insecticide for a particular
job, that job must be defined. Although this statement should not
have to be made to anyone engaged in pest control, all too often the
failure of a chemical control measure or unexpected side effects may
be due to failure to clearly define the problem. Chemicals now used
for pest control are more specific in their action than similar com-
pounds only a few years ago. It is therefore essential that the
specific problem be defined. Doing so can greatly simplify the pro-
cess of choosing the proper pesticide.
2. Consider non-chemical control measures
With our ever-increasing problem of pollution, it becomes imperative
that non-chemical control measures be used wherever possible. Culture
methods, water management, biological control agents, and other non-
chemical control methods should be considered before resorting to
chemical control.
3. Chemical control - the label
When considering the chemical for the job, use only those compounds
that are labeled for control of the specific pest in the specific
situation you have defined. In addition to the label, you should also
check your local State restrictions on pesticides. Many states have
now passed laws restricting certain compounds.
Years of research have provided background for the label and its
warnings and restrictions should be heeded.
The label contains much information including: the concentration and
chemical name of the active ingredient and the amount of inert ingredi-
ents; a listing of pests, crops, and methods of application for these
situations; restrictions on the number of days a compound may be sprayed
on a crop before harvest; and warnings of hazard to humans, animals,
plants, and property.
4. Chemical control - choice of the proper pesticide
Once the pest problem has been defined, non-chemical methods have been
considered, and information has been gathered on compounds that are
-------
26
labeled for the use intended, a decision must be made on which compound
to purchase and use. Elimination of compounds not labeled for that use
has reduced the number considerably. Factors that now become important
are:
a. The compound must be effective against the target insects.
b. The compound should present the least possible hazard to
beneficial insects and other non-target organisms including
birds, mammals.
c. The compound should present minimal hazard to humans including
the applicator.
d. The compounds must be available in the required formulation and
economically feasible to use.
In considering the requirements listed above, it is obvious that some
compromises may need to be reached. It should be remembered that every
application of a pesticide is a calculated risk.
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THE MATHEMATICS OF MIXING AND APPLYING
AGRICULTURAL CHEMICALS
John M. Wise
The one problem individuals working with agricultural chemicals al-
ways seem to have in common is the mathematics involved in mixing
and application of chemicals to obtain a desired effect. This does not
have to be such a troublesome task if it is approached in a systematic
manner, with a basic understanding of the materials you are working
with.
In order to achieve such an understanding, one must first have a know-
ledge of the terms most often encountered. Hence a definition of these
terms follows:
1. Oil Concentrate
Oil concentrates are liquid formulations containing, preferably, a
high concentration of active ingredient. They are generally used
after dilution to a practical or convenient low concentration with
an inexpensive hydrocarbon solvent such as fuel oil or diesel oil.
The concentration may be expressed either in terms of pounds of
active ingredient per gallon of concentrate or in terms of percent
by weight of active ingredient.
2. Emulsifiable Concentrate
Emulsifiable concentrates are similar to the oil concentrates with
the exception that they contain an amount of surfactant or emulsi-
fier suitably selected to permit dilution of the concentrate with
water for practical application. The majority of emulsifiable con-
centrates, especially those which are used for agricultural pest
control, contain the active ingredient expressed in terms of pounds
per gallon. Because of convenience to the user, emulsifiable con-
centrates may be considered the most popular form in which pesti-
cide formulations are used.
3. Dust base or concentrates
Dust bases or dust concentrates are dry, free-flowing powders con-
taining a high concentration of active ingredient which will vary
generally from 25 to 75%. Such products are seldom applied in
this concentrated form. They are usually diluted or cut back to a
with a suitable inert for final application
-------
4. Wettable Powders
Wettable powders are similar to dust bases with the important
difference that they are formulated for dilution into a final spray
with water. The speed of wetting of wettable powders when placed
in water is made possible by the proper choice of wetting agents
which will reduce the surface tension between the particles and the
water. Good suspensibility is attained by reducing the particle
size, preferably, to below 325 mesh (44 microns). Surfactant
types called dispersants are generally added to wettable powders
as a part of the regular formulation to prevent the agglomeration
of particles and in turn to slow down the rate of sedimentation which
occurs as a function of particle size.
5. Dusts
As the name implies, dusts are very finely powdered dry pesti-
cides. They are formulated to field strength which may vary from
as low as 1% to as high as 10% active ingredients, depending upon
the potency of pesticide and the rate of application. They must be
free-flowing so that they can be accurately metered in application
equipment. Particle size may vary although it is usually under
200 mesh (74 microns).
6. Granules
Granular pesticides are distinguished from powdered pesticides
according to mesh size range. It is generally accepted that a
granular pesticide is a product which is limited to a. mesh size
range from 4 mesh (U.S. Standard Sieve Series) to 80 mesh. For
any given material (for example, a product labeled 30/60), at least
90% of the finished product must be within this specified mesh
range, and the remaining 10% may be distributed on either side
of the specified mesh sizes.
The concentration of active ingredient in granular pesticides may
vary from as little as 1% to as high as 40% depending upon the
properties of the active ingredient and the characteristics of the
carrier or upon other factors such as the potency of the insecti-
cide and the desired rate of application of the finished product.
7. Pounds per Gallon
Pounds per gallon is a term commonly used to express the amount
of active ingredient in a formulation of either oil concentrate or
emulsifiable concentrate. For example, an 8 pound per gallon
Chlordane solution contains 8 pounds of actual Chlordane in each
gallon of solution.
8. Percent by Weight
Percent by weight is also a term used to express the amount of
active ingredient in a formulation. For example, a. 20% Chlordane
solution contains 20 pounds actual Chlordane for each 100 pounds
of solution, or 20% of the total weight.
The actual calculations involved in preparing a finished spray or dust
concentration are simple and accomplished by following a set of basic
-------
(1) Emulsifiable Concentrates - expressed in pounds per gallon
8.33 x Gx D
Gallons emulsifiable concentrate to use =
100 x C
G = Gallons of dilute spray desired
D = Percentage dilute spray desired
C = Pounds toxicant per gallon in emulsifiable concentrate
Example: Make 96 gallons Chlordane . 5% solution, using
Chlordane 8 pound per gallon Emulsifiable Concentrate
Gallons Chlordane 8 Ib. /gal. E. C. to use = — — = . 5 gal.
100 x
Use . 5 gallons Chlordane 8 Ib. /gal. E. C. with 95. 5 gallons of water.
Note: To convert from gallons to ounces, multiply by 128.
(2) Emulsifiable Concentrates - expressed in percent by weight
„ , , n 8.33 x Gx D
Gallons emulsifiable concentrate to use = 7: ~
C x W
G= Gallons dilute spray desired
D= Percentage dilute spray desired
C = Percentage active ingredient in emulsifiable concentrate
y\/ 0= Weight in pounds of one gallon of the emulsifiable concentrate
Example: Make 5 gallons Diazinon . 5% solution, using Diazinon
25% E. C.
Gallons Diazinon 25% E. C. to use = 8. 33 x 5 x . 5 _ ^ l gallon
25 x 8.3
Convert to ounces by multiplying by 128 » 12.8 oz.
J- oi The above two formulas will work also on oil concentrates, with one
V\ vr\\v>y', .v'^;-' slight change. The 8. 33 is the weight of one gallon of water. When oil
^ ' used, substitute the weight of one gallon of the oil used for dilution
-. ,
'. ,$'V*j'" (approximately 1 pounds per gallon).
(3) Wettable Powders
8. 33 x G x D
Pounds of wettable powder to use = - C-D -
G = Gallons water or gallons finished spray desired
D = Percentage diluted spray desired
C = Percentage concentration of wettable powder
Example: Make 100 gallons of 1% DDT solution using DDT 50% W. P.
Pounds DDT 50% W. P. - 8>3g0X_11°° X 1 = 17 pounds -
f) ' '
-~l
-------
(4) Dust Concentrates
D x G
Pounds of dust concentrate to use = —-r*—
G = Pounds of finished dust desired
D = Percentage of dust required
C = Percentage concentration of dust concentrate
Example: Make 1200 pounds of 5% Malathion Dust using Malathion
25% Dust Concentrate
Pounds Malathion 25% = . ^5 = 240 pounds
Use 240 pounds of Malathion 25% and 960 pounds of Inert Dust Base.
In order to apply agricultural chemicals, the first step is to have equip-
ment you are familiar with and know how to operate. Once you have
surpassed this obstacle, you can begin the mathematics of figuring the
application rate.
Determine first the proper recommended rate of application in either
gallons/acre or pounds/acre. If the rate is in gallons/acre, it will
usually be expressed in a given percentage of active ingredient. Exam-
ple, 200 gallons/acre of a 2% Chlordane solution. This is simply a
matter of calculating the number of gallons required to do the job and
using the formulas already given to mix the proper percentage solution.
The area of application which gives most individuals problems is in
rates expressed in pounds/acre. Here again, it need not be made as
complicated as we sometimes make it, if we approach it systematically.
First, determine the material you are working with. Is it dust, granu-
lar, or liquid? If it is liquid, is the concentration expressed in percent
by weight or pounds per gallon?
Next, determine the amount of material to apply per acre. This is
easily accomplished by following the following formulas:
(1) Dust or Granular
TS A * 1 A X 100
Pounds to apply per acre = =
A = pounds/acre active ingredient recommended for treatment
B = percentage active ingredient in base material
Example: Treat a field with 2 pounds/acre Malathion using
25% Malathion Dust
„ 2 x 100
Pounds to apply per acre = —2~5 = 8 pounds
-------
(2) Liquids expressed in percent by weight
n j . i A x 100
Pounds to apply per acre = ——
B
A = pounds/acre active ingredient recommended for treatment
B = percentage active ingredient in liquid concentrate
Example: Treat a field with 1-1/2 pounds/acre Chlordane using
75% Chlordane Emulsifiable Concentrate
Pounds of 75% Chlordane to apply/acre = "••' -yg = 2 pounds
(3) Liquids expressed in pounds/gallon
Fluid ounces of concentrate = —£~
A - pounds/acre active ingredient recommended for treatment
B = pounds/gallon active ingredient in liquid concentration
Example: Treat a field with 2 pound/acre Malathion using Mala-
thion 5 pounds/gallon E. C.
2x128
Fluid ounces of concentrate required = z = 51. 2 oz.
Use 51. 2 fluid ounces of concentrate to treat each acre.
In both examples (2) and (3) you should mix this amount of concentrate
with enough water to treat the acre of land. The amount of water to use
will vary with the output of your spray equipment.
At this point a brief word of warning is needed. All agricultural chemi-
cals are not chemically compatible when mixed together. Before mix-
ing two or more chemicals, check a reliable compatibility chart, such
as the one that follows, your state or county agricultural extension
service, or the manufacturer of the material. This may save you a
respraying job or, even worse, a complete destruction of the crop
being treated.
One final formula that will help you as much, if not more than any of
the others is:
A + B = X
A = 1 pound of chemical
B = 5 pounds of judgment
X = Fewer problems
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Compatibility of Common Spray Materials
Alphabetical List of Pesticides
Aldrin-9
BHC-10
Bordeaux-21
Calcium Arsenate-2
Carbamate fungicides-22
Chlordane-9
Copper Zinc Chromate-20
Cryolite-4
DDD(TDE)-8
DDT-8 .
Dieldrin-9
Dinitro compounds-1 6
Dormant oils-15
Endrin-9
Ferbam-22
Fixed Coppers-20
Heptachlor-9
Lead Arsenate-1
Lime-19
Lime Sulfur-17
Lindane-10
Maneb-22
Meta-Systox-R- 13
Methoxychlor -8
Methyl Parathion-13
Nicotine-7
Parathion-13
Paris Green-3
Perthane-8
Pyrethrum-6
Rotenone-5
Strobane-11
Summer oils-14
Systox-13
TDE-8
Tetraethyl Pyro-
phosphate-12
Thiram-22
Toxaphene-11
Wettable Limes-18
Zinc Sulfate plus
Lime-19
Zineb-22
Fully compatible
Not compatible
Compatibility questionable
Read this chart as you would a mile-
age chart. For example, if you want
to know if you can mix BHC and
Bordeaux in the spray tank, check the
square where these two lines or
columns meet. In this case, it is
cross-hatched; therefore, you should
not mix BHC and Bordeaux.
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SAFE USE OF PESTICIDES ON THE FARM
John I. Freeman, D.V.M., M.P.H.
Pesticides are designed, manufactured, and sold as a product to destroy
or alter a biological process, namely those things we classify as pests.
However, the selectivity of many pesticides is dependent largely on the
applicator and his ability to limit contact to the target organism.
Parathion, for instance, is just as effective in killing little children
as it is in killing flea beetles on tobacco. This has been demonstrated
quite well in North Carolina as well as numerous other states.
Perhaps highly toxic pesticides can be used safely, and it would then be
advantageous to keep such in our arsenal of tools against pests. However,
I think the amount of illness and death directly attributable to pesticides
is somewhat out of proportion. We have no balance in which to weigh the
benefits of pesticides, such as food production, recreation, disease control,
etc., against the human illness and morbidity. ' Perhaps it would even be
unwise to make such a comparison. The results may be to "cut off our nose
to spite our face;" that is, eliminate pesticides only to suffer greater
ills at some point in the future.
Assuming that pesticides are essential to our modern society, then we have
but one choice; i.e., the use of pesticides in such a way as to give maximum
benefit and minimize hazards to human health and the environment. We may
be approaching the maximum benefit from the use of pesticides, but we are
a long way from minimizing the hazards. Let's look at some statistics we
have accumulated in North Carolina. On July 1, 1970, we initiated a volun-
tary pesticide morbidity reporting system. A specific card was designed
and mailed to every practicing physician in the state. By the end of
December 1970, 132 of these cards had been returned to our office indicating
an exposure either with or without symptoms. Of these 132 cases, 55 were
marked as due to organic phosphorous pesticides. As of the end of June 1971,
a total of 38 cases have been reported; 9 of these were due to organic phos-
phorous compounds. Comparing these figures to our list of reportable
diseases, pesticides are a major cause of illness in North Carolina. Pesti-
cides ranked seventh numerically in a list of forty reportable diseases.
Pesticides as a cause of illness was exceeded by tuberculosis, hepatitis,
measles, salmonellosis, malaria (military), and shigellosis. I will be the
first to admit that reportable disease data is a rather poor indicator of
the true incidence of any disease; however, the above figures have indicated
to us that we have a major problem with pesticides-induced illness in North
Carolina.
-------
We have concentrated most of our efforts toward determining the "how and
why" of pesticides-induced illness at the farm level. North Carolina has
the second largest number of individual farmers and thus we have a large
population at risk; that is, a high percentage of these farmers use one
or more pesticides in their farming operation. In our investigations we
have found essentially every way conceivable to misuse pesticides. While
this paper is titled "Safe Use of Pesticides," perhaps it is worth our
time to explore some aspects of misuse.
It is perhaps unfortunate that the chlorinated hydrocarbon insecticide
preceded the organic phosphorous compounds. Farmers, at least in North
Carolina, developed rather reckless procedures for handling pesticides
during the chlorinated hydrocarbon era. One could dust cotton or tobacco
all day with DDT and by sunset look like a snow man, but you con't follow
the same procedure with parathion. The attitude, "well, I've done it this
way for twenty years," has gotten users of insecticides into trouble during
the transition from predominantly chlorinated hydrocarbon to organic phos-
phorous compounds. These reckless habits are evident not only during the
mixing and application but also in attitudes toward transportation, storage,
use of protective clothing, and disposal. I think it goes without saying
that before we can expect to see pesticides used safely at the farm level,
these kinds of attitudes must be changed. Now, how can this be accomplished?
Education is obvious for those that can be educated. Use and application
laws are perhaps necessary to protect those that cannot be educated to a
reasonable degree for self-protection and safe use. Not only the farmers
or users must be educated, but the dealer or seller must also be schooled
in the broad area of self-protection and safe use of pesticides. The
majority of farmers, at least in North Carolina, acquire their information
about pesticides from the dealer and this is generally at the time the
product is purchased. Thus it would appear that the dealer, with whom
the farmer is frequently acquainted, has the opportune time at which to
stress the importance of and, if necessary, give explicit details about
safety precautions in mixing, application, protective clothing, storage,
and/or disposal.
Use and application laws can have considerable impact on the safe use of
pesticides on the farm. The 1971 General Assembly of North Carolina enacted
a broad Use and Application Law which will be administered by our State
Department of Agriculture and governed by a seven-member policy board. This
legislation gives the board authority to promulgate rules and regulations
in the area of use and application of pesticides as well as formulation,
storage, container design, marketing, transportation, and disposal. Through
such legislation some of the inherent dangers can be removed or eliminated,
such as parathion in glass jugs or paper labels that can easily be washed
off by a rain.
Restricting the use of certain pesticides, generally the more toxic com-
pounds, will affect the safety at the farm level. The legislation pre-
viously mentioned restricts the use of certain pesticides in time and place
as well as the user or applicator. Under the North Carolina Use and Appli-
cation Law, the purchaser of restricted pesticides will sign a statement to
-------
the effect that he is aware of the dangers of the product and assumes the
responsibility of the product. It is quite evident that with a tenant-
landowner arrangement, the tenant is frequently subjected to undue hazards
due to his illiteracy and the unfortunate results are often justified by,
"well, he didn't follow the instructions on the label." The point is that
even the most explicit and detailed label is meaningless to a man who
cannot read or comprehend the message. Under this law, the landowner
will have the responsibility to see that the tenant exercises reasonable
safety precautions for self-protection or be liable for consequences.
Perhaps this is a hard-line approach to changing the attitudes of some
landowners, but it will probably be effective and the results will be a
reduction in morbidity and mortality due to exposure to highly toxic pesti-
cides on the farm.
I would now like to relate some of the specific problems we have encountered
on North Carolina farms. While most of what we have seen could more
correctly be classified as misuse or improper use, we have developed some
ideas that we feel are practical at the farm level for safe use of pesticides,
Concentrates
From the standpoint of human exposure, concentrate pesticides are particu-
larly hazardous. Spills that occur while pouring concentrates from the
original container to the spray tank are extremely common and perhaps the
use of a wide-mouth funnel would prevent a large number of the accidental
spills. Yet, farmers object to using a funnel for a simple and justifiable
reason; i.e., it collects dust and dirt participles which you then wash into
the spray tank and eventually clog up the spray nozzles. This then would
require disassembly of the spray rig with probably skin exposure to the
diluted material. Thus, the simple suggestion of using a funnel may be
totally impractical in a dusty field. Likewise, the use of rubber gloves
and a rubberized suit is somewhat impractical in July or August. There
is not much value in protecting an individual from exposure to organic phos-
phorous compounds to the point of heat prostration or sun stroke. So, while
the use of rubberized clothing will probably do the job, it is often quite
impractical.
If one minimizes the time that concentrate pesticides are on the farm, the
likelihood that an accident will occur is also reduced. I have observed
teenage tobacco primers and parathion on the same pick-up truck many times;
also, livestock feed and pesticides on the same pick-up truck. During the
spray season a farmer's pick-up truck frequently serves as a temporary
storage facility for pesticides. From the standpoint of safety, we strongly
urge that the farmer purchase only that required for the immediate applica-
tion. It is certainly safer to let the dealer store pesticides until the
next application than to haul it around on a pick-up or set it out in the
yard.
Another observation we have made appears to be somewhat reversed. Fre-
quently a farmer and one or more teenage children will be applying pesti-
cides and most often the teenager will be recharging the spray tank while
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36
the adult is operating the equipment. We had five such cases to occur
this year which involved Dysyston and Dasanit. In each case the farmer
had reached the conclusion that it was more hazardous to operate the spray
equipment than it was to handle the concentrates and recharge the spray
tank; thus, the teenager was assigned the less hazardous task. If teen-
agers are to be employed or, in the case of one's own child, and working
during application, they should in fact operate the equipment. While the
risk of minimum exposure is perhaps increased, the likelihood of sudden
acute illness is probably decreased. Children and teenagers are more
susceptible to the effects of organic phosphate compounds than are adults.
Therefore, accidental spills are probably less likely to occur when adults
handle concentrates, adults are more likely to be cognizant of the danger
of a spill, and the risk of acute illness would probably be less for any
given accidental spill.
While handling concentrates on the farm, one should always recommend the
use of protective clothing, pouring funnels, etc. It should also be
stressed that concentrates should be purchased and used immediately, thus
minimizing the time they are actually on the farm. Concentrates should
only be handled by an adult.
Application
During the past two years we have investigated numerous pesticide cases
that were the result of improper application practices. Most of these
cases were the result of prolonged exposure from several days to several
weeks. Both farmer-applicators and commercial applicators have been
involved; however, the epidemiology of these two groups have been almost
identical. Careless practices, the path of least resistance, and urge to
get the job completed sums up our experience with application cases. More
often than not, the operator of a spray rig in eastern North Carolina will
be seen with no shirt or mask. It is more comfortable to ride a tractor
without a shirt or mask - the path of least resistance. Farmers are
notorious for "getting in a hurry" once they finally get started. Many
hours may be spent at the local county store in heated debate of topics
ranging from A to Z. However, when they finally get on a tractor to apply
pesticides, they are suddenly behind schedule and little regard is given
to protective measures, wind direction, and resultant drafts. Repair of
clogged nozzles or leaking lines are frequently done in the field without
gloves or source of water to wash after completing repairs. Commercial
applications frequently schedule their work loads to the maximum acreage
load of their equipment, which gives little time to consider weather
conditions and repairs.
These practices result in excessive exposure during application which
have an accumulative effect to gradually lower one's cholinesterase level
to the point that symptoms of organic phosphorous poisoning occurs. While
it is reasonable to suggest that a farmer select the optimum weather
conditions to apply pesticides, this cannot always be accomplished. How-
ever, exposure can be minimized by wearing tight weave cotton clothing and
-------
a respirator, such as a Wilson, both of which are reasonably comfortable
even in extreme hot weather. It is our recommendation that a farmer or
commercial applicator completely change clothes at noon and that a change
of clothes be carried on the equipment. In the event of an accidental
spill in the field, the clothes should be changed immediately and then
proceed to the nearest place where water is available.
Clothing
I have heard many discussions and viewed numerous films that recommended
a complete rubberized suit including hat, gloves, and boots as the panacea
in protective clothing. I am not trying to belittle the value of this
type of clothing, but I have learned through experience the limitations of
such during hot weather. During the latter part of June of this year, we
assisted in the cleanup following a fire which completely destroyed a large
pesticide warehouse in eastern North Carolina. Since considerable liquid
waste was impounded at the fire site and many tons of granular material was
mixed in the rubble from the warehouse, we began by requiring all persons
working in the area to wear light weight rain gear plus rubber gloves, rubber
boots, and respirators. The temperature was approximately 90 degrees and
the rain gear lasted about four hours. While this may have been the best
way of protecting the workers against dermal exposure, it was totally
impractical. The rain suits were discarded in lieu of long sleeved shirts
plus the rubber gloves, boots, and a Wilson-Agratox respirator. The clean-
up was completed in six days without anyone developing illness and
apparently with minimal exposures. Twenty-four bloods were collected for
cholinesterase levels and they ranged from 10 to 17 m/min/ml.
Consideration must be given to protective clothing and each recommendation
must be applicable and practical to the given situation. The purpose is
either to eliminate or minimize dermal exposure; therefore, the more
comfortable the operator can be and still accomplish this objective, the
more likely he will be to follow a recommendation.
Availability of Water
It is reasonable to assume that accidents will continue to occur on the
farm that will result in dermal exposures. The results of such exposures
can range from death to only an irritation or rash of the exposed skin
area. While it is more important to give prompt attention to those
accidents that involve highly toxic compounds, the procedure that one
should follow regardless of the type of compound is the same. The clothing
should be immediately removed and one should proceed without delay to the
nearest source of water and thoroughly wash the area. Now, it is extremely
difficult to get farmers to understand that "immediately" does not mean
when they finish a particular field, or waiting till noon time. There are
several factors that affect dermal absorption, one of which is time, and
this is the only factor over which one has some control once an accidental
spill has occurred and the skin has been contaminated.
While water is generally not available in the field, at least in quantities
beyond that for drinking purposes, it is usually near by, at least in
North Carolina. In an emergency situation a farm pond, stock tank, creek,
-------
river, or neighbor's house may be reached in several minutes, thus reducing
the time variable and dermal absorption.
Storage
The simple answer to the storage problem is a lock and key. Yet, probably
no more than 10% of the farmers in eastern North Carolina store their
pesticides under lock and key. A survey of 245 farmers in one county
revealed that 10.9% of the farmers actually had pesticides stored in a
locked building. This is incredible when this is compared to the number
of locked gasoline storage tanks on the same farms. On every farm that
had a gasoline storage tank, it was locked.
Most of our experience with improper storage has involved children and
contamination of rural wells. We have investigated numerous cases of
illness and several deaths that were the results of leaving toxic pesti-
cides, generally parathion, in areas accessible to children. Children
drink a liquid and play in the dust and granules. It is quite amusing
to a 5-year-old to get a white powder all over him and then play "monster."
We have observed contamination of rural wells due to pesticides being
left in close proximity to the well. In most cases, the tractor and spray
tank was pulled alongside the well to be filled. The pesticide was added
to the tank and the container set down beside the well. Subsequently, the
containers were either broken or a child poured it out and contamination
of the well resulted.
If pesticides are to be stored on the farm, then the use of a locked
building is an effective and practical way of eliminating their accessi-
bility to children. This is a method of protection that farmers are
accustomed to and have accepted as effective. The real question is how
do you motivate farmers to exercise the same degree of protection for
their children and their neighbor's children as they do for a gallon of
gasoline? Storage under lock and key is the first step, but consideration
must also be given to other commodities within the building, which should
not include animal feed or edible products.
Disposal
Disposal of pesticides and/or containers at the farm level is indeed a
difficult question. Yet, disposal must be considered as part of the farm
safety pesticides program and it must be considered in light of the imme-
diate hazard as well as the long range effect. Much has been said about
incineration and compositing of pesticides, neither of which is practical
or available to the average farmer. So this leaves the farmer with three
methods of disposing of pesticides and their containers, i.e. landfill,
burial on premises, and the traditional method of open dump. The open
dump method, perhaps more descriptive would be "at site of last use", is
by far the most common method of disposal in North Carolina. The survey
mentioned earlier indicated that greater than 80% of the farmers who had
previously disposed of pesticides or their containers did so by either
leaving them in or near the field or discarded with the domestic and farm
refuse onto an open dump, generally on the immediate farm.
-------
The landfill method is perhaps the most feasible method available at the
present time. Yet without county-wide collection systems, even this is
somewhat impractical. Pesticide waste should not be mixed with general
refuse nor would it be desirable to have farmers deposit this material at
the landfill site on a routine basis. The trend in solid waste management
in general is toward area-wide collection systems and landfill ing. Once
area-wide solid waste management practices are established, it would seem
reasonable to integrate the disposal of pesticides and perhaps other
hazardous material into the system.
At the present time, the only reasonable avenue of disposal of pesticides
and their containers that is available to the farmer is to bury them on
the farm. While this may not be the most desirable method, it is the most
practical at this point in time. As long as little children continue to
experience illness and death, I cannot accept the approach of hold the
pesticides and containers until a method better than burying is developed.
We have arrived at the following recommendations from our experience in
the field.
1. Farmers should purchase only the amount of pesticides required for
each application.
2. Excess pesticides should be applied as per recommendations or returned
to the dealer.
3. Pesticide containers should be rendered unusable and buried at least
eighteen inches deep in a remote area away from sources of water.
These procedures are applicable only when incorporated into an over-all
safety program and adhered to throughout the usage season. Should one decide
on a general cleanup for the purpose of discarding all unused pesticides and
containers, we have suggested that a strong lye compound be added to the
liquids to raise the pH to the point that alkaline hydrolysis occurs and
the toxicity of the organic phosphate compounds are reduced. The containers
and liquids are then buried in a remote area away from a source of water
and preferably in an area under!ayed with clay.
We recently landfilled both the solid and liquid waste from the fire that
I mentioned earlier. This material is in two separate half acre cells.
This area will be monitored for several years to determine the movement
of pesticides from the landfill site.
There are twenty-seven pesticide formulation plants in North Carolina all
of which have no means of disposing their solid waste. Our current plans
are to work with these plants in getting this waste material into approved
landfills. This perhaps is not the ultimate answer to pesticide disposal
but appears to be the only practical approach for the,present and the
immediate future.
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Pesticides and institutional Environments
Frank S. Lfsella,* Ph.D./Eldon P. Savage.t Ph.D./and Harold G. Scott.* Ph.D.
Nursing and convalescent homes, hos-
pitals, child-care facilities, mental hos-
pitals, and other institutions have unique
challenges as far as environmental con-
trol is concerned. The problems involved
in maintaining a wholesome institutional
environment are magnified by the in-
creased number of persons served and the
services provided by these institutions as
well as by the increased number of such
institutions.
Pesticides are used to alleviate some
health problems in institutions, and the
use of these chemicals has helped to con-
trol many vector borne diseases. They are
a necessary part of institutional sanita-
tion programs. It is, therefore, extremely
important that sanitarians and other en-
vironmental health workers have the lat-
est information on both health hazards
and efficiency of various compounds
available for pest control.
In addition to the use of pesticides,
measures should be taken to prevent the
introduction of vermin into institutions.
[•or example, many of the occupants of
mental institutions are not capable of
keeping their living areas sanitary. These
areas can be the foci of insect and rodent
problems. Storing foodstuffs (particu-
larly home-cooked foods brought in) in
bedside stands may contribute to cock-
roach problems. Nursing home patients
'Department of Preventive Medicine and
Environmental Health, College of Medi-
cine, Univeriity of Iowa, Iowa City,
Iowa.
tAiiittant Profenor, Inttitute of Rural
Environmental Health, Colorado State
Univeriity, Fort Collini, Colorado.
(Deputy Attistant Administrator, En-
vironmental Health Service, Public
Health Service, U. S. Department of
Health, Education, and Welfare, Rock-
ville, Maryland.
may bring clothing, furniture, and books
into the institution from their homes
and bring roaches and silverfish in with
them. Routine inspections could help
prevent these incidents.
Pesticides are applied either by com-
mercial pest control firms or by house-
keeping or maintenance personnel in the
institution. Whoever is responsible, the
instituional environment may pose spe-
cial problems with respect to pesticide
use, and adequate precautionary meas-
ures must betaken.
Human Exposure
Before chemical treatment of an in-
festation, the problem of human expo-
sure to the pesticide becomes a major
concern. Pesticides enter the human body
through oral ingestion and respiratory
and dermal exposure.1 The size of the
dose and the duration of exposure are
important in determining what adverse
effects any pesticide may have on human
health.2 The institutionalized patient, re-
gardless of the reason for his confine-
ment, cannot afford the extra burden of
an illness caused by the improper or
careless use of any pesticide. The asso-
ciation between pesticides and human ill-
ness has been reported by several individ-
uals in other publications.3' «• '•6 Thus,
the decision to use any pesticide must
be based on the potential hazard of the
chemical to patients and applicators,
health status of the exposed patients,
persistence of the pesticide, alternative
methods of control, knowledge of the life
cycle of the insect or rodent species, and
a series of interrelated ecological factors.
These safety precautions should be
observed. All persons who use pesticides
should know the precautions shown on
the label for each compound, and the in-
formation should be followed carefully.
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42
Ideally, pest control operators or main-
tenance personnel should carry, on their
person, records indicating blood type,
history of transfusion reaction, signifi-
cant history of disease such as diabetes,
epilepsy or asthma and other allergies
including history of drug sensitivities,
and the name of any drug taken regu-
larly.' I ft his is not practical, the desired
information should be contained in the
individual's employee health record.
Cholinesterase values should be checked
periodically on those individuals who ap-
piv organic phosphorous chemicals.
Wilhin the administrative framework of
the institution, certain individuals should
be responsible tor advising all members
of the prolessional staff on what types
of pesticide compounds are being used,
and the appropriate antidotes should be
stocked in case of emergency.
Mixing the Chemical
When directed by the container label,
persons mixing wettable powders (or
applying toxic dusts) should wear pro-
tective clothing, gloves, goggles, and an
approved respirator. Gauntlet-type
gloves made of natural rubber or other
approved materials are preferred. The
pesticide material should be mixed ac-
cording to the directions contained on
the label. In no case should beverage bot-
tles, fruit jars, or other empty food con-
tainers be used to measure or store pesti-
cides. Each year, tragic preventable
poisonings occur when children obtain
food containers filled with insecticides or
other "empty" insecticide containers."
Personal Hygiene
After using pesticides, and before eat-
ing or smoking, people must wash their
hands. The clothing worn during appli-
cation of pesticides should be removed
and washed after the job is completed
and the person should bathe thoroughly.
In the event that a pesticide is spilled
on the skin, the affected area should be
washed with fresh water and medical
attention sought immediately. Contam-
inated clothing should be washed sep-
arately before reuse.
