Report of
Committee on Persistent Pesticides
Division of Biology and Agriculture
National Research Council
to
U.S. Department of Agriculture
May 1969
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Report of
Committee on Persistent Pesticides
Division of Biology and. Agriculture
National Research Council
to
U.S. Department of Agriculture
Washington, D. C.
May 1969
-------
CONTENTS
Introduction 1
Need for Pesticides 2
Man and the Ecosystem 5
Production and Use of Pesticides 6
Significance of Residues 7
Monitoring Residues in the Environment 19
Control of Pesticide Residues 22
Alternatives to Persistent Pesticides 25
Conclusions 27
Recommendations 29
Appendix
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PREFACE
Release of chemicals into the environment must be
evaluated continually in relation to human health, food
production, welfare of the biota, and status of the
environment. Some pesticidal chemicals persist long
after they are applied, and they retain such toxicity
that the advisability of their continued use has been
challenged.
The Committee on Persistent Pesticides was estab-
lished by the National Research Council (through the
Division of Biology and Agriculture) to examine the
subject of persistent pesticides. The Council's action
was in response to a request made to Dr. Frederick Seitz,
President, National Academy of Sciences-National Research
Council, by Dr. George L. Mehren, formerly Assistant
Secretary, U.S. Department of Agriculture.
In his request, made on November 29, 1966, Dr. Mehren
referred to certain recommendations contained in a report
on the use of pesticides that was issued by the President's
Science Advisory Committee in 1963.
The report included a recommendation for "a monitoring
program conducted by Federal Agencies to obtain timely.
systematic data on pesticide residues in the environment."
The report recommended that "the accretion of residues in
the environment be controlled by orderly reduction in the
use of persistent pesticides" and stated that "elimination
of the use of persistent toxic pesticides should be the
goal."
Pointing out that several agencies had undertaken
monitoring studies to obtain information on residues,
Dr. Mehren stated that it seemed appropriate to consider
the most recent information on residues and to appraise
the significance of residues from the standpoint of their
effects on "the safety of our food supply and on the safety
of man and our environment."
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The Committee held its first meeting in December 1967.
This was followed by a series of meetings in which the
Committee heard representatives of government agencies,
industrial and user groups, and conservation organizations.
The assistance of those who provided information to the
Committee is gratefully acknowledged. Without it, this
review could not have been made. A list of the persons
interviewed appears in the appendix.
The Committee believes that demonstrable progress has
been made in further understanding some of the issues raised
and in implementing some of the recommendations in the
report by the President's Science Advisory Committee. How-
ever, it is concerned about what remains to be accomplished
and about the many gaps in our knowledge of pesticides.
It is convinced that there is an immediate need for world-
wide attention to the problem of buildup of persistent
pesticides in the total environment.
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COMMITTEE ON PERSISTENT PESTICIDES
James H. Jensen (Chairman), President, Oregon State
University, Corvallis
Edwin F. Alder, Vice President, Agricultural Research and
Development, Eli Lilly and Company, Indianapolis,
Indiana
Martin Alexander, Professor, Soil Microbiology, Department
of Agronomy, Cornell University, Ithaca, N.Y.
William E. Dale, Analytical Chemist, National Communicable
Disease Center, Public Health Service, Savannah, Georgia
Donald E. Davis, Professor, Department of Botany, Auburn
University, Auburn, Alabama
Virgil H. Freed, Head, Department of Agricultural Chemistry,
Oregon State University, Corvallis
Don W. Hayne, Professor of Zoology and Experimental
Statistics, Institute of Statistics, North Carolina
State University, Raleigh
James G. Hilton, Professor, Department of Pharmacology,
University of Texas Medical Branch, Galveston
E. Paul Lichtenstein, Professor, Department of Entomology,
Russell Laboratories, University of Wisconsin, Madison
Louis Lykken, Specialist, Division of Entomology,
College of Agriculture, University of California, Berkeley
Ralph B. March, Professor, Department of Entomology,
University of California, Riverside
Tony J. Peterle, Professor, Department of Zoology and
Entomology, The Ohio State University, Columbus
Joseph C. Street, Professor, Department of Animal Science,
Utah State University, Logan
Robert P. Upchurch, Senior Research Group Leader, Agricultural
Research Department, Monsanto Company—V Building,
St. Louis, Missouri
C. H. Van Middelem, Biochemist and Professor, Pesticide
Research Laboratory, Department of Food Science,
University of Florida, Gainesville
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INTRODUCTION
Man's primary concerns have always been the
struggle for survival and improvement of his lot.
As his numbers increased, he attained greater
ability to manipulate his environment. In the
process he sometimes inflicted damage on himself
and on his surroundings. Advances have always
entailed a degree of risk which society must weigh
and either accept, or reject, as the price of
material progress.
A major step in civilization was the domes-
tication of food plants. With the birth of organ-
ized agriculture and the resultant concentration
of crops and animals, the stage was set for out-
breaks of pests. Until that time man had to
search for food as did the pests. Afterward
neither had to search; instead, pest control
became necessary. The welfare of an increasing
human population requires intensified agriculture.
This in turn enables the pests to increase, which
necessitates the use of pesticides with their
concomitant hazards. It thus seems inevitable
that, as the population increases, so do certain
hazards.--President's Science Advisory Committee,
Use of Pesticides, May 1963, p. 1
Most pesticide use involves release of chemicals into
an ecosystem that includes living organisms and the non-
living substances associated with them. In such use, the
intention is to restrict the chemicals to the treated areas.
However, in spite of this intention, pesticidal chemicals
often enter untreated areas of the biosphere.
Although much attention has been given to long-lived
organochlorine insecticides, they are not the only persistent
chemicals that cause concern. Inorganic pesticidal chemicals
are also persistent; among these are chemicals containing
lead, copper, arsenic, and mercury. Moreover, not all
problem-causing organic chemicals in the environment are
pesticides. Other organic compounds used or produced in
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industry, and industrial waste products, leave persistent
residues that add to the contamination in the biosphere.
The breakdown of a pesticidal chemical alters the
parent molecule, and the alteration often results in a
less toxic product. Some pesticidal chemicals break down
and disappear soon after application. Others degrade or
dissipate slowly, and their residues remain in decreasing
but measurable concentrations for varying periods of time;
it is to these that the relative term "persistent" is
applied. Some persistent pesticidal chemicals remain in
the environment for months or years, the rate of degra-
dation varying with the local environmental conditions.
Some of the organochlorine insecticides and certain other
persistent pesticides are disseminated by natural forces
throughout the biosphere, and they have characteristics
that favor accumulation and storage by organisms. Much
of the present public concern is directed to pesticides
having these characteristics.
This report discusses environmental contamination
resulting from the use of persistent pesticides in the
continental United States. However, the Committee is
well aware that, because of the mobility of some persis-
tent chemicals in the atmosphere and in water, contamina-
tion of the biosphere must be viewed as a global problem.
