THE NEED FOR PESTICIDES

Strong pressures—biological, economic, sociological, and esthetic—favor the use of pesticides. It is extremely important that these influences be understood if there is to emerge a system of regulating pesticides that strikes a balance between adequate safeguards and undue restriction.

ASSESSMENT OF THE PESTICIDE PROBLEM

Chemical pest control in the modern sense began around the middle of the last century. Sulfur was used against powdery mildew of grapes in 1821; Paris green was successfully used to control an outbreak of Colorado potato beetle in 1867; and the fungicidal properties of Bordeaux mixture, which is still used, were discovered in 1883.

Reservations about effectiveness and concern for hazard to nontarget organisms were expressed early in the development of chemical pest control. An editorial in the first number of the Practical Entomologist, October 30, 1865 (Entomological Society of Philadelphia, 1865), raised doubts as to the value of chemical pesticides in insect control and suggested the importance of biological studies. In 1894 it was proven that arsenicals killed bees when sprayed on fruit trees in bloom, and in 1903 a tolerance for arsenicals on foods was established by the British.

The era of the synthetic organic pesticides began with the development of DDT as an insecticide in 1939. The effectiveness of DDT was highlighted through its use during and after World War II to control vectors of human diseases.

After World War II, the chemical industry, government, and universities joined forces in adapting DDT and related compounds to peacetime uses. The discovery of many new synthetic compounds followed. This was augmented by equally rapid developments in formulation and methods of application. Thus, in a matter of a decade or so, synthetic organic pesticides became commonplace in agriculture, in industry, and in the home. Indeed, by 1962 some 500 compounds, in more than 54,000 formulations, were registered for use as pesticides in the United States.

It was at this point that Rachel Carson's Silent Spring appeared (Carson, 1962). The combination of timing, her literary skill, the popular cause she espoused, and the misgivings that had already arisen touched off a great debate. This debate extended throughout government, the scientific community, the chemical industry, and agriculture and conservation organizations, and provided a public forum whereby the advantages and disadvantages, the gains and the losses, the facts and the fantasies could be aired.

This controversy led to numerous investigations. Of these, five are especially pertinent to the impact of pesticide use on wildlife:

1.

The President's Science Advisory Committee's (PSAC) Panel on the Use of Pesticides began a study of the problem in the summer of 1962. This group's report is of particular interest because it represents the first official pronouncement after the outbreak of the pesticide controversy (President's Science Advisory Committee, 1963). The theme of the report, simply stated, is that the use of pesticides must be continued to insure adequate supplies of food and fiber, but that their use may endanger beneficial plants and animals as well as man himself. The report recommended:

a.

assessment of the level of pesticides in man and his environment;

b.

development of measures to allow greater safety in pesticide use;

c.

research on safer and more specific methods of pest control;

d.

amendments to strengthen public laws governing the use of pesticides; and

e.

public education of pesticide benefits and hazards.

2.

At about the same time, the Subcommittee on Reorganization and International Organization of the Committee on Government Operations began its study entitled “Inter-Agency Coordination in Environmental Hazards (Pesticides)” under the chairmanship of Senator Abraham Ribicoff. Hearings continued for 15 months and massive testimony was compiled on many aspects of the problem. The hearings served not only as a fact-finding forum, but also as a public sounding board for the diverse interests represented by the many witnesses. The final report of the subcommittee (United States Senate, 1966) was released in August, 1966.

Particularly significant is the broad ecological context within which the committee viewed the pesticide issue. The following is indicative of its view:

The public debate over pesticides is but one facet of a wider debate which reflects a greater sensitivity to the fundamental questions raised by the continuing and accelerating pace of man's modification of his total environment. Pesticides are but one factor and we are increasingly aware that our environment is being altered even more dramatically by air and water pollution, atomic fallout and the population explosion.

As we come to appreciate more keenly the significance of this fast accelerating, irreversible alteration of our environment, we recognize the need for stock-taking and the necessity of endeavoring to take into account all the multitude of complex relationships between man and his natural and artificial surroundings.

3.

In a comprehensive report titled “Restoring the Quality of Our Environment,” the PSAC Environmental Pollution Panel (President's Science Advisory Committee, 1965) considered pollution in its broadest context and made more than a hundred specific recommendations. The philosophy of the panel was based on the assumption that pollution is a by-product of a technological society and that pollution problems will grow with increases in population and improved living standards unless drastic counter-measures to reduce it are taken.

The panel offered some sweeping recommendations that placed problems of pollution in a new perspective. The report stated that freedom from pollution should be recognized as a human right, that responsibility for pollution control rests with the polluter, and that the polluter should bear the cost of pollution abatement and pass it on to the consumer as part of the cost of operation. Finally, the need for considering all pollution as a single problem was stressed; the responsibility for leadership in pollution abatement should be assumed by the federal government.

The study by the PSAC Environmental Pollution Panel was attuned to the needs of the times and the report provides a broad blueprint for constructive action. The philosophy, recommendations, and much of the material in the appendixes of that report are relevant to the question of land use and wildlife.