Insecticides
There are specific safety precautions
for using insecticides and rodenticides in
institutions. Insecticides can be classi-
fied on the basis of their chemical struc-
ture. For example, there are the chlorin-
ated hydrocarbon compounds such as
DDT, chlordane, endrin, aldrin. diel-
drin, heptachlor, and many others. The
organic phosphorous group includes
parathion, malathion, dia/inon', feri-
thion, ronnel, DDVP, dipterex", and
others. Rotenone and pyrethrum are
classified as botanical since these chem-
icals are of plant origin. The carbamate
insecticides include carbaryl and ba>-
gon". Specific recommendations for the
use of these compounds are outlined
elsewhere.1' The symptoms and treatment
for poisoning by these compounds also
differ for each class."1
Efforts for the elimination of insects
must be accompanied by environmental
improvement programs in food prepara-
tion, storage, and other sections of the
institution. Adequate housekeeping pro-
cedures should be implemented in the
main food service facilities, ward kitch-
ens, special diet kitchens, infant formula
preparation rooms, cafeterias, boiler
rooms, dumbwaiter shafts, laundry
chutes, vending machine areas, labora-
tories, and other likely places of infes-
tation. Extreme caution must be ob-
served when applying insecticides so that
food and food products do not become
contaminated with the spray material.
Careful attention should be paid to
label instructions on the insecticide con-
tainer to determine whether or not the
chemical is safe for use in rooms, wards,
or cells where persons ma> be confined
for extended periods of time The appli-
cator should avoid spraying bedpans,
emesis basins, carafes, and other items
which may be brought in direct contact
with the patients or attendants. When
applying pesticides for bedbug control,
the mattress must not be soaked with
spray. Treatment of infant bedding, in-
cluding the crib, should be avoided.9
Rooms in which oxygen is being ad-
ministered, or where isolation procedures
are in effect, should not be sprayed. In-
tensive-care units should not be treated
while occupied. In the event that it is
necessary to treat the grounds of the in-
-------
stitution with a chemical agent, humans
and animals should be kept off the
treated area until it has been well watered
and completely dried.
During recent years, metered intermit-
tent aerosol insecticide devices have be-
come available. Of widespread use are
those devices which utilize the chemical
pyrethrum in combination with piperonyl
butoxide as a syrergistic agent. In addi-
tion to the precautions listed on the label,
these devices should not be used in nurs-
eries or rooms where infants, ill or aged
persons are confined.
Insecticide-impregnated polyethylene
strips containing DDVP (dichlorovos)
are being marketed for insect control.
These strips should be used in accord-
ance with the instructions on the label,
and as an added precaution, they should
not be used in rooms where infants, ill
or aged patients are housed. Vaporizing
devices employing the chemical lindane
should never be used in the institutional
environment because of the highly toxic
nature of this material.
Rodenticides
Rats and mice are a major concern in
the institutional environment. The pres-
ence of vermin of this type can lead to
health and psychological problems
among the patients. Rats and mice are
usually associated with poor garbage and
refuse storage facilities and other insani-
tary conditions in the institution.
The use of rodenticides may frequently
be necessary as an adjunct to environ-
mental improvement programs. Rodenti-
cides may be classified on the basis of
their mode of action in the target animal.
The degree of safety associated with the
various compounds differs. All rodenti-
cides that are to be used within occupied
buildings or on the grounds of an insti-
tution must be placed where they will
be inaccessible to patients. Paraffin-
coated baits might be attractive to chil-
dren; therefore, their use must be care-
fully supervised.
Because of their high toxicity to man
and animals, chemicals such as sodium
monofluoracetate (1080) or fluoraceta-
mide should not be used in any structure
housing persons.' These chemicals should
be applied only by licensed pest control
operators to outbuildings or other struc-
tures which can be made secure against
entry by unauthorized persons. Norbor-
mide is a recently developed rodenticide
which has a low order of toxicity to man
and other mammals except the Norway
and brown rat. It can be used safely in
the presence of pets, livestock, and poul-
try.'
The low order of toxicity of the anti-
coagulant rodenticides to man make
these chemicals suitable for use in the
institutional environment. It appears un-
likely that poisoning with these pesticides
will occur except with suicidal intent or
as the result of gross carelessness and ig-
norance.9
The rodenticide, red squill, is also
reasonably safe. This material is a na-
tural emetic for man and animals and is
suitable for use against the Norway rats
where there is risk of human exposure.
Precautions must be taken when using
hydrogen cyanide for rodent burrow gas-
sing. This gas is active in a moist environ-
ment; thus, if applied when the burrows
are dry, fumes may be liberated for an
extended period of time. Frequently, ro-
dent burrows end at buildings on the in-
stitutional complex; therefore, caution
must be taken so that the gas is not used
in an area where there is any possibility
that it might escape into a housing unit.
Fumigants
When fumigants such as methyl bro-
mide are to be used, special precaution-
ary measures must be taken. This chem-
ical should be applied only by licensed
pest control operators with special train-
ing in fumigation techniques. Guards
should be posted at all entryways to the
building being fumigated before, during,
and after the fumigation process. Ap-
proved gas masks and other safety equip-
ment should be required.
Storage of Pesticides
As a means of preventing accidents, all
pesticides should be properly stored.
Areas in which food is prepared or stored
— main kitchen, ward kitchen, special
diet kitchens, utility closets, and similar
locations—are not suitable for storing
pesticides.
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44
All pesticides should be stored in a
locked cabinet or locked storage area re-
served for that purpose in the plant main-
tenance department or similar location
away from the main institutional com-
plex. The area should be inaccessible to
animals and unauthorized personnel,
and keys should be available only to au-
thorized persons. The storage area or
cabinet should be dry and well ventilated,
and maintained at room temperature. All
pesticide containers should be adequately
labeled and tightly closed." Under no
circumstances should pesticides be placed
in empty food or drink containers of
any kind. An important facet of proper
storage is the examination of pesticide
containers for leaks or damage.12 If this
occurs, the material should be transferred
to a leakproof container which is clearly
labeled and dated with the same date as
the original container. The old container
should be decontaminated, made unus-
able, and disposed of in an approved
manner.
Professional pest control operators
servicing the institution should be re-
quired to keep everything locked in the
service truck so that supplies cannot be
removed by anyone other than author-
ized servicemen.13
Disposal of Pesticide Containers
The disposal of large numbers of pes-
ticide containers from institutions may
pose a problem since used containers
might have to be stored prior to collec-
tion and transfer to the disposal site. If
this is necessary, the empty containers
should be stored in a locked, protected
area, especially if the labels have been
lost and the empty pesticide containers
are used for another purpose.14
The recommended disposal methods
for most types of solid wastes originating
from institutions include burial (sanitary
landfill) and incineration. The recom-
mended procedure lor sanitary landfill
operation includes strict engineering
practices in site selection, planning, de-
sign, and operation. Precautions must be
taken so that underground and surface
waters are not contaminated. The sani-
tary landfill operation should include
provision for daily covering of the com-
pacted refuse with six inches of com-
pacted earth. The finished landfill should
be covered with two feet of compacted
earth.12
Many pesticide containers can be dis-
posed of by incineration. This involves
burning the material in a properly de-
signed incinerator with a stack tempera-
ture of 1200 - 1800 degrees F. Many in-
stitutional incinerators are not capable
of attaining these temperatures: thus, the
local health authorities or manufacturers'
representatives of the incinerators should
be consulted. The incinerator design
should also provide for the disposal of
gases emitted from combustible materi-
als and the disposal of residual ash. In
all situations involving disposal of pesti-
cide containers, state or local health de-
partment authorities should be consulted.
Training
The cohesive nature of most institu-
tions creates an ideal situation for con-
ducting pesticide safety training pro-
grams. These programs should be di-
rected to all staff levels and should re-
volve around the safe use, storage, dis-
posal of pesticide containers, and poten-
tial hazards to patients and inmates.
References
I. Durham, William } and Wolfe. Homer R.
l%2 Measurement ul the exposure of work-
ers to pesticides Bulletin ol the World Health
Organization 26'7.v4|.
2. Savage, Lldon P. and Simmons, S W. W6X
The price for pesticide sat'ets Constant Vigil-
ance. Pest Control 36 {I) H. 'J. I I.
3 Brown, .1 R. 1967 Organo-thlunne pesticide
residues in human depot fat ( anadian Medi-
cal Association Journal. 97.372
4 West, Irma 1967 Human safely in the use of
agricultural chemicals Archives ol Environ-
mental Health IS 97-101
5 l.pstem. Samuel S 1967. The -.vncmstic tov
icily and carcinoecniciu of Ireons and pipcr-
onyl huloxide Nature 214.526
6 ( ooper. (lark W and Tabershaw, Irving R.
IV67 An apprais.il ol the potential effects on
health ol automatic pvrclhrin dispensers l^ni-
vcrsity of C'alilorma. Bcrkele\. Calilorniu (un-
published report)
7 I avvs. f-dward R 1966 What to do after a pes-
ticides accident Pesl Control 14(1) K-IO
X Wolfe. Homer R 1967 Sale use of pesticides
m forest areas Proceedings ol the I ourth In-
sect and Disease Work Conference, USIM,
horest Service, Atlanta, Cia
-------
45
9. Aedes aegypti Eradication Program. Public
health pesticides. 1968 National Communica-
able Disease Center Report. Pest Control. 36
(3): 9, II, 16.
10. Hayes, Wayland J., Jr. Clinical handbook on
economic poisons. Public Health Service pub-
lication No. 476. U. S. Government Printing
Office, Washington, D. C 1963
II. Pearson, J. Lincoln. 1966. Storage of pesti-
cides. Pesticides Information Manual. North-
eastern Regional Pesticide Coordinators. Rut-
gers University, New Brunswick, New Jersey.
12. Savage, Eldon P. and Simmons, S. W. 1968.
Pesticide Safety—all users are responsible.
Pest Control. 36 (2). 18, 20, 22, 24.
13. Oser, Maurice. 1967 Compartmcntali/ed
trucks boost our safety and efficiency. Pest
Control 35 (I): 11
14. Wolle, Homer R : Durham, W. K ; Walker,
K. C ; and Armstrong, J. I- 1961 Health ha/-
ards ol discarded pesticide containers Archives
ol hnvironmcnlal Health 3 531-537.
Reprinted from the Journal ol Environmental Health, Volume 33, No. 5, March/April, 1971
PuBUsm-n HY Tun NATIONAL ENVIRONMENTAL HEALTH ASSN.
1600 PENNSYLVANIA ST., DENVER, COLO. 80203
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SAFE USE OF PESTICIDES IN VECTOR CONTROL
Harry D. Pratt , Ph.D.
Effective, safe vector control is best accomplished by trained personnel who
1. Know the biology of the vector,
2. Understand the control equipment, its capacity and limitations,
3. Use only approved pesticides, and
4. Read the label and follow directions.
The four major groups of vectors are the rodents, mosquitoes, flies, and
fleas. Each group has such different habits, biology, and control techniques
that they will be considered separately.
RODENTS
Rodents cause an estimated $100 million to $1 billion economic loss each
year in the United States. They are of great public health importance be-
cause of rat bites, rat bite fever, salmonellosis, leptospirosis, murine
typhus, plague, and other diseases (1).
Rodent control procedures involve
1. Good sanitation (primarily good practices in the storage, collection,
and disposal of garbage and refuse, good storage of foodstuffs, and
harborage removal),
2. Rodent stoppage, and
3. Rat killing, including trapping and proper use of rodenticides.
The four rodenticides most commonly used to control commensal rats and mice
are the anticoagulants, red squill, zinc phosphide, and calcium cyanide.
The anticoagulants, such as warfarin, fumarin, pindone (Pival), diphacinone,
and chlorophacinone (Rozol) kill by decreasing the ability of the blood to
clot or coagulate (hence their common name "anti-coagulants") so that the
rodents literally bleed to death. With warfarin, fumarin, and pindone (Pival),
the rodents must eat the anticoagulant baits for four or five days or longer
before maximum kill begins. Therefore, the anticoagulants are called
"multiple dose poisons". Usually it is recommended that the baits be exposed
for two weeks or longer. On the other hand some people feel that rodents may
be killed three to five days after one feeding on diphacinone or chlorophacinone
anticoagulant baits. More research is being conducted at the present time on
this important aspect of commensal rodent control.
-------
The anticoagulants are used either as liquid or solid baits. The liquid
baits are usually prepared by adding a package of the powdered anticoagulant
to a quart of water for dispensing with chicken water fountains or similar
devices. The solid baits are used at the following strengths (2) as shown
on the table below.
Table 1. Multiple-dose rodenticides employed against mice,
roof rats and Norway rats.
_. , . . , Percent Concentration
Rodenticide
Mice Roof Rat Norway Rat
diphacinone
warfarin
Fumarin
pindone(Pival)
0.012-0.025
0.025-0.05
0.025-0.05
0.025-0.05
0.005-0.01
0.025
0.025
0.025
0.005-0.01
0.005-0.025
0.025
0.025
Dilution factors:
0.057» (500 ppm) = 1 part of 0.5% concentrate to 9 parts of bait.
0.025% (250 ppm) = 1 part of 0.5% concentrate to 19 parts of bait.
0.01% (100 ppm) = 1 part of 0.5% concentrate to 49 parts of bait.
0.005% ( 50 ppm) = 1 part of 0.5% concentrate to 99 parts of bait.
Many of the anticoagulants are available as 0.5% concentrates which can be
prepared as final baits by mixing 1 part of the 0.5% concentrate with 19
parts of yellow cornmeal or a mixture of yellow cornmeal and oatmeal, scratch
feed, or grain to give the final percentage of 0.0257= used to control Norway
rats. The addition of one part of sugar and/or vegetable oil may make these
baits more attractive to roof rats and house mice which are nibblers and have
more finicky appetites. Some authorities prefer to use 1 part of the concen-
trate to 9 parts of bait for controlling mice.
The anticoagulants should be placed in protected places in cardboard, foil,
metal, plastic, or crockery containers; in bait boxes, some of which can be
padlocked; or in paper or plastic bags, often stuffed down rodent burrows or
hiding places. Sometimes these plastic bags are manufactured with an attrac-
tive synthetic odor smelling somewhat like vanilla, maple syrup, roast beef,
apple, or citrus. Studies are currently being conducted to determine if
these synthetic odors increase attraction and bait acceptance. Sewer rats
may be controlled by the use of paraffin bait blocks containing these same
mixtures of the anticoagulant baits in paraffin. This type of preparation
prevents mould formation in the warm, damp sewer environment, and also the
washing away of bait in loose grain form when sewers are periodically flooded
following rainstorms. The paraffin bait blocks are usually fastened with wire
to a masonry nail driven into the sewer wall.
Great care should be taken to keep these anticoagulant rodenticides away from
people, particularly children, and pets. No harm is done by a single massive
feeding. Even if a child should eat the unappetizing dry bait mixture for
four or five days, he can be saved by the prompt administration of whole
blood or vitamin K.
Jled squill is a single-dose vegetable poison made from the powdered bulb of
an onion-like plant, Urginea maritima. It has a bitter taste and natural
emetic action, factors that contribute to its safe use as a rodenticide.
Rodents, unlike humans and most domestic animals, are unable to vomit and
are therefore not protected by the emetic quality of the red squill, which
kills them by paralyzing the heart. This poison is not well accepted by
roof rats and house mice, but it can be used effectively against Norway rats
if exposed in a very attractive fresh bait at the beginning of a killing
-------
The usual methods of application are (1) pieces of bread smeared with the
liquid red squill, or (2) "torpedoes" or "kisses" made with one part of
fortified red squill (with an IJD,n of 500 rag/kg.) and nine parts of fresh,
attractive bait materials such as ground meat, fish, or grains, or a combina-
tion of these materials.
The red squill baits are usually placed in rat burrows, in protected places
away from children and pets, or scattered over an open dump prior to its
conversion to a sanitary landfill.
Zinc phosphide is a single-dose rodenticide which is used at 17o strength,
such as 4 oz. of zinc phosphide and 25 Ibs. of fresh cubed sweet potato or
apple. The baitrs are placed in rodent burrows, or protected places away
from people and pets. In general, people and pets are repelled by the garlic-
like odor of the zinc phosphide but Norway rats accept these baits very well.
Calcium cyanide fumigation is used to supplement other methods of rat killing,
particularly to kill rats in burrows in banks, under slabs, along railroad
tracks, and similar situations well away from buildings. The calcium cyanide
dust is blown into the burrows with a foot pump, where the chemical reacts
with the moisture in the air or ground to liberate hydrogen cyanide gas which
kills both rodents and rodent fleas. This work should be done only by trained
personnel wearing masks, always working upwind to prevent the possibility of
accidental poisoning with the cyanide dust.
Many other rodenticides such as strychnine, thallium sulphate, arsenic tri-
oxide, 1080, 1081, and Gophacide have been used in the past, but their use is
restricted or prohibited today (1, 2, 3.). One promising new rodenticide,
norbormide, holds promise as the ideal type of rodenticide since it is lethal
to Norway rats, but not to most other mammals including man. Field trials
have indicated good kill but erratic acceptance. With new bait materials,
or attractants, norbormide may have an important role as a single-dose, safe
rodenticide for Norway rats.
MOSQUITOES
Mosquitoes cost the American public $75-$100 million in organized mosquito
control programs and much more for repellents, aerosol bombs, and screening
by the individual householder to prevent the discomfort, reactions, secondary
infections and diseases resulting from mosquito bites. Some of the diseases
transmitted by mosquitoes are malaria, yellow fever, dengue, filariasis and
the arbovirus encephalitides (4, 5).
Mosquito repellents for personal protection are widely used, including such
materials as deet (diethyl toluamide), dimethyl phthalate, Rutgers 612,
Indalone, and similar materials. Follow the directions in using these chemi-
cals, either as liquid or aerosol preparations, paying particular attention
to keeping them away from the eyes, nose, mouth and other mucous membranes,
and synthetics such as watch crystals.
Mosquito larval control includes draining and filling, proper water management,
and the use of approved larvicides. Some of the larvicides most widely used
include -
1. Fuel oil, preferably with a spreading agent such as T-Det,
Triton X-100 or Hercules B-1956 to reduce the application rate
to 2 to 5 instead of the usual 15 to 20 gallons per acre.
2. Flit MLO at 1 to 5 gallons per acre, depending on vegetation
and the type and temperature of the water.
3. Paris green granules at 15 Ibs. of 5% granules per acre.
Note: in some states the use of this copper-aceto-arsenite
is prohibited because it is considered an inorganic
arsenical, while in others its use is permitted as an
organic arsenical, depending on whether one interprets
-------
4. Organic phosphorus compounds such as -
Abate at 0.05-0.1 Ib. per acre; Dursban at 0.0125-0.05 Ib. per acre
fenthion (Baytex) at 0.02-0.1 Ib. per acre
malathion at 0.2-0.6 Ib. per acre
methyl parathion at 0.1 Ib. per acre
parathion at 0.1 Ib. per acre.
5. Methoxychlor at 0.05-0.2 Ib. per acre.
6. Pyrethrum at 0.006-0.007 Ib. per acre.
Care should be taken in the application of these materials to prevent damage
to vegetation or other non-target organisms. To obtain the dosage listed
above, follow label direction carefully. For example, to obtain 0.2-0.5 Ib.
of malathion per acre, apply 4 to 10 quarts of 2.5% malathion spray per acre;
to obtain 0.1 Ib. fenthion per acre, apply 2 Ibs. of 5% granules per acre, or
4 quarts of 1.257., 2 quarts of 2.5% or 1 quart of 5% spray per acre; to obtain
parathion at 0.1 Ib. per acre, apply one gallon of spray containing 0.1 Ib.
parathion per gallon per acre.
Adult mosquito control inside homes is usually achieved through proper
screening and the use of aerosol sprays containing pyrethrum or allethrin
because these insecticides give quick knock-down of the insects, a synergist
such as piperonyl butoxide, and a low-toxicity insecticide such as methoxy-
chlor to produce the final kill.
Space spraying is the chief method of achieving adult mosquito control in
many communities, through fogging, misting, or most recently, the ultra-low-
volume application with airplane or ground equipment. Only two insecticides
are currently approved for the ULV aerial method of application:
malathion at 1 to 3 fluid ounces per acre, and
naled (Dibrom) at 0.5 to 1 fluid ounce per acre
Specifications for airplane equipment for the ULV method have been published
by Kilpatrick (6) involving special tanks, electrically-driven pumps, spray
booms, and 8001 to 8008 Tee-Jet nozzles.
In general ULV applications should be made -
1. When temperatures are below 80 , or before any temperature
inversions occur (usually early morning);
2. With droplets averaging 25 to 60 microns MM) (Median Mass
Diameter) and at least 10 droplets per inch; and
3. By multi-engine aircraft flying at a height of 100-150 feet, at
speeds of about 150 miles per hour, with swath widths of 300-500
feet, or with single-engine aircraft flying at 100-110 mph with
pump pressures and nozzle sizes adjusted to provide the 25-60 MMD
micron particle size.
Great care should be taken not to fly airplanes over areas with new General
Motors type cars with acrylic finishes. Helicopters should not be used over
cities because of damage which may result from large particle size, above 100
microns, insecticide droplets, particularly to new automobile finishes.
-------
Other insecticides used in controlling adult mosquitoes are listed in the
1971 Public Health Pesticides as follows (2):
Table 2. Insecticides Employed as Outdoor Ground-Applied
Space Sprays
Lb./acre Dosage based on estimated swath width of 300 ft. Apply
, - 0.2-1.0 as mist or fog during the dusk to dawn period. Mists are
^ usually dispersed at rates of 7 to 25 gal. per mile at a
vehicle speed of 6 mph. Fogs are applied at a rate of
fenthion 0.01-0.1 40 gal./hr. dispersed from a vehicle moving at this speed;
occasionally at much higher rates and greater speeds.
i ,-u- n me /-, o Finished formulations contain from 0.5 to 8 oz./gal.
malathion 0.075-0.2 ,, . , , ., . *. --,
actual insecticide in oil, or, in the case of the non-
thermal fog generator, in a water emulsion. Dusts also
Id 0 02-0 1 can ^e U8e°l. For ground ULV application, technical
grade malathion is dispersed at a rate of 1 to 1.5 fl.
oz./min. and a vehicle speed of 5 mph or at a rate of 2
to 3 fl. oz./min. and 10 mph.
FLIES
Effective fly control can be achieved only by maintaining a high level of
environmental sanitation to reduce or eliminate fly breeding sources. These
measures can be supplemented by insecticidal treatments, including residual
sprays, impregnated fly cords, resin strips, fly baits, and space spraying.
Larviciding, which is of such great importance in mosquito control, has been
much less successful in fly-control programs (7).
Residual treatments. The chlorinated hydrocarbon insecticides, which were
used with great success in the late 1940's, have been replaced by the organo-
phosphorus compounds. Flies developed resistance to the chlorinated hydro-
carbon insecticides such as DDT, BHC, chlordane, and dieldrin. In addition,
when the chlorinated hydrocarbons were used, residues of these long-lasting
insecticides often appeared in milk or meat.
At present seven organic phosphorus compounds are labeled for residual appli-
cation as discussed in the 1971 Public Health Pesticides (2), and shown in
Table 3 reproduced from this publication.
Impregnated fly cords. Commercially manufactured fly cords impregnated with
parathion, diazinon, or ronnel have been labeled for use in dairy barns,
chicken ranches, and food-handling and -processing establishments. The cords
are installed at a rate of 30 linear ft. of cord per 100 ft. of floor space.
This method has given effective fly control in dairies, chicken houses, and
"pig parlors" for periods ranging from 6 weeks to an entire season. The use
of fly cords has not been approved in all 50 states. Resistance to the chem-
icals in fly cords has developed in some areas.
Fly baits. Quick control of flies for a few days can be achieved by using dry
fly baits containing Bomyl, diazinon, dichlorvos, malathion, naled, ronnel,
or trichlorfon, and an attractant such as sugar. Dry fly baits can be used in
dairy barns or outdoors near food-preparation areas. The baits are placed in
trays, jar covers, or permanent bait stations at a rate of 2 or 3 oz. per
1000 ft. of floor surface and are renewed about twice a week. Liquid bait
dispensers made from a chicken-watering device and a cellulose sponge have
been used successfully in chicken houses. The liquid bait contains 0.1%
dichlorvos or trichlorfon in 12.5% sugar solution.
-------
Outdoor space sprays. Spray treatments are employed against flies chiefly in
problem areas where residual treatments or larviciding fail to give satis-
factory control. This method is frequently used at open dumps and also in
disaster areas, such as stockyards where animals have been killed by flooding,
or warehouses where large quantities of food have been damaged following
flooding or power failure. According to the CDC 1971 Public Health Pesticides
(2), six organophosphorus compounds have been labeled for outdoor space sprays:
diazinon, dichlorvos, dimethoate, fenthion, malathion, and naled.
Table 3. Organophosphorus Insecticides for Use in Fly Control (2),
Type
Application
Toxicant
Diazinon
Formulation
Remarks
For 50 gallons of
finished spray,
add water to:
2 gal. 25% EC
or 16# 25% WP
R
£
S
I
D
U
A
L
-Maximum strength permit-
ted 1%. Labeled for use in
dairy barns, milk rooms, and
food-handling establish-
ments, but not poultry
houses.
dimethoate 1 gal. 50% EC —Maximum strength permit-
ted 1%. Can be used in
dairy barns (except milk
rooms), meat processing
plants, and poultry houses.
Gardona
malathion
8# 50% WP or
6# 75% WP or
2 gal. 2#/gal. EC
naled
•Maximum strength permit-
ted 2%. Labeled for use in
dairy barns but not poul-
try houses.
2-4.5 gal. 55% —Maximum strength permit-
EC or 32-64* ted 5%. Labeled for use in
25% WP dairy barns, poultry houses,
meat packing plants, pre-
mium grade material accept-
ed for use in milk rooms
and food-handling plants.
1 gal. 50% EC —Maximum strength permit-
ted 1%. For use in dairy
abrns (except milk rooms),
in food-handling establish-
ments", and in poultry
houses.
ronnel
fenthion
2 gal. 25% EC
or 16# 25% WP
— Maximum strength permit-
ted 1%. For use in dairy
barns, milk rooms, food
processing plants, and poul-
try houses.
0.7-1.3 I
93% E
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FLEAS
Fleas are annoying, blood-sucking pests whose bites may itch intensely and
cause serious discomfort to people, pets, and domestic animals. Some species,
particularly the oriental rat flea (Xenopsylla cheopis), are of great impor-
tance as vectors of plague, murine typhus and other diseases.
The chlorinated hydrocarbons, particularly 10% DDT dust, have been used with
great success from 1944 to 1968 to control the oriental rat flea in areas
where murine typhus or plague occurred, both in the United States and overseas.
However, with the development of resistance to DDT in some strains of the
oriental rat, cat, and dog fleas, and the restrictions on the use of this
chemical in recent years, alternate insecticides have been used.
The vegetable insecticides, rotenone and pyrethrum, continue to be the
insecticides of choice in controlling fleas on kittens, cats, and puppies.
Other insecticides which can be used on pets, particularly dogs, are listed
in Table 4 from the 1971 CDC Public Health Pesticides (2).
Carbaryl (Sevin) dust, a carbamate insecticide, is widely used to control
the oriental rat flea and wild rodent fleas, usually as 2 to 5% dusts. For
control of wild rodent fleas in western United States, various formulations
such as 3 ounces of 2% carbaryl dust, or 2 ounces of 5% carbaryl dust, per
prairie dog burrow have given good control (2).
*
Table 4. Insecticides Used On Pets For Flea Control (2).
Toxicant Formulation Percent Concentration
carbaryl
coumaphos
Dip or wash
Dust
Dip
Spray
Dust
0.5
2.0-5.0
0.2-0.5
1.0
0.5
lindane Dust 1.0
malathion Dip 0.25
Spray 0.5
Dust 4.0-5.0
pyrethrum Spray 0.2 + 2.0
synergist
Dust 1.0
rotenone Dust 1.0
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REFERENCES
1. Bjornson, B. F., Pratt, H. D., and Littig, K. S. 1969. Control of
domestic rata and mice. PHS Pub. 563, 41 pp.
2. Center for Disease Control. 1971. Public health pesticides. Pest
Control 32(3): 13-51.
3. Lisella, F. S., Long, K. R., and Scott, H. G. 1970-71. Toxicology of
rodenticides and their relation to human health. J. Environ. Health
.33(3): 231-237; .33(4): 361-365.
4. Pratt, H. D. and Littig, K. S. 1971. Mosquitoes of public health
importance and their control. USDHEW, PHS, HSMHA, BCEM, Atlanta, Ga.
94 pp.
5. American Mosquito Control Association. 1968. Ground equipment for
mosquito control. Amer. Mosqu. Cont. Assoc. Bull. No. 2, Rev. 1968,
101 pp.
6. Kilpatrick, J. W. 1967. Performance specifications for ultra low
volume aerial application of insecticides for mosquito control.
Pest Control 31(5): 80-84.
7. Pratt, H. D. and Bjornson, B. F. 1969. Vector control today. J. Milk
and Food Tech. .32(6): 220-223.
-------
THE DIAGNOSIS AND TREATMENT OF ACUTE
PESTICIDE INTOXICATION IN MAN
G. A. Reich, M.D., M.P.H.
Pesticide poisoning is reported by the National Clearinghouse for Poison
Control Centers at about 5,000-6,000, cases per year. This represents, for t
most part, accidental poisoning among children. Many more cases than this
occur,especially among pesticide exposed workers, but there are few reports
of these. The fatality rate in pesticide poisoning is considerably higher
than that seen with the more common agents in poisoning such as aspirin,
tranquilizers, and birth control pills.
The incidence of pesticide poisoning varies a great deal from region
to region in the U.S.A., being highest in agricultural areas and in urban
centers surrounded by agricultural areas.
Poisoning at times occurs on a mass scale when flour, sugar, or the
like, become contaminated with pesticides in transit or in storage, since
pesticides survive the cooking and baking processes quite well. Examples of
these are the food poisoning episodes of recent years in the Middle East,
Columbia, and Mexico. Episodes on a much smaller scale have occurred in
the U.S.A.
The Community Studies have been conducting prospective epidemiclogical
studies of workers exposed to pesticides to determine if their health is
being adversely affected. In addition to this, our Studies provide diagnosti
and therapeutic assistance in their local areas to Doctors handling cases of
acute poisoning. Most of our reports to date have come from south*Texas and
south Florida which represent primarily cases of individual poisoning but
at times are of group poisoning.
In south Texas, the incidence of poisoning increased for several years, then
declined only to rise again. Most cases occurred in June and July during
the period of greatest pesticide use. Most cases were among teen-agers
and young adults who were employed by farmers and spray pilots to assist in
mixing and applying pesticides. Parathion and methyl parathion were the
usual agents, and the route of exposure was almost always dermal. Very few
deaths occurred, even though pesticides are by far and away the leading
cause of poisoning in this area.
The signs and symptoms observed in these cases indicate that a variety of
biochemical and physiological functions are altered by pesticides. The
central nervous system, cardiovascular system, gastrointestinal system, and
musculoskeletal system are the most obviously affected in pesticide poisoning
The diagnosis may be difficult, because of this variety of signs and symptom:
which are suggestive of other conditions as well as pesticide poisoning.
-------
56
In south Florida, poisoning reflects three sorts of circumstances:
(1) accidental ingestion by 1 to 2 year old children in and around the house;
(2) accidental dermal exposure in occupational exposed workers; and
(3) suicidal ingestion in middle-aged to older adults. Numerous pesticides
have caused deaths in this area, ranging from old types like Paris Green
up to newer pesticides like 2ectran. In Florida, pesticide poisoning
is a year round phenomenon rather than coinciding with the season of
greatest agricultural use of pesticides. This is due to the importance
of the accidental cases among children and the suicidal cases among adults.
The highest death rates are among adults, but this represents the fact
that such a large proportion of these are suicidal. The agents of most
importance are the organophosphates, especially parathion, but numerous
compounds singly or in combination have been involved. There have been
several homicidal attempts with pesticides too, most of which have been
successful. In this area, the leading cause of death from poisoning
among children is pesticides.
How important pesticide poisoning is in your area will depend upon
several factors already noted. Determining what the true incidence is
in any particular area may be difficult, because of errors in diagnosis
and the lack of an effective system of reporting. Such poisoning is,
however, preventable — though suicidal cases present particular problems.
When one considers that only about 10% of the true incidence of poisoning
in the U.S.A. is reported, and that the Poison Control Centers report over
100,000 cases per year, it is apparent that poisoning (not just with
peaticides) represents an important public health problem.
-------
HOUSEHOLD USE OF PESTICIDES
Frank S. Lisella, Ph.D.
Introduction
Some common household uses of pesticides include ridding homes of insects
or rodents, defleaing or delousing pets, and destroying garden pests.
Thousands of pesticide formulations are sold through retail outlets for
use in the home environment and in garden areas. These chemicals, when
properly used, are desirable additions to our armamentarium of technical
agents which are used to maintain and improve our standard of living. On
the other hand, pesticides can present a hazard to people, pets, wildlife,
and desirable plant species if they are not used in accordance with the
appropriate recommendations.