NEED FOR PESTICIDES
During the past quarter of a century, nations in all
parts of the world have benefited from increasing use of
the synthetic organic pesticidal chemicals. Through use
of these chemicals, spectacular control of diseases caused
by insect-borne pathogens has been achieved, and agricul-
tural productivity has been increased to an unprecedented
level. No adequate alternative for the use of pesticides
for either of these purposes is expected in the foreseeable
future.
The President's Science Advisory Committee pointed
out in a 1967 study that, in the developed countries,
most of the increase in the use of pesticides has been in
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agriculture, whereas, in the developing countries, most
of the increase has been due to efforts to control insect
vectors of disease.* Moreover, as a result of the greatly
reduced incidence of diseases in some developing countries,
more food is needed—to feed those saved from disease.
These countries must turn to more intensive agriculture
to support their growing populations. Modern agricultural
productivity depends on coordinated increase in the use
of pesticides, fertilizers, machinery, and better crop
varieties.
Pesticides that persist in a biologically active form
offer certain advantages. If the material breaks down
slowly, frequency of application can be reduced and labor
costs are correspondingly lowered. If, as a result of its
being present in the environment over an extended period,
the material accumulates in the tissues of the target
species, low initial application rates may well provide
effective control. Certain of the persistent compounds
have additional advantages over many nonpersistent compounds
they are less hazardous to the persons handling them, and
there is less likelihood of immediate harm to nontarget
animal and plant species in the treated area.
Farmers sometimes apply more pesticide than the amount
needed for controlling pests. The public has come to insist
on attractiveness in produce, and this insistence weighs
heavily in determining market acceptability. Consequently,
extra applications of pesticide are made with the aim of
raising the level of control of insects or disease agents
from good, or reasonable, to the level of almost perfect.
The producer of vegetables for commercial canning may be
caught between two tolerance limits—one for pesticide
residues and the other for insect parts that are legally
defined as "filth." Both tolerances were set indirectly
by the decisions of society at large. In some instances,
*President's Science Advisory Committee, Panel on the World
Food Supply, The World Food Problem (Washington, U.S.
Government Printing Office, 1967), pp. 138-139.
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it may be desirable to reexamine the basis of market
quality in the interest of reducing pesticide residues
in the environment.
In home gardening and household uses, pesticides
may be applied at excessive rates because the user does
not know the proper type of pesticide for best results
and because he applies them improperly. In doubt as to
proper quantity, he may reason that "if some is good,
more is better" and thus may apply too much.
Under some conditions, persistent pesticides are
the most effective means of controlling pests; under
others, they are the only practical means. Many serious
public health problems associated with insect vectors of
human disease still require the use of persistent pesticides
in some countries, either because a suitable short-lived
alternative is not available or because the developing
countries cannot bear the cost of nonpersistent pesticides,
which are usually more expensive than persistent pesticides.
Reasonably priced alternative chemicals or nonchemical
means may be found in time. Meanwhile, any action to
reduce the availability of persistent pesticides needed
by developing countries might have serious health conse-
quences in those countries.
There is no satisfactory alternative to persistent
pesticides for protecting wood against insects. Long-lived
materials may be placed in the soil, or timber may be impreg-
nated to achieve long-term protection, without danger of
contaminating the environment.
In the United States, persistent pesticides have some
uses for which satisfactory alternatives do not exist.
Economic entomologists state that at present, the only
chemicals that effectively control certain insects are
the persistent ones. The insects to which they refer
include certain pests of cotton, corn, wheat, alfalfa,
fruit, forest trees, lawns, and turf.
Despite the present need for persistent pesticides,
their availability must not inhibit the search for more
desirable means of pest control.
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MAN AND THE ECOSYSTEM
Any undisturbed land mass is eventually occupied by
an assemblage of plants referred to as climax vegetation.
This vegetation is stable and self-perpetuating and may
consist of many species living together in a small area.
When it is destroyed, the area is quickly occupied by
plants that have the ability to grow and multiply rapidly.
In due course other species invade the area and restoration
of the climax begins.
When the human population was small, it was possible
for man to depend on climax vegetation and its associated
organisms for food, fiber, and shelter. However, it was
necessary for man to disturb and to modify some of the
earth's climax systems in order to provide sufficient
food, fiber, and shelter for the growing human population.
Besides being an initial step in establishing present-day
civilizations, the development of agriculture was the first
stage in destroying the relatively stable ecosystem in which
man once lived. To maintain the resultant ecologically
unstable situation, he was obliged to initiate many remedial
actions, including pest control.
Basic ecological principles dictate that an unstable
state will change unless maintained by balancing forces.
Monoculture, which is essential today to food production,
is ecologically unstable. Continued effort is necessary
to maintain it. The effort includes pest control and the
use of fertilizers, machines, and selected plant varieties.
At present, pests are controlled primarily by use of pesti-
cides, but no matter what method is used, the basic problem
remains: monoculture is inherently unstable.
Society could allow farmers to maintain monocultures
by any means that they chose, except for the fact that man
is a part of the whole ecosystem. Whatever is done in one
part of an ecosystem often produces an effect in other parts.
Pesticides applied in one area may be transported to remote
areas and produce unexpected results. Complete insect
control in a cotton field may destroy the bees necessary
for pollinating an adjacent alfalfa field. Therefore,
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for the good of mankind, it is conceivable that society
may wish to put restraints on the use of certain pesticides
regardless of economic considerations and crop quality.
PRODUCTION AND USE OF PESTICIDES
The worldwide increase in the use of persistent pesti-
cidal chemicals is cause for concern, and, if trends continue,
problems of environmental contamination by such chemicals
may become more serious. During the first half of the
10-year period ending June 30, 1967, the use of the prin-
cipal organochlorine insecticides (DDT, aldrin-dieldrin,
toxaphene, etc.) in the United States continued at about
the same level. During the last half of the period, a
slight decrease occurred. During the whole 10-year period,
the use of DDT decreased substantially, but the use of
aldrin and dieldrin increased. Undoubtedly, the decrease
in the use of the principal organochlorine insecticides
from 1962 to 1967, inclusive, resulted from (1) changes
in government regulations and agency recommendations con-
cerning use, (2) public pressure to reduce the release of
persistent pesticides into the environment, (3) a marked
increase in the development of strains of insects resistant
to persistent pesticides, and (4) the availability of use-
ful new pesticides of other types.
In the United States, total production of the principal
organochlorine insecticides for domestic use and export
increased by about one-third in the 10-year period ending
June 30, 1966, but the 225 million pounds produced in the
last year for which information is available (1966-67)
represents a decline from the values of the previous 5 years.
During the same 10-year period, the production of DDT
increased to a peak value of about 185 million pounds in
1962-63 and decreased to about 60% of this value in 1966-67.
The use of herbicides and fungicides expanded steadily
in the last decade of record; the use of herbicides showed
a substantial growth. Continued substantial increases are
anticipated for herbicides, but little increase is seen
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for fungicides. These two groups do not contribute impor-
tantly to the problems commonly associated with persistent
pesticides.