Although the approach was different, the recommendations growing out of the Ribicoff hearings (United States Senate, 1966) agree essentially with those of the Environmental Pollution Panel report. This is not surprising since the counsel of many of the same individuals or agencies was sought by the two groups in the course of their investigations.

4.

In early 1966, a symposium on “Scientific Aspects of Pest Control,” sponsored by the National Academy of Sciences-National Research Council (1966) was held in Washington, D.C. The objective was to bring together the current scientific knowledge of the various aspects of pest control, and communicate it not only to the scientific community, but to lay leaders, the press, and government policymakers as well.

The symposium provided an opportunity for review of the progress made on the recommendations of the PSAC Panel almost 3 years earlier. It was a unique experiment in seeking to bridge the communication gap between persons developing specialized knowledge and persons responsible for translating that knowledge into broad policy and future environmental quality goals.

5.

The most recent report was by the Committee on Persistent Pesticides, which was established by the National Academy of Sciences-National Research Council (1969b) at the request of the U.S. Department of Agriculture. This report is of special interest because it addresses the problem of persistent pesticides as they relate to wildlife. The report reiterates many earlier findings regarding the benefit-risk features of persistent pesticide use. In addition, it stresses that while present methods of pesticide regulation adequately protect man's food supply, “they do not appear to insure the prevention of environmental contamination.”

These five reports provide useful assessments of the relationship of pesticides and, to a lesser degree, other pollutants to wildlife. Many other studies have contributed to our knowledge of the problem. Two committees established by agencies of the federal government in the late 1960's undertook to study the relationship of pesticides to human health and environmental pollution—the Commission on Pesticides and Their Relationship to Environmental Health, an 11-member committee appointed by Secretary Finch of the Department of Health, Education, and Welfare, and the Environmental Quality Council established by executive order of President Nixon.

In all of these studies the problem of pesticide pollution as it affects wildlife was recognized. The plea for more research is common to all of them. Lacking, however, are statements fixing responsibility for well-being of the ecosystem and specific proposals to reduce inputs of persistent pesticides to avoid the adverse consequences that are fore-told in these reports if their use continues unabated.

REGULATING THE USE OF PESTICIDES

The three major concerns in the use of pesticides are: (1) direct poisoning of humans and wildlife through accidents or exposure during manufacture, transport, storage, or use; (2) toxic residues that may pose a hazard to the consumer; and (3) environmental pollution arising from introduction of pesticides in the ecosystem.

The need has long been recognized for legislation to regulate the use of pesticides and minimize the undesirable effects. The original Federal Insecticide Act of 1910 controlled the sale of pesticides in the United States to protect consumers from substandard or fraudulent products. The concern for human health was first demonstrated with the Federal Caustic Poison Act of 1927, which regulated the labeling of any dangerous, caustic, or corrosive substance put up in containers suitable for household use. The present regulatory responsibilities of the U.S. Department of Agriculture and the Department of Health, Education, and Welfare have been described in detail (National Academy of Sciences-National Research Council, 1966: 385-398).

It was not until after World War II, when the variety of pesticides had greatly increased and commercial use became widespread, that concern for protection of human health led to the replacement of the Insecticide Act of 1910 with the Federal Insecticide, Fungicide and Rodenticide Act of 1947 (FIFRA), administered by the Pesticides Regulation Division of the Department of Agriculture. This law is the basic federal act governing pesticides in interstate commerce. A 1959 amendment to the FIFRA added nematocides, plant regulators, defoliants, and desiccants. Further amendments in 1964 (a) eliminated the controversial section of the 1947 act that allowed sale of an unregistered product when a protest had been filed, (b) required a federal registration number on each label and conspicuous precautionary labeling of poisonous and potentially hazardous pesticides and (c) required manufacturers to remove unwarranted safety claims from the labels. The 1964 act requires:

1.

Registration of economic poisons prior to their sale or introduction into interstate or receipt from foreign commerce;

2.

Prominently displayed warnings on the labels of all pesticides with an LD₅₀ of less than 5,000 mg/kg;^*

3.

The coloring or discoloring of certain economic poisons to prevent their being mistaken for flour, sugar, salt, baking powder, or other similar articles used in preparing foodstuffs;

4.

Prominently displayed statements on the label of the economic poison to advise the user of potential hazards to man, wildlife, vegetation, and other nontarget organisms; and

5.

Instructions for use to provide adequate protection and to assure effectiveness of the formulations against stated target organisms.

Besides the above requirements, a three-way agreement was concluded in 1964 between the Departments of Agriculture, of the Interior, and of Health, Education, and Welfare on the review of pesticide registration applications relative to considerations of human health and hazards to wildlife. The Department of the Interior reviews for implications as to hazard to wildlife all data on compounds submitted to the Department of Agriculture for registration or re-registration. When a hazard to wildlife is believed to exist, the Department of the Interior advises the Department of Agriculture of appropriate action to restrict use, to require additional warnings, or to eliminate certain use patterns.