Pesticide Products
In choosing a pesticide to apply to eliminate a pest species, there are
a number of factors which must be considered—among these are the nature
of the pest, location of infestation, toxicity of the product to be applied,
and the ease of application of the product.
Some information with respect to the use of the common pesticides for the
control of household pests is summarized in the following tables:
RODENTICIDES
RODENTICIDES PEST SPECIES COMMENT
Warfarin
Norway Rats
Pindone
Anticoagulants - must be available to
Diphacinone rats at least 2 weeks
Roof Rats
Fumarin
Norbormide Norway Rats Ineffective against mice
Red Squill Norway Rats Emetic
Mice Mice - Tracking Dust
-------
INSECTICIDES (Household Use)
INSECTICIDE
Pyrethrins
Ma lathi on
Ronnel
Malathion
Chlordane
Chlordane
Propoxur
Dichlorvos
(DDVP)
Kepone
Malathion
Dursban
Fen th ion
Diazinon
PEST SPECIES
F
L
I
E
S
s
p
I
D
E
R
S
Ants
C
0
C
K
R
0
A
C
H
E
S
COMMENT
Quick knockdown
5% maximum concentration
Exterior use - vegetation and wall
surfaces - resting areas
1% maximum concentration
Exterior use only
2-3% water-based spray - harborage areas
5% dust
2% water-based spray
5% dust
10% dust - runways, cracks in concrete,
garbage pails, etc.
1% spray - odor and staining reported
2% bait
0.5% spray
1.9% bait
0.125% bait - aging a problem
5.0% spray or dust - odors
0.5% spray - PCO use only - 1971
2.0% spray - PCO use only - 1971
0.5% spray (coarse) Spray treatment -
1.0% dust baseboards, cabinets
under refrigerators,
stoves
1% spray, 2-5% dust - PCO use only - 1971
-------
Safety Practices
A pesticide should be used only when it has been established that a need
exists. When a product is selected for use, it should be the least toxic
chemical which will achieve the desired results. The following precautions
should be noted:
General
1. Read the label each time the pesticide is used and follow the stated
instructions label exactly.
2. Keep the pesticide in a plainly labelled container, preferably the
one in which it was bought. Never transfer pesticides to unlabelled
or mislabelled containers.
Before Application
3. When handling, mixing, or applying pesticides, avoid inhaling dust
and fumes and avoid getting materials on the skin.
4. When directed by the label, wear protective clothing, such as goggles,
gloves, aprons, respirators, and masks.
5. Check sprayers before each use, to make certain that hose connections
are tight and that valves do not leak.
6. Check the label of the product before using, so that you know what
to do quickly if there is an accident. If clothing or skin becomes
contaminated, wash the skin and change to clean clothing. If the
slightest illness appears, call a doctor or get the patient to a
hospital immediately.
7. The very few people who suspect they may have a special sensitivity
to pesticides should consult an allergist, and, if necessary, take
steps to avoid any exposure to the offending agent.
During Application
8. If indoors, work in a well-ventilated area, to avoid inhalation of
fumes.
9. If outdoors, do not spray into the wind.
10. Cover food and water containers when using pesticides around areas
for livestock or pets.
11. When mixing or using inflammable chemicals, be especially careful
to avoid the fire hazards caused by smoking, defective wiring, and
open flames.
12. In applying pesticides to food plants (a) use the proper dose re-
commended for the purpose, and (b) allow the full recommended time
between applying the pesticide and harvesting the plant to avoid
having a harmful amount of pesticides remaining on food to be eaten.
Do not plant food crops near ornamental plants which are to be
sprayed.
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60
After Application
13. Get rid of used pesticide containers in a way that will not leave
the package of leftover contents as a hazard to people—particularly
children—or to animals.
14. Wash hands thoroughly after using pesticides and before eating or
smoking.
15. Change clothing after each day's operations and bathe thoroughly.
Pesticides should be stored in a locked cabinet or storage area and out of
the reach of children, pets, and people who might not be able to understand
their danger. The storage area or cabinet should be dry and well ventilated.
The chemicals should never be placed in empty food or drink containers of
any kind.
Environmental Sanitation
Proper environmental improvement measures must be associated with the appli-
cation of all pesticides. For example, in order to achieve adequate control
of rodent populations, it is necessary that all harborage and sources of
food be removed. Structural harborage, such as small protected enclosures
under cabinets, shelves, and stairs should be eliminated. The proper storage
of usable materials reduces the food and harborage available to rodents to
a minimum.
The improper storage of refuse (garbage and rubbish) and of food products
invites insect and rodent infestations. Refuse storage facilities should
include enough containers to hold all garbage and rubbish that normally
accumulates between collection days. A satisfactory refuse container should
be rust-resistant, water-tight and not exceed 32 gallons in capacity. All
garbage should Be drained and wrapped in newspaper prior to being placed in
the refuse containers. The containers should be washed periodically to
further prevent fly, rodent, and odor problems.
REFERENCES
1. Safe Use of Pesticides. Published by the Subcommittee on Pesticides
of the Program Area Committee on Environmental Health. American
Public Health Association, 1740 Broadway, New York, New York 10019.
1967.
2. Public Health Pesticides, 1971. Publication of the Technical Develop-
ment Laboratories, Center for Disease Control, Savannah, Georgia 31402.
3. Savage, Eldon P. and Simmons, S. W.: Pesticide safety—all users are
responsible. Pest Control. February 1968.
4. Lisella, Frank S., Savage, Eldon P. and Scott, Harold G.: Pesticides
and institutional environments. Journal of Environmental Health. 33:5,
March-April, 1971.
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DISPOSAL OF WASTE PESTICIDES: PROBLEMS AND
SUGGESTED SOLUTIONS
H. C. Johnson and L. P. Wallace, Ph.D.
One of the many problems encountered in the disposal of our nation's
solid wastes is the handling of toxic and/or hazardous materials includ-
ing pesticides. Within EPA's Office of Research and Monitoring, the
Solid Waste Research Office (SWR) has been and is presently studying
effective means of handling and disposing of these hazardous wastes,
particularly pesticides. Because of their toxicity, some pesticides
must be detoxified before any disposal or reclamation processes can be
safely applied, while other pesticides can be disposed of directly.
Emphasis in this presentation will be centered on those solid waste
management systems which are applicable to, or hold promise for, the
disposal of pesticides and pesticide containers.
Land Disposal Methods
The sanitary landfill is currently regarded as the most important land
disposal method and consequently, considerable research is directed
towards improving this technique and assuring that the environment will
be properly protected when this method is used. If correctly located
and engineered, one of the most favorable qualities of the sanitary land-
fill is its ability to receive heterogeneous solid waste loads. These
loads vary from being relatively innocuous and chemically inert to being
putrescible and even toxic. It is, however, most important that the
requirements given in the following definition be met in order for a
facility to be considered a "sanitary landfill":
Sanitary landfilling is a method of disposing of solid waste
on land without creating nuisances or hazards to public health
or safety, by utilizing the principles of engineering to con-
fine the refuse to the smallest practical area, to reduce it to
the smallest practical volume, and to cover it with a layer of
earth at the conclusion of each day's operation or at such
more frequent intervals as may be necessary.
For every sanitary landfill, and particularly those receiving such toxic
materials as pesticide residues, it is important to assure that there is
no contamination of nearby ground and surface waters. A Solid Waste
Research sponsored study is being performed by researchers at the Univer-
sity of Illinois on the hydrology of several solid waste disposal sites.
Data from the study are useful in evaluating the factors that control
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62
ground water and landfill leachate movement. Five different hydro-
geologic environments were selected for the study and piezometers were
installed in drill holes, strategically located to define fluid potential
distribution, and water samples were taken for chemical analysis. In
addition to total dissolved solids and chlorides, which are good indi-
cators of leaching, a host of chemical determinations were done on those
samples. The results were used to predict the best physical placement
of landfills to avoid leaching. No pesticides were detected in the
leachate during the time of the study.
At one in-house project, Solid Waste Research is operating a field-scale
landfill in Walton, Kentucky, to further study leachate movement and gas
formation. The cell being used has been lined with clay and plastic to
assure total collection of rainfall or applied water. Information from
this study will give further guidance in the safe operation of sanitary
landfills for hazardous materials such as pesticides.
Another land disposal system has been under investigation in Alkali Lake,
Oregon. Under the sponsorship of Solid Waste Research, scientists at the
Environmental Health Sciences Center at Oregon State University have been
studying the feasibility of transporting the waste liquor and by-products
from 2, 4-D and 2, 4, 5-T manufacturing process to an arid area in Oregon
where they are being diluted and applied to the land for natural degra-
dation. The 55-gallon drums used for transporting are chemically
cleaned, compressed, and buried or baled and reused as scrap metal. The
theory behind the project is that herbicides and pesticides do not have
an infinite life in the environment. In every instance where persistence
of pesticides in soil has been studied, it has been found that the
chemical disappears within acceptable time limits (2-3 years) to a level
of little biological significance. The factors causing the disappearance
are photochemical decomposition, chemical decomposition, microbiological
degradation, and physical factors such as adsorption, volatilization, or
leaching. The physical factors, however, only take the pesticides from
one place to another, they do not really make them disappear.
Data from trial applications at the site have supported the degradation
theory. Application to small plots have shown that very little vertical
or lateral movement occurs during the degradation period which has been
twenty months for 60 percent degradation. It is planned to start using
subsoil injection routinely for the waste liquor presently being stored
at the site.
In conjunction with this study, the Oregon State University group is
also investigating pesticide container cleanup in Klamath Falls, Oregon.
Attempts will be made to chemically clean the containers to such a level
that they can be accepted for baling and placement in an electric fur-
nace for scrap metal recovery. Facilities for this study have been con-
structed and cleanup investigations are presently underway. Liquids from
the cleanup operation will either be used as a pesticide or disposed of
at the Alkali Lake site. In order to make the container cleanup easier,
the researchers have taken an active role in persuading pesticide users
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to rinse their containers w.th
prepare, adding the rinse back
tests have shown that rinsing a.
eral quarts of water reduces trie
affords the user a financial Savi
costs $20/gallon, and greatly fac-
Oceanic disposal of solid waste,, -.,'
materials, may be an alternative to
ever, there are many questions t D<
Research Office could endorse cr^ "
tract with the Applied Oceanog .pr.,
San Diego, California, describe —a natu.-a -..-.d nagnltude of -resent
ocean disposal practices. In c.i.:..iectior< 'AV«:-, t.ne study, on-slte surveys
were conducted at 16 United States citiei s~."uated on or near the Atlantic
and the Pacific coasts, and tht. (L'f of »L<' ..o.
•r <•• tr the fcrmt at.on they
'-. -s ~ .t formulation. Laboratory
.tic :.' ./.ner t:.ree ti...as -.nit/, sev-
si,iu.' ..^ticide content by 90 percent,
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64
The report indicated the structural and compositional requirements
necessary for combustible pesticide containers and the possible use of
polyethylene liners to aid combustion. It was shown during the course
of the project that representative pesticides were virtually volatilized
or sublimed when incinerated unless a binder was present to increase the
residence time in the flame. By using polyethylene, which under heating
or combustion conditions softens or degrades to products of lower mo-
lecular weights, the advantages of a liner and a binder were obtained
with one material and the pesticides studied could be essentially des-
troyed at temperatures normally achieved by burning wood, paper, card-
board, etc.
In all the thermal studies performed, less than five milligram amounts
of the pure pesticide chemical were used. Since some undesirable emis-
sions were detected under these conditions, bench and field studies with
larger samples need to be investigated before definite conclusions can
be drawn.
Destructive distillation (pyrolysis) of pesticides shows great promise
as a detoxification reduction method. It should leave an easily handled
residue and should thermally degrade effluent gases to acceptable limits.
Additional research is needed to verify the possibilities of this method.
A great deal of concern is being directed to recycling of waste material.
Some of the present barriers to increased reclamation and recycling are
technological in nature and others are economic. Success in overcoming
these barriers has the dual advantage of reducing the amount of waste to
be disposed of while conserving the nation's natural resources. Cellu-
losic wastes, including wood, bark, sawdust, oat hulls, corn cobs,
bagasse, and other agricultural residues are generated in truly prodi-
gious quantities. Little, if any, significant portion of these wastes
is beneficially used and, since they are commonly burned, cellulosic
wastes often contribute to air pollution in areas where they accumulate.
Under a research grant, the Institute of Forest Products, University of
Washington, in Seattle, is developing a unique means for utilizing
cellulosic wastes which will at the same time allow safer and more effi-
cient application of pesticides to the soil.
Some common properties of the wood and agricultural wastes are that they
consist predominantly of polymeric cellulose macromolecules; they con-
tain an abundance of replaceable hydrogen atoms, and all are biodegrad-
able. Since these waste materials are polymers containing replaceable
hydrogen atoms it should be possible to attach pesticides to these sub-
strates in the same way that acetic acid, for example, becomes attached
to cellulose in the manufacture of cellulose acetate. Research has
shown that pesticides can be attached to such solid waste as sawdust,
bark, and lignin by means of ester linkages. Herbicides have been com-
bined with natural as well as synthetic polymers. The herbicides used
were 2, 4-D, 2, 4, 5-T, 4(2, 4, 5)-TB, and Dalapon. It was found that
each of these polymeric combinations prevented the germination of cer-
tain seeds longer than the herbicide alone under controlled laboratory
-------
conditions. Similar results have been obtained in field plots using
herbicides and in Costa Rica using the insecticide carbofuran. In the
Costa Rican study, it was found that a treatment with the pesticide-
polymer combination was effective for eight weeks as opposed to one week
for the pesticide alone. Plans are to repeat this study in Puerto Rico
where environmental conditions are quite different.
The practical implication of the ability to chemically bond pesticides
to cellulosic materials is that very large quantities of cellulosic
wastes, so treated, could be utilized as a mulch for gardens and in
agriculture. The pesticide in the mulch would be released in controlled
fashion with distinct advantages over present procedures for applying
pesticides to soils. Now, pesticides usually have rather short useful
lives because they may be degraded by bacteria to inactive metabolites,
or washed by rainwater into the subsoil where they are inaccessible to
pests they are intended to control. Also, and more important from the
public health standpoint, this leaching into the subsoil often means
that some rather stable pesticides, or their degradation products, find
their way into potable water supplies.
In contrast, if the pesticide were chemically combined with the poly-
meric solid waste, its useful life should be prolonged; attack by bac-
teria should be reduced; and the pesticide should not be Teachable into
the subsoil and hence will not pollute streams and rivers. As the solid
waste-pesticide mulch lies on and in the soil, it will gradually decom-
pose, continually releasing the active pesticide over a long period of
time. With this technique the problems and potential errors of measuring
and diluting liquid concentrates are eliminated. Spillages of solids
are, of course, less likely than liquid leakages and are easier to rectify
when they occur. Controlled releases of the pesticides may also allow
lower dosages and fewer applications.
Another very important benefit from this project is the prospect it may
hold for development and use of extremely short-lived biodegradable
pesticides which, in combination with solid waste polymeric substrates,
would be sufficiently stable for practical use. For example, many
organophosphorous pesticides are liquid and are too dermally toxic to
permit their use by anyone other than an expert. Combinations of these
materials would perhaps render them safe, while not destroying their
biological activity. The currently "unuseable" pesticides are often
effective at much lower dosages than the superficially less hazardous
products that are not used in relatively massive amounts.
Composting of municipal and agricultural refuse is not widely used as a
means for solid waste disposal in the United States. However, there are
several compost plants in operation and one may reasonably expect to see
the continued composting of solid waste on limited scale in areas where
the product is marketable. A research grant to the Western Research
Laboratory of the National Canners Association, Berkeley, California, is
supporting a study of the fate of insecticides in composted agricultural
wastes. A substantial part of the fruits and vegetables received for
-------
preservation by canning or freezing is discarded as solid wastes. That
portion of the raw product which is discarded—vegetable skin and rind--
generally has the highest level of insecticide residue, and this fact has
limited the use of such material as animal feed, and it also raises
questions about possible harmful effects of spreading composted cannery
wastes on agricultural lands. This concern is especially justified if
toxic degradation or transformation products remain in the compost mixture.
The Canners Association study aims to obtain a better understanding of
the mechanism by which insecticides are degraded by microbial or chemical
action during aerobic composting, and also to obtain information which
will make it possible to dispose of waste materials containing concen-
trated insecticide residues without hazard to public health. Insecti-
cides selected for the study represent examples of the three principal
classes: chlorinated hydrocarbons, organophosphates, and carbamates.
The selection of specific insecticides was based upon the extent of
usage in agricultural products, variety of chemical structure, and
availability of reliable analytical methods. These included: dieldrin;
parathion; Diazinon; p, p-^DDT; pentachlorophenol, and with further
studies planned for Sevin and Zineb.
During the study, breakdown products of several insecticides have been
identified and the varying effects of batch-type and thermophilic com-
posting processes have been noted. The summary in a recent progress
report contained the following information:
1. Concentration of Diazinon and parathion rapidly declined in
both composting processes with the thermophilic process being the
more efficient. Breakdown products identified for Diazinon were
oxodiazinon and sulphotepp. Those identified for parathion were
aminoparathion, p-aminophenol, and p-nitrophenol.
2. Continuous thermophilic composting caused some reduction in DDT
whereas the batch process had little effect. No breakdown products
have been identified.
3. Dieldrin was more efficiently degraded in the batch process and
none of its breakdown products have been identified.
4. Following the active compost period (120 days), the curing or
aging phase (180 days) of the process had little or no effect on
the insecticides.
The consideration of pesticide disposal is one facet of hazardous waste
disposal. In Section 212 of the Resource Recovery Act, Congress commis-
sioned a study on the feasibility of strategically locating national dis-
posal sites to safely process hazardous materials. The first phase of
this two-year study has been initiated through a contract to the Booz-
Allen Applied Research Company. Their responsibility is to make a survey
and list the quantities, location, generation rate, and present disposal
practices of our nation's hazardous wastes. Throughout all the phases
of this study, pesticides will be given particular attention in hopes
that some safe and effective means of their disposal can be developed.
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INDUSTRIAL HYGIENE PRACTICE IN THE MANUFACTURE,
FORMULATION, AND PACKAGING OF PESTICIDES
Clyde M. Berry, Ph.D.
In this presentation I shall define industrial hygiene as that art and
science directed toward the anticipation, detection, evaluation, control
and continued evaluation of untoward physiological response potentially
associated with the manufacture, formulation and packaging of pesticides.
To establish a point of embarkation on a discussion of this kind a number
of assumptions can be made. These are offered with no sense of chrono-
logical occurrence, of severity, of associated hazard or of feasibility.
1. Too much of anything may be deleterious to physical, mental or
emotional well being.
2. Prudence indicates a need for a plant material balance. Pound
for pound, ton for ton, the amount of total product, by-products
and waste,should equate with the amount of all incoming ingredi-
ents.
3. A flow chart is an indispensable navigational aid in traversing
the labyrinths of any plant product.
4. It is still necessary to "inquire locally". Ask questions, in-
plant, about what happens, where, how and when.
5. Management may not know that operational changes are routine
that are not a part of procedural specifications as detailed
in process manuals.
6. Most chemicals are of technical grade and are usually not pure
chemical compounds.
7. Many (most?) products and by-products are reaction mixtures.
8. People are required to build, maintain and operate equipment.
9. Machines do not get tired, become poisoned, make fewer mistakes.
10. Few engineers design with worker health and safety aspects taking
priority over cost/performance.
11. New legislation (Example: Occupational Safety & Health Act of
1970) is going to force a re-ordering of priorities.
12. Inertia/tradition/pride can inhibit adoption of improved work
patterns or process changes.
13. Legal, Public, and Employee Relations Departments are exquisetely
sensitive with respect to safety ind health verbiage.
14. Labor-management conflicts will sometimes be over safety/health
items when these are not the basic issues at all.
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oo
Pesticides are used because they affect protoplasm, plant or animal.
They can, and do, affect humans, usually deleteriously. To protect the
in-plant workers some general principles can be stated:
1. Keep it inside the unit.
2. If it gets out, keep it as confined as possible.
3. Try to put it back in the process, if feasible.
4. Dispose of contaminated materials and wastes before they get
into the general environment - and do it safely.
5. Keep it off (and out of) the worker.
One needs to know the toxicities of the materials to which a worker may
be exposed, the clinical effects that may be produced, the threshold
limits of exposure, how these can be measured, and the levels to which
a worker may be exposed.
Some workers perform their job at a single location. Others move about.
To make professional judgements on hazard potential it may be necessary
to make three types of measurements:
1. At the source
2. In the general workroom air
3. The individual worker's exposure
Puddings may be proved by eating them. A successful industrial hygiene
approach requires similar clinical proof of absence of injury, acute and
chronic. There should be a plant physician, full time or on call. His
contributions can be roughly categorized as follows:
1. Know the toxic effects of the materials.
2. Do pre-placement examinations to screen out susceptibles and
avoid exacerbating existing conditions.
3. Be prepared to handle emergencies.
4. Do routine physical examinations.
5. Advise on transfers.
6. Authorize all returns to work after illness absences.
7. Maintain records that are epidemiologically useful.
8. Routinely tour the plant.
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An industrial hygienist should be consulted early in the design of a
facility for manufacturing, blending or packaging pesticides. Prevention,
true prevention, begins here. Besides contact with toxic materials
there are other aspects of worker exposure to be considered. Some of
these would be:
1. Trauma
2. Heat extremes
3. Radiation (ionizing and non-ionizing)
4. Noise
5. Vibration
6. Personal services (as locker rooms and lunch rooms)
7. Ergonomics
8. Possibility of fire or explosion
9. Fatigue
The industrial hygienist will view each step in the process, each
machine, each job against the backdrop of general control measures and
their applicability. These would include:
1. Isolation
2. Remote control
3. General ventilation
4. Local exhaust ventilation
5. Enclosure
6. Personal protective equipment
7. Personal hygiene
8. Good housekeeping
Specific details will vary from plant to plant but the approach may be
illustrated by viewing a hypothetical plant along the lines of the
above. Let us assume that a large plant is involved which makes a
pesticide that is highly toxic, can be absorbed via inhalation, inges-
tion and skin contact. It is a liquid. It is blended with a powder
to a low percentage of active ingredient and then packaged in bags,
boxes and drums. These are warehoused awaiting orders from jobbers
and shipping is by rail and truck. On a departmental basis one might
have industrial hygiene interests as follows:
Purchasing
Who are the suppliers?
How much of each material is purchased?
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safety data sheet as required by law?
Is it appropriately labeled?
Receiving
If tank trucks, tank cars or barges, how is it transferred?
Will inclement weather produce (or exacerbate) problems?
Do the attendants have protective gear?
Are eye-wash and deluge showers present?
Is the area included in a disaster plan?
Can pneumatic conveying solve dust problems?
Would pressure transfer be preferred over pumping?
Storage
Are the tanks reasonably protected against damage by mobile
equipment?
Do dikes (large enough to hold entire contents) surround the tanks?
If storage is inside is the lighting and ventilation adequate?
Is a regular check made for leaks and spills?
Are emergency preparations adequate? (lighting, personal protective
equipment, neutralizing chemicals, etc.)
Manufacturing
Are the pumps of-a type to minimize leakage?
Have covers and exhaust ventilation been provided at reaction vessels?
If the reaction is exothermic and could "run away" have quench
tanks been provided?
Is the equipment durable, corrosion resistant and accessible for
inspection and cleaning?
Has provision been made for equipment handling during turn-around?
Is there adequate general ventilation - and with tempered make-up
air?
Are casuals kept out of high risk areas?
Has suitable personal protective equipment been furnished the
operators? Is it kept clean and properly maintained?
Is housekeeping maintained at a high level?
Are hand washing facilities available and used prior to eating
and toileting?
-------
Can a batch method be changed to continuous mixing?
Is the actual blending done in an enclosed vessel, under negative
pressure, with well designed hoods and ductwork to take away dusts,
fumes, gases and vapors?
Are respirators, gas masks and/or other appropriate personal
protective devices provided?
Do the workers wear clean clothing daily?
Packaging
Can it be more completely automated?
Are bottles checked for cracks and loose caps?
Is there any exterior contamination of bags or drums?
Will the labels meet ICC and other regulatory agency requirements -
size, location, wording, coding?
Is there a printed warning against container re-use, except when
returned for the same service?
Are all air contaminants controlled by effective ventilation at
the point of discharge?
It will be apparent that the foregoing are just some of the points an
industrial hygienist will keep in mind. He would extend this into the
warehousing of the packaged product. He would similarly view shipping
where he would seek maximum mechanization, minimum potential for
container damage, applaud the use of experienced truck drivers, dis-
courage mixed cargoes, etc.
The industrial hygienist will also find himself to be a candidate for
service in additional capacities:
1. Advise the applicator on safe use of the formulated product.
2. Back-stop the physician if a Poison Information Center calls
for information.
3. Participate in employee education programs on how to work
safely.
4. Work with plant personnel and management on
a) Salvage operations
b) Waste disposal
c) Air pollution
d) Water pollution
e) Disaster planning
5. Share his knowledge and experiences
a) With other industrial hygienists
b) Physicians
c) Safety engineers
d) Reeulatorv personnel
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ENVIRONMENTAL
(INDUSTRIAL
HYGIENE)
SAFE USE OF
PESTICIDES
EMERGENCY
DECONTAMINATION
& WASTE DISPOSAL
ISOLATION
REMOTE CONTROL
GENERAL
VENTILATION
MEDICAL
RESOURCE ASSEMBLING
PRE-PLACEMENT CLEARANCE
CLINICAL SUPERVISION
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ROUTINE
CLEANING
ROUTINE
WASTE DISPOSAL
LOCAL EXHAUST
VENTILATION
ENCLOSURE
PERSONAL
PROTECTIVE
EQUIPMENT
PERSONAL
HYGIENE
GOOD
HOUSEKEEffl
FIRST AID
EMERGENCY
TREATMENT
CONTINUING
TREATMENT
ADEQUATE RECORDS
RETURN-TO-WORK
AUTHORIZATION
REPORT TO AUTHORITIES
(IF REQUIRED)
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-f f-r^f A,
•/ ,4 . / tt ,' .
MINIMIZING FISH AND WILDLIFE
LOSSES DUE TO PESTICIDES
William E. Martin
Fish and wildlife are the barometers of our natural environment. If the;
are in trouble, we are in trouble.
I. Types of fish and wildlife losses due to pesticides
A. Direct or primary losses
l) Thallium/Eagles/Wyoming
A number of bald eagles and golden eagles are believed to
have fed on antelope treated with thallium sulfate in
Wyoming. Twenty-two of these birds are known to have died
from thallium poisoning.
I 7 >JfS f('fi
2) Azodrin/ELrds/Arizona
At least 4,000 birds, 50$ of which were dove and quail,
were killed with Azodrin following its use to control
pink bollworm in Arizona cotton fields.
3) Arsenic/Deer/Tennessee
Eleven deer, including some does carrying fawns, and some
small game died from feeding on forage in an area treated
with an arsenical herbicide to control Johnson grass.
4) Toxaphene/Fish/Nevada
Fish were killed after exposure to toxaphene used as a
cattle dip to control scabbies.
5) Aldrin/Game Birds and Small Mammals/Illinois
Aldrin used for Japanese beetle control caused mortality
within 3 weeks. Meadowlarks, robins, brown thrashers,
starlings and grackles were virtually eliminated.
-------
Populations of pheasantsf quails, moles, shrews, and
muskrats appeared to have taken severe losses.
6) Zinc Phosphide/Geese/California ' ''
.'•'" <• - ,'••.- S,-. -,-
At least 455 wild geese died from eating zinc phosphide-
treated oat groats applied from mouse control on leased land
at Tule Lake. "(' ' -...., .. :
7) Fenthion/Songbirds/North Dakota
/ • ' - // •
As many as 5,000 songbirds succumbed following a mosquito
control application of fenthion in North Dakota. The
spraying was done at the peak of a warbler migration;
thus, exposing many more birds than would normally be
affected.
8) Heptachlor/SLrd and Small Mammals/Southeast
Early fire ant eradication efforts resulted in numerous
incidents of losses of cottontail rabbits, bobwhite, other
small game and many songbirds throughout the Southeastern
United States. y ,, .<-,,, • ,,
B. Indirect or food chain losses
l) Diazinon/Grasshoppers/Fish /'' '•
• ' r i'
Grasshoppers treated with Diazinon hopped into streams
during death throes. Fish gorged themselves on the insects,
and were subsequently poisoned.^ /•><•/ ••'- ;, j>, */, " •'
2) Dieldrin/Aquatic Producers/Fish/Bald Eagles^7//;.-' /,, '"<'.,-,;,,
Dead bald eagles known to have fed on fish containing
dieldrin from the aquatic food supply had sufficiently high
brain residue levels to indict dieldrin as the cause of
death.
C. Losses through incapacitation
l) Mirex/Blue Crab and Shrimp ' ^ -n •, «•'< ; », - .'
Very small quantities of mirex cause disorientation in certain
crustaceans. The estuarine ecosystem is such that even
slightly disabled individuals become easy prey.
2) Cholinesterase Inhibition in Birds
Birds depend heavily on their ability to react quickly to
external stimuli when feeding and in escaping predators.
When their nervous systems are not functioning properly they
are severely handicapped.
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D. Biological magnification/phenomenor/reproductive failure
:. . • , ' * ' ' • •'•''•
l) DDT/Bald Eagles, Ospreys, Brown Pelicans, et-al. DDT has
been demonstrated to move through various food chains with
increasing concentration as it is translocated upward
through the trophic levels. Sublethal concentrations have
been implicated in reproductive failures caused by
physiological disruption leading to eggshell thinning in
many species of birds at or near the top of aquatic food
chains.
2) DDT/Lake Trout £ '
Trout in Lake George, New York, continued to concentrate
DDT in sac fry egg lipids until the last part of the sac
was absorbed; at this point there was sufficient toxicant
released in a single dose to cause death.
E. Habitat changes resulting from pest control efforts
l) Loss of food and cover for wildlife results from killing
large tracts of sagebrush to "reclaim" rangelands.
2) Forest insect control spraying may seriously reduce food
supply of canopy feeding songbirds.
3) Aquatic weed control may enhance the habitat for some
organisms and make it intolerable for others.
II. Why losses occur
1) Monoculture croplands with related build-up of pests and need
for pesticides.
2) Excessive application of pesticides ("Oressing-up" the edges).
3) Effects of pesticides are unknown prior to application (New
"use-patterns" of established chemicals).
4) Pesticide applied to other than target area (Improper guidance;
drift).
5. Effects may not be obvious immediately after application, but
develop with time (Subacute physiological damage).
6) Pesticide known to have toxic effect, but alternatives are not
available (Mosquito control using parathion because mosquitoes
are resistant to other chemicals).
7) Industrial discharge or accidental spillage (Settling pond
overflow; broken containers; improper handling of bulk;
8) Runoff (Application made prior to heavy rain or on steep or
eroded slopes).
9) Improper disposal (Equipment washed out in streams; containers
used for other purposes; dumping).
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III. Who should be responsible for mitigating fish and wildlife losses
A. Manufacturers and distributors
l) Demonstration of efficacy and safety.
2) Extensive testing prior to marketing new products or methods.
3) Development and selling practices in the interest of long
term benefits rather than immediate profit.
B. Federal and State Government agencies
l) Federal and State registration of chemicals and methods
of use.
2) On-site regulation of accepted use patterns.
3) Field appraisals of non-target effects under operational
conditions.
4) Monitoring of invertebrates, fish, wildlife, soil, water,
vegetation, etc.
5) Technical assistance to manufacturers and prime users, and
education of the general public.
C. Universities and associated organizations
l) Safe use and adverse environmental effects should be standard
parts of any academic training in economic use of pesticides.
2) Education of the public a primary task.
D. Users
l) Choose the most selective chemical for the problem.
2) Read the label and act accordingly.
IV. Sources of information needed for forecasting potential fish and
wildlife hazards
l) LDcg, !£CQ» et, al data from laboratory testing.
2) Simulated field studies under controlled conditions.
3) Field appraisals conducted under operational conditions.
4) Short term monitoring projects.
5) Feedback and extensive exchange of information between
knowledgeable individuals and agencies.
6) Crystal Ball.
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FUTURE TRENDS IN CHEMICAL AND NONCHEMICAL METHODS
FOR PEST CONTROL (Safer?)
L.A. Richardson, Ph.D.
Insect pests are responsible for vast economic
losses in the production, processing, distribution,
and storage of food, fiber, and forest products. They
assist in the transmission of diseases in animals,
plants, and man, create intolerable annoyance problems,
and effectively destroy items of beauty as well as
those of man's basic needs. The annual economic loss
due to insect activity over the period 1951-1960, has
been estimated at 6.8 billion dollars. Consequently
it might seem ideal to eradicate all destructive insects
However, while insects constitute one of man's most for-
midable enemies, they are essential in our complex
ecological system. Insects function in the pollenation
of many useful and ornamental plants and act as para-
sites and predators where they no doubt aid in reducing
the potential transmission of diseases. In addition,
experience has shown that single species eradication
programs are successful only in limited geographical
areas, usually are expensive, and are only temporary.