The total worldwide production of persistent pesti-
cides is not known. This information is necessary if the
residues of pesticidal chemicals entering global transport
systems and accumulating in the biosphere are to be evalu-
ated and if a realistic appraisal of the effectiveness of
residue control measures is to be made.
SIGNIFICANCE OF RESIDUES
Analytical Problems
Residue measurement, as performed in monitoring pro-
grams, consists in detecting and measuring minute quantities
of pesticidal chemicals. The task requires not only the
skillful use of precise, highly sensitive analytical methods
but also a proper interpretation of resultant data.
For convenience and speed, pesticide residue chemists
generally adopt gas-liquid chromatography (GLC) as their
primary analytical technique. Where only GLC is employed,
one or more of the following conditions could contribute
to erroneous results: (1) failure to utilize adequate
confirmatory identification of the pesticide residue,
(2) lack of adequate extraction and cleanup procedures,
(3) lack of standardized analytical methods, (4) lack of
sufficient comparisons to permit the measurement and evalu-
ation of variability between cooperating laboratories and
between analyses performed in the same laboratory, (5)
presence of artifacts that are interpreted as pesticide
residues, and (6) lack of biological materials for controls
that are free of pesticide residues.
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Health
Understanding of the toxicology of persistent pesti-
cide residues is increasing steadily insofar as warmblooded
animals are concerned. However, extrapolation of toxico-
logical data from test animals to man remains uncertain.
Several recent studies that have been conducted with
man as the subject do not indicate that the present levels
of pesticide residues in man's food and environment produce
an adverse effect on his health. These studies have been
principally epidemiological.
—Workers involved in the manufacture of DDT, chlor-
dane, dieldrin, heptachlor, and endrin have been the sub-
jects of long-term studies designed to determine whether
their exposure had caused any significant alterations in
disease frequency or pathology. The evaluations included
comprehensive health examinations and monitoring of exposure
rates and pesticide residue levels in the workers' tissues.
The health of those workers was not found to differ signif-
icantly from that of the general population. Yet the pesti-
cide storage levels in the tissues of some of the pesticide
workers were 10 to 20 times higher than those found in the
general population.
—A nationwide epidemiological study of persistent
pesticide residues in several thousand persons has not
produced evidence that pesticide residues in the body have
an adverse effect on health. A substantial number of the
persons involved in this study were exposed to relatively
high concentrations of pesticides as a result of occupation
or residence; the others were exposed in no unusual way.
Data are available from recent studies concerned with
the relation between dosage rates and storage levels.
Studies on the storage dynamics of DDT and dieldrin in
human volunteers confirmed observations, made in studies
of other mammals, that a dosage-storage equilibrium
develops.
Many persistent pesticides have been subjected to
basic toxicological reevaluations in various test animals.
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These studies were conducted to measure chronic effects,
including, in most cases, effects on reproduction and
carcinogenicity potentials. Studies of aldrin, dieldrin,
endrin, heptachlor, heptachlor epoxide, and chlordane in
animals have not shown that these chemicals produce
significant toxicological effects at dosage levels under
1.0 ppm in the diet, although they produce reversible
"adaptive responses" of the liver at a level of 1.0 ppm
or higher. These data include results from reproduction
studies of rats (in which all six of the above chemicals
were used) and dogs (endrin) and from long-term exposure
studies of mice, rats, and dogs (endrin and heptachlor);
dogs (chlordane); and monkeys (dieldrin).
Increases in liver size induced by these chemicals
are accompanied by increased activity of the hepatic
microsomal enzymes, and this response increases the toler-
ance of an animal to the chemical. This adaptive liver
response in animals occurs with the administration of any
one of more than 200 compounds, including some chemicals
naturally present in the environment, many drugs, and
various synthetic compounds. Hence, the response in
animals is common, and it would be expected to occur in
humans also if a sufficient quantity of pesticide were
administered.
Steroid hormones are also degraded by the microsomal
enzymes of the liver. A widely held view is that increased
steroid degradation occurs when persistent organochlorine
compounds accumulate in man and other animals. Experi-
mental evidence supports this view, but, as with other
toxicological effects, the minimum dosage is apparently
above 1.0 ppm of these compounds in the diet.
The ultimate effects, if any, of long-term low-level
exposure to persistent pesticides are not understood.
Although the existing studies do not indicate the low-level
exposure to persistent pesticides is a health hazard for
the general public or that higher-level, but subacute expo-
sure is a hazard to persons in certain occupations, addi-
tional research on the effects of long-term, low-level
exposure is essential.
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From this statement of the need for information about
possible effects of long-term exposure, it does not neces-
sarily follow that such exposure would be deleterious to
health. The point is that definite information is lacking.
Both the epidemiological and the mammalian experimentation
should be continued, and this experimentation should include
studies of the biochemical and physiological effects of
prolonged low-level exposure to persistent pesticides.
Food
For as long as persistent organic pesticides have
been used, there has been concern about their presence in
human food. The primary objective in regulating pesticide
use has been to keep residues in food supplies at minimal
and safe levels, because food is the principal route by
which pesticides normally reach man. Increasing effort has
been devoted to inspecting food supplies, and supplies in
which residue levels were found to exceed legal tolerances
have been condemned. As a result, residues in the food
supplies of the United States have been maintained at
remarkably low levels during a time of great increase in
pesticide use. The Committee believes that, at present,
pesticidal chemical residues in food are being maintained
at safe levels.
The interaction of inspection and enforcement with
research on agricultural practices has resulted in the
discontinuance of some uses that were once approved. For
example:
—DDT was once used to control flies and other insects
on dairy cattle, but this practice was found to result in
unacceptable residues in milk.
—Forage grown on fields the year after application
of certain organochlorine insecticides sometimes transmits
residues to the milk of dairy cattle grazing on the forage.
—Many of the residue tolerances for aldrin, dieldrin,
endrin, heptachlor, and DDT were recently reduced or with-
drawn. These actions led to discontinuance of some pre-
viously recommended uses.
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Some pesticides, notably DDT, are so widely distributed
that few, if any, food-producing areas are free of their
residues. Thus, most foods contain measurable traces of
such residues. There is no evidence that these traces are
of significance to human health.
Wildlife
Damage to wildlife was recorded soon after persistent
pesticides came into general use. Direct mortality of some
birds, mammals, and fish followed the application of organo-
chlorine insecticides at heavy rates over large areas.
Alarm expressed by various groups, each concerned about the
fate of a particular group of animals, has generated strong
public reaction to these effects of the use of pesticides.
The period of large-scale, very heavy applications
of persistent pesticides appears to be coming to a close
in the United States; methods are being refined, applica-
tion levels are being reduced, and other materials are
being substituted. Because of this change in the use of
chemicals, some persons expect that serious damage to the
biota will be substantially reduced or eliminated.
The Committee concludes that there is substantial
evidence of continuing damage in some areas, particularly
to fish and birds, by pesticide residues at present envi-
ronmental levels. There are examples of concentrations
in food chains at levels that are lethal to predators.