In addition to the 1947 FIFRA and its amendments and regulations, the Federal Food, Drug and Cosmetic Act of 1938 and its “Miller Amendment” of 1954 (Public Law 83-518) further control the use of pesticides. This act and its amendments are administered by the Secretary of Health, Education, and Welfare through the Food and Drug Administration. They provide that tolerance levels be established for pesticide residues in raw agricultural commodities upon which pesticides are used. Any raw agricultural commodity may be condemned as adulterated if it contains a residue of any pesticide that has not been formally exempted or that is present in excess of the tolerances. This law is also concerned with the adulteration of foods with insects, insect fragments, hair, excreta of rodents, and any other extraneous filth that may offend the sensitivities of consumers or endanger their health.

These two federal statutes (FIFRA and Miller) in their present form supplement each other and are interrelated by law and practical operation. Both require stringent evaluation of the safety and effectiveness of the toxicants. Both are primarily concerned with the protection of the health of the user, the consumer, and the public in general. Because both statutes apply to interstate sale of the chemical or commodities treated with pesticides, there is no provision for federal control over the final use of a USDA-registered pesticide. Control of actual use of pesticides rests with the states. Present pesticide use laws vary considerably between states. However, many of the states now have pesticide control boards or panels that include representation from fish and wildlife groups as well as from agricultural and industrial interests and that are working in the public's behalf to reduce pollution by pesticides and to minimize their harmful effects on fish and wildlife.

By 1969, 48 states regulated the marketing of pesticides within their own borders through labeling or tolerance laws, or both, patterned after the federal acts. In addition, 37 states regulate the use and commercial application of pesticides, which includes the licensing of commercial applicators. Unfortunately, many states use pesticide laws as a means of providing additional revenue and exercise little regulatory authority. The need for state legislation and enforcement, in addition to the federal, is based on two facts: (1) Federal legislation applies only in interstate commerce, and there are many instances where sale either of the pesticide or of the agricultural commodity is transacted completely within a single state; and (2) neither of the two federal laws (FIFRA and Miller) provides for control of the actual use of a given chemical.

State legislation frequently deals specifically with the use of toxicants for control of birds, mammals, or fish. In 1967, for example, 12 states prohibited completely the use of poisons for eliminating such birds as starlings, feral pigeons, or house sparrows, which frequently become a nuisance. The use of rotenone or other toxicants to control or eliminate unwanted fish is usually regulated by the state fish and game laws. The use of these materials ordinarily requires a permit from the state.

As indicated above, numerous legislative regulations exist at both state and federal levels designed to control residues and promote safe use of pesticides. These impose direct legal controls on the manufacturer and shipper to insure proper labeling and acceptable standards of quality. The chief control over the user is the regulations on residue tolerances that must be met if the commodity is to be safe from condemnation. For the commercial farmer this is a strong incentive for compliance, but there are obviously many uses that do not fall within these regulations.

How effective have state and federal regulations been in protecting the public? The evidence suggests that existing regulations are effective in avoiding excessive residues in food, if established tolerances are in fact realistic. The so-called Market Basket Surveys lend support to this view (Duggan et al., 1967; Martin and Duggan, 1967), and the recent report of the Committee on Persistent Pesticides (National Research Council, 1969b) reaffirms this presumption.

In the matter of direct human poisoning the record indicates that the number of poisonings by pesticides is reasonably low compared with poisonings by common drugs, household chemicals, and similar substances. The National Clearing House of Poison Control Centers, reporting on 83,704 poisoning cases among all ages, stated that in 1967, 51.5 percent of accidental ingestions involved medicines; cleaning and polishing agents ranked second with 14.3 percent; cosmetics third with 6.1 percent; and pesticides fourth with 6.0 percent (U.S. Department of Health, Education, and Welfare, Public Health Service, 1968).

In the third area of concern, environmental pollution, the regulatory framework provides inadequate safeguards. There are a number of reasons for this. Early concern over pesticide use centered chiefly on matters of human health, and experience in regulatory control for environmental quality is therefore limited. Responsibility could be rather easily established with respect to the manufacturer, shipper, and user in the case of food products. For the user not concerned with residue tolerances there is little or no control. While label directions can specify the timing, concentration, and number of applications, compliance is essentially voluntary. Into this gap in the regulations fall numerous uses such as municipal and public health programs and treatment of turf, soil, and ornamentals.

Another void in the regulations is the virtual exemption of the homeowner, who is free to purchase numerous pesticides in countless formulations and to use them as he likes. The cabinet at a summer cottage attests to industry's innovativeness and the buyer's eagerness for a vast array of pesticides for pushbutton use.

The welfare of wildlife is presumably represented in the pesticide regulations issued by the Department of the Interior; however, that agency's judgments must be made without full knowledge of the errors and abuses that may result from the human factor. And fully adequate information on the quantity of pesticides involved in various uses and the movement of a pesticide in the ecosystem is not available.

Of increasing concern is the chance of accidents in transporting pesticides that could lead to poisoning of humans or massive pollution of an area. These possibilities are increased when pesticides are employed in area treatments in conjunction with military operations.

The striking feature of our dilemma is that the persistent pesticides, which are so widely distributed and are in some cases adversely affecting wildlife, were acquired chiefly through practices that conformed to existing regulations. This fact alone speaks to the inadequacy of existing regulations. As this situation has become clear, public interest has focused on more stringent legislation designed to halt the accumulation of pesticides known to be serious environmental contaminants.