Thus, the eradication of all insect pests is not only
undesirable but, currently impossible.
Since insect species are both beneficial and harm-
ful, the "balance of nature" philosophy is often sug-
gested as the appropriate way of life. Insect pests at
various stages in their life cycles, are subjected to
disease, starvation, desiccation, natural enemies, and
adverse environmental factors, all of which limit their
reproduction potential. However, insects have great
adaptability and readily adjust to adverse ecological
conditions; develop resistance to diseases and man-
made control methods; frequently tolerate parasitic
infestations for sufficient periods of time to complete
their mission and reproduce; and are, in most cases,
V
A \
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highly mobile. It is currently estimated that 150-200
insect species frequently cause serious damage and that
an additional 400-500 species may create problems from
time to time. Thus in a man-insect confrontation,
waged on a live-and-let-live basis, man is hopelessly
outclassed.
Economic and cultural patterns, together with the
requirements of a constantly increasing population,
greatly complicate the development of pest management
programs. Increased agricultural production must be
accomplished on an ever decreasing percentage of the
land area and the products therefrom transported,
stored, and processed for use by high density urban
populations. These two factors provide additional
advantages to the insects. The shrinking rural area
necessitates a high production density of specific
crops and virtually eliminates many tillage practices
useful in insect control. Simultaneously, through the
assurance of a recurring and ample food supply in an
area where little mobility is required, the potential
for such crop-specific insects to reach devastating
numbers is greatly enhanced. Specifically designed
equipment and facilities of large capacity are neces-
sary for the transportation, storage, and processing
of agricultural products in order to supply densely
populated urban areas. Such facilities and equipment
provide a localized, constant, and ample food supply
for insects and thus ideal destruction and reproduction
potentials.
Densely populated areas create additional condi-
tions which provide advantages to the insects. The
potential for disease transmission, sensitization,
allergic responses and general annoyance are greater
in urban and recreational areas. Crowded conditions
frequently create problems in waste disposal and gene-
ral sanitation practices resulting in optimum conditions
for insect reproduction.
In order for man to exist in a world where insects
appear to have the advantage, it is necessary to
modify this "balance of nature." Historically, both
physical and chemical methods have been used, with the
methods of choice being dependent upon economics, avail-
ability, and efficacy. Within the last thirty years
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chemical insecticides have been the principal means of
effective insect control. Currently, the development
of alternate control methods and the potential health
hazards ot chemical insecticides are under intense
investigation. Pest control management programs are
certain to change as a result of these investigations
and the current general attention to ecological problems.
Chemical insecticides have been used in the struggle
between man and insect since before the First Century
AD. In the last thirty years, however, the development
and use of such products has increased at a phenomenal
rate. The efficacy, persistency, and economy of the
early insecticides are undoubtedly responsible for vir-
tually eliminating many insect-borne diseases and pre-
venting starvation for untold numbers of people.
Insecticides are currently our first line of defense
in control of insect outbreaks. They are useful be-
cause they are highly effective, provide an immediate
effect, are able to bring large insect populations under
control, and can be employed as needed.
Unfortunately insecticides possess a number of dis-
advantages. The principal ecological problems are that
all of the commonly used insecticides are broad spec-
trum agents and do not limit their destruction to the
target organism, and all contribute to ecological pol-
lution either as the parent compound or a degradation
or reaction product thereof. From the standpoint of
human and animal health and welfare, many of these
agents accumulate in the tissue of man and animals and
may be associated with chronic health problems. Others
are acutely toxic and have brought serious illness and
death not only to their users but to innocent bystanders.
Development of insect resistance has severely hampered
the utility of many useful and inexpensive chemical
agents. Finally, additional disadvantages have accrued
because of careless use and overuse to the complete
ignorance, in many instances, of alternative or support-
ive methods of pest control.
Trends in the utilization of insecticides, both
the agents and the means of application, have undergone
noteworthy changes. During the last three decade era
insecticide usage has shifted almost completely from
the very persistent and toxic arsenic compounds, the
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organochlorines, are considered to be rather persistent,
broad spectrum, contact and stomach poisons, which have
the unfortunate characteristic of leaving cumulative
residues in man and the environment. Insect resistance
and general overuse initiated the trend toward the more
acutely toxic and less persistent organophosphate com-
pounds. Organophosphates, useful as contact, stomach,
and systemic insecticides, were able to effect control
of resistant insects and in addition, did not appear to
leave toxic, cumulative residues. More recently, fear
of human health problems and ecological considerations
have tended to shift the usage patterns toward the rela-
tively safer carbamate insecticides. In this move,
organochlorines have been extremely limited in their
usage and the phosphates have come under closer scrutiny.
A second trend has been to shift toward the use of
the less persistent and less toxic compounds within
these chemical groups. Methoxychlor, for example, has
been used in certain applications instead of DDT because
it is less persistent and has a lower mammalian toxicity.
Malathion is preferred to other organophosphates,
wherever it is an effective insecticide, due to a lower
mammalian toxicity. More recently there has been a con-
certed effort to formulate certain of the common insecti-
cides in such manner that they will rapidly degrade to
ecologically safe chemicals.
While the ecology will benefit from the reduced
usage of persistent insecticides, the cost of food pro-
duction is destined to increase because of the necessity
for more frequent applications of more expensive chemi-
cals. Alternate methods of pest control hopefully will
alleviate a portion of this problem. Currently, insecti-
cide application by ultra low volume techniques is being
used as an aid to improved distribution and thus a means
of reducing the total quantities of insecticides re-
quired. A second technique, that of using encapsulated
organophosphates in order to increase their persistence,
has also been suggested. The development of insecticides
which would effect eradication of the target insects
with no persistence, toxic residues, or effect on other
species has not as yet been accomplished.
Cultural procedures are the best known and most
used alternate pest control methods in agricultural
-------
production. Basically, such procedures attempt to elimi-
nate insect breeding areas by general sanitation prac-
tices and methods of exposure to the elements or to con-
fuse the insects by altering production practices.
Such practices as fall plowing, rotation of crops, strip
cropping, changing planting time or plant spacings, and
fertilizer and water management have been found to be
effective in minimizing crop damage. Cultural control
procedures require considerable planning and extremely
good fortune in effecting complete control, however,
safety and efficiency dictates that such methods be in-
cluded in insect pest control programs for agricultural
production.
Physical and mechanical methods include some of the
oldest and most primitive control procedures as well as
ones which will no doubt be used for many years. They
consist of direct or indirect measures to destroy the
insect, disrupt its normal activity, or modify its envi-
ronment to an unacceptable degree. Physical and mechan-
ical methods are most useful in the protection of people
and products in structures. Techniques involved include
temperature and humidity control, exposure to radio-
frequency energy and sound waves, barriers and excluders,
artificial environments, and traps and grids. Certain
techniques such as hand picking, use of flame and heat,
and mechanical trapping have been used in agricultural
practices. Trapping, utilizing chemical attractants,
are currently becoming more important as insect control
methods in agriculture and forest conservation.
Various chemical attractants have been used in con-
junction with mechanical trapping and poisonous baits.
Successful eradication programs, utilizing traps for the
Mediterranean fruit fly in Florida and a toxicant bait
for the oriental fruit fly on a Pacific island, have
been accomplished with attractants.
The most recent development in the area of attract-
ants is sex attractants. To date sex attractants for
twenty-one insect species are undergoing active field
trials. Sex attractants fall within the broad category
of pheromones, substances which are secreted to the out-
side by one individual and when received by a second
individual of the same species, will elicit a specific
response. Uisparlure, the pheromone produced by the
female gypsy moth, is the best known, and one of the
most potent, of the sex attractants. Disparlure has
been extensively studied and synthesized by U.S. Depart-
ment of Agriculture scientists. This synthetic pheromone
has been shown to attract male gypsy moths in field
trials in the presence of as little as 0.1 nanogram, is
an effective trapping aid at 1 microgram, and will out-
draw the female moth at a concentration of 10 ug. Field
trials, currently in progress, will attempt to so per-
meate the air that the odor signals of the female moths
will be jammed. By this procedure it is hoped that com-
Dlete control anrl eventual eraHirati nn ran be «>rro .
-------
Induction of sterility as a means of insect control
has been under investigation for about thirty years.
Perhaps the best known applications were the essential
eradication of the screw-worm fly from the West Indies
island of Curacao and the southeastern portion of the
United States, and the eradication of the oriental fruit
fly from Guam. This technique requires that insects be
reared in captivity, sterilized, and released to compete
in the natural population. Proper sterilization tech-
niques generally do not interfere with the mating habits
of insects, however, rearing in captivity severely
limits the number of species to which this technique can
be applied. Many species of insects are not suited to
control by the rear-and-release method. Some are not
adaptable to laboratory rearing and others would require
excessive numbers to compete favorably with the large
native population. In addition, certain species would
be too hazardous, annoying, or destructive to release.
Thus a second sterilization technique is available, the
use of chemosterilants. Chemical agents, combined with
mechanical trapping, allows the efficient sterilization
of both males and females, at considerably less expense
than irradiation. These agents are most efficient if
placed in the food of the insect, however, they are
effective if placed on the body. Chemosterilants are
mutagenic and must be made available to the target insect
in such manner that they will not endanger other insects,
animals, and man.
Slightly over 30 years have been spent in the devel-
opment of sterilization techniques for a very few insects.
One would anticipate that a tremendous amount of time is
needed to develop sterility techniques for the many in-
sect species remaining. Such investigations and devel-
opment will require the efforts of non-profit organiza-
tions since the profit potential is not currently visible.
Insect control by sterility techniques depends to a large
extent on mass action, is highly dependent on insect
mobility and is a long-term method, relatively speaking,
thus its principle benefit may be in eradication pro-
grams. Proponents are currently suggesting the use of
a non-persistent insecticide followed by release of
sterile males, to complete the eradication. Sterility
techniques are safe, assuming chemosterilants are con-
trolled, and should be useful in long-term insect con-
trol management programs.
One of the oldest and most natural insect control
procedures is the use of so-called natural enemies, para-
sites and predators. The basic reason for incorporating
these procedures into a pest control program is to main-
tain a pest species at a population below the point of
economic importance. One of the chief problems in these
programs is to control the predator-prey or parasite-
host populations. Entomologists have predicted coinci-
dental population cycles of both predator and prey,
indicating that with those studied, the predator is
totally dependent upon the target insect for food. Data
are available, however, which show that such is not
always true. Certain predators, while fastidious, are
-------
devastating
tors may themselves become pests. With those species
for which a stable predator-prey or parasite-host rela-
tionship can be maintained, below the economic threshold
of the target insect, these control procedures are ideal.
Such techniques do not leave toxic residues nor would
they be expected to endanger other species.
Predator-parasite control procedures have been under
study since about the middle of the 19th century. The
accomplishments of these investigations emphasize the
difficulty of locating and developing sufficient popula-
tions of specific predators and parasites. To date, the
only successful man-made controls have evolved from immi-
grant insects. Control of the citrus cottony-cushion
scale in California is an example of one of the earliest
and most successful accomplishments. Importation of the
Vedalia Beetle from Australia, the home of the citrus
scale, is currently providing control of this scale
problem. In addition to the difficulty of developing
the proper predator-prey relationship one must also keep
in mind that such control procedures are slow and must
be carefully planned.
Control of insect pests by microbiological proce-
dures are currently receiving considerable attention.
Insect diseases have been recognized since the time of
Aristotle and undoubtedly have been an unheralded weapon
in man's survival. Scientists initiated studies de-
signed to utilize microorganisms in insect control early
in the 19th century. Bacteria and viruses, which cause
insect diseases, are believed to be specific, do not con-
stitute a known hazard to man or ecological components,
and are biodegradable. The time element between appli-
cation and effect is frequently much shorter than other
alternate insect control methods and indeed approaches
that of insecticides. Experience has shown that appli-
cation of microbiological controls in the presence of
insecticides does not reduce their effectiveness.
Microbiological agents, however, are plagued by
some formidable disadvantages. They are considerably
more difficult to produce than chemical insecticides and
do not currently offer the profit potential. Thus the
development of such agents have been, and will no doubt
continue to be, in the domain of non-profit organizations.
Their specificity dictates that a tremendously large
number of species will need to be developed to effect
control of the various insect pests in existence. Thus
a long period of time will be required to make micro-
biological controls available for all destructive insects.
In addition, the effectiveness of both bacteria and
viruses are dependent upon precise time of application
and environmental conditions.
The best known microbiological insect control agents,
at the present, are Bacillus thuringiensis and the virus
Viron/H, a virus effective against members of the genus
Heliothis. Bacillus thuringiensis is the least fastid-
ious and the most simple to produce of the two. However,
it is most sensitive to environmental conditions and is
-------
effective in field triil^ .^ai;.-• ,.-. _.• rp\ liars,
cankerworms, cabbage loopers, ana ,ths_rs Viron, Hi, on
the other hand, is mosr fastidiou- and ve^v difficult
to produce. It is muc.i more stable to envir;nment3l
conditions and has been found to <• e effective against
the cotton bollworm, corn earwor^, tobacic sadworm, and
tomato fruitworm, in pilot-plant applications. Both of •
these agents can be applied in spray or dust formulations
The obvious
the future is
logical answer to insect pest control
in the future is integrated pest control management pro-
grams. Integrated centre 1 -3 ,ne join: utilization of
several suitable technique to eradicate pests or to
maintain their population^, r _ lev* the economic threshold.
Such programs are not ne out have been disregarded to
a large extent in the presence of the very effective
chemical insecticides. We arc currently in a position
such that, both by necessit) and by opportunity, inte-
mu.-t be intuited. Ecologi-
:r.. needed improvements in
lieJT,ion cost.- oz non-
i._ctbCr1 that w, take advantage
• :^, , It cent .evelopments i~
grated pest control prog:
cal problems, insect res.
pest control, and high a]
persistent insecticides,
of alternate control met •- ^, .
attractants, sterility t-.^.^r.j.
cultural procedures, wh; r. :--..
with, or following the a;_
cides, will assist in pr . .. ii
Integrated programs are ;_ .-,.,-,
achieve on a universal ba=i:.
programs will require the ccnu
cultural, chemical and bioiog:
cooperation of all people concern-:a ,'itr. insect contrc^.
CO
/
ult
ana
together
in.-,ecti
, iTilC
used
of
e nece. . a
but d:. ."f _cult to
deveiopir,ent of such
-cnc.vlenge of the ..g
and the
REfcKENCES
1. U.S. Dept. Health, - ^u:,at
of the Secretary's Comriissicn
Relationship to Environmental
Printing Office, Wash. : .2. (
2. National Academy o: ii,a
and Animal Pest Control, ,. .
and Control. Washingtc.
Welfare. Report
cide i and Their
j .
o ve rnment
' _s of P]anv
_se, i est Manage , ~
3. Beroza, Morton.
Scientist. Volume 59,
4. Greer, Francis, Cu
Anderson. The First V
Chemtech, June (1971).
5. Ramsey, Lcssel L.
cides. FDA Papers. F
.. c ->. American
ry
Fc:;, -Stent Pesti-
-------
WHY SOME CHEMICALS FAIL TO CONTROL
Amir A. Badiei, Ph.D.
The success or failure of an attempt at chemical regulation depends
on the ability of the operator to distinguish the factors affecting
pesticidal action and to take advantage of them. Because of the
diversity of chemicals, pests, and environments, however, there is
often insufficient information available to allow firm statements
to be made. It must be realized that variables frequently interact
with each other and in consequence deliberate alteration of one may
not have a simply predictable effect. Nevertheless, an understand-
ing of environment-pest-pesticide interactions and the specification
of some of the parameters controlling field performance is therefore
an essential step towards increasing the reliability and effective-
ness of pesticides.
Resistance; Many experts in pesticidal work consider the phenomenon
of pest resistance to pesticides as one of the biggest problems
posing their profession. This phenomenon has been a real source of
worry since the introduction of DDT and its many companion insecti-
cides. Within 2 years after DDT was available to Government workers
for laboratory tests, a strain of houseflies resistant to it had
been selected. By the late 1940's the reason for the houseflies
resistance to DDT was known. The degradation of DDT to DDE was more
rapid in the resistant insects than in the susceptible insects.
Brown lists 171 species, divided into two general categories of
agriculture and public health, which are now resistant to one or
more insecticides. A 1969 publication raises this number to 224.
The first instance of resistance in the U.S. was noted in 1908,
when the San Jose scale resisted lime-sulfur sprays in certain
orchards of Washington State.
When an insect population develops resistance to a given material,
it is usually cross-resistant to related chemicals. But developed
resistance to DDT, for example, does not necessarily involve a
cross-resistance to cyclodien derivatives or lindane, and vice
versa, and none of these resistances carries a cross-resistance to
organophosphorous compounds. Therefore, in order to contfolthe
resistant population, an insecticide in a different class must be
selected or a different method of control should be used.
-------
Plants can also develop resistance to a pesticide. 2,4-D, the
oldest of the systemic herbicides, was developed only about a
quarter of a century ago. Yet as a result of the widespread use
of this herbicide (about 100 million acres annually), shifts in
weed population are evident. Weeds that are resistant to 2,4-D,
such as the grasses and certain species of broadleaves,are becom-
ing more prevalent. At the same time, the development and spread
of ecotypes and races of "resistant" weed species is becoming
encouraged. For example, it is now possible to grow several
ecotypes of bindweed and to selectively control all but one
ecotype by spraying with 2,4-D. This process of resistance is
comparable to tnat which occurs in insects but it takes longer
in plants for two reasons: (1) Insects may reproduce several
times within a year but plants form seeds only once a year, and
(2) the susceptible plant population is constantly being renewed
by seeds buried in the soil which germinate over long periods of
time.
Specificity: Although many insecticides are effective against a
broad spectrum of insect types, a particular pest species is
often more effectively controlled with certain insecticides than
with others. Some exceptions to this are the systemic insecticides
which may be incorporated in the soil. This is true of some her-
bicides as well.
Whatever specifity a given pesticide possesses usually derives
from its relative ease of entry into the pest and to the active
sites of poisoning. Nicotine was a specific for aphids because
it was a potent contact insecticide and readily penetrated the
nervous system, while Paris green was the choice material for the
Colorado potato beetle because it was a suitable stomach poison.
DDT is particularly effective against houseflies and adult mos-
quitoes because it is a residual insecticide, and against mosquito
larvae and catepillars because its toxicity is caused by contact
as well as stomach action. Many beetles, however, that have heavy
cuticular defenses, require the cyclodiene derivatives as chemical
control agents on nonedible crops, e.g., the boll weevil on cotton.
The most widely used and best known herbicides are chlorophenoxy
compounds. Characteristic of the group is effectiveness against
many broadleaves and consequent selective use in cereals and
grasses. TCA and dalapon, the chlorinated aliphatic acids are
selective against grasses. Barban, a carbamate herbicide, is
specific against wild oats in spring cereals. The stage of growth
is very critical. The oats must be at about the two-leaf stage
for best results, and the wheat at about the same stage. Oats
become less sensitive as they grow older, but the cereal may be
more severely affected.
Life Cycle and Timing; The development stage of a pest influences
its susceptibility to pesticides. In general, larvae and nymphs
are easier to kill than pupae and adults, and the early instars are
often more susceptible than the later ones. Eggs are usually most
susceptible just before hatching.
Behavior of the insect pest sometimes dictates modifications in
treatment timing. The need for insecticidal treatment against the
European corn borer, for example, is based primarily upon evidence
-------
of leaf feeding by young larvae. At this time the larvae population
feeding in the corn whorls may threaten the crop, but due to natural
mortality, only a fraction of the original larval population may
actually become established as borers and injur the plants. The
treatment, however, is effective only when applied before the larvae
bore into the stalks and become invulnerable to insecticidal control.
Thus, a treatment at this late stage will result in a failure.
In lepidoptera, the damaging stage is larva - control practices are
always aimed at this stage with little effort toward control of
other stages. Early instar larvae are most susceptible to chemical
control. Pupae are often protected in soil and adults seldom feed.
The timing of the treatment is also of prime importance in herbicidal
applications. In general, susceptibility often decreases with age
or maturity. The coast fiddleneck is very sensitive to 2,4-D in the
rosette stage but becomes resistant as soon as the plants start to
flower. Tansy ragwort, a biennial, is moderately susceptible to
2,4-D in the first year. In the second year, when it begins to
flower, it is much more difficult to kill. Unfortunately, in the
first year, it is relatively inconspicuous, in the second year, when
it is conspicuous because of its bright yellow flowers, it is then
recognized as a serious problem but it is too late to spray
effectively.
Plant responses may differ between chemicals also for example,
pepperwort becomes decreasingly susceptible to MCPA as the growing
season progresses, yet shows an increasing susceptibility to
2,4-D until flowering time, followed then by decreased susceptibity.
Generally speaking, plants that grow rapidly - i.e. those that grow
under optimum conditions of adequate moisture, warmth, and nutrients -
are most susceptible. Seedlings of perennial weeds should be treated
within a few days after germination before the plant has begun to
compete seriously with the crop or before it has established an
extensive root system that will enable it to withstand chemical
treatment.
Dosage: Correct dosage is very important, since less than the correct
dosage will surely result in failure to control the pest, and more
than the correct dosage may injure plants or animals or cause
excessive residue. It appears that a sufficient amount of most
chemicals will be lethal, a lesser amount harmful, a still lesser
amount stimulatory, and an even smaller amount of negligible effect.
The chemical or its metabolic products must persist on or in the
pest in a toxic form and in sufficient amount for as long a time as
necessary for the killing action to take place.
Computing dosages requires simple arithmetic. Error usually arises
from the variety of ways in which dosages are given and from
carelessness.
Dosages are often given as a range. Sometimes the treatment is
intended to control two or more species, one of which might inher-
ently be more tolerant of the pesticide than the others. When this
tolerant species is absent from the complex, the lower dosage will
suffice; when the tolerant species is* present, the higher dosage is
necessary.
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Formulations: Treatment effectiveness is much governed by the choice
of formulation. The effectiveness of an insecticide, for example, is
enhanced by a formulation that concentrates the initial deposit of
insecticide at the critical site, or by a formulation that yields
a more persistent residue. To illustrate granular formulations
were invented to carry mosquito larvicides into water covered by
dense foliage that shielded the water from dusts or sprays. Granules
also concentrate insecticides in the whorl of corn where the larvae
of several insects habitually feed. The coarse particles roll down
the corn leaves and are funneled into the throat of the plant whorl.
In both examples, the effective initial deposit is multiplied by
this particular formulation. Herbicides in granular form for soil
application also have several advantages over spray or dust applica-
tions. It is possible to modify the properties of the granules so
that the rate at which the pesticide is released can be controlled.
The elemental makeup of a pesticidal formulation is also important
in the effectiveness of a treatment. The esters of 2,4-D, for
example, are generally considered more toxic to plants than the
amine salts. This greater toxicity is probably due to their compati-
bility with the cuticle and leaf waxes which they may be able to
penetrate more readily. Also, they have greater wetting ability
because of the oil-like nature of the ester. The oil carrier may
aid penetration of the stomates and volatility permits entry of the
vapors through the stomates.
Compatability; Pesticides are often applied in conjunction with
other pesticides, or with plant nutrients and it is important
that the separate ingredients of these multicomponent sprays or
dusts do not reduce the biological efficiency of any of the other
components, i.e., that they are compatible. Incompatibility may
be the result of chemical reaction between the individual compo-
nents of the mixture - either the chemicals themselves or their
formulating agents - or it may be caused physically, as in the
flocculation of suspensions by oil emulsions and in the preferential
adsorption of one toxicant on the carrier of the other. There .are
many examples of chemical interaction: pyrethrum, rotenone, and
- to a lesser extent - DDT, are inactivated by lime sulfur. The
orgonophosphorus insecticides such as parathion, malathion, and
phosdrin are rapidly hydrolyzed by the alkaline bordeaux wetting
agents; a cationic fungicide such as dodine can react with anionic
wetting agents. To aid practical spray application, numerous com-
patibility charts have been prepared by official and commercial
organizations. These charts are invaluable for determining gross
compatibility characteristics but it must be remembered that the
rate and extent -o.f any chemical reaction is a function of the
concentration of reactants and that the property of the formulation
supplements, such as wetting and emulsifying agents, are not usually
considered in the construction of these tables.
Reactions - either chemical or physical adsorption displacement -
involving the s.urface-active agents which stablize the suspension
or emulsions in the tank mixture can destroy the formuation and
therefore the pesticidal properties, of pesticides. •
Environmental Factors:* An invaluable property of an ideal pesticide
would be complete independence of environmental conditions: the
capacity to be fully selective and fully active against pests
-------
environmental conditions do alter effectiveness of pesticides.
The rate at which a pesticide is absorbed into the pest body and
its subsequent translocation and metabolic breakdown are affected
by the temperature. Thus the most effective temperature conditions
for a successful kill are a* high temperature to get the poison
inside the insect followed by low temperatures which slow the rate
of detoxification. Some chemicals (DDT, methoxychlor, and TDK)
are an exception to this rule in that they are most effective
at continual relatively low temperatures. Usually the quick-acting
poisons are more effective at higher temperatures and the slow-
acting poisons at lower temperatures. In herbicidal treatments,
high temperature before and after spraying appears to increase weed
susceptibility and mortality, but supraoptimal temperature may
reduce herbicidal entry by causing wilting, closure of stomates,
and rapid drying of spray deposits.
Rains wash off water-soluble sprays, but many pesticides (insecticides
and fungicides) now in use do not fall into this category. Wind and
rain cause the "weathering" of the less tenacious portions of spray
deposits. The effect of rainfall depends on the quantity of rain
and its timing. In the case of foliage - applied herbicides, for
example, rain during or closely following spraying can reduce or
nullify toxicity. Rain before spraying may increase leaf wettability
and hence susceptibility to a herbicide. Granular lawn herbicides
should be applied to a wet foliage to be more effective.
Sunlight causes breakdown of pesticides for as long as residues
remain exposed. This phenomenon, the disappearance of the chemical
from the surface in regions of high light intensity is termed
photodecomposition. It has been shown that the effectiveness of
many pesticides applied to soils exposed to bright sunlight and
little rainfall might be drastically reduced due to photodecomposi-
tion. The formative and growth responses of plants to light
which in turn affect the performance of a pesticide should also be
kept in mind.
Low relative humidities have a deleterious drying effect on the
fine mists produced in spraying. Penetration might cease with
droplet desiccation.
Many pests are controlled most readily by application of pesticides
to the soil. The consequences of this are that the toxicant may
persist in the soil for periods ranging from a few hours in the case
of fumigants and unstable materials to several years in the case of
residual compounds. Like foliar-applied chemicals performance of
soil-applied chemicals is conditioned on many factors. Adsorption,
leaching, decomposition, and volatility are among these factors.
When one considers all the factors that can influence the response
of pests to pesticides and hence the effectiveness of a pesticide
application, it is perhaps surprising how often pesticidal treatment
is successful.
-------
Treatments, as we all know, occasionally fail to fulfill expectations.
The practice of pest management and control is an art, and herein
lies room for mistakes in judgment and execution. One precaution
however, is to allow sufficient time for maximum effort, and here
familiarity with the chemical is imperative. A nonresidual contact
pesticide causes maximum mortality quickly; a systemic pesticide
may not produce maximum mortality for days, although indication of
probable results is usually visible sooner.
References:
1. Brown, A. W. A., "Insect Resistance," Farm Chemicals, November,
December 1963 and January 1964.
2. Hammerton, J. L., "The Environment and Herbicide Performance,"
Proc. 9th British Weed Control Conference 1968.
3. Hightower, B. G. and D. F. Martin, "Effects of Certain Climatic
Factors on the Toxicites of Several Organic Phosphorus Insecticides,"
J. Econ. Entomology Vol. 51:669-71, 1958.
4. Hoskins, W. M. and A. S. Perry, "The Detoxification of DDT
by Resistant Houseflies and Inhibition of this Process by Piperonyl-
cyclonene," Science III, p. 600, 1950.
5. Lorston, L. H. and C. E. McCoy, "Introduction to Applied
Entomology," 1969.
6. Muzik, T. J. , "Weed Biology and Control," McGraw-Hill Book
Company, 1970.
7. National Academy of Sciences, "Principles of Plant and
Animal Pest Control," Vol. 3, Insect-Pest Management and
Control, 1969.
8. Pfadt, R. E., "Fundamentals of Applied Entomology," The
MacMillan Company, 1962.
9. Terriere, L. C. , "Chemical, Legal, and Biological Aspects of
Pesticides," A Syllabus for Economic Entomology, 1969.
10. Torgeson, D. C. , "Fungicides an Advanced Treatise," Academic
Press, New York and London, 1967.
11. Upchurch, R. P., "Behavior of Herbicides in Soil," Residue
Reviews, Vol. 16:46-85, 1966.
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FEDERAL LEGISLATION - ITS IMPACT ON PESTICIDE SAFETY
Emerson R. Baker, J.D.
A. Occupational Safety and Health Act of 1970 [Public Law 91-596] ; -
An act to assure safe and healthful working conditions for men and
women; by authorizing enforcement of the standards developed under the
Act; by assisting and encouraging the states in their efforts to assure
safe and healthful working conditions; by providing for research, infor-
mation, education, and training in the field of occupational safety and
health; and for other purposes.
Contents:
Section 1.
2.
3.
4.
5.
6.
7.
8.
9.
11 10.
" 11.
11 12.
" 13.
11 14.
" 15.
11 16.
" . 17.
11 18.
19.
11 20.
11 21.
" 22.
" 23.
" 24.
11 25.
" 26.
11 27.
11 28.
Short Title
Congressional findings and purpose
Definitions
Applicability of act
Duties of employers
Occupational safety and health standards
Administration; advisory committee*/^
Inspection, investigations and reports
Citations for violations
Procedures for enforcement
Procedures to counteract imminent dangers
Representation in civil litigation
Confidentiality of trade secrets
Penalties
Variations, tolerances, and exemptions
State jurisdiction and State plans
Federal agency safety programs and responsibilities
Research, training and related activities
National Institute for Occupational Safety and Health
Grants to States; statistics
Audi ts
Annual report
National Commission on State Workmen's Compensation Laws
Economic assistance to small businesses
Additional Assistant Secretary of Labor
Separability
Appropriations
Effective date
B. Federal Environmental Pesticide Control Act of 1971
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Senate Bills
232 - (Prohibits sale or shipment of aldrin, chlordane, DDD/TDE,
dieldrin, endrin, heptachlor, lindane, toxaphene)
272 - (Prohibits sale or shipment of DDT)
660 - "National Pesticide Control and Protection Act"
745 - "Federal Environmental Pesticide Control Act of 1971"
House Bills
26 - (Prohibits importation of certain agricultural commodities to
which pesticides have been applied)
1077
1722
4152 - "Federal Environmental Pesticide Control Act of 1971"
4596
5182
6576
6761
House Committee Print 3 (July 13, 1971)
This document represents current thinking of the House Committee on
Agriculture after hearing testimony from many different individuals.
It varies considerably from H.R. 4152, which was drafted by EPA and
submitted by the administration. Nearly 1,000 pages of testimony
were printed by the House Committee and almost an equal amount by the
Senate Subcommittee on Agricultural Research and General Legislation.
Probably an equal volume of material was presented to the committees
and placed in their files.
Section 1. Short title and table of contents.
Sec. 2. Definitions
(e) Certified pesticide applicator, etc.
Sec. 3. Registration of pesticides.
(d) Classification of pesticides
(1) Classification for general use, restricted use, or
both.
Sec. 4. Use of restricted use pesticide; certified applicators.
(a) Limitation on use.
(b) Certification procedure.
(1) Federal certification.
(2) State certification.
Sec. 5. Permits for experimental use.
(a) Issuance.
(b) Use under permit.
(c) Temporary tolerance level.
d) Studies.
(e) Revocation.
Sec. 6. Cancellation and suspension of registration of pesticides.
Sec. 7. Registration of establishments.
Sec. 8. Books and records.
Sec. 9. Inspection of establishments, etc.
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Sec. 10. Protection of trade secrets, etc.
Sec. 11. Standards applicable to pesticide applicators.
(a) In general.
(b) Separate standards.
Sec. 12. Unlawful acts.
Sec. 13. Stop sale, use, removal; and seizure.
Sec. 14. Penalties.
(b) User or applicator.
Sec. 15. Indemnities.
Sec. 16. Administrative procedure; judicial review.
Sec. 17. Imports and exports.
Sec. 18. Exemption of Federal agencies.
Sec. 19. Disposal and transportation.
(a) Procedures.
Sec. 20. Research and monitoring.
Sec. 21. Solicitation of public comments.
Sec. 22. Delegation and cooperation.
Sec. 23. State cooperation, aid, and training.
Sec. 24. Authority of States and political subdivisions.
Sec. 25. Authority of Administrator.
Sec. 26. Severability.
Sec. 27. Authorization for appropriations.