Exposure to pesticides at sublethal levels probably pro-
duces more subtle effects, causing changes in the physi-
ology, biochemistry, or behavior of animals that may be
harmful to the population as a whole. Certain game fish
accumulate pesticidal chemicals by storage in the body
and in the fat-rich yolk of egges; there may be no injury
to adult fish, but lethal or harmful amounts are acquired
by the newly hatched offspring when they absorb the egg
yolk. Studies on two continents show that the reproductive
success of certain birds of prey is impaired by DDT and
its metabolites, which apparently act to reduce eggshell
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thickness and thus to increase premature breakage of the
eggs.
Certain organochlorine pesticides are hazardous to
many species because they are readily absorbed, are stored
in body lipids, and are slowly metabolized and excreted.
The body lipids are metabolized continually to support the
life processes and are continually being replaced. If a
predator loses the pesticidal chemical it receives in
food as fast as it takes it in, accumulation of the chemical
is avoided, whether the loss is by metabolism, excretion,
or chemical degradation. If it loses the pesticide at a
lesser rate, it accumulates the chemical in its fat. The
concentration attained is tolerated without any ill effect,
or it causes sublethal injury, or it is lethal. Assuming
that a given organism in a food chain is not killed by the
pesticide it stores, the next higher predator generally
increases the concentration by accumulation. This process
repeated several times may result in tissue residue levels
several thousand times greater than the level existing in
the environment.
The same process occurs in the food supply of man,
who is at the top of many food chains. However, it has
been possible to stabilize the accumulation of residues
in man's food below tolerance levels by controlling the
pesticide input for the major food chains.
Where the ecology of pesticide residues is concerned,
there are important parts of the biota about which almost
nothing is known. Research on the effects of persistent
pesticides in the ecosystem is concerned almost entirely
with the relatively few forms of life of direct interest
to man. These include economic plants, economic insects
(both harmful and beneficial), economic fish, shellfish,
sport fish, game animals, and birds. Reports of new
research may suddenly increase interest in other compo-
nents of the biota. For example, interest in soil micro-
organisms increased because of their role in the biochemical
degradation of pesticides.
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Research on natural populations is a difficult,
undeveloped field that is poorly supported at the national
level. Methods of field study are imprecise, yet they
must be used for populations that fluctuate continually.
It is not difficult, for example, to demonstrate the
massive lethal effect of a control agent, but it is almost
impossible to measure a low-order change in the balance
between reproduction and mortality by ordinary field
studies. Information on subtle effects can come only
from carefully coordinated field and laboratory investi-
gations. Large-scale field experiments will be required
to establish whether effects found in the laboratory occur
in the field and to allow more general extrapolation from
laboratory results to what may be expected in the field.
There are no research programs of this magnitude. No
public agency is conducting or sponsoring research on the
broad ecological effects of pesticides. The Committee
believes that such research programs on natural popula-
tions should be initiated.
The Environment
Residues of DDT and, occasionally, of other organo-
chlorine insecticides have been recorded in biota in all
parts of the world. After being released into an eco-
system, these pesticides are transported about the bio-
sphere by a variety of little-understood mechanisms and
are concentrated in the biota. The pesticides about which
the greatest concern is felt are those having, to a marked
degree, all of the following characteristics: toxicity,
persistence, mobility in natural environments, and affinity
for the biota.
Wide distribution of DDT and some of the other organo-
chlorine insecticides is inferred from scattered observa-
tions. The amounts in environmental stores cannot be
compared with the amounts dispersed, because there is too
little information on the amounts in the environment. The
general presence of DDT and its metabolites in man and
other animals is taken by some to imply that large quanti-
ties are stored in the biosphere; possibly the observations
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reflect only a relatively small circulating store concen-
trated in the biota. Scattered measurements of DDT in
rain and the atmosphere emphasize the need to know what
is in the atmosphere. The ready sorption of pesticidal
chemicals by silt suggests that the chemicals may be
stored in silt deposits in reservoirs, rivers, and estu-
aries and on the continental shelf, but a few observations
support or refute this supposition. Order-of-magnitude
estimates of even a few of the important environmental
stores of residues would be valuable.
Accumulations are investigated at sites of applica-
tion in areas where the organochlorine insecticides have
been applied heavily. There is increasing evidence that
when they are applied to farm fields year after year, the
measurable residues in the soil reach a steady state, the
amount disappearing each year being about the same as the
amount that is applied. In a number of fields in the South,
the steady-state level approximates the amount applied in
1 year. Other studies show much greater persistence at
the site of application. Nevertheless, continued use of
even the long-lived organochlorine insecticides does not
result in a constantly increasing accumulation at the site
of application. Therefore, the problem of high-level local
contamination by pesticidal chemicals is not the same as
that presented by arsenical insecticides in orchards.
Disappearance of a pesticide from the site of appli-
cation may or may not mean that the chemical is being
destroyed. Two processes act to reduce the local concen-
tration of pesticide. The first transforms the chemical
by biological, chemical, and photochemical degradation.
The second transports the chemical to another place.
Organic pesticides are degraded in a number of ways.
As a result of work in the last few years, much new infor-
mation exists on the degradation, metabolism, and fate
of persistent pesticides in soil, water, animals, and
plants. Some persistent pesticides are subject to photo-
chemical decomposition or are destroyed by nonbiological
components of the environment. Some are degraded biolog-
ically. Biological degradation occasionally takes place
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through enzymatic processes that may result in a complete
conversion of organic chemicals to simple, well-known
products. In other instances, biological degradation
yields organic compounds that are normal constituents of
living organisms. Although the return from this research
investment has been impressive, vast gaps in knowledge
remain. There is relatively little information about the
ultimate fate of persistent pesticides in soil or in other
parts of any ecosystem, or about the sequence in which the
degradation processes take place. For some chemicals of
interest, the initial products formed are known and are
measurable in monitoring programs; but for these chemicals,
the products formed next and the sequence in which they are
formed are not known or are known for only a few types of
natural habitats. Until these products are identified and
their potential biological activities are ascertained, it
is impossible to assess meaningfully their toxicity to man
or to the biota or their residence times in nature.
Rates of degradation differ with the chemical, the
type of degradation, and the place in the environment. In
some instances, the parent material or a product generated
from it is highly resistant to degradation in all major
environments into which it enters. In other instances, the
pesticide is long-lived in one habitat but short-lived in
another, or it is short-lived in almost any environment.
With some chemicals, the degradation is partial; in others,
it is extensive. Whether the overall ecological storage
of a chemical increases or decreases in a given period
depends, of course, on the balance between the rate of
input and the rate of degradation during the period.
Like many other chemicals, organochlorine insecticides
move about the biosphere. Knowledge concerning this trans-
port is growing, but it is still incomplete with respect
to the relative importance of the various mechanisms.