A number of bills have been introduced or suggested to ban DDT and other persistent chlorinated hydrocarbons. Restrictive regulations are in effect in several states and action at the municipal level is increasing.

There are, of course, arguments for and against a total ban on persistent pesticides. General prohibition denies the public the benefits of uses that do not seriously contribute to environmental contamination. Such action substitutes legislative fiat for the exercise of judgment, and reduces the diversity of pesticides available to meet varied needs. Because pesticides are mobile, local prohibition may create a sense of false security unless it is applied so generally as to have an effect on area pollution.

A point in favor of legislative bans is that while many voluntary measures could have been adopted to reduce pollution, progress by this route has been disappointing. A number of factors—economics, market standards, and provincial environmental concepts—operate against concerted action on a voluntary basis. A system of licensing or issuing of permits has been employed with reasonable success in the case of commercial pest-control operators, but issuing permits involves costly overhead and is of questionable effectiveness for control of the diverse uses of pesticides.

The ultimate solution to the problem of pesticides and, indeed, of environmental quality in all its aspects will require both regulatory and educational programs. At best, regulations can be effective only as they reflect the understanding of the public at large. The greatest factor in insuring a viable environment will be an informed public.

PRODUCTION AND USE OF PESTICIDES

The total worldwide production of pesticides is not accurately known, a fact that complicates assessments of the inputs of pesticides in the ecosystem. General trends in pesticide production and use are, however, available. The reports on production and use published annually by the U.S. Department of Agriculture are particularly useful.

Based on information from this source (Agricultural Stabilization and Conservation Service, USDA, 1968) it is estimated that in 1967 the United States produced from 50 to 75 percent of the total worldwide supply of pesticides. It is expected that this proportion will decrease as other countries improve their capacity to produce these chemicals. In both domestic and foreign use, total quantities showed an overall increase of 37 percent during the 5-year period 1963-1967. In the United States, use of herbicides continued to increase more rapidly than did the use of either fungicides or insecticides. This trend did not apply overseas, where insecticides and fungicides are expected to dominate, reflecting the close relationship of herbicides to advances in mechanization of agriculture.

Total production of chlorinated hydrocarbons in the United States for domestic use and export increased by about one third in the ten-year period ending June 30, 1966, but the 225 million pounds produced in 1967 represents a decline over the levels of the preceding five years. The reduction is greater for DDT than for the related compounds of the “aldrin-toxaphene group.” Production of DDT reached a peak of 185 million pounds in 1962-63 and declined by 40 percent by 1966-67. Thus, in terms of total production of persistent insecticides, there was no dramatic change between 1957 and 1967.

Insecticide exports of 1967 comprised 59 percent of the total value of pesticide exports; DDT accounted for 8 percent of the total and related chlorinated hydrocarbons added another 14 percent.

There are certain striking features in domestic and foreign patterns of pesticide use. Data compiled for 1964 indicate that 42 percent of the total production of pesticides was used in agriculture in the United States, the remainder going for export and domestic nonagricultural purposes. Farmers applied two thirds of the total quantity of all insecticides used on farms that year to three crops—cotton, corn, and apples. The cotton market accounted for more than half of this total—70 percent of the DDT, 86 percent of the endrin, and 69 percent of the toxaphene. It is recognized, of course, that there are other agricultural pollutants (Secretary of Agriculture and the Director of the Office of Science and Technology, 1969).

While similar comparisons cannot be made for foreign insecticide use, it is known that over half of the DDT exported is used for control of the mosquito vector of malaria. In both foreign and domestic use patterns, a few insects account for a high proportion of insecticide application; alternative methods of control of these pests could result in marked reductions in insecticide consumption.

Another major domestic use of insecticides is for control programs conducted by the Plant Pest Control Division, U.S. Department of Agriculture, in cooperation with the various states. Municipal programs of pest control and the operations of resort owners, homeowners, etc., must also be considered as sources of pesticide pollution.

The significance of these points in terms of environmental pollution are:

1.

Systems of reporting on pesticide production and use are not adequate for accurate determinations of total production and specific uses, and for identification of site of employment.

2.

There has been no dramatic decrease in the production of persistent chlorinated hydrocarbon insecticides.

3.

Total production of synthetic organic pesticides has increased consistently since their introduction, and this pattern is expected to continue.

OUTLOOK FOR IMPROVED PEST-CONTROL PRACTICES

The accumulation of pesticides in the environment could be reduced by: (1) adopting improved methods of pesticide use, (2) adopting alternative methods of control, and (3) using pesticides that are less troublesome as pollutants. The series of six volumes on principles of plant and animal pest control published by the National Academy of Sciences (National Research Council, 1968a, 1968b, 1968c, 1968d, 1969a, 1970) provides useful background information on these alternatives. Other pertinent summaries are available (National Academy of Sciences-National Research Council, 1966, p. 39-218; and President's Science Advisory Committee, 1965, p. 230-291).

It is obvious that much progress can be made in methods and application, in formulations, and in timing of treatments. Likewise, biodegradable pesticides can often be substituted for persistent ones. There is also great promise for control methods that do not require chemicals. In practice, however, these possibilities have thus far had but limited impact on the problem of pesticide pollution, and the outlook for marked change within the existing economic and regulatory framework is limited.