C. Other Pesticide Related Legislation
1. Poison Prevention Packaging Act of 1970 [Public Law 91-601]
The following information has been extracted from the March 1971
issue of FDA Papers:
"Among the important bills signed into law...during the...91st
Congress was the Poison Prevention Packaging Act of 1970 (P.L.
91-601), which will be administered by FDA. The basic concept
of the legislation is to protect children from accidentally
ingesting toxic substances by requiring safety closures and
other safety packaging.
"FDA has already acted under the Federal Hazardous Substances
Act against certain liquid drain cleaners containing more than
10 percent sodium or potassium hydroxide by publishing a pro-
posal to require child-resistant packaging. Products failing
to comply would be classified as banned hazardous substances.
"The legislation is aimed specifically at protecting children
under five years of age.
"Coverage of the Act extends beyond that of the Federal Hazardous
Substances Act and includes all hazardous substances, economic
poisons, foods, drugs, cosmetics, and household fuels in portable
containers., .(and)... to items customarily stored around the
household even when such products may not be destined for use
around the household.
-------
"The bill authorizes the Secretary of Health, Education, and
Welfare to establish special packaging standards for virtually
all household substances after consultation with a technical
advisory committee.
"One of the major controversies that had arisen over this legis-
lation... related to the exemption permitted for the benefit of
the elderly and handicapped. The Senate, recognizing this con-
tingency, provided that one size of a product could be marketed
in noncomplying packages for this purpose if such packages bore
a label stating that the noncomplying packages are intended
for households without young children.
"Establishment of a technical advisory committee of up to 18
members by the Secretary is mandatory under the Act and consul-
tation with the committee prior to making findings and in estab-
lishing standards is required.
"The legislation provides for accomplishing enforcement by amend-
ing the misbranding sections of the Federal Insecticide, Fungi-
cide and Rodenticide Act; the Federal Food, Drug, and Cosmetic
Act; and the Federal Hazardous Substances Act."
2. Hazardous Materials Transportation Act of 1970 [Public Law 91-458]
3. Federal Food, Drug, and Cosmetic Act
4. State use and application laws and regulations
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PESTICIDE POISONING: A MEDICAL EXAMINER'S VIEW
Joseph H. Davis, M.D. •
The diagnosis of poisoning is usually considered in terms of characteristic
symptoms corroborated by specific laboratory findings. However, the first
step in a diagnosis is to think of the possibility. The next step is to
carry out the necessary investigations. In order to achieve the ultimate
in accuracy in poison death or injury investigation, the physician, or in-
vestigative agency, should possess the following:
1. A high index of suspicion
2. A background knowledge of the community
3. Familiarity with the variables of clinical manifestation
4. Facilities for careful initial and subsequent scene investigation
5. Facilities for prompt use of laboratory testing, bearing in mind
the limitations of such procedures
Only by knowledge of community experience may the physician be alert to the
possibilities of pesticide causing an illness or fatality. In Dade County,
Florida, a ten-year review of over 1000 poison deaths investigated by the
Office of the Medical Examiner has revealed that pesticides comprised approxi-
mately 9.7 per cent of the total of all poison deaths including accidents,
suicides, and homicides. If intentional poison deaths are excluded, leaving
313 accidental cases, pesticides comprised 11.8 per cent of the cases. With
children under 5 years of age, a total of 45 deaths in 10 years, pesticides
comprised 49.0 per cent, 22 cases. This was double the number of deaths due
to medications, the majority of which were salicylates."'
Of all the pesticide deaths and injuries studied in this one community,
organophosphates, usually parathion, were the most common and produced the
greatest number of clinically observed cases.
The clinical manifestations of organophosphate pesticide poisoning are well
described and include miosis (constricted pupils), weakness and collapse,
muscular fasciculations (twitchings), cutis anserina (goose flesh), diaphoresis
(sweating), pulmonary edema, nausea, vomiting and diarrhea. Unfortunately, not
every patient follows a set pattern of clinical response when initially viewed
by the physician. The clinical signs may be confused with encephalitis, brain
injury, hypertensive encephalopathy, pneumonitis, gastroenteritis, asthma, and
congestive heart failure, to name a few.
-------
Clinical laboratory data might confuse the clinician. In a local study of
60 hospitalized parathion cases, one-third has glycosuria in the acute phase
of poisoning. This could lead to a misdiagnosis of diabetes. Leukocytosis
coupled with pulmonary edema could easily lead to a diagnosis of infectious
prteumonitis. Miosis, constriction of the pupils, has been frequently empha-
sized as a diagnostic sign. However, it was noted in only 50 per cent of the
series of hospitalized cases. Another recent review of hospitalized cases
revealed 6 out of 44 who had mydriasis (dilation of the pupils) instead of
miosis.(2)
Specific laboratory tests for organophosphate poisoning may be confusing
unless all circumstances are carefully considered. For example, the bromothymol
blue screening procedure for cholinesterase activity may be "normal" due to
the blood having an initial acid pH or a very high hematocrit. This may lead
to an error in diagnosis in what would otherwise be considered an organo-
phosphate poisoning or death.(2'
Examples of the problems of diagnosis, investigation of circumstances, and
treatment are typified in the following cases:
Case I (63-1713) A 5-year old child developed diarrhea and foaming at
the mouth while playing in the backyard. He was dead on arrival at a nearby
physician's office. Poison was suspected in the form of some palm leaves
with which the child was playing. The postmortem appearance of miotic pupils,
watery foam from the mouth, and rapid onset of symptoms and death indicated
an organophosphate poisoning. Police were directed to search for parathion
which was subsequently found in a whisky bottle from which the child drank
under the mistaken belief that it was eggnog.
Case II (63-1485) This 70-year old vagrant, whose home consisted of a
discarded packing crate, was found dead. Because of the agricultural area
in which he lived, the autopsy study was directed along the lines of organo-
phosphate poisoning with resulting positive results. This type of case could
easily be misdiagnosed in view of the age of the victim, his social status
and the additional fact that he was beginning to decompose.
Case III (61-1854) This 31-year old female was admitted to a hospital
unable to speak due to pulmonary edema. She wrote a note to the nurses indi-
cating that her soft drink had been poisoned. Despite this she was treated
with antibiotics for pneumonia and died 4 hours after admission. Her boy-
friend was charged with murder.
Case IV (62-1602) This 53-year old male became ill while drinking beer
in a saloon. He died in a taxi cab on the way home. Small pupils, coupled
with the fact that he died in association with a saloon, led to an investi-
gation of organophosphate. Parathion was detected. The police arrested a
woman who confessed to putting a drop of 80 per cent parathion into his beer
"just to make him sick."
Case V (64-343) This 16-month old Negro child collapsed to the ground
while playing. Ineffectual small doses of atropine were given. Twitching of
muscles (fasciculations) were treated with Dilantin. Head trauma was suspected.
-------
He died the following morning. The postmortem appearance, small pupils»
pulmonary edema, suggested an organophosphate. Chemical tests for parathion
and its metabolic by-products were negative. Subsequently it was found that
the family used Guthion concentrate as a fly spray in the bedroom of the
child. Empty pesticide containers were being used in profusion throughout
the community as utility cans for water, kerosene, gasoline, garbage, etc.
Case VI (65-2103) This 18-year old male was found unresponsive and
admitted to a hospital with a story of having drunk from a soda pop bottle
containing turpentine. He died 3 hours and 45 minutes after admission. The
stomach contained a chemical having similar characteristics to the contents
of the soft drink bottle. Red cell cholinesterase activity was markedly de-
pressed. The contents of the bottle were found to be Zectran-2E, a carbamate
insecticide obtained from his place of employment.
It was initially assumed, because the family said so, that the material
in the soft drink bottle was turpentine. A significant part of the initial
determination of the type of poison is a scene search and knowledgeable in-
terrogation of witnesses. This is difficult to do on an emergency basis in
view of the usual lack of community facilities for this type of investigation.
Case VII (Ace. 61) A small child was admitted to a hospital. The physi-
cians suspected poisoning but ruled out pesticides because the family acknow-
ledged only that the house had been fumigated. Subsequently it was found that
the "fumigation" consisted of having an unlicensed door-to-door "structural
pest control operator" sprinkle "roach powder" in the home. The physician had
assumed that fumigation meant the classical tent fumigations. The family
thought the word meant what had occurred in its home the day before. Fortu-
nately the father had enough concern to bring some of the powder to the labora-
tory where it was immediately determined to be parathion. The physicians were
alerted, and energetic therapy with atropine and PAM led to a speedy recovery.
Case VIII (66-924) This small child was found playing with some powder
obtained from a container marked D-Con whose label indicated it to contain
0.023 per cent warfarin. A physician called on the telephone, assumed the
label to be correct and advised no therapy was needed. The child died. In
view of the circumstances the death was erroneously certified as being due
to warfarin poisoning. With subsequent interest in civil litigation the
body was exhumed and transported to a distant medical examiner laboratory for
study. Material from the container as well as from the embalmed body revealed
parathion. In this case the source of confusion was due to the substitution
of one insecticide for another.
Case IX (Ace. 68) This man was admitted to a hospital and stated that
he had been poisoned. He had dilated pupils. A physician commenced treat-
ment for organophosphate poisoning. Initial chemical tests were confusing
due to the presentation of late stomach washings to the laboratory, rather
than the initial stomach content. Energetic therapy over a period of several
days, coupled with an equally energetic epidemiological background investiga-
tion, led to the proper solution of the case. The victim had drunk approxi-
mately 2 ounces of concentrated Guthion shortly before admission to the hospital
-------
Case X (Ace. 59) Moonshine still operators have found that pesticide
barrels are useful for fermenting mash.
REFERENCES
1. Davis, Joseph H., The Changing Profile of Fatal Poisonings, Ind.Med. Surg.
36:340-346, May, 1967.
2. Davis, Joseph H., Davies, John E., and Fisk, Arthur J., Occurrence, Diag-
nosis and Treatment of Organophosphate Pesticide Poisoning in Man,
Biological^ Effects of Pesticides in Mammalian Systems, New York Academy
of Sciences, To be published.
-------
SAFETY IN TRANSPORT AND STORAGE OF PESTICIDES
James F. Byrne
A discussion of the above topic must necessarily consider pesticide
containers; Department of Transportation regulations; protection of
the public, workers, and environment in handling pesticide spills;
and, finally, manufacturers' assistance to provide such protection.
A discussion on containers should be limited to those designed for
pesticide products which if released would represent an immediate
hazard to human Hfe. The higher the degree of hazard, the more
urgent the problem. Parathions, for instance, are a case for
urgency, whereas DDT or CHLORODANE are not.
Hazardous liquid pesticides are transported in steal containers,
lined and unlined, from one-gallon size up to 55-gallon drums.
Glass, though an excellent container, is fragile and represents a
hazard in itself:. Hazardous pesticides are not kno\m to be pack-
aged in plastic containers.
Failure in steel containers can be grouped in tv/o general areas:
(a) failure due to abuse in handling, and (b) failure due to struc-
tural defects in manufacturing the container. It can also be
stated that the rate of failure attributable to manufacturing
increases as the container gets smaller. Conversely, the rate of
failure attributed to abuse climbs as the container gets larger.
Aside from exposure to a larger volume of product as a result of a
larger container leaking, the knowledge docs exist on how to reduce
these leakers significantly. These failures (leakers) occur
largely through mishandling in loading, transportation, and ware-
housing, which can be reduced through education.
Failure due to manufacturing defects or inadequacies are a serious
problem related to small containers. Despite years of investiga-
tion, the problem still exists in the one-gallon container.
Aluminum, glass, plastics and copolymcrs, combinations, and com-
posites still have not replaced steel pails and manufacturers con-
tinue having difficulty fabricating a one-gallon can without
damaging the lining as well as properly sealing flex spouts.
The Department of Transportation, of course, is concerned over the
transportation of hazardous materials, in particular, on movement
of Class B Poisons with food stuffs, which is banned.
Since special tariff regulations apply to the transport of certain
classifications of poisons, an explanation of these several classes
follows: extremely dangerous poison - Class A, less dangerous
poison - Class B-, tear gases or irritating substances - Class C;
radioactive materials - Class D.
-------
Class A Poisons are listed specifically as to the name and chemical
make-up of the product. Thirteen such poisons are listed by the
tariff. Some materials so classified are Bromacetone, Diphosgene
(Phosgene), Nitrogen Peroxide, and Mustard Gas.
Class C Poisons are those materials, liquid or solid, ''which upon
contact with fire or when exposed to air give off dangerous or
intensely irritating fumes.' Some materials so classified are
Monochloroacetone (stabilized), Tear Gas grenades or candles (with-
out ignition elements or fuses), and Chlorocetophenone.
Radioactive materials are designated as a Class D Poison, however,
the regulations concerning packaging and transportation of radio-
active material differs from the regulations covering toxic materials
and would not pertain herein.
Class B Poisons, to which this discussion is addressed, are described
by the tariff as "those substances, liquid or solid...other than
Class A or Class C Poisons, which are known to be so toxic to man as
to afford a hazard to health during transporting or which, in the
absence of adequate data on human toxicity, are presumed to be toxic
to man on the basis of tests conducted on laboratory animals. If a
product meets any of the lethal dose criteria, it must be classified
as a Class B Poison and carry a flammable "JOT" label. Although prod-
ucts may have the characteristics of a Class B Poison, tariffs
stipulate that the products which meet the requirements to be classi-
fied as more than one class of Dangerous Article, must be labeled with
the classification designating the highest degree of danger. In other
words, the products' flammable aspects take precedence.
Further, with respect to Class B Poisons, a Motor Carrier regulation
specifies that "material marked or known to be poison (Class A or B)
must not be transported in the same vehicle with material known to
be food stuffs, feeds or any edible material intended for consumption
by humans or animals. ' Nothing is said about poisons of less than
Class B potency but still dangerous, or a mixed personal use cargo,
such as clothing. that might be contaminated by Class li Poisons and
also hazardous to the user.
As of December 31, 1970, the Department of Transportation has required
each carrier transporting hazardous materials to report by telephone
to the DOT at the earliest practical moment after an incident in which
as a direct result of hazardous transporting, a person is killed,
hospitalized, property damages exceed $50,000, or a continuing danger
to life exists at the scene of the incident. Transportation regula-
tions include, as well, loading, unloading and temporary storage.
Written reports of such incidents involving highway or railroad
accidents are required of the carrier within 15 days of the discovery
of the incident. Also required are reports of any "unintentional
release of hazardous materials. '
It is obvious from the above that the carrier plays a significant
role in protecting the public from Class B pesticide exposure and
cannot delay reporting and seeking assistance when he has an upset
or discovers a leaking container. Responsible manufacturers of
pesticides provide the necessary warning information of their prod-
ucts being transported.
-------
Safe pesticide storage or "warehousing" is a matter of prime impor-
tance. There are no government rules or regulations on warehousing.
Pesticide manufacturers as well as the National Agricultural Chem-
icals Association do publish storage guidance with respect to the
several classifications of pesticides. The only general or non-
specific collection of rules for safe pesticide storage, known to
this author, was prepared by Cornell University in Supplement II
of its Northeast Pesticide Information Manual. Chapter V of this
Supplement is quoted as follows: "Rules for safe pesticide storage:
Identify pesticide storage with prominent waterproof signs over each
entrance, including windows if present and on all sides of building.
Keep locked when not in use. Inform police, fire department, and
public health officials in writing of the location and layout of the
storage, types of materials stored, and hazards involved. Leave
phone numbers of persons responsible for storage with fire chief.
Fire companies should map the locations of pesticide chemical stor-
ages in their respective areas. Inform local physicians and hospital
of potential hazards and be sure they know how to treat and that
antidotes are on hand. (The U. S. Public Health's Clinical Handbook
on Economic Poisons should be available.) Antidotes should include
an adequate supply of atropine sulfate and 2-PAM (Protopam chloride).
Post list of chemicals (organophosphates, carbamates, herbicides,
chlorinated hydrocarbons, flammable solvents, etc.) on outside of
building, along with storage plan. Obtain desirable firefighting
equipment, familiarize yourself and your help with its operation.
Be sure it works. Keep pesticide containers, particularly glass,
away from windows and out of sun so they will not be subject to
heat and ignition. Do not store partly empty containers of pesti-
cides containing chlorates. Keep combustibles away from steam
lines and heat. Read label for information on flammability and
store accordingly. Store highly toxic pesticides in one area.
Store herbicides separately from other pesticides to prevent cross-
contamination and to prevent mistakes in choice of material. Dispose
of unlabeled pesticides. Treat them as highly toxic. Keep a quan-
tity of hydrated lime on hand for detoxification of spills."
Major pesticide manufacturers normally provide information on safe
storage and handling as well as on site decontamination kits at
their own and public warehouse locations.
With respect to assistance rendered in the event of a pesticide
spill endangering the general public, workers and the environment,
major manufacturers are, for the most part, prepared to assist imme-
diately on notification of a spill of one of their products. To
better ensure that complete national coverage is provided by all
major manufacturers, the National Agricultural Chemicals Association
has sponsored membership participation in a national network of
trained safety teams, designed to minimize the risk arising from the
accidental spillage or leakage of pesticide chemicals in the Class B
Poison category. This network began operation on March 9, 1970.
More than 38 teams were initially involved in the NACA program known
as the Pesticide Safety Team Network, and many more have since joined.
Each participating company has been assigned one of 10 specific areas
in the United States within which it will act as the Area Coordinator.
The Area Coordinator is notified by Telephone Central, which operates
monitors on a 24-hour basis in Cincinnati, Ohio, reports of any acci-
dent involving a Class B Poison pesticide occurring in his area.
After receiving such an emergency message, the Area Coordinator imme-
diately will attempt to communicate with the manufacturer or producer
of the involved product and agree on a procedure to be followed. The
-------
and advised on what immediate steps to take. If a safety team is
needed, it is dispatched to the scene of the accident by the Area
Coordinator from a roster of teams in his area, or by the manufacturer.
In the first year of operation, 47 cases were handled by the Network, and as
its existence has become better known, reports of spills have increased accordingly
At this point, the question naturally arises as to the purpose and
responsibilities of pesticide decontamination teams. Essentially, a
pesticide team attempts to minimize hazards to people from exposure
to hazardous chemical spills; to minimize damage to plant property
and animal life, to better confine the effect of the immediate inci-
dent by guarding against its extension or the occurrence of secondary
incidents: to provide appropriate coordination and return to normalcy
at the site of the incident; to provide for discriminate release of
information on the incident to avoid undue public speculation and hysteria.
In meeting the above objectives, the teams will recommend to local
authorities that the contaminated area be roped off and confine entry
to those persons who are properly protected. If there is visible
spread of hazardous material, recommend to local authorities to
evacuate all residents in the path of spread and maintain a close
check of wind conditions and direction until the hazard abates.
Recommend prompt medical attention of persons known to have been
exposed or suspected of having been exposed to poisonous materials.
Advise local, state and Federal health authorities of possible
contamination of water supplies, if such a hazard appears to exist.
The teams will then advise local workers on decontamination, removal
and safe disposal of residue, ensuring all the while their personal
protection. As is often the case, the team members will themselves
perform many of the manual chores required in the decontamination process.
No two situations are the same, therefore, the technical ability and maturity
of the individual team member is carefully considered before his assignment.
The team captain, under most circumstances, will be a plant manager at a
pesticide basic manufacturing or formulating plant. He must possess the ability
to make intelligent on-the-spot judgments. He must be able to take charge of an
emergency situation and formulate a plan of action which will insure maximum
safety to the public. He must be willing to carry out the plan and go to any
length necessary to insure himself and any authorities which may become
involved that the situation has been rendered safe.
The following listing of qualifications are considered to be of
utmost importance and essential in the selection of team captains
to meet the high standards which must be established by the PST
Network. First-hand experience working with toxic pesticides prefer-
ably gained from previous and/or present* responsibilities in a plant
or plants manufacturing or formulating Class B Poison pesticides.
Extensive knowledge of the safe handling and operational precautions
of toxic pesticides to be able to give special advice, direction,
and guidance in the case of a spillage incident. Extensive knowledge
of requirements and limitations of protective clothing and equipment
for working with toxic pesticides. Sufficient knowledge of personal
hygiene, signs and symptoms of intoxication by toxic pesticides, and
first aid treatment to insure maximum safety to all persons possibly
exposed to toxic pesticides until such time as a physician is contacted.
The National Agricultural Chemical Association and its participating members
have been gratified by the results of its efforts. Future success should
continue so long as cooperation continues between all interested parties, the
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CALIBRATION OF EQUIPMENT
Robert D. Black
A. Nozzle Types and Uses
There are basically 8 different types of broad-
cast spraying for use with all the spraying and metering
techniques employed in the farm chemical spray field. It
is recommended that all nozzles are designed and fabricated
under quality control methods to assure precise calibration.
Most nozzles are available in a choice of materials to meet
requirements of application. These include brass, aluminum,
stainless steel, and nylon. In addition, it is recommended
that these nozzles be of the material that offers the greatest
resistence to corrosion and erosion relative to the chemical
used.
The 8 methods of broadcast spraying are:
1. Overlapping Boom Spraying Nozzles
a. Tee-jet
b. Flood-jet
c. Vee-jet
2. Ban Spraying Nozzles
a. Even Spray Nozzles
3. Boomless Spraying Nozzles
a. Doc-jet
b. Boom-jet
c. Field-jet
d. Off Center
4. Row crop nozzles
a. Cone-jet
b. Disc type tee-jet
5. Fertilizer and Furaigant Metering and Spraying
Nozzles
a. Vee-jet
b. Tee-jet Flow Regulators
6. Spray Gun Applications
a. Gun-jets
7. Airplane and Helicoptor Spraying Nozzle
a. Diaphragm tee-jet
8. Misblower Nozzles
a. Whirl-jet
b. Disc type tee-jet
-------
B. Manipulations of properly calibrated equipment
(Ibs./ozs./acre-verses nozzle)
1. Graft (will show slides and explain 80°
Tee-jet Nozzles)
C. Determination of accuracy of application.
Because conditions in farm areas vary with each
locality, it is recommended that the individual
follow the directions given by local specialists
from chemical manufacturers, universities, and
the USDA. Also, before applying chemicals, read
the label and follow all safety instructions.
2. Show graphs on useful information.
After useage the spray tip may clog or wear; there-
by resulting in improper, often costly, chemical
application. It is most important to clean your
equipment and spray tips and check the flow rate
before each use.
-------
CAPACITY TABULATIONS BASED ON SPRAYING WATER
Water weighs 8.34 Ibs. per gallon. When spraying solutions are
heavier or lighter than water, multiply tabulated gallonage figure
by factor shown below.
Weight of Solution
7.0 Ibs. per gallon
8.0 Ibs. per gallon
8.34 Ibs. per gallon— WATER
9.0 Ibs. per gallon
10.0 Ibs. per gallon
11.0 Ibs. per gallon
12.0 Ibs. per gallon
Specific
Gravity
.84
.96
1.00
1.08
1.20
1.32
1.44
Conversion
Factori
1.09
1.02
1.00
.96
.91
.87
.83
G.P.A. TABULATIONS FOR BOOM SPRAY NOZZLES
The spacing of nozzles is illustrated and stated in
nozzle tabulations of this catalog. Where spacing of noz:
on a boom is other than listed in the tabulations, multi
the tabulated G.P.A. coverages by one of the follow
conversion factors that applies.
Where Tiblet Arc Bated On 20* Nozzle Spacing
Other Spacing
Conversion Factor
8"
2.5
10'
2
12'
1.67
14'
1.43
16'
1.25
18'
1.11
22'
.91
24'
.83
Where T.blei Are Bated On 40* Nozzle Spacing
Other Spacing
Conversion Factor
28'
1.43
30*
1.33
32'
US
34'
1.18
36'
1.11
38'
1.05
42'
.95
44'
.91
USEFUL FORMULAS
G.P.M. _G.P.A. xM.P.H.xW'
(Per Nozzle) 5940
5940xG.P.M.
M.P.H. x W «
G.P.A. •
*W—Nozzle spacing (in boom spraying)
or spray swath (in boomleia spraying) in
inches.
ABBREVIATIONS
G.P.A.—Gallons per Acre
G.P.M.-Callons per Minute
C.P.H.-Gillons per Hour
M.P.H.-MIIOI per Hour
N.P.T.—Tapered Pipe Thread
P.S.I.—Pounds per Square Inch (gauge pressure)
MISCELLANEOUS CONVERSION FACTO
One Acre—43,560 squire feet
One Mil*-5,2SO feet
On* Gallon-121 fluid euncet
-Iplntt
—4 quartt
One Foot Head—,4J pound* por equar* Inch
25.4 micron*- JOT
TRACTOR SPEEDS
RATES OF FLOW
Speed/MPH
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
S-fl
Time Required in SECONDS to Travel a Distance of:
100 Feet
68
45
34
27
23
20
17
15
14
200 Feet
137
91
68
55
45
39
34
30
27
100 Feet
205
136
102
82
68
58
51
45
41
G P M;
.05
.06
.07
.08
.09
.10
.11
.12
.13
.14
.If
Secondi
To Collect 1 Quart
300
250
214
188
167
150
136
125
115
107
100
G P M
.175
20
.225
.25
JO
.325
.35
.40
.42$
.45
.no
Seconds
To Collect 1 Qusr
86
75
67
60
50
46
43
38
35
»
10
-------
108
i zo" j
KSPACINOH
FLAT
i
I1
1
i
1
' SPRAY
Teejet
rip No.
800067
4.3 GPA
(100 MESH)
8001
£.4 GPA
(100 MESH)
80015
9.7 GPA
(100 MESH)
8002
12.9 GPA
00 MESH)
8003
19 GPA
(SO MESH)
8004
26 GPA
(SO MESH)
8005
32 GPA
(50 MESH)
8006
39 GPA
(SO MESH)
8008
52 GPA
(SO MESH)
8010
64 GPA
8015
97 GPA
Liquid
Pressure
in p.i.i.
20
25
30
40
50
60
20
25
30
40
50
60
20
25
30
40
50
60
20
25
30
" 40
50
60
20
25
30
40
50
60
20
25
30
40
50
60
20
25
30
40
50
60
20
25
30
40
50
60
20
25
30
40
50
60
20
25
30
40
50
60
20
25
30
40
50
60
8020 25
128 GPA Jo
»
Capacity
1 Nozzle
in C.P.M.
.05
.055
.06
.067
.07
.08
.07
.08
.09
.10
.11
.12
.11
.12
.13
.15
.17
.18
.14
.16
.17
.20
.23
.25
.21
.24
.26
.30
.34
.37
.28
.32
.35
.40
.45
.49
.35
.40
.43
.50
.56
.61
.42
.47
.52
.60
.67
.73
.56
.63
.69
.80
.89
.98
.70
.78
.86
1.00
1.11
1.22
1.06
1.23
1.30
1.50
1.67
1.83
1.41
1.58
1.73
2.00
J.2J
GALLONS PER ACRE
2
M.P.H.
7.0
7.8
8.6
9.8
11.0
12.0
10.5
11.8
12.9
H.9
16.7
18.2
15.7
17.5
19.2
22
25
27
21
23
26
30
33
36
32
35
38
45
50
55
43
47
51
59
66
73
53
59
64
74
83
91
63
70
77
89
100
109
84
94
103
119
132
145
105
117
128
148
165
181
157
176
193
222
248
272
209
235
257
297
331
3
M.P.H.
4.7
5.2
5.7
6.6
7.4
8.1
7.1
7.8
8.6
10.0
11.2
12.2
10.5
11.7
12.9
14.9
16.7
18.2
14.0
15.7
17.2
20
22
24
21
23
26
30
33
36
28
31
34
40
44
49
35
39
43
49
55
61
42
47
52
5?
66
73
56
63
69
79
89
97
70
78
86
99
111
121
105
117
129
148
165
181
140
156
171
198
2?l
4
M.P.H.
3.5
3.9
. 4.3
4.9
5.5
6.0
5.3
5.9
. 6.4
7.4
8.3
9.1
7.8
8.8
. 9.7
11.1
12.4
13.6
10.5
11.8
• 12.9
14.8
16.5
18.1
15.7
17.6
19
22
25
27
21
24
•26
30
33
36
26
29
32
37
42
45
31
35
'39
45
50
55
42
47
•52
59
66
73
53
59
64
74
83
91
79
88
97
111
124
136
105
117
•128
149
166
5
M.P.H.
2.8
3.1
3.4
4.0
4.4
4.9
4.3
4.7
5.1
6.0
6.7
7.4
6.3
7.1
7.7
8.9
10.0
10.9
8.4
9.4
10.3
11.8
13.2
14.4
12.6
14.1
15.4
17.8
20
22
16.8
18.7
21
24
27
29
21
23
26
30
33
36
25
28
31
36
40
44
34
37
41
48
53
58
42
47
51
59
66
73
63
71
77
89
100
109
84
94
103
119
1:12
7.5
M.P.H.
1.8
2.1
2.3
2.6
3.0
3.3
2.8
3.1
3.4
4.0
4.5
4.9
4.3
4.7
5.2
6.0
6.7
7.4
5.6
6.3
6.9
7.9
8.8
9.7
8.4
9.4
10.3
11.8
13.2
14.4
11.2
12.5
13.7
15.8
17.7
19.4
14.0
15.7
17.2
19.8
22
24
16.9
18.7
21
24
27
29
22
25
27
32
35
39
28
31
34
40
44
49
42
47
52
59
67
73
56
63
69
79
it
10
M.P.H.
1.4
1.6
1.7
2.0
2.2
2.5
2.2
2.4
2.6
3.0
3.4
3.7
3.2
3.6
3.9
4.5
5.0
5.5
4.2
4.7
5.2
5.9
6.6
7.2
6.3
7.1
7.7
8.9
10.0
10.9
8.4
9.4
10.3
11.9
13.3
14.6
10.5
11.7
12.9
14.9
166
18.2
12.6
14.1
15.5
17.8
20
22
17
19
21
24'
27
29
21
24
26
30
33
36
32
35
39
45
50
55
42
47
51
,59
60
-------
Addendum
Study Book for the Training Course
SAFETY AND PESTICIDE USAGE
1971
Table of Contents
Hazards Associated with Different Methods of Application 1C
W. E. Yates and N. A. Akesson
*Safe Use of Pesticides in Structural Pest Control 12
P. Spear
Evaluation of Pesticide Applications i;
N. A. Akesson and W. E. Yates
Herbicides—What We Know, What We Need to Know and Where We are Going 1:
V. H. Freed
Equipment Maintenance:
Operational and Maintenance Requirements of Respiratory Protective Apparatus
for Pesticide Users 1
S. E. Law
Pesticide Equipment Maintenance
H. B. Goolsby ]
Equipment Maintenance--Rinsing and Washing for Environmental Integrity 1
C. E. Rice
*See enclosed Service Letter 1249 of the National Pest Control Association - Good
Practice Statements.
ENVIRONMENTAL PROTECTION AGENCY
Petticidet Programs
Division of Ptsticid* Community Studies
-------
ADDENDUM TO FACULTY LISTING:
* Henry Johnson, Research Chemist
Ultimate Disposal Branch
Toxic Materials, Waste Management
Office, EPA
5555 Ridge Ave.
Cincinnati, Ohio 45213
Harold B. Goolsby, Extension Engineer
Department of Agricultural Engineering
University of Georgia
College of Agriculture
Athens, Ga. 30601
S. Edward Law, Ph.D.
Department of Agricultural Engineering
University of Georgia
College of Agriculture
Athens, Ga. 30601
Charles E. Rice, Ph.D.
Department of Agricultural Engineering
University of Georgia
College of Agriculture
Athens, Ga. 30601
* Mr. Johnson replaced L. P. Wallace, Ph.D., on the program.
ERRATA:
1) Page 6, Table #1, should read:
Sales in thousands of pounds
1968 130 318 511 960
1969 124 311 493 929
2) Page 29, Example: Make 96 gallons of chlordane...
Gallons chlordane 8 Ib/gal E.G. to use = 8^Q^X'5 = .5 gal
3) Page 100, reference No.2 should read:
2. Davis, Joseph H., Davies, John E., and Fisk, Arthur J.: Occurrence,
Diagnosis, and Treatment of Organophosphate Pesticide Poisoning in Man,
Biological Effects of Pesticides in Mammalian Systems Monograph in Ann.
N.Y. Acad. Sci.. 160 (1): 383-392, June 23, 1969.
4) Page 102, paragraph beginning with"dass B Poisons...," 8th line, "ICC" should
read "DOT."
vi ii
-------
HAZARDS ASSOCIATED WITH DIFFERENT METHODS
OF APPLICATION
W. E. Yates and N. B. Akesson
Pollution of pesticides in our biosphere has resulted in wide-
spread public concern during recent years. The magnitude of the problem
has increased tremendously during the past decade due to the development
and expanded use of synthetic organic pesticides. In the period 1964 to
1967, the U. S. sales of synthetic pesticides rose from 6.9xl08 Ib. to
nearly 9xl08 Ib. California accounts for approximately 20% of the total
U. S. pesticide useage. From 1964 to 1969 the area treated by licensed
pest control operators in California increased from 8.4 to 13.1 million
acres with aircraft operators accounting for over 75% of this acreage.