Most of the persistent pesticidal chemicals have an extremely
low water solubility and a high affinity for colloidal sur-
faces. These two characteristics explain why the materials
are resistant to leaching and move no more than a few inches
in the soil profile during a period of several years.
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- 16 -
Evidence suggests that general environmental contamination
by the chemicals is more likely to occur from wind and
water erosion of the soil than through leaching into
ground water. One means of transport is the sorption of
pesticides to soil particles, especially the fine silt
and organic fractions, both at the site of application
and in the aquatic environment. Normal processes of
erosion transport the soil into streams, rivers, estuaries,
and the sea. There are records of pesticides being carried
on the ocean winds in association with particles of the
talc diluent used in application, and pesticides are prob-
ably carried on particles of soil in the same way. Al-
though many chemicals used as pesticides have low vapor
pressures, substantial amounts can be transported in the
vapor state. Pesticides in the atmosphere are returned
to the earth in rain. In addition, a direct air-soil
exchange may take place.
Pesticides are carried in the biota, but the relative
importance of biological transport is unknown. On the one
hand, living things carry relatively high concentrations
of residues because of the process of biological concen-
tration; on the other hand, the mass of the biota is very
small compared with the total environment. Fish and shell-
fish may remove certain organochlorine insecticides from
their water environment, despite the very low concentrations
present, and, if mobile, excrete the chemicals or their
metabolites back into the water at a new site. Consumption
of one species by a mobile predator species, with consequent
transfer of a portion of their body burden of residues,
provides an additional avenue of distribution.
Where little or no information is available concern-
ing the transport, accumulation characteristics, and
degradation products of a long-lived (persistent) synthetic
chemical, it would appear prudent for man to refrain from
needlessly releasing the chemical into the biosphere. The
crucial questions are: What are the degradation products?
How toxic are they? What is their behavior in nature?
If a long-lived chemical is released and is later found
to be toxic, nothing can be done about the store already
dispersed; it must remain in the biosphere until dissi-
pated by the slow processes of degradation and removal.
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- 17 -
Release of short-lived material is a different matter.
If such a material is released and is later found to be
hazardous, the store in the biosphere will be rapidly
reduced once the use of the material is discontinued.
Biosphere Stores
The threat of continued accumulation of residues
in the environment is responsible for much of the appre-
hension about the future use of the organochlorine insec-
ticides. Therefore, their rate of degradation to nontoxic
compounds of known biological behavior is a crucial factor.
Evidence that degradation destroys residues about as
fast as the pesticides are released would be reason to
believe that global environmental levels can be controlled
by raising or lowering the rate of release. Evidence of
continued accretion in the biosphere should force a prompt
reappraisal of continued use.
Three kinds of evidence can be examined in deciding
whether chemical residues are increasing in the biosphere:
—Evidence gained in studying degradation processes
to determine how rapidly chemicals are being destroyed.
--Evidence from monitoring to detect changes in con-
centration in selected compartments of the biosphere.
--Evidence from measuring residue storage in the total
biosphere.
The first two procedures are producing considerable
knowledge; however, the third is receiving too little
attention.
Chemical degradation of pesticidal chemicals has
been investigated extensively in the laboratory. Some
studies have been made under selected field conditions,
but it is difficult to evaluate the significance of
transport away from the study area. Available infor-
mation indicates that rates of degradation vary with
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- 18 -
environmental conditions. Evaluation of the overall rate
of disappearance from the biosphere requires quantitative
knowledge concerning (1) partitioning of the total residue
store and (2) rates of degradation in the principal envi-
ronmental components. The data now available do not permit
estimation of the rate of disappearance of any of the
persistent pesticides from the biosphere.
The main objective of the present monitoring programs
is to detect changes of pesticide concentration in selected
parts of the biosphere. To obtain information on changes,
it is necessary to operate a program for several years.
The best-organized parts of the present programs relate to
pesticide residues in man and his food supply. They cannot
furnish reliable indications of changes in the total envi-
ronment. (See "Monitoring Residues in the Environment,"
page 19 -)
Estimates of the total amounts of residues stored
throughout the biosphere would make it possible to establish
whether present stores are about the same as the amounts of
pesticides that have been manufactured or whether degrada-
tion processes have already disposed of most of the pesti-
cides that have been manufactured.
It seems essential at this time to estimate the store
of persistent chemicals in the environment and determine
whether this store is increasing or decreasing. To be
meaningful, the estimate must be on a global scale.
Modern sampling design would probably make such an under-
taking feasible if international cooperation could be
obtained. Presumably, residues are stored primarily in
the soil, the water, and the atmosphere; the biota is
probably too small to store a significant mass of pesticides,
Metallic Compounds
Several metallic elements are used as pesticides
in both the organic and the inorganic form. No matter
what form is used, the element persists. Traces of
arsenic, lead, and copper occur naturally and are widely
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distributed in the biosphere; hence, they are generally
found at low levels in crops and soils. Application of
pesticides containing any of these elements augments the
natural level.
Metallic pesticidal chemicals are highly toxic and
are excreted slowly from the body. They were used in the
inorganic form in the past, but the current practice is
to use organic compounds of these metals. The organic
compounds are less toxic on a single-dose basis, but the
body metabolizes them to their inorganic form. Precautions
concerning degree of exposure and accumulation in the body
are the same for the organic derivatives as for the corre-
sponding inorganic compounds.
The use of many of the metallic pesticides is on the
wane. However, the increasing use of organic arsenical
herbicides presents a growing arsenic-contamination problem,
MONITORING RESIDUES IN THE ENVIRONMENT
The 1963 report of the President's Science Advisory
Committee recommended that "current pesticide levels and
their trends in man and his environment1' be determined
and that "a continuing network to monitor residue levels
in air, water, soil, man, wildlife, and fish" be developed,
In response to these recommendations, several federal
agencies set up the National Pesticide Monitoring Program
(NPMP), following guidelines provided by the Federal Com-
mittee on Pest Control, an interagency body. The agencies
that set up NPMP were already engaged in monitoring activi-
ties, and they continue to administer the activities that
are now identified with NPMP. Some NPMP activities were
instituted after NPMP was formed.
In June 1967 the Federal Committee on Pest Control
began publishing the Pesticides Monitoring Journal, the
purpose of which is to report results of monitoring inves-
tigations—both those conducted by agencies associated
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with NPMP and those conducted by other agencies. In the
first issue, the Journal defined pesticide monitoring as
the determination of "the distribution of pesticides in
the various elements of the environment and the changes in
these levels with time." As NPMP is now conducted, however,
the emphasis is on measuring changes in the concentrations
of pesticides in selected components of the environment.
Those parts of NPMP that follow pesticides in people
are designed to measure changes that occur in selected
communities or in tissues obtained from designated hospi-
tals. In contrast, programs related to food emphasize
careful objective sampling to determine the average content
of a standard diet. Enough dietary components are analyzed
separately to permit calculation of residue content for a
number of basic diets. In addition, raw produce and meat
are randomly sampled. Thus, for food, the program provides
not only for measuring changes but also for calculating
meaningful average values.