Chemical control has continued as the first line of defense against pest outbreaks because it can be employed as needed and the results are immediate. These advantages weigh heavily whenever other possibilities are considered as alternatives. There has been no great tendency to shift to biodegradable pesticides except where there are advantages other than those pertaining to environmental quality. The development of resistance to certain pesticides has, in some cases, been responsible for some instances of changing to less persistent pesticides. Persistence is, in many cases, a prerequisite to effectiveness, and industry has for many years sought broad-spectrum, persistent pesticides because of their more general use and sales appeal. This is a natural response on the part of industry, considering the several million dollar investment required to develop and market a new pesticide. As indicated earlier, economics is a major factor in the selection of a pesticide and no appreciable change can be expected as long as “raw” economics is the major factor in decision-making by the individual who is not in a position to place a price tag on environmental quality.

In addition, the side-effects of shifting to pesticides believed to involve less hazard to the environment cannot be predicted with accuracy. It is, therefore, essential that vigilance be maintained as changes are made in materials and practices.

While the lists of alternative methods of pest control are impressive and promising, research on their refinement is a time-consuming effort that cannot be programmed with certainty, and their effective employment requires precise supporting information if sound judgments are to be made.

PESTICIDES AS POLLUTANTS

While not all factors in the benefit-risk equation of pesticide use will be known to our satisfaction, a few facts are highly pertinent. We should have rather complete knowledge of the quantities of pesticides produced, where they are applied, and for what purpose. In addition, we need to know the chemical characteristics of these compounds as regards toxicity, stability, and solubility. Information is also needed on mobility in the ecosystem and on levels in living organisms and components of the biosphere.

MONITORING PESTICIDES IN THE ENVIRONMENT

The need to monitor residues in the environment was stressed by the President's Science Advisory Committee (1963). The committee specifically recommended that current pesticide levels and their trends in man and his environment be determined and that a continuing network be established to monitor residue levels in air, water, soil, man, and wildlife. In response to this recommendation the interagency Federal Committee on Pest Control provided guidelines for establishing the National Pesticide Monitoring Program (NPMP). The findings of NPMP, as well as the monitoring findings of other agencies, are reported in the Pesticides Monitoring Journal which began publication in June 1967 under sponsorship of the Federal Committee on Pest Control. This monitoring program is described in the first issue of the journal (Federal Committee on Pest Control, 1967).

Phases of the NPMP designed to measure pesticides in humans follow the levels in selected communities. Pesticides in foods are considered in terms of average levels in a standard diet as well as in selected components of basic diets. These findings provide baselines for determining changes and also for calculating average values.

Soil monitoring is based on sampling of agricultural, range, and forest soils. Monitoring of water is based on sampling of rivers at selected sites. Oysters and clams, freshwater fish, waterfowl, and starlings have been selected as representative substrates for monitoring residues in wildlife. The importance of comprehensive air monitoring is obvious, particularly in view of the growing recognition of air as a transport medium in the movement of pesticides.

It is perhaps too early to judge the adequacy of the monitoring program, but it would appear in view of their mobility that persistent pesticides should be monitored on a global scale, with emphasis on the pattern of pesticide “fallout” in the biosphere.

PESTICIDES IN WILDLIFE AND THEIR SIGNIFICANCE

A voluminous literature establishes the fact that persistent insecticides are widely distributed in the biosphere and occur in a wide variety of animals throughout the world. A review of some pertinent evidence on this topic has been provided by Stickel (1968).

The mere presence of a pesticide in a living organism does not mean, per se, that it has a harmful effect. In fact, the tolerances established for DDT in the human diet are based on the assumption that, at these levels, DDT will accumulate in the fat, but at levels that are not harmful to human health.

Unfortunately, diagnosing a cause of mortality as it relates to residue content in the animal is fraught with difficulty. Much research has been directed to this question in insect toxicity studies and many anomalies remain. Such studies are complicated by the fact that the mode of action of chlorinated hydrocarbons is not precisely known. Even in the case of organophosphate insecticides, whose mode of action is known to be generally through the inhibition of cholinesterase of the nervous system, the relationships between dosage levels, inhibition rates, and toxicity are not readily established experimentally; these relationships would be even more difficult to establish in animals taken in their natural habitats. Despite these considerations, the literature includes many reports of residue content of tissues or whole bodies of animals on the assumption that such evidence is diagnostic of pesticide poisoning. Some meaningful correlations have apparently been established for the relationship between DDT residue levels in the brain and DDT poisoning that do apply to a wide range of species (Bernard, 1963; Dale et al., 1962; Stickel et al., 1966). Obviously, it will not be possible to regulate pesticides effectively unless the significance of pesticide levels in living organisms is better understood.

Levels of pesticide residues in animals are influenced by many variables, such as contamination of the food supply and the abilities of different species to absorb, metabolize, and excrete the toxicant. In birds, for instance, raptorial and fish-eating species in general have higher residue levels than do plant-feeding and omnivorous species because of magnification through the food chain.