If the estimated area treated by California farmers is added to the
above figure for 1969, the total area treated would be 17.9 million
acres.
Although there are many routes by which pesticides pollute the
environment, one of the major routes is through the air. For example,
the Panel on Monitoring Persistent Pesticides in the Marine Environment
by the National Research Council Committee on Oceanography (1) concluded
"It is at least plausible that the atmosphere is the major route for
transfer of DDT residues into the oceans." The panel estimated that
26,000 tons of DDT residues (25 percent of the annual production) enters
the air by drift when pesticides are applied and vaporize from water,
plant or soil surfaces. They further concluded that the residues in the
air may travel great distances before they eventually fall into the sea,
are washed out by rain or precipitated as dry particles.
This paper discusses the major factors affecting the drift or move-
ment of pesticides in the air to nearby nontarget areas as a result of
pesticide applications. A potential hazard exists during every spray
or dust application since current techniques releases a certain fraction
of material as fine particles or gases of the pesticide formulation dir-
ectly into the atmosphere. The inhalation of gases and fine particles
of pesticides as well as collection of larger particles on exposed skin
and on clothing poses a potential health hazard, particularly to appli-
cation crew, to farm workers or others nearby. Large area applications
may produce enough aerosols during certain stable atmospheric conditions
to significantly contaminate areas within several miles or possibly with-
-------
no
in a given air basin. The drift of pesticides onto edible crops near
harvest times and into water and soil resources poses a health hazard
as a direct contamination of our food and water supply or indirectly
through the contamination of our meat or milk supplies. Also low
levels of drift residues may have serious long term effects on wild
life, agri-eco systems, and estuarine food chain. To protect the con-
sumer each pesticide is registered with a specific tolerance or maxi-
mum limit on specified foods and feed products that go to market. For
example, the tolerance for Parathion on dry alfalfa is 1.0 ppm. Since
this is an extremely small level to visualize it may be more graphic
to state that this is equal to the distribution of one tablespoon of
technical Parathion distribution over 10 acres. As another illustration
of the potential drift hazard, consider the treatment of a cotton field
with an equal size alfalfa field adjoining it on the downwind side. In
this case, if 99.8% of the spray remained on the target crop, the re-
maining 0.2% of the pesticide would represent enough Parathion to con-
taminate an equal area of alfalfa to a level of 1.0 ppm.
Specific research on the drift and deposit of pesticide chemicals
have been conducted by our group at the University of California, Davis,
with support in part by PHS grants during the past 10 years. Results from
this program have been reported in numerous publications (2,3,4,5,6).
Fig. 1 illustrates the general field layout for the drift experiments.
Most of the aircraft applications were made with a Stearman aircraft
flown 1-5 feet above crop level. Each spray mixture contained a tracer
or a pesticide material. Six to eight passes were made over a single
marked course at least 1/2 mile long and oriented perpendicular to the
wind. Drift fallout samples were collected on Mylar sheets placed near
the top of the crop. The air burden was assessed at strategic locations
with high volume Staplex air samplers and the particle size measure from
collections with Unico cascade impactors. All deposits were corrected
to a common basis of micrograms per square foot per pass and for an equiv-
alent of 1 pound active material released in 1320 ft. of travel.
Figure 2. illustrates typical results of drift recoveries plotted on
log-log axis. As shown, the fallout residues drop very rapidly and at a
distance of 1 mile downwind are approximately 1/10,000 the concentration
under the aircraft. Figure 2 also shows that at a distance of 1 mile down-
wind the concentration of material collected by the air samplers was over
100 times as much as the fallout at that distance.
This paper summarizes the'basic effects of the following five phys-
ical factors on the potential drift hazards; (a) Type of application
equipment and operating techniques, (b) Nozzle types and operating con-
ditions, (c) Physical properties of the formulation, (d) Microweather
factors, and (e) Field size and dosage.
-------
TYPE OF APPLICATION EQUIPMENT
The type of application equipment plays a significant role with
respect to the number, size, velocity and location of particles re-
leased in the atmosphere. For example, fixed wing aircraft produce
characteristic wing tip vortices that have a major affect on the
movement of fine particles released from an aircraft. Theoretically,
for a simplified rectangular spanwise loading of a wing the circula-
tion is proportional to the weight of the aircraft and inversely pro-
portional to the aircraft velocity. A few years ago a study was con-
ducted to measure the effect of air currents on fine particles released
at various locations on an aircraft. Motion-picture cameras were used
to record the trajectories of small gravitationally balanced balloons
released from cages along the boom on the aircraft. Figure 3 illus-
trates the trajectories and velocity of balloons released from a high
wing monoplane. To avoid severe entrainment of fine particles in the
vortices, nozzles should not be located near the wing tips. A heli-
copter produces a similar wake behind its rotary wing. The major dif-
ference is that it is capable of flying at a lower forward speed and
can consequently produce stronger circulation patterns. Figure 4 illus-
trates the theoretical velocity field while Figure 5 shows the velocity
and trajectories of balloons released from a Bell helicopter operating
at a 15 mph forward speed. It is obvious that the circulation is
stronger than that produced by a fixed wing aircraft. Thus, it is par-
ticularly important that the nozzles be located as far forward as
practical and only in the central area in order to reduce the amount
of fine particles that may be entrained in the vortices.
Air blast ground sprayers are frequently used for orchard appli-
cations and may produce an initial air velocity of over 100 mph near
the machine. If fine spray particles are introduced into the air
curtain a serious amount of material may be carried well above the
tree level and likewise drift a significant distance downwind. Ground
boom type or broadcast type sprayers have a potential of producing a
minimum amount of drift since the vehicle doesn't produce any vertical
air currents. However, it should be recognized that if a very fine
spray is used, the terminal velocity may be extremely low and conse-
quently the atmospheric wind velocity and turbulence may produce sig-
nificant drift residues downwind. However, Figure 6 illustrates the
potential reduction in drift residues with the use of a large drop size
emitted from a ground broadcast sprayer. As shown the ground sprayer
produced 1/6 to 1/10 the spray residue of an aircraft sprayer.
NOZZLE TYPES
The particle size distribution is one of the major factors influ-
encing the potential drift residue hazard. The basic problem is that
presently available nozzles suitable for agricultural sprayers produce
-------
a wide spectrum of drop sizes. Figure 7 illustrates typical hydraulic
nozzles used for pesticide applications. From left to right, the first
is a simple circular orifice or jet used on aircraft to produce a large
droplet size, the second and third are two types of hollow cone nozzles
commonly used for aircraft applications, the fourth, is an eliptical
orifice that produces a flat fan pattern frequently used on ground
sprayers, and the last nozzle is a bi-fluid (atr and liquid) nozzle
commonly used to produce a very fine or coarse aerosol spray at very
low flow rates.
Figure 8 shows the drop size distributions for various types of
nozzles. The curves reveal that a wide range of different drop size
spectrums can be selected for special requirements. However, it should
be noted that the slope of all spectrums are similar which means the
uniformity or coefficient of variation is nearly the same for all nozzle
types. Drift could be significantly reduced if an atomizer was avail-
able that could eliminate or reduce the percent of drops less than 100
microns. One recent development that looks promising is the use of
small nonturbulent jet stream atomizers. A system developed by Amchem
Products Inc., called the MicrofoilTM utilizes over 3000 needles with
a 0.013 inch ID for use on a helicopter. With the jets directed back
and in line with the relative air velocity a very uniform drop size of
approximately 800 microns is produced. Figure 9 shows the very signi-
ficant reduction in spray drift fallout that can be achieved with this
system operating at a forward speed of less than 60 mph on a helicopter.
It should also be noted that the 800 micron droplets aren't stable when
introduced into a 100 mph airstream of a fixed wing aircraft. Conse-
quently, the drift from the Microfoil and conventional D6 jet are sim-
ilar if used on a fixed wing aircraft.
The maximum stable droplet size for a shock exposure of 100 mph
air velocity is 390 microns. Thus we are currently attempting to develop
a jet stream nozzle system that will produce a uniform drop size of 250
to 300 microns. The system will incorporate a 0.005 inch orifice along
with an electromagnetic oscillator to provide a control of the critical
oscillation of from 6000 to 1000 Hertz. We hope to field test this sys-
tem later this year.
PHYSICAL PROPERTIES OF THE SPRAY FORMULATION
The physical properties of the spray fluid are important variables
that may be utilized to reduce the number of fine particles and also to
control the evaporation rate of the droplets. Numerous adjuvants are
available to modify the viscosity of the spray to reduce the number of
particles. Commercially available materials include; invert emulsions,
water swellable polymers or particulate spray (NORBAK.Dow Chem.Co.),
-------
hydroxyethyl cellulose (VISTIK, Hercules Powder Co.). and thixotropic
gel (DACAGIN, Diamond Alkali Co.). Figure 10 shows a comparison of
drift residues from a conventional normal emulsion application and a
thickened particulate spray. A dramatic reduction in drift is evident,
with approximately 1/7 as much residue for the first few hundred feet
downwind. This is of particular importance in right-of-way applications,
where a sharp cut-off will reduce the brownout zone from herbicide appli-
cations.
The evaporation rate can be controlled by the type of solvent or
carrier used to dilute the toxicant. Although water is frequently used,
fine sprays may require a low volatile carrier to achieve satisfactory
recoveries in the target area. It should also be recognized that the use
of a lower volatile carrier may also increase fallout recoveries in the
immediate downwind area. Figure 11 shows a direct comparison of the
drift fallout residues from an application with a normal oil in water
emulsion and an application with 100% diesel oil. The greatest difference
in fallout occurred at approximately 1000 ft. downwind with the drift from
the diesel oil application producing more than 4 times as much residue as
the normal emulsion application.
MI CROWEATHER FACTORS
The field drift tests have shown that one of the most important fac-
tors affecting drift residues is the atmospheric turbulence or stability.
Further, it has been found that the stability ratio is a convenient in-
dex of atmospheric conditions that can be related directly to drift fall-
out residues. The stability ratio is defined as:
Stability Ratio = 32_9 8 105
IT
where T is the air temperature in degrees Celsius at 32 and 8 ft. eleva-
tions and U is the mean horizontal wind speed in cm/ sec. at 16 ft. Thus
the temperature gradient with respect to height and the wind velocity are
basic measurements that can be combined to predict the drift fallout
residues.
Table 1
Range of microweather and classification of atmospheric stability
temperature gradient (T32 - Tg) -1.7 to 5.7 degrees p
wind velocity 3.0 to 19.0 mph
-------
114
atmospheric stability stability ratij)
unstable -1.7 to-0.1
neutral -0.1 to 0.1
stable 0.1 to 1.2
very stable 1.2 to 6.0
Table I shows the range of microweather conditions that have occurred
during our tests along with the classification we have used in reference
to different calculated stability ratios. Figure 12 illustrates the im-
portant relationship between the stability ratio and the drift residue
pattern. Although the regression curves of the drift fallout were nearly
the same for the first 100 to 200 feet the curves are quite divergent
and at a 1/2 mile distance the residues were over 13 times as great
during very stable conditions as during neutral conditions.
It should be mentioned that the above results are attributed to
greater vertical mixing during conditions with a lower stability ratio.
Another important factor that may be related to the concentration of
pesticides remaining in the air is the depth of the inversion layer.
We have plans for investigating the vertical profile, (up to several
thousand feet in height) of pesticide contamination and temperature
gradients in an effort to identify the fate of 100% of the material
that is emitted by the pesticide applicator. Figure 13 shows a
typical inversion layer and lapse conditions that varies diurnally
during the summer months in the central California valley.
Another technique that we are investigating is the use of a sigma
meter to directly indicate the standard deviation of wind direction
fluctuations. This may provide a useful field technique for an immed-
iate indication of drift hazards during applications. Figure 14 shows
the response of the sigma meter during very stable (S.R.= 6.0) and
unstable (S.R. = -0.7) conditions.
FIELD SIZE AND DOSAGE
Figure 15 illustrates how the exposure to drift increases when the
number of progressive swaths or size of treatment area increases. The
20 swath application (equivalent to 40 acres with a swath width of 33 ft.
and a 1/2 mile field length) indicates that at a distance of 1/4 mile
downwind the residue is 0.34 ppm on dry alfalfa. If the swaths were
doubled to 40, the residue at 1/4 mile goes up to a maximum of 0.6 ppm.,
and at 80 swaths, extrapolated data indicate the residue would mount to
1.0 ppm, or a three-fold increase from the 20 swath to 80 swath appli-
cation. Also, if a field were exposed to the drift of more than one
hazardous chemical or to additional nearby applications, the total of
these are additive.
The above values of contamination in ppm on alfalfa are based upon
a upper 99% confidence limit. This means that,statistically, 99% of the
~ th— yciHii — c '-ruil/H K~ K — Tr-- 4-h« c + a+^/H wall--
-------
11
References
(1) Panel on Monitoring Persistent Pesticides in the Marine Environ-
ment, E. D. Golberg-Ch.; Chlorinated Hydrocarbon in the
Marine Environment, National Research Council Committee on
Oceanography, 1971.
(2) Yates, W. E. and N. B . Akesson, Fluorescent Tracers for Quan-
titative Microresidue Analysis. ASAE Trans. 6(2) 104-107.
(3) Akesson, N. B. , and W. E. Yates. Problems Related to Application
of Agricultural Chemicals and Resulting Drift Residues,
Annual Review of Entomology, 9, 285-318, 1964.
(4) Yates, W. E. , N. B. Akesson and H. H. Coutts, Evaluation of Drift
Residues Resulting from Aerial Applications. Trans, of ASAE
9(3) 389-398, 397, 1966.
(5) Yates, W. E. N. B. Akesson and H. H. Coutts, Drift Hazards Re-
lated to Ultra-Low-Volume and Diluted Sprays Applied by
Agricultural Aircraft. Trans, of ASAE, 10(5) 628-632, 638,
1967.
(6) Yates, W. E. , N. B. Akesson and K. Cheng. Criteria for Mini-
mizing the Hazard of Drift from Aerial Applications. ASAE
Trans. No. 67-155 June, 1967.
This study was supported in part by PHS research grant FD 00261 from
the Consumer Protection and Environmental Health Service, Food and Drug
Administration, Washington, D. C.
-------
116
I
.,.
Spraytd ana 4750 HI * 33 ft //\
9330'
$839'
Micro met
station
J.3JOO'
4990.
Mop of 1968 Drift
Test Area
Conwoy Ranch
Davis, Calif
7S9O
CD Rio Stubl>l»
• B»«ls
t o Sampling Stations
„ 10,090'
Fig. 1 Spray line and downwind sampling locations for drift tests,
DAVIS RUN C
OCT 1966
GROUND FALL OUT
TOTAL AIR BURDEN
\
90 f00 300 1000 5000 IOOOO
DISTANCE DOWNWIND, FEET
-------
51
a
FAIRCUILD - Model 24
B60M L^J
MPl\~ UIGU FLIGW
Fig. 3 Trajectories of hydrogen filled balloons released in wake of
fixed wing aircraft.
BLADE
Z/R
-.2
\ \~*
\T:
Vs
-ID
-1 2
' / \ i
fe~)i i ijffy 1
>-^l^ j j I
^xy y *
1 '
* ? i
1 ' i
^ \<
1 2 .8 .4 0 -.4
Y/R
ADV
fcl
C"
-£
ROTOR RADIUS
\ *
H
-x
n
>'/
/
-1.2
RET.
-------
118
BLLL
15 MPH- UIGVX FLI6WT
Fig. 5 Trajectories of hydrogen filled balloons released in wake of
a helicopter.
10'
81
600
400
200
100
80
60
40
20
S 10
a
.
° ,
.08
06
04
.02
01
TRACER DRIFT
Normal Emuliion
Dry Fldd (Maci)
o Nov 10'61 Ground Application
X Oct. 16'61 Air Application
I Sepl 28'61 Air Application
10 20 40 6080100 200 400600 1000 2000 4000,
DISTANCE, FEET
-------
Fig. 7 Typical hydraulic nozzles used for pesticide applications.
10,000
5,000
I.OOO
50O
100
50
.O745"/go/ Norbok, D8 bock, 2.5% O/W, 65mph,3Opsi
Dffeoct, 2.5% O/W, 65mph, 30psi
D8baclt, 2.5% O/W, lOOmph, SOpsi
D7-45, SOpti wat»r, no air
-46 back, 2.8% O/W. 4Opsi, lOOmph
D6-46ttown, 2.8% O/W, 40psi. lOOmph
M.S., 8000 RPU. IOO% oil,40psi, lOOmph
S.S. 8OO05 45'down, 100% oil.
40p*i, lOOmph
E ISC 2-Fluid, 5p$i oirQwattr, no air
i i i i
J 3 2 5 IO X SO 70 909598
z*
-------
120
I.OOO -
OOI
Fig.
Crop* Noult DropSizt Atrcroff FormuJotion S R V»l mph Dare
VMO %oil »M
06-46 490 u StioriMB EC 2 8
bock
OI3MF 800 /i PoneiM
06-Jct 9OO jj Sttormon
0 15 5 88-2
EC 70 0 09 17 71 -Z
EC 2 8 -0 27 12 68-5
OI3MF 8OO /I Helicopter EC 2 8 52 54 69-5
500 IOOO
FEE T DOWNWIND
9 Effect of nozzle types on drift
residues.
5.5. D6-46, back
2.8% O/W Emulsion
S.ft.= 0.2
5O IOO 5OO IOOO 5OOO
Distance downwind- feet
Fig. 10 Effect of a water-swell able
polymer (Norbak) on drift residues.
IOOO —
5OO
too
I
0.5
D6-46. BACK
— fOO% Oil (D*9d) O.ll Jur»66',D
2.8% O/W «MN/AKOT O.O8 Jun*66',C
Fig. 11 Effect of controlling rate of spray
evaporation on drift residues.
-------
IOOO
500
too
50
I
IO
I
0.5
O.I
D6-46 Back, 2.8 % Oil
S.ff. M.PH. AT
— 3.23 4.2 3.9'F Oct. 66'0
-O.OI 13.3 O.O'F Oct.66'A
5O K)O 2OO 500 IOOO 200O 50OO
DISTANCE DOWNWIND, FEET
Fig. 12 Effect of very stable and nearly neutral conditions on drift residues,
k.
6000
§
o
DAVIS, CALIF., July 13, 1965
-—8-45 PST
— -I--45 PST
&y N
s
i i
50 60 7O 8O 90
TEMPERATURE, °F
Fig. 13 Typical atmospheric temperature inversion and lapse conditions durina
-------
122
10
(A
0)
2>
o>
STABLE CONDITIONS
(S.R.«6)
UNSTABLE CONDITIONS
(S.R. «-0.7)
10
TIME (minutes)
15
20
Fig. 14 Standard deviation of the variation of the elevation angle with a 30-second
sample time for two weather conditions.
10.0
s: 5.0
a.
CO
_ 1.0
CO
LU
a: 0.5
0.1
1 Ib/acre
420 u vmd
Stable ; S.R. 0.1 to 1.2
99% C.L.
• 80 Swaths
40 Swaths
20 Swaths
I
100 500 1000
DISTANCE.FEET
Fig. 15 Upper 99% confidence limits on the-cumulative residues that could be expected
alfalfa fr\v H-i f f« *>'»«+• cii^e r\f +v>~*+ -»«•*• •*<*~nf:
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123
Service Letter
National F^est Control Association
A NON-PROFIT MEMBERSHIP ASSOCIATION
GOOD PRACTICE STATEMENTS
THE BUETTNER BUILDING
250 WEST IERSEY STREET
ELIZABETH, N. J. 07207
201-354-3738
NUMBE
124£
DATE
3/18/'
Good Practice Statements of the National Pest Control Association
are officially adopted documents which provide practical guidelines
to safe and effective pest control work. They are developed by
committees and undergo careful review by experts and by the
general membership of the Association so as to reflect the best
current knowledge and skills of the Pest Control Industry.
The significance of Good Practice Statements is indicated by
the following statement accepted by the Board of Directors in 1969:
"Good Practice Statements of the National Pest
Control Association describe activities of a prudent,
well-informed pest control operator. They are in-
tended to guide:
the Pest Control Industry as to what members
of NPCA consider generally acceptable as a
safe and effective practice;
the Public as to the service they may reason-
ably expect from members;
the Association if it asks a member to justify
departure from generally accepted practice when
such departure endangers persons, property or
the Industry image."
The Good Practice Statements are guidelines - not standards.
They are for guidance - not for enforcement. An important
reason that our Good Practice Statements are not standards is
that pest problems are not standardized. If an unusual pest
problem is encountered, a PCO may deviate from the details
of the Good Practice Statement if he is able to take adequate
safeguards to protect the public, property and the environment.
The operator's experience should enable him to determine the
needed additional safeguards and to justify their adequacy.
(Over)
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124
(Service Letter 1249 - Page No. 2)
NPCA's Good Practice Statements should be incorporated
into every pest control company's operations. They should be-
come an essential element in servicemen's training programs.
In both cases they will need to be used in conjunction with other
related and reliable sources of information -such as NPCA Technical
Releases. PCO's expanding the scope of their operations will
find Good Practice Statements as valuable guides based on the
experience of veteran, knowledgeable workers.
There will be numerous uses for Good Practice Statements
in informing the public and various official agencies concerning
acceptable procedures in pest control. Distribution to firms out-
side the NPCA membership is encouraged. As indicated on the
attached order form the non-member price is $6.00, while the
price to members is $3.00.
We believe that the importance of NPCA's Good Practice
Statements will increase as they become known and used. It is
anticipated that there will be increased pressure from within and
without the industry to comply with good practice. As their
importance grows, members and outsiders as well will give
greater weight to them. An expected result is that existing
statements as well as those under development will receive
increasingly careful review. As new information, equipment
or skills become available, existing statements can be revised
to reflect current Good Practice.
-------
ORDER FORM
1971 COMPILATION, NPCA GOOD PRACTICE STATEMENTS
The 1971 Compilation of Good Practice Statements contains
the 17 statements listed on the reverse side of this sheet, plus
an Introduction and Table of Contents. They are attractively
bound in a plastic-covered Duo-Tang binder into which additional
statements can be inserted as they become available. The price
is $3.00 per copy to members of NPCA and Public Agencies
engaged in regulatory, educational or research activities related
to pest control. For others the price is $6.00.
Ordered by: Name
Firm
Address
City and State
Copies at per copy. Total $
Complete and send to:
National Pest Control Association
P. O, Box 586
Elizabeth, New Jersey 07207
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126
NPCA GOOD PRACTICE STATEMENTS
TABLE OF CONTENTS
NUMBER
Fogging
Thermal Fogging of Insecticides Indoors TR 21-70
Fumigation
Fumigation TR 23-63
Tarpaulin Fumigation TR 1-67
Vehicle Fumigation TR 22-68
Insect Control
German Cockroach Control in Residences TR 1-71
Labeling
Labeling Service Containers for Pesticides TR 15-66
Rodenticides, use by PCO's
\
Anticoagulant TR 22-70
Antu TR 24-70
Arsenic Trioxide TR 3-71
DDT TR 25-70
Phosphorus TR 6-71
Red Squill TR 23-70
Sodium Fluoroacetate TR 19-70
Strychnine TR 5-71
Zinc Phosphide TR 2-71
Termite Control
Preconstruction Soil Treatment TR 8-65
Use of Chlorinated Hydrocarbon
Insecticides in Subterranean
Termite Control TR 20-70
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EVALUATION OF PESTICIDE APPLICATIONS
Norman B. Akesson and Wesley E. Yates
The use of various pesticide chemicals, and pathogens to control weeds,
insects and plant disease as well as application of defoliants, fertilizers
and trace nutrients constitutes a highly complex practice, and a significant
factor affecting the total system of agricultural, forest, and rangeland
culture and ecology. The effect on the immediate environment surrounding
the area of application, or in the areas that are a part of the air and
water basin systems involved, can be examined and in many instances the
effects of chemicals on the non-target crops and on human and animal habitat
have been drastic and dramatic. But the effects on the more distant or total
environment, which includes the wildlife areas, is not easily examined and
little if any reliable data exists on the extent and damage done to this over-
all environment by the use of various plant protection, pesticides and nutri-
tion chemicals.
A great deal of speculation has been made with regard to pesticide pollution
of the air, water and soil systems, and including global dispersion; but
good data on the actual numerical losses of these materials from the fields
and areas being treated during the following specific treatments is lacking.
Observers have indicated these losses may vary from 5 percent to as high as
70 percent, but depending primarily on particle size and formulation of the
applied material and weather factors at the time of application.
The basic purpose of most of the applications being made is for either plant
protection or nutrition. Along with the question being raised about the
losses to the environment is a basic question of the efficiency and dosage
requirements to control specific weed, disease and insect pests, and how this
efficiency can be improved. The materials used include the great variety of
pesticide chemicals, certain plant materials such as pyrethrum and rotenone,
as well as the more recently available pathogens, such as bacilli and viruses.
In addition, the basic fertilizer chemicals, nitrogen, phosphorus and potassium
as well as a host of trace nutrients, can and have become contaminants in
differing degrees.
Thus, the type of material, the extent of its use, and its specific effects on
sensitive organisms determines not only the fundamental use being made of the
material but also its potential hazard as a contaminant. The basic toxicity
to the animals and plants which it could possibly contact as well as its effec-
tiveness and requirements or modes of action on the target organisms will not
only control which material is to be used, but also indicates the relative
hazard of use and safety precautions that need to be followed when it is applied,
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128
The concerns expressed over large scale environmental pollution caused by
agricultural chemicals have come from wildlife and conservation-minded forces.
Of much greater impact on the local agricultural, forest or rangeland com-
munity is the immediate damage done to crops, ornamental and esthetic planting,
by actual plant destruction or disfigurement, and to contamination of foods
and feeds by unwanted and illegal residues on edible portions. These damages
are generally within the community concerned and do not become a rallying
point for the conservation interests. However, they do result in widespread
damages and frequently in lawsuits where farmer A sues farmer B, his appli-
cator and the chemical company producing the material, for losses sustained
either through direct crop damage or from seizure of crops due to illegal
residue. A more subtle form of widespread damage characterized by the troubles
with cotton insect control over most of the world has been the result of the
increased use of broad spectrum insecticides which knock out predator and
parasites in cotton that would normally provide protection from economic in-
sects. Thus, excessive and sometimes careless use, as well as poor techniques
of application have resulted in actual crop reverses and even the abandonment
of cotton culture in certain areas. However, it must be pointed out that
newer practices such as integrated control where reduction and withholding of
early chemical treatments are advocated will quickly help to restore the
normal insect population and make possible rational cotton insect control
programs.
Operajbional Responsibi 1 ities
The primary base of discussion, inasfar as application of agricultural chemi-
cals is concerned, must start by identifying the chain of responsibility and
the roles played by each group in relation to the overall crop, chemical,
pest and application problems.
Chemical Manufacturers
The responsibility of the manufacturers starts with his development of the
chemical, the series of tests and data required to obtain registration label-
ing, and finally to the sales and field service representatives who are the
basic advisors to the applicators and farmers on the use of the particular
material and its relation to crops and pests. There is increasing concern
for the obvious conflicts of interest that a chemical salesman has in trying
to objectively evaluate a grower's need and still maintain a brisk sales
program. Thus, we are seeing more restrictions on field people as well as
required licensing of these in some states such as California. The salesman
must not only have knowledge of the chemical, pest and plant complex but
also be able to advise regarding the best means of application. Again a
conflict of interest arises because application techniques which provide
the greatest degree of safe use or least loss hazard are also restrictive
in use, such as: (1) hours of the day or night when they can be applied
safely, (2) limits of particle size dispersed, where coarsest sprays are
safest, but not most effective in control, and (3) formulation restrictions
where granular materials being the safest from a loss viewpoint cannot
always be used due to lack of coverage or contact with plants and pests.
-------
The chemical company field man will have to revise his thinking in terms
of application methods and direct his thoughts more to safe application and
less to control efficiency. In this regard, the farmer and commercial
applicator must also share the burden of decision for chemical safety
which is difficult to do when a crop is in jeopardy from a pest complex.
Commerci al Appli cator
The commercial applicator shares some of the same legal responsibilities
as does the manufacturers, but since he takes the manufacturer's product
and makes the actual application, he takes on that specific responsibility
of safety as well as control efficacy, which again introduces the basic
conflict of interest between these concepts. The commercial applicator is
usually licensed by the state and it is through this license that regulation
of the commercial applicator takes place. If trouble occurs, he will re-
ceive a suspension or loss of license in accord with findings of a State
regulatory office. Thus, because of this and his key position in the appli-
cation, the operator—either ground or aircraft—becomes the most significant
person in the application picture and must be knowledgeable and prepared to
consider all facets of his job, particularly the hazards not only to his
pilots and handling crew but to nearby crops and to the overall environment.
Farmer or Crop Advisor
The grower and his representatives, foremen, advisors and crop consultants
are also part of the legally responsible chain along with the operator and
chemical manufacturer. But here the conflict between use efficacy and loss
hazards, as well as worker safety, come into sharpest conflict. The farmer
must protect his crop and to do so will frequently demand application
practices from the operator and chemical men that can and do lead to damages,
lawsuits and financial disasters, not to mention over-reactive regulations
enforced by state agencies who are held accountable to legislative bodies
for the misuse of pesticides by the farmer.
It should be evident from this analysis of the viewpoints of the three
principal groups involved that further licensing and other qualification
regulation, as well as specific application control, will likely be seen
at all levels of chemical use since competitive practices both in growing
crops and selling chemicals virtually make it impossible for these people
to regulate themselves.
Application^ Techniques and Machines
The machines and methods used to apply crop protection materials can be
reviewed in brief, with consideration for factors of safety in use as well
as effective pest control. Since the physical/chemical formulation greatly
alters the application machine, it would be well to first examine the
various alternatives in this area.
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130
Formulations
Formulations or physical forms of the chemical materials have evolved over
the many years of use and in general consist of (1) dry materials as dusts
and granules (Table I) and (2) liquids as solutions, suspensions or emulsions
with a wide range of basic particle size generated at the time of application
of the liquids. This may range from aerosols to very coarse sprays as shown
in Tables II and III.
Dry Materials: Dusts and Granu1es
This is a particle size definition and carries the broad identification of
dusts as consisting of particles manufactured to a size range such that 85 to
90% of the particles are under 25y (microns) major diameter, while only a few
percent are above 44y or can be passed through a 325 mesh screen. The granu-
lars range in size from 1 to 6 mm (millimeters) or 1000 to 6000 microns. Con-
siderable differences exist in the mode of action of the various sizes as well
as in the machines used to apply them. Table I gives the sieve size, the
opening size in mm, the average number of particles per pound (and gram) and
the coverage or distribution of these in a ft2 (or m2) basis when 10 pound
(or 1,200 g/ha) are applied. It can quickly be seen that if we are going to
need to contact an immobile insect or fungi on plants, a granular formulation
is not the answer. So we would use a very finely divided dust instead which
has the tremendous coverage potential that the millions of small particles
(under 20y) gives. Granular formulations of translocated chemicals are available and
where useable, constitute a very effective and safe application means.
Spray Materials
Table II presents data on water droplets but would be largely applicable to
solid particles as well, with some changes needed if the particle density
is varied greatly from water. As can be seen in Table II, the terminal
velocities of the particles goes up rapidly as their size is increased. Thus,
up to a 20 micron drop, the terminal velocities are extremely low (less than
4 x 10"2 ft/sec.) and even a 50y drop settles only at 3 inches per second.
However, far more importantly, these are all for still air and in a normal
atmosphere, the air movement as indicated by horizontal and vertical measure-
ment will show that only under unusually quite temperature inversion (warmer
air overhead than at the ground level) condition, is the vertical motion
likely to be less than 3 inches/sec. This means that particles under 50y
(as an arbitrary identified aerosol size) do not settle out under normal atmos-
pheric conditions, and can be transported for considerable distances with any
air motion. Conversely the settling rate of ZOOOy (2mm) size particles, such
as granules, is 21 ft/sec, and settling is very rapid and positive.
Further data 1n Table II indicates the coverage capabilities of small parti-
cles and drops if the spray were all one particle's size range. That this
1s not true in normal atomization, has been pointed out; and in fact, a
spray atomization or grinding process actually produces a normal distribution
of sizes covering a range of perhaps 10 to lOOOy for a given atomizer setting.
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1-
As in the case of *he larger granules, the smaller particles (1000 oz/A or
approx. 7.8 gals/A) show a rapid increase (related to the cube of their dia-
meter) as size is reduced. The last column of Table II is for the air
burden in a depth of 65.6 (20 M) in particles/MJ of air at the particle
size shown, and if the volume of 7.8 gals/acre applied were all atomized
to that stated size. This illustrates the necessity for using very small
drops as aerosol when contact with adult forms, such as flying mosquitoes
is desired. When a given volume of material is used, a reduction of particle
size will result in a vastly improved contact with insects or fungi on plant
surfaces, or with the plants themselves in the case of herbicides.