These studies of man and his food have, of course,
been set up for good public-health reasons, and statements
of objectives are outstandingly clear. If any increase in
residues is noted in the samples of man or his food, cor-
rective action generally is taken promptly. However, these
studies do not provide data needed for assessing the presence
of pesticides in natural environments.
The program for monitoring soils is based on selected
sampling of forest, range, and agricultural lands. Most
samples of agricultural soils are taken from farms where
the history of pesticide use is known. More extensive
sampling according to a well-established sampling design
is required to provide information on the accumulation of
residues in the total soil mass. A plan for expanding soil
monitoring to include more general sampling on a statistical
basis is being developed.
Pesticides in water are monitored by sampling rivers
at selected sites. Changes at these sites are measured,
but information on average conditions is lacking. Related
samplings are those of shellfish in estuaries, the surface
of estuarine sediments, freshwater fish (three species)
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- 21 -
taken at a number of points on rivers, and birds (three
species). Like the river samplings, these studies are
concerned with selected parts of the ecosystem and measure
changes; they are not capable of determining the distri-
bution or extent of residues in the various parts of the
ecosystem.
Thus, it is seen that the National Pesticide Monitor-
ing Program has two groups of studies and that they differ
markedly in their objectives:
—The measurement of residues in human tissues and
in food is designed to follow pesticides in man and his
food, not to reflect residues in the general environment.
—The sampling of water, shellfish, estuarine sedi-
ments, freshwater fish, birds, and (to some extent) soil
is designed to furnish index values for measuring changes
in the amounts of residue in selected components of the
biosphere.
The air-sampling program of NPMP, which is only
beginning, should be expanded. Although the technology
of air sampling is not well advanced, air sampling must
be included in any effort whose aim is to monitor the
health-related aspects of man's immediate environment.
Further, the absence of quantitative information about
transport of pesticides in the atmosphere is a critical
deficiency in our understanding of the biosphere circu-
lation of the persistent materials. The Committee believes
that an air-sampling network should be established. Pri-
mary attention should be given to man's immediate environ-
ment, but the network should also monitor the environment
generally.
The Committee believes that monitoring programs
should include determinations of the concentrations and
amounts of pesticide chemicals in the major reservoirs
of the biosphere and assessments of the changes in con-
centration with time. Such information would permit esti-
mation of the amount and rate of change of residues in
the biosphere.
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- 22 -
The Pesticides Monitoring Journal is a practical
response to a real need. Underlying this enterprise is
the principle that relevant data should be readily avail-
able to the scientific community. Recorded data have
lasting value, although early interpretations, being
limited by the state of knowledge then existing, some-
times are ephemeral. For this reason, the Committee urges
that the various segments of NPMP promptly publish relevant
data in the Journal, even when the implications of recorded
measurements are obscure.
It should be recognized that monitoring is an impor-
tant service activity and should not be confused with
research. Research is necessary to provide tools for
monitoring, but the two activities have different objec-
tives . As soon as information-gathering can be standard-
ized, the monitoring should be separated, administratively
and financially, from research. Continuance of monitoring
as a function of a research unit can lead to reduced qual-
ity in both endeavors.
The Committee believes that the National Pesticide
Monitoring Program is at a stage where a thorough examina-
tion of objectives and procedures will be beneficial.
CONTROL OF PESTICIDE RESIDUES
Dangers inherent in the use of pesticides have led
to adoption of regulations, in the United States and
elsewhere, designed to control residues and promote safety,
Official regulation must be combined with informed use by
applicators. No matter how strict the law may be, its
objectives cannot be achieved without understanding and
cooperation on the part of applicators.
Legal controls in the United States are partly direct
and partly indirect. Direct legal controls are applied to
the manufacturer and the shipper of pesticides by federal
and state label-registration processes and by inspection
for adulteration, misbranding, or inadequate labeling of
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- 23 -
the products. Label-registration regulations protect
the users of pesticides with regard to quality and effec-
tiveness of the purchased product. They also help to
prevent the release into the biosphere of one chemical
when the release of another is intended. Certain highly
toxic materials (e.g., the rodenticide 1080) are permitted
to be used by licensed pest-control operators only. In
some states, another mechanism of control is the licens-
ing of applicators.
Agricultural Commodities
A major legal control over pesticide use is the con-
demnation of agricultural commodities that contain residues
in excess of the stated maximum permissible level. Labels
on pesticide containers provide, for the guidance of
farmers, directions for using the pesticides. If followed,
these directions should prevent above-tolerance residues.
The directions for use are the result of careful investi-
gations of the effectiveness of a product and of residue
levels obtained from stated rates of application. State-
ments on the label, including directions for use and
warnings about harmful effects, are controlled by
regulation.
Compliance by farmers is on a voluntary basis, but
the fact that they operate under the threat of condemnation
of their products if they fail to comply with recommended
practices tends to enforce compliance. A precedent has
been established for governmental reimbursement for produce
found to be contaminated despite the use of approved mate-
rials in accordance with recommended practices. Evidence
indicates that the objectives of this indirect method of
control are being achieved, and that the entry of pesti-
cides into the human diet is being kept at a minimal and
safe level. This method of control can be used to reduce
further the levels of pesticidal chemicals in food. When
new information reveals a formerly unsuspected health
hazard, tolerance levels can be lowered, though not below
the level of ecological availability.
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- 24 -
The Environment
The present indirect method of regulation places
emphasis on voluntary compliance by the user and penalizes
him only if his own crops carry excessive levels of a
pesticide. Despite its limitations, this method is effec-
tive locally. However, it seems to lack potential for
exercising control over materials that may have an effect
in an area remote from the site of application.
If application of a pesticidal chemical results in
drift to an area under different ownership and such drift
is found to be the cause of loss or condemnation of a
crop, losses can be recovered by legal action against the
landowner responsible for applying the chemical. This legal
principle also extends to protection of fish and other wild-
life. Losses of this kind are recoverable by a state in
the form of replacement costs. Although fixing individual
responsibility is often difficult, the possibility of legal
action by either private or public parties moderates the
use of pesticides and tends to reduce contamination result-
ing from drift. In addition, the indirect method is inef-
fective where pesticides are applied for purposes other
than control of crop pests—for example, application of
DDT for control of Dutch elm disease or dieldrin for control
of the imported fire ant.
In general, present regulations contain inadequate
provisions for protecting the environment. That some agency
should be responsible for the well-being of the ecosystem
seems to be a new idea. Concern for environmental contam-
ination that is not subject to control by any state or
federal agency may force a resolution of this question
of responsibility.
The Committee believes that attention must be given
to the problem of controlling residues in the biosphere.
It is doubtful that control of residues in the biosphere
can be achieved by the same methods that are effective in
food production, because of the impossiblity of fixing
individual responsibility for contamination. Regulations
to achieve this type of control would be concerned with
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- 25 -
benefits in which few citizens have a direct interest.