The effects of pesticides on living organisms may be acute or chronic. Acute effects generally become evident soon after treatment, and are readily apparent by symptoms of abnormal behavior or death. Chronic effects, on the other hand, are in many cases not readily detected and may manifest themselves by death or in subtle ways over an extended time span. Chronic poisoning is of major concern as it might relate to mortality or physiological disturbance resulting in reproductive impairment or behavioral change. Mortality of wildlife due to pesticide poisoning has been reported for a number of species and under varied circumstances (e.g., Robbins et al., 1951; DeWitt, 1956; Rudd and Genelly, 1956; Wallace, 1959, 1962; Hunt, 1960; Hickey, 1961; Roelofs and Shick, 1962; Rosene, 1965; Ames, 1966; Keith, 1966).

More recently, concern has centered on less obvious effects of pesticide residues, such as reproductive failure. Estrogenic activity of DDT in mammals and birds has been demonstrated by Bitman et al. (1968). In both fish and birds, cases of reproductive failure have been established. Burdick et al. (1964) showed that the reduced hatch of eggs of lake trout in Lake George, New York, was due to DDT. Similar cases have been reported elsewhere. Apparently, in the maturation of eggs, the female draws on fat reserves containing DDT, which is transferred to lipids in the egg and acts on the embryo as it metabolizes this source of food in the yolk sac.

The evidence on impaired reproduction in birds by chlorinated hydrocarbon residues has been reviewed by Wurster (1968a). DDT apparently stimulates the liver to produce enzymes that act on steroids; these in turn control metabolism of calcium and its deposition in eggshells. Decrease in eggshell weight, resulting in breakage and reproductive failure, has been cited in the United States and Great Britain (Ratcliffe, 1967; Hickey and Anderson, 1968). Laboratory studies have confirmed that DDT may cause reproductive decline through reduction in eggshell thickness, resulting in mechanical breakage, and through behavioral changes, resulting in abandonment of eggs. Retardation in sexual maturity has also been reported (Jefferies, 1967).

Behavioral responses that could have important survival implications have been reported for New Brunswick salmon from DDT-sprayed rivers. Very low doses resulted in increased sensitivity to low temperatures, causing a shift in temperature selection (Ogilvie and Anderson, 1965). Behavioral changes have also been cited in gulls on Lake Michigan where high DDT levels were associated with aggressive behavior and high egg breakage (Ludwig and Tomoff, 1966). In a study of cowbirds that were fed DDT, mortality was reported following the stress of disturbance (Stickel, 1965).

While birds and fish are of general interest and are subject to observation and study with relative ease, some other important components of the biota are less conspicuous, and possible ill effects may escape detection. For instance, marine algae, which are important components of marine food chains and which play a major role in total photosynthetic activity, show reduced photosynthesis at low concentrations of DDT under laboratory conditions (Wurster, 1968b). It has also been shown that microorganisms accumulate DDT and dieldrin from soils and culture media (Chacko and Lockwood, 1967). Changes in such essential components of the ecosystem could have profound biological implications. Thus, the evidence on wildlife is important not only as it relates to wildlife directly, but to wildlife as living monitors of the environment that they share with man.

It is clear from the evidence cited that:

1.

Pesticide residues occur very generally in wildlife—in some cases at high levels.

2.

Pesticide residues may in some species cause death, or physiological disturbances that result in reduced reproductive potential and behavioral changes.

3.

The numbers of some species of wildlife are declining and the evidence strongly implicates pesticides as a causative factor.

The conclusion seems inescapable that pesticides, as currently employed, constitute a threat to wildlife, and that future practices for their use should be formulated with this in mind.

IMPLICATIONS FOR EDUCATION AND RESEARCH

The evidence cited above establishes a number of points as the framework for consideration in the future employment of pesticides.

1.

During two decades of use, some adverse side-effects of persistent pesticides on wildlife have become evident.

2.

In terms of biological adjustments in the global ecosystem, two decades has been insufficient to assess the ultimate effect of these pesticides.

3.

No decrease is anticipated in worldwide production and use of pesticides.

4.

Persistent pesticides continue to play an important role in providing for man's food, fiber, health, and comfort.

5.

The replacement of persistent pesticides and adoption of alternative methods of control are desirable but have proceeded slowly for lack of economic and other incentives and because so much time is needed for research on other methods.

6.

While pesticide regulations in the United States are believed to provide adequate safeguards for human health, they are inadequate for controlling pesticide levels in the environment.

7.

Knowledge of the movement of pesticides in the environment, their degradation, and fate is inadequate.

8.

Contamination of the biosphere with pesticides is a worldwide problem, but no international body is charged with responsibility for environmental quality.

These conclusions have strong implications for programs in education and research. While these are somber conclusions, there is encouragement in the national awakening to abuses of the environment and the need for constructive programs to restore its quality. Central to this point are the questions, “What level of environmental quality does society want?” and “What level is it prepared to pay for?”

It seems reasonable to proceed from the premise that knowledge of the relationship of man to his environment is an essential component of an educational program at both the secondary and college levels. It is entirely practical to make such training an integral part of the high school curriculum and to provide it for college students in the humanities as well as those in the sciences.

Beyond this general need is the special need to provide training for a cadre of scientists and technicians who can conduct research on the myriad problems associated with environmental pollution. Challenging opportunities are available for young people interested in careers in improving environmental quality (President's Science Advisory Committee, 1965: 39-56).