However, where material is applied to the soil and is worked in, as in the
case for weed control or soil insects and disease control, the fineness of
the material is not as much of concern. Similarly material applied to water,
as in the case of certain rice insect and weed control materials, is dissemi-
nated by the water and control is effective with quite low concentrations of
active chemical, as little as 6 ppm in case of certain insect pests.
The spray materials may be made with as large particles as the granulars,
but a significant difference exists. This is the fact that the dry materials
may be air screened to remove all particles below a certain size. Thus, the
mesh ranges of Table I do specify that a high percent (95 - 98%) of the
material in a 30/60 mesh range will pass a 30 mesh screen and be retained
on a 60 mesh size. When spray materials are made very coarsely (see Fig. 1)
a special low turbulence type nozzle, such as the Microfoil device (regis-
tered by Amchem Corp.) can be used to achieve almost uniform, large drops
of 800 to lOOOy size. However, such a nozzle is limited to the low turbu-
lence wake of a helicopter at less than 60 mph, and as has been pointed out,
when used with a fixed wing aircraft the higher speed tends to break up the
large drops into smaller ones. The lower nozzle of Figure 1 indicates a jet
type device which consists of a simple orifice with no whirl plate or other
spreading mechanism in the jet stream. The drop size produced is of the
order of 600 to 900p VMD (volume median diameter, which is the drop size
that precisely divides the drops produced into two equal halves by volume).
This means that the normal distribution (usually slightly skewed toward the
small drop end) prevails and a wide size range of drops are produced.
Figure II shows two nozzles in a 80-100 mph air stream of a fixed wing
aircraft. Both are hollow cone types which have a whirl plate and chamber
behind the orifice which swirls the spray stream and creates considerable
more break up of drops than what the straight jet does. The nozzle on the
left is directed with the 100 mph airstream and if this were a D6-46* hollow
cone nozzle operated at 40 psi (pounds per in.) the VMD would be around 420y.
The right hand nozzle (the same as the first) is directed across the airstream
at 90 degrees, which causes the spray to be broken into drops of about 300u
VMD.
Drop sizes finer than this may be created by (1) increasing the liquid pres-
sure, (2) decreasing orifice size, or (3) decreasing the whirl plate size
which speeds the whirl and atomizes more thoroughly. However, practical
*The D6-46 hydraulic nozzle designation is Spraying Systems Co. hollow cone
type. 06 stands for 6/64 in. orifice dia. and 46 is an arbitrary designation
Ll 1
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132
limitations control these effects and in order to go below lOOy VMD extra-
ordinary measures need to be taken, such, as twtn-fTuid or other special
powered atomizers. Rotary screen, grid, and gauze type devices have also
been used, but the same lower limit of around lOOy VMD also appears with
these. Table III gives a very rough approximation of the recoveries of
spray in a 1000 ft distance downwind under near neutral (no strong inver-
sion or strong turbulence) conditions of weather. As can be seen, the
amount lost from a field being treated (to 1000 ft downwind) can be as high
as 85% when a highly transportable aerosol of less than 50p VMD is applied
by aircraft at 10 ft. altitude. However, when the Microfoil boom is used,
the recovery can be as high as 99% of the released spray. The drop size
ranges in between represent the need to balance the requirement for coverage
with the losses by drift that would occur. For example, because of the in-
creasing difficulty in confining the sprays to the fields being treated, the
University of California pest control recommendations do not advise drop
sizes smaller than 300y VMD as produced by a D6-46 nozzle directed 90 degrees
to the airstream and operated from a fixed wing agricultural aircraft using
at 40 psi liquid pressure.
Ground Equipment
The discussion thus far has centered on use of aircraft principally because
in California, the use of agriculture, forest, range-land and vector control
probably averages out with aircraft applying 75 to 85% of all materials
applied commercially. Of this, the helicopters constitute less than 15%
of all aircraft used in agriculture in California.
Ground equipment is used for orchard spraying and to a limited extent in
field crops, and perhaps to 50 to 60% of the vegetable crop work. A very
few ground rigs are used for rice spraying and a considerable number for
vector control work, particularly in urban and suburban areas.
Ground equipment for dusting has practically disappeared, but a considerable
number of machines are used for distributing or injecting various soil
applied liquids and granulars.
It has been suggested that use of ground equipment would eliminate problems
of drift losses of chemicals during treatment. However, air carrier and
high pressure, fine atomizing hydraulic nozzles on ground rigs can be equally
as guilty of causing air pollution by losses of material as can the aircraft.
The distinct advantage of the ground rig in this case is in its relative un-
obtrusive appearance, not easily spotted by the passersby, and its relatively
low rate of acreage treated or amount of material discharged in a given day.
Refinement of application machines in California would appear to be moving
toward more helicopter use rather than toward ground rigs. While helicopters
cost 1/3 to 1/2 more than a fixed wing aircraft, the helicopter productivity
and ability to work in small fields and also to land close by, puts its pro-
ductivity close to the fixed wing aircraft. In terms of cost per acre
treated, all aircraft at around 2.00/A. (application alone) for a 5 gal/A.
application rate compares very favorably with ground rig costs. This, plus
the ability to fly over irrigation checks, ditches and even the crop itself,
-------
13
plus the rapidity of treatment, as much as 200 A/hr of usual agricultural
work, gives a sharp competitive edge to aircraft use. Tests of helicopter
use in orchards and vines show that at low speeds (under 20 mph) the
effectiveness of coverage can be adequate for many control problems, parti-
cularly of fungi as dormant period sprays. Precision of application with the
helicopter makes the machine more competitive with ground equipment rather
than with fixed wing aircraft.
Spray Additive
Aside from the wide variety of emulsifiers, stickers and spreaders used in
spray formulations to obtain better contact and greater persistence of deposit,
there have been many materials introduced into the spray formulation for
thickening and thereby causing very large drops to be formed during atomi-
zation. The earliest of these were phase crowded emulsions and since the
discontinuous phase had to be of the order of 85 to 90% of the mixture this
was best achieved by putting water (as a discontinuous phase) into a petroleum
oil as the continuous phase. This is the reverse of the normal w/o emulsion
and is called an invert emulsion, or o/w. This technique while producing very
coarse up to 10,000y VMD drops does not eliminate small drops due to viscosity
reduction under stress when passing through the nozzle. Consequently, these
and other thickening agents, such as cellulose, seaweed and plastics, will
not eliminate small drops causing drift but do cause very large drops to form
thus requiring large applied volumes in order to obtain coverage. However,
for spraying weeds on canals, roadsides and power line rights of way, the
large drops using translocated herbicides are very effective and produce only
low drift levels.
More recently another additive as a form agent has been introduced, which
causes very large drop formation (Fig. 3) of hollow drops. The action of
this formulation is such as to reduce the volume of liquid while maintaining
the bulk collected particle size. If air buoyancy is not too much increased
by the hollow drops, this may offer a logical means to reduce liquid volume
while still maintaining coarse collected drop size.
E1 e c tro-Sta t i c Cha rge
The promise of attracting particles, liquid or dry, to plant surfaces from
the application machine has intrigued researchers for at least 40 years.
Laboratory and closed system studies where atmospheric conditions can be
controlled and distances are limited have shown the tremendous capabilities
of this technique. However, the practicability of these systems has yet to
be proven either by ground or air. A system is presently under study for
aircraft use and has shown considerable promise. However, its success is
related to an initial, very fine (coarse aerosol) spray, and if all of this
is not captured by the charging process, a certain amount of highly trans-
portable spray particles would be released.
Application techniques and machines, along with adherence to safety in use
as a primary objective can spell the difference in continuing the use of
plant protection and nutrition-materials or being forced to reduce and abandon
these in increasing numbers, particularly of the pesticide chemicals. While
-------
134
the farm growers have been able to manage continued crop production under
increasing restriction, it is not being accomplished without changes and
displacement of crops as well as increased costs of production. Since the
three groups involved with pesticide chemicals have almost equal legal
responsibility, it should follow that they should also stand together and
accept the responsibility for supporting better application means which
research now indicates can result in near 100% confinement of materials to
the target fields.
Mesh or MM
Sieve Size Opening
TABLE I
Average Granules
per Ib per gram
10 Ib/A or 11204,g/ha
granules
per ft'
per M'
8/16
16/30
18/35 0
25/50 0
30/60
Terminal
2.36/0.99
0.99/6.465
.749/0.417
.673/0.283
0.52/0.246
Velocities
145xl03
1150xl03
2708xl03
7722xl03
12,500xl03
TABLE
of Water Drops and
to Unit Area
0.32xl03
2.5xl03
6.0xl03
17.0xl03
27.0X103
II
Numbers per Given
and Mr Volume
30
260
620
1770
2820
Volume
323
2800
6674
19050
30355
in Relation
No. of drops at applied rate of 1000 oz/A
(12,000 cc/ha) on flat (7.8 gal/A) surface
In air to depth
Drop Dia.
Microns y
1
5
10
20
50
70
100
150
200
1,500
ft/sec
.OlxlO"2
.25xlO-2
1. xlO"2
4. xlO'2
0.25
0.4
0.9
1.5
7.0
13.
m/sec
.033xlO"3
.76xlQ-3
3.0 xlO'3
12 x 10~3
.076
.12
.27
.46
2.13
4.0
Per in2
9000xl06
716xl06
9xl06
1.1 xlO6
710. xlO2
265. xlO2
90. xlO2
27.1X102
70.
R.R Per ft2
Per cm2
1400xl06
llxlO6
14xl06
17xl06
110. xlO2
41. xlO2
14. xlO2
4.2xl02
11.
1.36
of 65.6 ft.
per cnr* air
7000. OxlO2
SS.OxlO2
7. OxlO2
85
5.1
2.1
0.7
1267
-------
13
TABLE III
Spray Prop Size
General
Description
Aerosols (airborne)
Special Atomizers
Size Range
Microns y _VMD
<50
Fine Sprays - Cone, 120-200
Fan or Rotary
Medium Sprays - Cone 250-300
Coarse Sprays - Cone 400-450
Min. Drift - Jet
L.T.N. (Microfoil
on helicopter)
600-900
800-1000
% est. Recov. in 1000 ft.
ITelease not Swath
Height 10 ft. Neut. Hea.
General Use
35-50
60-75
75-85
85-95
99
Adulticiding Vector
Control; not recom.
for aircraft use.
Large area programs.
Low toxicity material1
low dosage.
Low toxicity Agr. Spr.
demanding best coverai
All Toxic Agr. Sprays
restricted materials.
Translocated, highly
toxic, residual larva
ending in water
Highly toxic herbicidi
as 2,4-D paraquat,
propanil
LESS THAN 60 mph
AIR VELOCITY
VERY COURSE UNIFORM
SIZE SPRAY
80 - 100 mph
COURSE SPRAY
-------
136
80- 100 mph
MEDIUM SPRAY
80-100 mph
FINE SPRAY
Figure 2
.Figure 3
-------
HERBICIDES—WHAT WE KNOW, WHAT WE NEED TO KNOW, AND
WHERE DO WE GO FROM HERE
Virgil H. Freed
Of the chemicals for pest control, those used for control of plants were the
slowest to be developed. This is not at all remarkable in view of the fact
that the problems caused by insects and the crop losses resulting from fungal
disease are much more dramatic than the problems posed by unwanted plant
species. However, as our knowledge developed particularly from the mid-
1940's, the discovery and use of herbicides have grown dramatically. Herbi-
cides now are the number one pest control chemicals having surpassed in-
secticides a few years ago. Appreciable tonnages of a wide variety of
chemicals are now being used as herbicides on crops, right-of-way sterili-
zation, and other purposes.
The effect of common inorganic chemicals on living systems was known even to
the ancients. Chinese, Greek, and Roman writings indicate their awareness
that such things as sulfur and certain of the heavy metals were toxic to
organisms. Far back into antiquity, man of course attempted to apply chemicals
in medicine. It wasn't until the mid-19th century, however, that more systema-
tic studies of the use of chemicals for control of pests were attempted. At
this time, it was demonstrated that compounds known in that day would control
insects, were effective against plant diseases and were capable of killing
unwanted vegetation. In the latter half of the 19th century, particular
attention was directed to the discovery of chemicals capable of controlling
man's insect enemies. Parallel but less intensive efforts were concerned with
fungal diseases of plants.
During the last few years of the 19th century and the beginning years of the
20th century, a few plant scientists engaged in the development of chemical
tools for the control of weeks. Inorganic compounds, such as iron or copper
sulfate, sulfuric acid for selective weed controls, sodium chlorate, the arse-
nicals and borates for non-selective weed control resulted from these early
investigations.
From the period of 1920 to the early 1940's, some attention was given to organic
compounds with the result that such things as petroleum oils and phenols were
discovered and used for weed control. In the mid-1940's came the discovery of
the herbicidal properties of 2,4-D and other phenoxy acetic acids. This
ushered in a whole new era part by intensive search for new and more effective
herbicidal compounds and the value of their application. Today we have as a
result of all that activity a hundred or more highly active and widely used
chemicals, many more whose herbicidal activity is known and occasionally used.
-------
138
A wide variety of different classes of organic compounds show a remarkable
activity against one or more species of plants. Similarly, a number of
organometallic as well as inorganic compounds exhibit valuable herbicidal
activities.
Herbicides are used in a wide variety of ways to achieve control of an un-
wanted vegetation. First there is the use of these materials in crops to
destroy competitive species. Selective control, that is differentiating be-
tween the weed species and crop, takes advantage of a number of factors.
Among these factors are differences in growth habit and morphology of the
plant as well as purely biochemical differences. Advantage may be taken
also of differential location of roots in the soil horizon or ability of
the plant to absorb the chemical.
On the other hand, general control of the vegetation may not be concerned
with differential toxicity to species, often rather the objective will be
control of all types of species in a given area. It is important to note
that very often a chemical, used at a lower rate of application for selective
weed control, when the dosage is increased is able to kill wider range of
species. This, it may be observed, is another example of dose-response re-
lationship that, despite recent assertions to the contrary, seems to be a
valid and widely encountered phenomenon. On the other hand, there are some
chemicals that by virtue of a broad spectrum of activity is toxic to many
commonly encountered species.
General vegetation control may range from control of a single brushy species
to what is termed soil sterilization or complete vegetation control. The
control of a singular or small number of brushy species, is usually accomplished
by foliage application of the phenoxy acetic acids or similar growth regulating
products. Only occasionally is it effected through use of a soil active chemi-
cal. On the other hand, it is often desired to kill all vegetation, as for
example along a right-of-way of a highway or utility or around an industrial
site. To accomplish this, one of the several soil active and persistent
chemicals may be employed. In early days inorganic materials such as sodium
chlorate and arsenic were used but today more reliance is placed on triazines,
ureas and uracils. Depending on the dosage, type of soil, climatic conditions
and species, vegetation control may last anywhere from one to three years.
The variety of chemicals used as herbicides has been mentioned several times.
Inorganic chemicals such as the arsenicals, sodium chlorate and borates, were
indicated as having been developed very early and still enjoy some use. The
organo-arsenicals are the primary representatives of the metalo-organics
employed as herbicides. On the other hand, the purely organic substances cover
a wide range of classes. It starts with the simple petroleum hydrocarbons,
ranges through alkyl acids to a large number of aromatic and heterocyclic com-
pounds. The tables given as an appendix illustrate the wide variety of organics
that are used.
In order not only to use the chemicals most effectively, but to evaluate their
effects and hazards as well, one needs an appreciation of the behavior and fate
of the chemical once applied in the environment. Fortunately, the behavior of
chemicals in the environment and to some extent their fate or persistence can
be interpreted in light of known physico-chemical principles. Thus, having
-------
some knowledge of the properties and chemical reactions of the material, we
are able to predict with some confidence the probable persistence and mobility
of the chemical in the environment and assess its possible hazard to non-
target species.
Before describing some of the principles that are applicable, it is necessary
to discuss the matter of formulating these chemicals.
The formulation or condition of the chemical as it's used often has an important
bearing, particularly during the application operation. Chemicals range in
properties from being gases or liquids to high melting solids. Chemicals also
vary widely in solubility characteristics. Many chemicals, particularly the
salts of compounds and simple molecules are usually soluble in water. Other
chemicals dissolve only in certain types of organic solvents and others show
a resistance to dissolving in almost any solvent. Further chemicals are
markedly different in their vapor characteristics or tendency to change into
gases.
In the application of chemicals, one wants as concentrated amount of chemical
as possible. This makes for ease of handling, cheapness of transportation,
and small volume for storage. Ideally of course one would use the technical
chemical; but because of lack of solubility and difficulty of distribution,
it may not be amenable to distribution in the spray, dust or granular form.
It becomes necessary then to formulate the chemical or put it into a form
that is readily used.
One of the simplest formulations is that of a dust. Here the chemical is
ground with an inert filler such as a clay to a degree of fineness that makes
distribution easy. The dust, though simple to formulate and easy to apply,
has notorious disadvantages. One of the disadvantages is that the mixture
with the clay often reduces the activity of the compound. The other is that
dust, because they are fine particles, will often drift during the application.
Another common formulation is that of the emulsifiable concentrate. Here the
chemical is dissolved in organic solvent and an appropriate surface active
agent added. Mixed with water, the concentrate will then emulsify. In recent
years there has been developed emulsifiable concentrate that instead of pro-
viding an oi 1 in water, it provides water in oil emu1sion. The water in oil
emulsions are thicker, have a higher viscosity, and offer advantages in re-
ducing drift during application.
The third type of formulation that might be mentioned is that of the. granular.
The granular is prepared much as the dust with the chemical being ground or
mixed with an appropriate inert carrier, but here the formulation is prepared
in particles or granules of an appreciable size. Granules are then distri-
buted over the surface of the area to be treated and through moisture or some
other mechanism, the chemical is released for activity. As is readily apparent
the dust and spray applications are much more fraught with problems or drift
than would be granular applications.
Turning back now to behavior and fate of the chemical during and following
application, we find that drift of the dust or spray particles is a common
-------
140
occurrence during the application. This is true of any chemical and for any
method of application. The amount and distance of drift depends on the
variety of factors including particle size, particle weight, wind speed,
height above ground at release and in the case of a liquid particle, rapidity
with which the diameter changes due to volatility. Studies have shown as high
as 80% of the material released or as little as 10% may reach target. Drift
from the target area may be a matter of just a few hundred yards up to several
miles, again depending on conditions and the material being applied.
Once the chemical has lighted on the target area, it comes in contact with a
variety of surfaces. It may be the surface of an insect or a plant, or it
may be the soil. In any event, there is an interaction with the surface. If
it happens to be the waxy cuticle of a plant, the chemical may dissolve it.
On the other hand, if it is a soil particle, the material will be sorbed.
This interaction is extremely important for a variety of reasons. For example,
if the chemical interacts with a soil particle, its rate of movement by water,
its ability to volatilize and its accessibility for biological action are all
reduced. It has been found in recent years that there is good correlation
between certain fundamental characteristics of the molecule and the strength
with which it will be bound. The tighter the binding or adsorption, the
greater the reduction and availability for biological action.
Another phenomenon in behavior of chemicals in the environment is the movement
with water—particularly, through the soil profile. This is really analogous
to chromatography and many of the same principles apply. Each chemical will
move in a characteristic fashion with water as it moves through the soil and
the rate of movement will be modified by the character of the soil through
which it is moving. Chemicals strongly sorbed by soil are only poorly leached.
A striking example of this is the insecticide DDT which is leached poorly or
almost not at all by water.
Vapor behavior of the chemical is also very important. All chemicals have a
measurable tendency to change from either liquid or solid state to a gas, but
the rate and amount varies widely depending on the nature of the compound. It
is a common experience with more volatile substances such as the herbicide EPTC
to experience a substantial loss of the chemical in the early hours after appli-
cation. It has been found that these losses can be minimized by immediately
incorporating the chemical into the soil where two different phenomenon are
operative. The first phenomenon is that of the adsorption of the chemical by
the soil, thereby rendering it comparatively unavailable for vaporization. The
second phenomenon is the operation of Raoult's Law which states in essence that
if you reduce the amount of surface of the evaporating species the amount of
chemical being lost is thereby reduced. Even though a chemical may be only
poorly volatile, when spread out over very large surface areas, appreciable
amounts of the vapor can be lost. Many have postulated the premise that exten-
sive if not even universal contamination of the world eco-system has insued
from the use and wide distribution of certain pesticides and industrial chemi-
cals. Certain evidence just now coming to light brings this postulate into
question.
It is of considerable interest and importance to know how long a chemical will
persist at biologically significant concentrations. Some chemicals we class
as persistent, others as relatively non-persistent depending on the rate at
which the biologically significant concentrations disappear. We attribute the
-------
difference to the rather more rapid breakdown of the non-persistent chemical.
All chemicals once released into the environment are subject to a breakdown.
It starts with the breakdown by ultraviolet light of the chemical exposed
to that agent, through chemical reactions mediated by the surface on which
the chemical may reside, to biological breakdown or metabolism. The rate at
which this breakdown occurs determines the degree of persistence.
Persistence of the chemical in the environment in part determines the availa-
bility of that chemical for transport. With chemicals that breakdown rapidly
to less than biologically significant concentrations, we see little or no
evidence of its transport even though it may occur. Mechanisms or transport
include those of drift during the application, volatilization and transport
as a vapor or the transport of the chemical sorbed to a dust particle. This
latter mechanism of transport may be accomplished either by wind or water
erosion of the particle. There is some evidence to suggest that perhaps the
matter of erosion of the contaminated particle is one of the principal means
by which the chemical appears in non-treated areas far removed from the point
of use. Certainly it would appear that the principal contamination of our
water systems in continental United States is most probably through a water
erosion of contaminated soil.
Herbicides bring about effects on plants by a variety of biochemical mechanisms.
In all cases the effect of the chemical can be shown due to the result of the
interaction of the chemical with the biochemical processes of the plant. It
should be emphasized that very few chemicals act through a singular event,
but rather that they effect a number of different processes in the living
organism with perhaps one process being slightly more evident than others.
Thus, for example, the ureas, triazines, and certain other herbicides are
known predominantly for their effect on the photosynthesis of plants. The
chemicals such as the growth regulators appear to have a fundamental mode
of action at the level of the nucleic acids.
While the chemical is effecting metabolic processes of the plant, many plants
in turn are metabolizing the chemical. There are many cases of selectivity
known where the ability of the resistant plant to rapidly metabolize the herbi-
cide accounts for its resistance.
The type of metabolism of herbicides carried on in plants is parallel to the
type of metabolic actions seen in animals. The chemical may be hydrolyzed,
oxidized, reduced, conjugated or otherwise altered by the metabolic processes.
Usually this metabolism results in a compound of less biological activity than
the parent substance.
Of particular importance in light of the large quantities of chemicals used
as herbicides, the question is, "What hazards may arise from these chemicals?"
Such hazards may be classified into two large categories; namely, toxicological
hazard to man and important animals species and secondly, ecological hazards.
It must be remembered that there is a distinction between intrinsic toxicity
of a compound and the hazards it affords. Materials such as mercury we know
to be toxic, but when it is in the form of the ore cinnaber, we do not consider
it as a particular hazard. The same is true of many other substances. Hazard
as contrasted to toxicity is dependent on the following factors: (1) the
spectrum of organisms affected, (2) the intrinsic toxicity, (3) the resistance
of the chemical, and (4) mobility of the chemical.
-------
142
Fortunately, among the herbicides there are very few materials having a very
high mammalian toxicity. Many of these compounds have LD 50s greater than
100 mg/kg of weight and some running into as high as three to four thousand
millograms per kilo of body weight. There are materials like the herbicide
paraquat that have a realtively higher order of toxicity. This compound has
the unique feature that when ingested, causes a fatal overgrowth of lung
tissue. Some herbicides, notably 2,4,5-T, may have reaction by-products that
contaminate the material and have a high order of toxicity. The dioxin which
is a by-product in the manufacture of 2,4,5-T is such a chemical. Considerable
concern is generated over 2,4,5-T as a result of a study that indicated that
it was a possible mutagenic agent. The issue was confused by the presence of
dioxin though subsequent studies purported to show that 2,4,5-T alone was
capable of mutagenesis. The whole problem has recently been reviewed by an
expert panel, the majority opinion of which was that properly purified 2,4,5-T
used in good agricultural practice would afford little if any hazard.
Herbicides by virtue of their ability to affect plant growth possess potential
for ecological effects in non-target areas. We have seen instances of this in
the result of spray drift, the evidence that use of herbicides is causing
problems from latent transport however is rather scant.
Because of our knowledge on many of these chemicals is still incomplete, proper
care and precaution should be exercised. It would be suggested that best
exercise of prudence would be to insure that only knowledgeable individuals
have access to their use. The recent proposal to license applicators on the
basis of training and knowledge is commended as reasonable step toward this end.
References
1. Oregon Weed Control Handbook (Pub. yearly), O.S.U. Coop Bookstore,
Corvallis, Ore.
2. Herbicide Handbook, 2nd Ed., Weed Soc. of Am.
3. Principles of Weed Control - NAS/NRC (Principles of Plant and Animal
Pest Control Series)
4. Organic Pesticides in the Environment - Adv. in Chem #60, Am. Chem. Soc.
5. Montgomery, M. L. & Norris, L., Res Notes PNW for a Range Exp Sta. #116
-------
Chemical
Name
C ouunoo Name
?WSA *BSI
M.W.
Structural Formula
INORGANICS
1. Arsenous
oxide
Arsenic
trioxide
197.2
A»2°3
Sod Ida aeta
Arsenite
Sodium Araenite
129.9
HaAsO
Ortho-arsenic
acid Hemihydratfi
araenic acid
141.9
4. Sodiun
chlorate
106.4
HaClOo
5. Sodium tetraborate Borax
OH
/0-B-0X
HO-B 6 B-OH
\-i-o'
OH
201.3 as
N'2B4°7
-2
8H 0
2
2Na
-------
m
Solubility
Iff TP ma Hg Solvent G/100ml "C
1. «ubl water 1.2 0
Comments
oral U>5Q rats
138 ag/Kg
AH solution
-7.5 KcaI/mole
2.
water v.s.
alcohol si.s.
oral ll>50 various
animals 10-50 ag/Kg
3.
cold 14
water
intravenous LD^
rabbits 8 mg/Kg
AH solution
-0.4 KcaI/mole
4. 248
decomp
water 81
5. 742
water 1.31
4.71
11.21
•ethanol 18.61
acetone 0.61
glycerol
(93.51) 52.61
0
20
40
25
25
20
oral LDcQ rat
12 g/Kg
dermal LDso 20 g/Kg
LD50 man 15-25g
LD50 child 1 JT old 2g
AH solution
-5.6 KcaI/mole
0.1 M solution
pH 9.25
oral 11)50 male rat
5.6 g/Kg
AH solution
-25.8 Kcal/nole
Freed
-------
Chemical
Name
DRAGIIS
6. 3-sec-butyl-5-bromo
6-methyluracil
AMITROLE
Common Name
#WSA *BSI
bromacilf*
14E
M.W.
Structural Formula
261.1
H-CH(CH3)CB2CH3
7* 3-amtno
1,2,4-triazole
amitrole#
ATA
8A.1
ORGANOMETALLICS
8. Dine thy Ijiralnic
acid
cacodylic
acid
0
CH3-A8-OH
CH,
138.0
9. Methylarainic
acid
MAA
0
CH3-A8-OH
OH
140.0
»u iff "- • t-4-> —
-------
146
Solubilit
V? am Hg Solvent C/IOO ml ^T Comment*
6. 158-159 water 815 ppa 25 oral LD50 mala
benzene, rat 5.2 g/Kg
methano1,
acetone,
acetonitrlle a.
7. 153-154 water 28 23 oral LD50 rat
w«ter 53 53 25 g/Kg
ethanol 26 75 pk 11.0
acetone si.a.
pyrrolidone v.a.
ether insol.
8. 200 water 190 25 oral LD50 rat
(Ca aalt 800 ag/Kg
in water) 75
106 water 28 25 oral LD rat
(Ca salt 1.3 g/K|°
in water) 100 ppm
Freed
-------
14
Chemical
Name
Gnomon Name
*WSA *BSI
M.W.
Structural Formula
10. Ammonium
aolfaaate
11. Sodium
metaborate
AMS
HH4 • 0-S-NH2
Sodium
Ijl-borate
PHEMOXYALKAHOIC ACIDS
H
0
I
HO-B-OH
0
H
114.1
131.6 as
2 Hi • 4 H20
12. 4-Chlorophenoxy
acetic acid
4-CPA #*
13. 2,4-Dichloro- 2,4-D #*
phenoxyacetic acid
Cl-
186.6
0-CH2-COOH
221.1
Cl-
-0-CH2COOH
Cl
14. dl 2-(2,4-dichloro- dichlorprop
phenoxy) propionic acid 2,4-DP#
235.1
CH3
-0-CHCOOH
\
Cl
Chemistry of Herbicides
-------
148
MP
Hg
Solvent C/lOQml °C
Comments
10. 132
water
571
oral LD_n rats
3.9 g/Kg°
11. 965
-------
Chemical
Bane
Common Name
#WSA
M.W.
Struetural Formula
15. 4-(2,4-BUhloro-
phenoxy)
butyric acid
2,4-DB #*
249.1
Cl-
16. 2-Methyl-4-chlorophenoxy MCPA #*
acetic acid MCP
17. dl 2C-methyl
4-chlorophenoxy)
propionic acid
18. 4-(2-methyI
4-chlorophenoxy)
butyric acid
19. 2,4,5-Trichloro-
phenoxy acetic acid
Cl-
Mecoprop *
MCPP
2-MCPP
Cl-
MCPB #*
Cl-
2,4,5-T#*
-0-(CH2>3-COOH
Cl
200.5
-0-CH2-COOH
CH3
214.7
CH3
-o-cncooH
CH3
228.6
•0-(CH2)3-COOH
CH3
255.5
Cl-
-O-CHj-
COOH
Chemistry of Herbicides
-------
150
Solubility
HP V? mm HR Solvent C/100ml °C
Comments
15. 119-
120
water 53ppm
•thanol
chloro- i.
form
benzene 8.
hexane sl.s.
pk 5.0
16. 119
water 825
25 UV absorption maxima
at 199,229,279 nu pk 3.4
solution 8.2 KcaI/mole
17. 94.5
water 620ppn
water 895ppm
acetone a.
•thanol •.
ether a.
20 oral U>so 700-150mg/Kg
25 UV absorption maxima
at 287 nra
pk 3.38
18. 100
water 4A-48ppm
pk 4.86
19. 158
water 251ppm 25
oral LD5Q dogs 100 ng/Kg
pk 3.17
AH solution
8.4 Kcal/aole
Freed
-------
Chemical Common siane rt.W,
Name #WSA *BSI Structural ?o
20. dl 2-(2,4,5 - S.lvex
Trlchlorophenoxy) <%,$*-!!
*» A
CB
5 4 S«TP ^/ \* ' ••
2>4,5~T* 7/ \, ,
\\ 0-' CiXfl
.«»,j*-Ar« g
propionic acid i'siioproii1' \
PICOLINIC ACID
22. 3,5,6-trichloro
4-aminopicclinic
UREAS
21. 4-(2,4,5- ',4,5 1W* 263.6
Trichlorophcnoxy)
butyric acid
1 /.' \\-0- «"
\
/
23. NN-dimethyl- ttuurov* ^o4,
H1-phenyl uraa
i
t
-------
Solubility
MP
20. 181
VP mn Hg
water
benzene
methanol
acetone
140ppm
0.095
0.47
13.4
18.0
25
Comments
oral LDSO rata 650 aig/Kg
pk 3.1
21. 1U-
115
water
42ppn
pk 4.78
22. 233 6.1x10
-7
(35°C)
1.07xlO'6
(45°C)
water
benzene
ether
aceton-
nitrile
iaoprop-
anol
ethanol
acetone
450ppm
ZOOppm
0.12
0.16
O.S
1.0
2.0
25
25
-25
25
25
25
25
23,
130
water
oral LD50
8.2g/Kg-r«bblt 2g/Kg
pk 2.94
AH Solution
1.6 Kcal/mole
0.4 25 Oral LD5o rat
3.9 g/Kg-rabbit 1.5 g/Kg
0V absorption maxima at
240 mu
Freed
-------
ChMieal
M.W.
Structural Foriuli
24. l-(2-««tfcyJ
cyclohtxyl)
3-ptenyl
232.3
«»_•»
y.i_4~\
jB"""—"" —
elf"a
25. M1-(4-chl«roph«nyl)
11,11-diMtfcyl urM
Cl-
198.7
Tl
26. I'-(4-Chloroph«nyl)
•-••tko»y-II-»«tkyl
214.7
Cl-
27.
•-itobutynl
M-»«tkyl
234.7
01-
T] ^
•«-«>r
CNililry of
-------
154
Solubility
HP 7P mm Hg Solvcnj S/fffOal C Comment!
24. 133- water 18ppm 25 oral LD50 male
138 ethanol rat approx 5 g/Kg
dichloro-
•ethane, • '
dimethy1-
aeetamide,
dimethy1-
formamide^lO
25. 170.5- water *' 161p,pm 25 oral LD^Q vale rat
171.5 ' 3.5g/Kg
QV absorption
maxima at 245 mu
26.