Special efforts, including educational efforts, are needed
to explain the benefits and promote public acceptance of
the regulations.
Controlling residues in the biosphere is an inter-
national problem, and any effective control over the
accumulation of long-lived materials in the ecosystems
of the world must be through control of use in all nations.
Clearly, the United States must do something about its own
problems before it can advise other nations to change
practices. There exists in our economy a loop of cause
and effect that tends to perpetuate the present pattern of
materials used. The organochlorine insecticides are of
relatively low cost; for many purposes, they are highly
effective; from a restricted viewpoint, they are relatively
safe. Therefore, they are used in large quantities. Sub-
stitute materials having less persistence would probably
be used if they were available at equal cost and if they
were equally effective. But such substitute materials will
not be developed while the present persistent materials are
in their advantageous position. Unless there is a change
(possibly in the form of regulatory action) by which the
persistent materials lose their advantage, they will prob-
ably continue in general use.
ALTERNATIVES TO PERSISTENT PESTICIDES
A number of nonchemical approaches to pest control
are being developed. These include the growing of resistant
crop varieties; cultural and management practices; and con-
trol of insects by the use of light traps, attractants,
radiation, sterilization, and biological means. Some of
these approaches are being used with impressive success.
The nonchemical methods may be used more widely in
the future, but speed of adoption and ultimate usefulness
are restricted by cost and by lack of applicability to
many problems. Often there is an unavoidable delay before
control is attainable by biological means. For most purposes,
nonchemical methods of control are not expected to supplant
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- 26 -
the use of chemicals in the foreseeable future. Hence,
some of the pesticidal chemicals are likely to have a
place in pest control for many years to come.
Lack of wide-scale adoption of nonchemical control
procedures is not the result of any lack of attention
devoted to them. They have been under study for many
years, and, in recent years, public agencies have com-
mitted increasing percentages of their research budgets
to the development of nonchemical control. In the same
period, financial support for improved chemical control
has not kept pace. Paradoxically, resources for studying
pesticidal chemicals have decreased in a period in which
their use has increased. The Committee believes that the
research effort on pesticidal chemicals should be increased
and that the present effort on nonchemical methods of pest
control should be maintained. A balanced research program
should include substantial investments in the search for
better nonchemical methods of control, similar commitments
for research on new pesticides and improved application of
old and new pesticides, and continued study of integrated
approaches that include both chemical and nonchemical
methods. An integrated approach provides an opportunity
for introducing, on a cost-competitive basis, small amounts
of new, less persistent materials to replace the low-cost
persistent pesticides now in use.
Although environmental contamination can be reduced
by substituting a nonpersistent pesticide for a persistent
one, this substitution can lead to other problems. Certain
nonpersistent pesticidal chemicals are much more hazardous
to apply than the chemicals they replace. Others tend to
cause immediate injury to pollinating insects or to other
animal species of interest to man. Such potential hazards
and side effects should be evaluated thoroughly before
substitutions are made.
Expanded research on pesticidal chemicals will help
in identifying the best one for a given pest-control problem
as well as the best method of using it in each situation,
thereby providing opportunities for reducing the dissemi-
nation of persistent pesticides. To be fully successful,
expanded research on pesticides must be accompanied by
effective action in three areas: registration of labels.
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state and federal recommendations, and education. The
educational effort should be directed to insuring that
pesticides are used with minimum contamination of the
environment.
CONCLUSIONS
1. Persistent pesticides are contributing to the
health, food supply, and comfort of mankind, but, in the
absence of adequate information on their behavior in
nature, prudence dictates that such long-lived chemicals
should not be needlessly released into the biosphere.
2. Although persistent pesticides have been replaced
in some uses and are replaceable in others, they are at
present essential in certain situations.
3. No decrease in the use of pesticides is expected
in the foreseeable future. On a world basis, increased
use is probable.
4. Although the use of DDT has decreased substan-
tially, there was no important change in the use of other
organochlorine insecticides in the United States during
the 10-year period ending June 30, 1967.
5. Available evidence does not indicate that present
levels of pesticide residues in man's food and environment
produce an adverse effect on his health.
6. Registration requirements for persistent pesti-
cides appear to provide adequate safeguards for human
health, but continuing attention must be given to accom-
modating new knowledge and insuring against subtle
long-term effects.
7. Residues of certain persistent pesticides in the
environment have an adverse effect on some species of wild
animals and threaten the existence of others.
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- 28 -
8. The availability and low cost of effective per-
sistent pesticides have slowed the development and adoption
of alternative methods of control.
9. Work on nonchemical methods as alternatives to
persistent pesticides has been emphasized in recent years,
and continued support for this work is needed.
10. Inadequate attention and support are being given
to developing pesticidal chemicals and to improving tech-
niques for using them.
11. Persistent pesticides are of special concern
when their residues possess—in addition to persistence—
toxicity, mobility in the environment, and a tendency for
storage in the biota.
12. A few organochlorine insecticides and their
metabolites have become widely distributed in the Ibdosphere,
appearing in the biota at points far from their places of
application.
13. The biosphere has a large capacity for storage
of persistent pesticides in the soil, water, air, and
biota, but little is known concerning amounts of persistent
pesticides and of their degradation products that are
stored in the biosphere.
14. Knowledge is incomplete concerning the fate and
degradation of persistent pesticides in the environment,
their behavior in the environment, the toxicity of the
degradation products, and the interaction of these products
with other chemicals.
15. Present methods of regulating the marketing and
use of persistent pesticides appear to accomplish the
objectives of providing the user with a properly labeled
product and holding the amounts of residue in man and his
food at a low level. However, they do not appear to insure
the prevention of environmental contamination.
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- 29 -
16. Public demand for attractiveness in fruit and
vegetables, and statutory limits on the presence of
insect parts in processed foods, have invited excessive
use of pesticides.
17. The National Pesticide Monitoring Program pro-
vides adequate information about residues in man and his
food, but it does not provide adequate information about
the environment generally, because it can detect changes
in residues only in selected parts of the biosphere.
18. Contamination of the biosphere resulting from
the use of persistent pesticides is an international
problem. Changes in techniques for using these pesticides
and the substitution of alternatives here and abroad are
questions of immediate concern to all mankind.
RECOMMENDATIONS
The Committee recommends—
1. That further and more effective steps be taken
to reduce the needless or inadvertent release of persistent
pesticides into the environment.
2. That, in the public interest, action be increased
at international, national, and local levels to minimize
environmental contamination where the use of persistent
pesticides remains advisable.
3. That studies of the possible long-term effects
of low levels of persistent pesticides on man and other
mammals be intensified.
4. That efforts to assess the behavior of persistent
pesticides and their ecological implications in the envi-
ronment be expanded and intensified.
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5. That public funds for research on chemical methods
of pest control be increased without sacrifice of effort
on nonchemical methods.
6. That the present system of regulation, inspection,
and monitoring to protect man and his food supply from
pesticide contamination be continued.