It is particularly important that narrow specialization be avoided in training scientists. In retrospect, the failure to consider pest control in terms of ecological principles accounts for some failures in the tactics employed in pest control. It is equally clear that interdisciplinary effort will be required to solve problems of environmental quality and that receptiveness to such team effort is greatly influenced by the breadth of training provided.

In addition to more adequate formal education in high schools and colleges, there is the need for education of the general public on environmental quality in all its aspects. The pesticide problem is typical of the kind of issue that will continue to arise in a technological society. In the end, society must decide, but our system of informing the public is rather ineffective in providing a useful fund of knowledge on which the concerned individual can draw. Furthermore, the existing options are not made clear and the result is a polarization of opinion “for” or “against,” with little regard for the consequences of either course. In the present debate on regulating the use of persistent pesticides, no estimates have been provided on the cost of food produced without benefit of these materials.

In considering the problem of public understanding of the impact of science and technology, an intriguing proposal has been offered by Morison (1969):

As for less formal methods for presenting science to adults, we should devise some analogy that would do for the general public what agricultural extension courses have done for the farmer and his wife. The average successful farmer, although he is far from being a pure scientist, has an appreciation for the way science works. Certainly he understands it well enough to use it in his own business and to support agricultural colleges and the great state universities that grew out of them.

The important point is that in terms of an informed public, we can do far better than we have done and an immediate objective should be that of developing an informed and responsible public to which alternatives may be directed.

We are only beginning to understand the delicate interrelationships among living creatures in biological communities. Similarly, there are great voids in our knowledge of cellular functions on which the survival of the individual organism depends. When these matters are considered, it should be recognized that most pesticides were developed empirically rather than by designing a molecule that would induce toxicity in a predictable manner. Thus, the mode of action of the most intensely studied insecticide, DDT, is still unknown—a striking example of the kind of bottlenecks that exist.

It is obvious that a tremendous research effort is needed at the basic and applied levels, that research is costly, that achievement of research goals cannot be predicted with accuracy, and that competition for able young minds is always keen.

It is reassuring, however, to note the progress that can be made in science and technology, once clear national goals are established. The success of Apollo 11 in placing men on the moon is a dramatic case in point. The current public interest in pesticide pollution offers promise for significant advances in our knowledge through research.