27.
Freed
-------
Chemical
Name
Common Name
»WSA nsi
M.W.
Structural Formula
28. N'-4(4-Chloro-
phenoxy)-phenyl-
H,I-dlmethyl urea
chlorox-
uro»
290.7
29. H'-(4-chloro-
ph«nyl)-0,K,!l-
trimathyliao urea
triaaturonf*
Cl-
212.7
n:
,CH.
-< '
CHj
H3
30. 3-(4-bromophenyl)
-1-methyl-l-Bttthoxy
orca
•a tobroaurortf *
259
31. l-(3-trifluoron«thylph«nyl)
-3,3-dtB«thyl araa
213.2
Chemistry of Herbicides
-------
156
Solubility
MP VP ma Hg Solvent C/100ml °C Coanenta
28. water 3.7ppm 20 oral LD^Q male rat
acetone a. 3.7g/Kg
mouse l.Og/Kg
dog lOg/Kg
29.
30. 95.5- water 320ppm 20 oral LD50 rat
96 acetone, 3 g/Kg
ethanol,
chloroform a.
31. 163- water 60-70ppm 25
164.5 ethanol,
acetonitrile
acetone,
chloroform a.
etaer,
hexane al.a.
Freed
-------
M.W.
Structural Formula
32. r-(3,*-
-------
158
Solubility
HE YP aa Hg Solvent C/lOOal °C Comment*
32. 158- 3.U10"6 water 43pp« 25 oral U>50 rat
159 (50°C) 3.4 g/K|
UV absorption
naxima at 250 am
33. 93-94 water 75ppm 25 oral LD male
acetone, rat 1.53 g/Kf
•thanol, UV absorption
benzene, aaxina at 250 cm
toluene a.
34. 101.5- water 4.8pp» 24 oral ID., male
103 rat llug/Kg
33. 163- water 90pp« 25 oral LD50 male rat
164.5 8.9 g/Kg
female rat 7.9 g/Kg
•ale vice 0.9 g/Kg
fenale sice 2.4 g/Kg
dog 10 g/Kg
Freed
-------
Chemical
H»»e_
Common
*BSI
M.W.
Structural Fotaula
36. 1,3-bls-
(2,2.2-tricbloro-
l-hydroxy«thyl) ur««
DCU
354.9
rO OH
H||H!
CUC-C-N-C-N-C-CCL,
3 H H -
37. H'cyclooctyl-K.M-
dlactbyl urea
Cycluroirf*
OHO
198.3
/-\
(J
38. 3-(h«x«hydro-
-4v7»B«thjnoladan
-5-yl)-1,1-dimethyl ur««
222.3
NCH3
Chemistry of Herbicides
-------
160
Solubility
HP VP am Hg SolTtat C/100ml °C Garment*
36. 191
decamp
37. 138 water ISOppm 20 intraparateneal
acetone 9.8 20 ^50 Bcm8* 0.3g/Kg
methanol 109 20 U>50 rat 1.5g/Kg
benzene 4.2 20
38. 171.2 water ISOppa 25 oral LD.Q Wiatar
polar organic rat 1476 ing/Kg
•olventa a Sprager Dawley rat
aonpolar organic 6830 ng/Kg
aolventa inaol doga 3700 ng/Kg
dermal U>sn to
rabbits 3Z3 g/Kg
Freed
-------
Chemlca1
Item*
Couuuon Name
»WSA *BSI
BEHZOIC AHD PHEHYLACKTIC ACIDS
M.W.
Structural Formula
39. 2-methoxy-
3,6-dicblorob«ncoie
acid
Diemba #*
Cl
221.0
:OOH
40. 2,3.6-Trlchloro-
benzole acid
2,3,6-TEA
225.5
OOH
41. 2,5-dichloro-
3-«minob«nzoic
acid
AvidbcnF
Chloraabcn*
206.0
-COOH
Chemistry of Herbicides
-------
162
mm Hg
Solubility
Solvent G/IOOml °C
nts
39. 114
3.78xlO'3
(100° C)
water 7900ppm 25
•thanol sol.
oral LD-n rat
1.04 g/*g
DV absorption maxima
at 275 mu
pk 1.94
AH Solution
KcaI/mole
40. 118
water 7200ppm 25
oral LD50 .7-1.5g/Kg
pk 2.6
AH Solution
1.6 leal/mole
41. 204 7xlO~3
(100° C)
water
cci4
benzene
630ppm
insol.
0.02
chloroform 0.09
ether 7.01
•thanol 17.28
methane1 22.26
oral LD.. 3.5 to
5.6 g/Kl0
UT absorption
maxima at 297, 238 mu
Freed
-------
Chemical
Mane
Common Hsne
#WSA *BSI
TRIA2INES
M.W.
S true tural Forault
163
42. 2-Chloro-
4,6-dl«thyUmino-»- Siaazlnef*
trlazlne
43. 2-chloro-
4-ethyl*mtno-
6-i«opropyl«mlno-s-
triazine
Atrarlne**
Cl-
44. 2-chloro- prop«zine#*
4,6-dll»opropyl«nlno-»-
triazine
Cl-<
215.7
KHCHjCHj
I
i
HHCH(CH3)2
229.7
MBCH(CH3)2
45. 2-chloro- Chlorazin«#*
4,6-biadl«thylanino-a
triazln*
257.8
%M(CH2CH3)2
-------
164
Solubility
HP
Solvent gy100ml 2£
enta
42.
225-
227
(§abl)
vater
water
vater
n-pent-
ane
ether
aethanol
chloro-
form
' 2ppm 0
Sppn 20
84ppm 85
3ppm 25
300ppm 25
400ppm 20
900ppm 20
oral UD«Q mouse,
rat, rabbit,
chicken, pigeon
5.0 g/Kg
pk 1.65
AH eolation
9.0 K caI/mole
43. 173-
175
vater
vater
vater
n-pent-
ane
ether
methanol
chloro-
form
22ppm 0
70ppm 27
320ppm 85
360ppm 27
1.2ppm 27
l.Sppm 27
oral LD50 mouse
1.75 g/fcg
rat 2 to 4 g/Kg
rabbit 600-750 mg/Kg
hen 2.2 g/Kg
pk 1.68
AH solution
6.1 K cal/aole
5.2
27
44. 212-
vater
8.6ppm 20
oral II>5o mouse,
rat 5.0 g/Kg
45.
vater
lOppm
Freed
-------
Chemical
Mane
Common Kara*
#WSA *BSI
M.W.
S true turaL Formula
46, 2-chloro-
4-diathylamino-
6»«thylaaino-a-
triazina
triatazin***
Cl-
229.7
/
47. 2-chloro- ' Ipazinrf*
4-die thylamino-
6-iaopropylamino-a-
triazin*
243.7
48. 2-methoxy- •imetlnef
4,6-diethylamino-a- aiaicton*
triazine
197.2
49. 2-m«thylthio-
4-athylavino-
6-iaopropyla»ino-a-
triazina
227.3
BHCHCH
H(CH3)2
-------
166
HP 7P am H j
Solubility
tolTent Q/ioOal °C
Consents
.46.
water 20pp»
47.
48. 89.5-
92
water 0.32
49. 84-
86
..t.r 185pp. 20 T.1 W5g r.t 1.4 t/I«
•CM* 0.95 g/Kg
Freed
-------
Cheatcal
•an*
>n lame
*BSI
M.W
S true tura 1
50. 2-»«thylthio- »
4,6-dtiaopropylamino-a-
trlazin*
•tryncf*
CH3S-
241.4
51. 2-aethoxy- Atratone*
4-«thyla«lno- Atraton*
6-iaoprop7lani0o-a-
triazine
CH.
211.3
1IHCH2CH3
/
1=>C
%MBCB(CE3).
52\ 2-aethoxy- pron«ton«*
4,6-dit»opropylamino-a- pro««ton*
triazina
225.9
Chemistry of Herbicides
-------
168
Solvent C/100ml Jg
ents
MP YP «nH£ — "
20
uo
51.
».ter 0,18 22
52. 91- »«t«r 750ppm 20 oral LD50 r«t
benzene 33 20 2.2 g/Kg
chloroform, mooae 1.05 g/Kg
••tbanol, diitillable under
acetone 100 reduced pressure
pk 4.3
Freed
-------
THE OPERATIONAL AND MAINTENANCE REQUIREMENTS
OF
RESPIRATORY PROTECTIVE APPARATUS
FOR
PESTICIDE USERS
S. Edward Law
INTRODUCTION
Concern today in maintaining our environmental quality has caused a
reevaluation of many of the effective methods and materials used for
protecting agricultural crops from insect, disease and weed pests.
Chemical pesticides have well protected our food and fiber production
from about 10,000 kinds of insects and 1,500 plant diseases . In some
instances, environmental abuse has resulted from the use of certain
pesticides. While research on alternative control methods (radiation,
biological, cultural, etc.) is well underway, these methods at present
appear to be only promising complements to chemical pest control. Thus,
environmental preservation has made it imperative that drastic improve-
ments be incorporated into the use of chemical pesticides.
Two improvements which can considerably lessen the deleterious environ-
mental effects caused by chemical pest control are: (1) reducing
pesticide output rates per unit area, and (2) reducing the persistence
of the toxic chemicals used. Agricultural engineering research has
demonstrated encouraging improvements by utilizing electrostatic
deposition of pesticide particles to achieve satisfactory coverage of
field-crops with pesticide output from nozzles reduced typically to
half-rates^* 3.
The formulation and use of less persistent pesticides (such as the
organic phosphates) has certainly reduced the severity of the environ-
mental hazard associated with the "hard" chlorinated hydrocarbons.
However, the mammalian toxicity of these less persistent materials is
often extremely high. So while the environmental hazard is reduced,
the personal safety hazard is greatly increased for workers who mix
and apply some of these less persistent pesticides. The proper use
and maintenance of personal protective apparatus by these workers
becomes an absolute requirement of any pest control program.
Papers presented earlier this week have discussed the acute toxicity
hazard encountered in the use'of many pesticides. Possible routes of
-------
170
entry of the toxic materials into the body may be: (1) dermal, (2)
through skin wounds, (3) oral, and (4) respiratory. The extreme impor-
tance of the dermal route of entry has been noted, and protective clothing
to minimize dermal exposure has been discussed.
The purpose of this paper is to now consider certain aspects of personal
protective apparatus available to reduce pesticide entry via, the respi-
ratory route. Particular emphasis will be placed on the routine operational
and maintenance requirements that these devices require in order to satis-
factorily provide the protection for which they were designed.
TYPES OF RESPIRATORY HAZARDS AND PROTECTIVE DEVICES
The several governmental agencies and professional scientific groups
directly concerned with occupational respiratory hazards are the U.S.
Bureau of Mines, the Entomology Research Division of USDA, the American
Industrial Hygiene Association and the American National Standards
Institute, Inc. Specific and detailed information on respiratory 4557
protection is contained in publications available from these groups ' ' '
as well as from commercial sources .
At the present time the U.S. Bureau of Mines is the official governmental
agency responsible for testing and approving respiratory protective
equipment. Complete protective devices are tested and passed under one
of a number of Approval Schedules setting forth the minimum requirements
that the various types of respiratory protective equipment shall satisfy
for safe use.
In general, there are three broad classes of respiratory protective
devices tested by the Bureau of Mines: (1) air purifying, (2) air
supplied, and (3) self-contained apparatus. The Bureau of Mines
selection chart (Figure 1.) illustrates the utilization of these three
classes of devices for protection against a number of general respiratory
hazards. Using this chart as a guide, a brief discussion follows to in-
dicate the various types of protective devices available to minimize
pesticide entry into the body via, the respiratory route. The maintenance
requirements common to all of the devices will then finally be considered.
OXYGEN DEFICIENCY HAZARD
An oxygen deficiency hazard exists when the ambient oxygen content drops
below 16% volume concentration from its normal value of 20.97«. Such a
hazard is fairly uncommon in agricultural pesticide application except,
perhaps, in the fumigation of closed spaces such as grain elevators and the
holds of ships. Adequate protection against an oxygen deficiency is pro-
vided by either: (1) self-contained breathing apparatus carried by the
wearer, or (2) a hose mask with blower which delivers breathing air from
a distant uncontaminated region. Furthermore, these two type devices
provide adequate respiratory protection against toxic contaminants since
the wearer is completely free of respiratory exchange with the atmosphere
surrounding him.
-------
TOXIC CONTAMINANT HAZARD
Respiratory hazards may occur when breathing from atmospheres contaminated
with: (1) toxic particulate matter in the form of dusts and sprays,
(2) toxic gases and vapors, or (3) a combination of these toxic agents.
Devices appropriate for protection against each of these respiratory
hazards are available.
Toxic Particulates - Mechanical filter respirators provide respiratory
protection against dusts, mist and fumes. Toxic particles are physically
trapped in a fibrous material as the inhaled air passes through the
filter. Particulate filtration theory indicates that the individual
dust or spray particles are deposited onto individual fibers within the
filter medium by the combined action of three filtering phenomena: (1)
a straining effect in which particles too large to pass between fibers
are collected, (2) an impingement onto fibers by particles having
sufficient momentum to penetrate through the slipstreams flowing around
the fibers, and (3) interception. The efficiencies of these filter
phenomena are functions of particle size, and the maximum difficulty in
filtration occurs for particles of approximately 0.3 micron diameter.
Certain mechanical filter respirators are available commercially with
filter efficiencies guaranteed to be not less than 99.987. as established
using 0.3 micron diameter OOP (di-octyl phthalate) test smoke.
The American Conference of Governmental Hygienists annually publishes a
listing of the Threshold Limit Values (TLV) for airborne contaminants in-
cluding certain pesticides . These TLV's define concentration levels of
toxic airborne particulates (and gases) above which respiratory hazards
are probable for continual eight-hour workday exposures. Technical spec-
ifications describing many mechanical filter respirators indicate their
approval for protection against the inhalation of dusts and mists having
a TLV as low as 0.1 milligram/cubic meter.
It must be emphasized that the mechanical filter respirator alone does not
offer adequate protection against the volatile particulate matter typical
of many pesticides.
Toxic Gases - Respiratory protection against certain toxic gases and vapors
is provided by two types of air purifying devices: (1) chemical cartridge
respirators, and (2) gas masks. These two types of devices differ in size,
service life, and the contamination level in which they may be utilized.
In both the inhaled air is usually drawn through a bed of activated char-
coal in which the toxic gas is adsorbed onto the surface of the finely
divided charcoal particles.
Chemical cartridge respirators provide protection against certain toxic
gases and vapors in concentrations as high as 0.1% by volume. These are
half-face masks which cover the mouth and the nose, but do not protect
the eyes.
Gas masks protect against certain toxic gases and vapors in concentrations
up to 2% by volume. These are full-face masks which also protect the eyes.
-------
172
Models are available with the chemical canister chin-mounted directly
onto the mask, and chest or back-mounted using a length of flexible hose.
The back-mounted canisters are advisable when very high vapor concentra-
tions exist directly in front of the wearer as, for example, when pouring
fumigant directly onto the surface of stored grain. The smaller size of
the chin-mounted type limits it use to gas concentrations no greater than
0.5%.
Combined Toxic Gas and Particulate - Most agricultural pesticides are
applied as either particulate dusts or sprays. In many instances the
pesticide formulation is quite volatile. Thus, the most common respira-
tory hazard encountered by pesticide users is a combined gaseous and
particulate exposure. Adequate protection is provided by utilizing an
appropriate gas or vapor adsorber in conjunction with a high efficiency
particulate filter.
Chemical cartridges and canisters are available with particulate filters
assembled as an integral part. These combination units are very compact.
Their one disadvantage is that the particulate filter usually becomes
clogged before the more expensive chemical cartridge part is exhausted.
The whole unit must then be discarded. Some commercial respirators with
independently replaceable particulate filters are available as an alter-
native .
As recently as 1966 the Entomology Research Division of USDA routinely
tested the protective efficacy of commercial air purifying filter-
cartridges and canisters against particulate and gaseous exposures of
certain pesticides. A listing is given of those cartridges and canisters
found to provide adequate respiratory protection specifically against
dust, mist, and low vapor concentrations of some fifty pesticides .
These units tested are recommended for use in airborne pesticide con-
centrations of no greater than 5 milligrams/cubic meter and 50 milli-
grams/cubic meter when installed in half-mask respirators and in full-
face gas masks, respectively. The purifying units were not tested
against high vapor concentrations of commercial fumigants.
RESPIRATORY EQUIPMENT MAINTENANCE
No matter how well suited a respiratory protective device is for a
particular job, it cannot provide the protection for which it was designed
unless it receives proper maintenance. A number of maintenance require-
ments are common to most of the above mentioned devices, and these are
discussed in detail below. Specific details on maintenance of the more
complicated self-contained apparatus should be obtained from the man-
ufacturer.
TIGHTNESS
Tightness of face-fit and mechanical connections should routinely be
checked to prevent leakage. Less than 0.17. contaminant leakage from
toxic atmospheres may be obtained using a properly fitted full-face
mask . This degree of tightness is generally not possible with half-face
-------
173
chemical cartridge respirators since they must fit a portion of the face
having more individual variation. Factors which prevent a satisfactory
face-fit are beard growth, heavy sideburns, temple pieces of eye glasses
and absence of dentures. Two simple field tests for checking face-fit
follow.
Positive Pressure Test - The exhalation valve cover is removed and the
valve closed by covering. Air is exhaled gently into the facepiece
and held. If the slight positive pressure built up in the mask can be
maintained without any evidence of outward leakage, then the face-fit
and the seating of the intake valve are considered satisfactory.
Negative Pressure Test - The intake opening of the cartridge or canister
is covered with the palm of the hand. The wearer inhales gently and
holds his breath to cause the mask to slightly collapse. If the mask
remains slightly collapsed for ten seconds and no inward leakage is
detected, then the face-fit and the seating of the exhalation valve are
considered satisfactory.
Realistic Test For Face-Fit - Two additional face-fit tests are sometimes
used7. in both of these tests a fairly harmless airborne material is
dispersed into a small plastic enclosure or vacant room in order to
create a realistic test condition. To detect gas leaks, isoamyl acetate
vapor is dispersed, and the wearer checks for odor. To detect particulate
leaks, an irritating smoke is dispersed using stannic chloride - impreg-
nated pumice. Particulate leakage is indicated by throat irritation.
PARTICULATE FILTER REPLACEMENT
The useful life of the particulate filter depends upon: (1) filter area,
(2) level of exertion of the wearer, (3) airborne particulate concentration,
and (4) the particulate size distribution. The independently changeable
type particulate filters should be changed twice daily or oftener if
breathing becomes difficult.
CHEMICAL CARTRIDGE REPLACEMENT j
The service life of chemical cartridges and canisters depends upon: (1)
gas or vapor concentration, (2) level of exertion of the wearer, (3)
volume of the unit, and (4) humidity. The wide variations in these ex-
posure conditions makes it impossible to rigidly specify service life.
Thus, generally it is recommended that chemical cartridges be changed
after eight hours of actual use or oftener if any pesticide odor is
detected by the wearer. It should be mentioned that since the first
detection of odor by the wearer indicates the end of the service life of
chemical cartridges, these should never be used for protection against
odorless gases or gases which paralyze the olfactory nerves so quickly
that detection by odor is unreliable.
WASHING AND DISINFECTION
Respiratory protective devices should be thoroughly cleaned inside and
-------
74
out following each use with pesticides. In the interest of personal
hygiene, it is also desirable to disinfect any device which is worn by
more than one worker. Cleaner-disinfectants which contain bactericidal
agents are available from respirator manufacturers; these are recommended
for convenience. After removing any filter or cartridge or canister, the
whole facepiece and breathing tube is immersed into a solution of the
cleaner-disinfectant, then rinsed in clean water, and air-dried. When a
commercial cleaner-disinfectant is not available, the facepiece and
breathing tube may be washed with household liquid detergent and then
disinfected in either a hypochlorite solution or an aqueous iodine
solution. All disinfectant solutions must be thoroughly rinsed since
they may cause dermatitis, corrode metal parts and age rubber.
DECONTAMINATION
Any respirator which has become contaminated with organic phosphate
pesticides must be treated before reuse. It should be washed thoroughly
with strong alkaline soap. This hydrolyzes parathion and produces a
yellow color. Thoroughness of the decontamination is conveniently
indicated by the disappearance of the yellow. The alkaline soap is
corrosive, and it must be completely rinsed from the respirator with
ethyl or isopropyl alcohol (50%).
STORAGE
Respirators and gas masks should be stored in their original packing
cartons or in closed plastic bags. The rubber parts should rest in an
uncratnped position so that no permanent distortion will occur in
storage. Protection should be provided against heat, sunlight, dust,
excessive moisture and damaging chemicals. Rubber parts which have
become stiff during storage can be made pliable and flexible by stretching
and massaging the rubber.
REPAIR
Respiratory protective devices should be repaired using only the manu-
facturer's recommended parts and instructions.
SUMMARY
The high mammalian toxicity of many presently used pesticides poses a
serious personal safety hazard to users. In particular, the dermal and
the respiratory routes of entry into the body require protection. The
respiratory hazard may exist as an oxygen deficiency or a toxic contaminant
hazard due to the presence of airborne particulate matter and poisonous
gases and vapors. Appropriate respiratory protective devices are available,
and they should be selected and used only against the specific hazard for
which they were designed.
Maintenance recommendations for respirators and gas masks are simple,
quick and easy. If this maintenance is routinely implemented, then
these devices should reliably provide adequate respiratory protection
«»o-l«ei«- t-V>A r\ha ^na'[ r~o^•^r•^<^ao -for wTrlrVi fSnv on*
-------
l/b
Self-Contained
Hose Mask
Gaseous
Apparatus
(13)
1
Immediately
Dangerous
To UCe
1
1 1
Self -Contained
Apparatus
(13)
Hose Mask
With
Blower
(19)
With Blower
(19)
Gas
Mask
(1U)
1
P
Not
Immediately
Dangerous
To Life
Air-Line
Respirator
(19)
1
Hose Mask
Without
Blower
(19)
Chemical
Cartridge
Respirator
(23)
Gaseous
and
Particulate
Self-Contained
Apparatus
(13)
Hose Mask
Without
Blower
(19)
Chtmical
Cartridge Respirat
With Special Pilt
(23)
Figure 1. Selection of appropriate protective devices for various respiratory hazar
(Numbers refer to USBM Approval Schedules)
Figure 2. Respiratory protective devices commonly used against pesticides,
n\ FnTl_far- nac ict --t+h rMn- -Minted
-------
76
REFERENCES
1. Freeman, 0. L. 1966. Protecting our food; the 1966 yearbook of
agriculture. U.S. Government Printing Office, Washington, B.C.
2. Bowen, H.D. and Splinter, W.E. 1968. Field testing of improved
electrostatic dusting and spraying equipment. ASAE Paper
No. 68-ISO, ASAE; St. Joseph, Michigan.
3. Law, S .E. 1968* Charge Iocs phenomena active on liquid droplets.
Unpublished Ph.D. thesis, Department of Biological and
Agricultural Engineering, North Carolina State University,
Raleigh.
4. U.S. Bureau of Mines information circular 7792. U.S. Department of
Interior, Bureau of Mines, 4800 Forbes Ave., Pittsburgh, Pa.
5. Yeomans, A.H., Fulton, R.A., Smith, F.F. and Busbey, R.L. 1966.
Respiratory devices for protection against certain pesticides.
Publication No. ARS 33-76-2. U.S. Department of Agriculture,
Agricultural Research Service, Entomology Research Division,
Beltsville, Md.
6. Respiratory protective devices manual. 1963. American Industrial
Hygiene Association, 25711 Southfield Road, Southfield,
Michigan.
7. Practices for respiratory protection, ANSI Z88.2.1969. American ^
National Standards Institute, Inc., 1430 Broadway, New York, N.Y.
8. Basic elements of respiratory protection. 1971. Mine Safety Ap-
pliances Company, 201 North Braddock Ave., Pittsburgh, Pa.
9. Whitby, K.T., and Lundgren, D.A. 1965. Mechanics of air cleaning.
Trans, of ASAE, Vol. 8, No. 3, pp. 342-352.
10. Threshold limit values of airborne contaminants. 1970. American
Conference of Governmental Industrial Hygienists. 1014
Broadway. Cincinnati, Ohio.
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17'
PESTICIDE EQUIPMENT MAINTENANCE
H. B. Goolsby
The farm sprayer is a versatile machine that must be capable of many dif-
ferent uses in applying pesticides to farm crops.
This paper deals only with the operation and maintenance of the farm
sprayer for protecting the environment against any after effects from
pesticide usage.
Due to the possibility of using a sprayer for many different jobs in which
the sprayer must be changed often, its maintenance Is directly related to
over application and incorrect application of pesticides.
One of the most important things on a sprayer that must be kept in excel-
lent working order is the tank agitator. This agitator must continue to
operate in the sprayer tank even while moving from field to field so that
the pesticide will not tend to settle out.
Sprayer hoses should be flexible and reinforced to prevent collapsing under
vacuum. They must also be able to withstand a much higher pressure than
under average operating conditions. All hoses must be able to resist sun-
light, oil and chemicals.
Adjustments on the pressure regulator of a sprayer are used in calibrating.
Maintenance of the adjustments is imperative in maintaining correct cali-
bration so that excess amounts of material will not be applied to the crop
and, in turn, contaminate the environment.
All recommendations of pesticides for crops made by the Cooperative Exten-
sion Service are designed to apply only enough pesticide to do the job
without harmful effects to wildlife, livestock and humans. Any excess of
spray material Is in direct conflict with environmental protection.
Sprayers for farm crops, especially ground driven sprayers, generally oper-
ate in a range of 0 - 100 psl. Any deviation upward of this pressure is
generally used for the specialized jobs.
Tanks on sprayers should be made of corrosive resistant materials or
should be lined with an anti-corrosive substance to minimize flaking
sediments that cause screen stoppage, excessive wear and ineffective
spraying.
Maintaining the nozzle and sprayer tips are of uppermost importance in
protecting our environment. The majority of nozzle tips being sold today
are fast wearing. In some cases, after 10 hours of use and with certain
pesticides, some nozzles will apply as much as 12 to 15 percent more
material. Chrome plated and stainless steel nozzle tips will tend to
wear less. Farmers that utilize fast wearing nozzles should calibrate
their machine more often to offset fast wear of nozzle tips. If abrasive
materials are used, calibration should be done twice daily. The selec-
•-' •-«-- '-1- •-- K- JAmA
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application is going to be effective by putting the material only where
it should go. Strainers in nozzles are provided to keep down nozzle wear
but often these strainers become clogged and must be removed, cleaned and
reinserted into the nozzle. It is necessary for farmers and sprayer oper-
ators to check the discharge from each nozzle many times during the days
operation.
The use of hand sprayers in and around the home should be handled in a
like manner as sprayers used on the farm. Wire or knives should never be
used to clean nozzle tips. Their use will destroy the spray pattern and
also increase the material applied. At the end of each spray season and
after the sprayer has been cleaned, the nozzles should be removed, cleaned
thoroughly, covered with thin oil and stored.
The farmer and/or sprayer operator must be well informed as to the sprayer
setup for various jobs to be done. Maintenance of the sprayer in this re-
gard is very important for doing a good job and in protecting the environ-
ment.
Sprayers for certain jobs use complete coverage applications. Some sprayers
must be set up to direct application to certain parts of plants and to the
soil. In many cases, pesticides must not come in contact with plants or
crops which the farmer wishes to protect. The complete maintenance of the
sprayer setup during operation is a must if farmers wish to do the best job
protecting his crop and apply the material only where it should go. In
many cases during the actual spraying operation, nozzles need adjusting
since dangers could result not only to the crop itself but to the environ-
ment as well.
In view of the fact that sprayer users must calibrate often, in 1957 equip-
ment manufacturers, chemical companies, agricultural research and the Co-
operative Extension Service established a Georgia standard for calibration.
This was done so that the farmers would not be confused by the many hundreds
of ways in which to calibrate. The main objective of this standard was to
apply certain materials to certain pests in order to make crops more pro-
ductive. The farmers ability to calibrate would greatly limit the danger
that might be incurred when using an incorrectly calibrated machine.
Farmers of Georgia are supplied vest pocket cards giving the Georgia
standard of calibration for various jobs.
Each crop and pesticide requires different rates and application tech-
niques. Sprayer users must be cognizant of these recommendations and
adjust his sprayer so that these rates of application can be maintained.
All types of sprayers must be cleaned often and stored properly during
the off season if they are to be effective in doing a good job and not
contaminate our environment.
Operators should use extreme care while maintaining and operating a
sprayer by wearing the correct clothing, face mask respirators and
having available washing material in case the pesticide gets on the bare
skin.
The farm sprayer is a necessary tool for the farmer to carry out an ef-
fective pest control program. Care in handling and maintenance can guard
against unnecessary damage to the environment.
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179
EQUIPMENT MAINTENANCE
RINSING AND WASHING
FOR ENVIRONMENTAL INTEGRITY
Charles E. Rice
The Summary of Interim Guidelines for Disposal of Surplus or Waste
Pesticides and Pesticide Containers^ gives the best guidance available
for the rinsing and washing of agricultural spray equipment. These
guidelines will be discussed and developed for application to the
problem.
Excess mixed pesticide disposal can be minimized by close calculation of
required amount so as to have a smaller gallonage for disposal. The use
of low-volume application will also decrease the gallonage problem.
The guidelines give the following recommendation of the disposition of
dilute pesticides.
"(1) When it is necessary to dispose of dilute pesticide mixtures or
rinsings, whenever possible they should be carefully applied to the area
that has been treated, adjacent borders or safe, protected waste area.
Extreme care must be exercised so that the extra pesticide applied will
not result in phytotoxicity, over-tolerance residues or other undesirable
results."
To follow these guidelines, it is considered desirable to cut mixed dilute
pesticides by adding ten (10) parts of water to one (1) part of the
pesticide. After the mixture is cut, then apply to the treated area. This
small ten percent added treatment would not be expected to exceed the
tolerance or produce other undesirable results. Rinse water would be
expended directly on another part of the treated area or safe borders.
The guideline for the occasions that do not fall under the first item
raises a few problems.
"(2) When this method will not suffice, the dilute pesticide solution,
emulsion or rinsing should be run into a shallow holding pit dug in a
area where there will be no runoff or downward percolation and where the
water table is at least 10 feet below the surface. Under no circumstances
should dilute pesticides or rinse water be allowed to enter streams, lakes,
sewers, drainage ditches or other areas where water contamination can
result. The holding pit area should be properly identified so that no other
use is made of this area, and so that subsequent contamination of other areas
will not occur."
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The handling and disposition of the dilute pesticide under this guideline
should not occur frequently, but there will be many occasions for rinsing
out equipment, and washing equipment that will fall under this guideline.
The holding pit must be located so there is no surface drainage from the
area. A small dike around th« area will assure no loss of soil or water
from runoff. The water will be removed by evaporation.
To minimize downward percolation, the pit should be dug in a soil that
can be puddled and compacted. This will normally be a clay soil, or clay
will have to be brought in to line the pit. Clay is recommended in the
expectation of some of the pesticides combining with the soil. We
recommend that the pit be filled with gravel so that the equipment can
be driven onto the gravel for washing and rinsing. A small dike around
the area will assure no loss of soil or runoff water.
The condition of 10 feet above the water table will be very difficult to
meet in our Coastal Plain *reas. In th«se cases select the best available
site, and do an excellent Job of puddling the pit to minimize percolation.
The pit should be located down grade from any well or other water supply.
The distance recommended for burial is 500 feet from a water source. It
may be impossible to locate the pit or to obtain wash water 500 feet from
a water source, but it is a good figure to keep in mind. An antisiphon
device should be used on the water supply hose bib.
The practice of washing a sprayer close to a well can be dangerous.
Lewallen reported on a polluted well dug near where a sprayer was washing
area for the backfill. It was monitored for 4 years during which time there
was a gradual decline.
The wash area should be fenced and a permanent sign posted. The fence will
prevent the area from being used for other purposes such as grazing. The
sign will warn any new management of the past use of the area and hopefully
prevent it being used, for example, as a garden plot.
All used spray equipment should be kept in safe storage to prevent children
from placing their hands or bodies on the equipment because of the potential
danger of the chemical residues. j
All washing and rinsing of the equipment should be done using the individual
protective equipment recommended when applying the particular pesticides.
"References"
1 Working Group on Pesticides. Summary of interim guidelines for disposal
of surplus or waste pesticides and pesticide containers. NTIS.
Operations Division, Springfield, Virginia 22 151, Dec. 1970.
2 Lewallen, W. J. Pesticide Contamination a shallow bored well in
Southeastern Coastal Plains. Paper presented at the National Ground
Water Quality Symposium, Denver, Colorado, August 25-27, 1971.
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Environmental Protection Agency
fcagicn V9 Liimir-y
230 South D.'f.T'jorn Street .•
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