7. That the objectives and procedures of the National
Pesticide Monitoring Program be reviewed and that the feasi-
bility of obtaining data on quantities of persistent pesti-
cides in the biosphere be studied.
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Appendix
PERSONS INTERVIEWED BY THE
COMMITTEE ON PERSISTENT PESTICIDES
W. J. Aunan, American Meat Institute
Jack Barnes, Cooperative State Research Service, U.S.
Department of Agriculture
Harold L. Barrows, Agricultural Research Service, U.S.
Department of Agriculture
William F. Barthel, Chief, Toxicology Laboratory, National
Communicable Disease Center, U.S. Department of Health,
Education, and Welfare
George A. Bevier, Aedes aegypti Program, National Communicable
Disease Center, U.S. Department of Health, Education, and
Welfare
W. Frank Blair, Ecological Society of America
Parke Brinkley, President, National Agricultural Chemicals
Association
G. S. Buck, Jr., National Cotton Council
John L. Buckley, U.S. Department of the Interior (now with
Office of Science and Technology)
William Buren, Grants Office, National Communicable Disease
Center, U.S. Department of Health, Education, and Welfare
Philip A. Butler, Gulf Breeze Biological Laboratory, Bureau
of Commercial Fisheries, U.S. Department of the Interior
D. A. Chant, Ecological Society of America
Roland Clement, National Audubon Society
Robert Courter, Pesticide Program, National Communicable
Disease Center, U.S. Department of Health, Education,
and Welfare
E. A. Crosby, Agricultural Research Institute, Pesticide
Committee, and National Canners Association
Fred H. Dale, Bureau of Sport Fisheries and Wildlife,
U.S. Department of the Interior
Edward S. Deevey, Ecological Society of America
William Durham, Chief, Pesticide Research Laboratory,
National Communicable Disease Center, U.S. Department
of Health, Education, and Welfare
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- 32 -
Walter H. Durum, Water Resources Division, Geological
Survey, U.S. Department of the Interior
Eugene H. Dustman, Bureau of Sport Fisheries and Wildlife,
U.S. Department of the Interior
Walter W. Dykstra, Bureau of Sport Fisheries and Wildlife,
U.S. Department of the Interior
R. P. Farrow, National Canners Association
John Ford, Hercules Incorporated
Milton J. Foter, Pesticide Program, National Communicable
Disease Center, U.S. Department of Health, Education,
and Welfare
D. Lee Fowler, Agricultural Stabilization and Conservation
Service, U.S. Department of Agriculture
Leo R. Gardner, Chevron Chemical Company (arsenic)
Ben Gladdings, California Department of Fish and Game
Arthur Gohlke, Tennessee Corporation (copper)
S. A. Hall, Agricultural Research Service, U.S. Department
of Agriculture
Robert E. Hamman, Geigy Agricultural Chemicals
J. Ralph Hansen, Hercules Incorporated
T. H. Harris, U.S. Department of Health, Education, and
Welfare
Wayland J. Hayes, Chief Toxicologist, National Communicable
Disease Center, U.S. Department of Health, Education, and
Welfare
Harry W. Hayes, Agricultural Research Service, U.S.
Department of Agriculture
Patrick Healy, National Milk Producers Association
Lyman S. Henderson, Agricultural Research Service, U.S.
Department of Agriculture
Joseph J. Hickey, Ecological Society of America
John Hillis, California Department of Agriculture
Ralph E. Hodgson, Agricultural Research Service, U.S.
Department of Agriculture
C. H. Hoffman, Agricultural Research Service, U.S.
Department of Agriculture
Eldridge Hunt, California Department of Fish and Game
Phil C. Kearney, Agricultural Research Service, U.S.
Department of Agriculture
E. F. Knipling, Agricultural Research Service, U.S.
Department of Agriculture
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O. F. Kolari, American Meat Institute
Sheldon M. Lambert, Shell Development Company (soil-chemical
interactions)
L. C. LaMotte, Jr., Community Studies, National Communicable
Disease Center, U.S. Department of Health, Education,
and Welfare
Kendrick Lee, Bureau of the Budget (Aedes aegypti Program)
Allan B. Lemmon, California Department of Agriculture
L. A. Liljedahl, Agricultural Research Service, U.S.
Department of Agriculture
Bernard H. Lorant, Velsicol Chemical Corporation
James H. McDermott, Federal Water Pollution Control
Administration, U.S. Department of the Interior
Lewis E. Mitchell, Shell Chemical Company
Donald Mount, National Water Quality Laboratory, U.S.
Department of the Interior
William Murray, Federal Committee on Pest Control
Joseph Noone, National Agricultural Chemicals Association
Don Pierce, Forest Service, U.S. Department of Agriculture
P. B. Polen, Velsicol Chemical Corporation
R. D. Radeleff, Agricultural Research Service, U.S.
Department of Agriculture
L. L. Ramsay, Food and Drug Administration, U.S. Department
of Health, Education, and Welfare
George Reich, Community Studies, National Communicable
Disease Center, U.S. Department of Health, Education,
and Welfare
William Reichel, Bureau of Sport Fisheries and Wildlife,
U.S. Department of the Interior
Robert L. Rudd, Ecological Society of America
Paul F. Sand, Agricultural Research Service, U.S. Department
of Agriculture
Eldon Savage, State Services Section, National Communicable
Disease Center, U.S. Department of Health, Education,
and Welfare
K. L. Schultz, Velsicol Chemical Corporation
David J. Sencer, Director, National Communicable Disease
Center, U.S. Department of Health, Education, and Welfare
W. C. Shaw, Agricultural Research Service, U.S. Department
of Agriculture
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- 34 -
H. H. Shepherd, Agricultural Stabilization and Conservation
Service, U.S. Department of Agriculture
S. W. Simmons, Chief, Pesticide Program, National
Communicable Disease Center, U.S. Department of Health,
Education, and Welfare
M. Joe Sloan, Shell Chemical Company
Edward H. Smith, Committee on Agricultural Land Use and
Wildlife Resources, National Academy of Sciences-National
Research Council
Donald A. Spencer, National Agricultural Chemicals
Association
Robert Stevens, Forest Service, U.S. Department of
Agriculture
Lucille Stickel, Bureau of Sport Fisheries and Wildlife,
U.S. Department of the Interior
William Stickel, Bureau of Sport Fisheries and Wildlife,
U.S. Department of the Interior
Edward Swift, Agricultural Extension, University of
California, Berkeley
Ely M. Swisher, Rohm and Haas Company
Alan W. Taylor, Agricultural Research Service, U.S.
Department of Agriculture
Edward J. Thacker, Agricultural Research Service, U.S.
Department of Agriculture
William Upholt, Federal Committee on Pest Control
Charles R. Walker, Bureau of Sport Fisheries and Wildlife,
U.S. Department of the Interior
George M. Woodwell, Ecological Society of America
Anne Yobs, Pesticide Surveillance Unit, National Communicable
Disease Center, U.S. Department of Health, Education,and
Welfare
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