REFERENCES

• Abbott, D. C., R. B. Harrison, J. O'G. Tatton, and J. Thomson. 1965. Organochlorine pesticides in the atmospheric environment. Nature 208: 1317-1318.
• Agricultural Stabilization and Conservation Service. 1968. The pesticide review. U.S. Department of Agriculture, Washington, D.C. 54 p.
• Ames, P. L. 1966. DDT residues in the eggs of the osprey in the north-eastern United States and their relation to nesting success. J. Appl. Ecol. 3(Suppl.): 87-97.
• Bernard, R. F. 1963. Studies on the effects of DDT on birds. Publ. Mus. Mich. St. Univ. 2(3): 155-192.
• Bitman, J., H. C. Cecil, S. J. Harris, and G. F. Fries. 1968. Estrogenic activity of o,p′-DDT in the mammalian uterus and avian oviduct. Science 162(3851): 371-372. [PubMed: 5677532]
• Burdick, G. E., E. J. Harris, H. J. Dean, T. M. Walker, J. Skea, and D. Colby. 1964. The accumulation of DDT in lake trout and the effect on reproduction. Trans. Amer. Fish. Soc. 93(2): 127-136.
• Carson, R. 1962. Silent spring. Houghton Mifflin Co., Boston. 368 p.
• Chacko, C. I., and J. L. Lockwood. 1967. Accumulation of DDT and dieldrin by microorganisms. Can. J. Microbiol. 13: 1123-1126. [PubMed: 6049598]
• Dale, W. E., T. B. Gaines, and W. J. Hayes, Jr. 1962. Storage and excretion of DDT in starved rats. Toxicol. Appl. Pharmacol. 4(1): 89-106. [PubMed: 13883190]
• DeWitt, J. B. 1956. Chronic toxicity to quail and pheasants of some chlorinated insecticides. Agr. Food Chem. 4(10): 863-866.
• Duggan, R. E., H. C. Barry, and L. Y. Johnson. 1967. Pesticide residues in total diet samples II. Pestic. Monit. J. 1(2): 2-12.
• Entomological Society of Philadelphia. 1865. Practical entomologist, Vol. 1-2. Philadelphia.
• Federal Committee on Pest Control. 1967. Pestic. Monit. J. 1(1).
• Hickey, J. J. 1961. Some effects of insecticides on terrestrial birdlife in the middle west. Wilson Bull. 73(4):398-424.
• Hickey, J. J., and D. W. Anderson. 1968. Chlorinated hydrocarbons and eggshell changes in raptorial and fish-eating birds. Science 162: 271-273. [PubMed: 4877438]
• Holden, A. V. 1962. A study of the absorption of C¹⁴ labeled DDT from water by fish. Ann. Appl. Biol. 50: 467.
• Hunt, B. L. 1960. Songbird breeding populations in DDT-sprayed dutch elm disease communities. J. Wildl. Manage. 24(2): 139-146.
• Hunt, E. G., and A. I. Bischoff. 1960. Inimical effects on wildlife of periodic DDD applications to Clear Lake. Calif. Fish Game 46(1): 91.
• Jefferies, D. J. 1967. The delay in ovulation produced by p,p′-DDT and its possible significance in the field. Ibis 109: 266-272.
• Keith, J. A. 1966. Reproduction in a population of herring gulls (Larus argentatus) contaminated by DDT. J. Appl. Ecol. 3(Suppl.): 57-70.
• Ludwig, J. P., and C. S. Tomoff. 1966. Reproductive success and insecticide residues in Lake Michigan herring gulls. Jack-Pine Warbler 44(2):77-84.
• Martin, R. J., and R. E. Duggan. 1967. Pesticide residues in total diet samples III. Pestic. Monit. J. 1(4): 11-20.
• Morison, R. S. 1969. Science and social attitudes. Science 165: 150-156. [PubMed: 5787157]
• National Academy of Sciences-National Research Council. 1966. Scientific aspects of pest control. Publ. 1402. Washington, D.C. 470 p.
• National Research Council. 1968. a. Plant-disease development and control. Principles of plant and animal pest control, Vol. 1. Publ. 1596. National Academy of Sciences, Washington, D.C. 205 p.
• National Research Council. 1968. b. Weed control. Principles of plant and animal pest control, Vol. 2. Publ. 1597. National Academy of Sciences, Washington, D.C. 471 p.
• National Research Council. 1968. c. Control of plant-parasitic nematodes. Principles of plant and animal pest control, Vol. 4. Publ. 1696. National Academy of Sciences, Washington, D.C. 172 p.
• National Research Council. 1968. d. Effects of pesticides on fruit and vegetable physiology. Principles of plant and animal pest control, Vol. 6. Publ. 1698. National Academy of Sciences, Washington, D.C. 90 p.
• National Research Council. 1969. a. Insect-pest management and control. Principles of plant and animal pest control, Vol. 3. Publ. 1695. National Academy of Sciences, Washington, D.C. 508 p.
• National Research Council. 1969. b. Report of Committee on Persistent Pesticides to Administrator, Agricultural Research Service, U.S. Department of Agriculture, Washington, D.C. 34 p.
• National Research Council. 1970. Vertebrate pests: problems and control. Principles of plant and animal pest control, Vol. 5. Publ. 1697, National Academy of Sciences, Washington, D.C. 164 p.
• Ogilvie, D. M., and J. M. Anderson. 1965. Effect of DDT on temperature selection by young Atlantic salmon, Salmo salar. J. Fish. Res. Board Can. 22: 503-512.
• President's Science Advisory Committee. 1963. The use of pesticides. U.S. Government Printing Office, Washington, D.C. 25 p.
• President's Science Advisory Committee. 1965. Restoring the quality of our environment. Report of Environmental Pollution Panel. U.S. Government Printing Office, Washington, D.C. 317 p.
• President's Science Advisory Committee. 1967. The world food problem. Panel on World Food Supply. U.S. Government Printing Office, Washington, D.C. p.138-139.
• Ratcliffe, D. A. 1967. Decrease in eggshell weight in certain birds of prey. Nature 215: 208-210. [PubMed: 6049131]
• Robbins, C. S., P. F. Springer, and C. G. Webster. 1951. Effects of five-year DDT application on breeding bird population. J. Wildl. Manage. 15(2): 213-216.
• Roelofs, E. W., and C. Shick. 1962. Spray programs and wildlife. Mich. State Univ. Coop. Ext. Serv. E-375: 1-8.
• Rosene, W. 1965. Effects of field applications of heptachlor on bobwhite quail and other wild animals. J. Wildl. Manage. 29(3): 554-580.
• Rudd, R. L., and R. E. Genelly. 1956. Pesticides: their use and toxicity in relation to wildlife. Calif. Fish Game Bull. 7. 209 p.
• Secretary of Agriculture and the Director of the Office of Science and Technology. 1969. A report to the President—control of agriculture-related pollution. U.S. Government Printing Office, Washington, D.C.
• Stickel, L. F. 1968. Organochlorine pesticides in the environment. Special Scientific Report—Wildlife No. 119. Bureau of Sport Fisheries and Wildlife. U.S. Government Printing Office, Washington, D.C. 32 p.
• Stickel, L. F., W. H. Stickel, and R. Christensen. 1966. Residues of DDT in brains and bodies of birds that died on dosage and in survivors. Science 151(3717): 1549-1551. [PubMed: 5909590]
• Stickel, W. H. 1965. Delayed mortality of DDT-dosed cowbirds in relation to disturbance. Effects of pesticides on fish and wildlife. U.S. Fish and Wildlife Service, Circ. 226.
• U.S. Department of Health, Education, and Welfare, Public Health Service. 1968. National clearinghouse for poison control centers bulletin. Washington, D.C.
• U.S. Senate. 1966. Pesticides and public policy. Report of the Committee on Government Operations. Made by its Subcommittee on Reorganization and International Organization. Senate Report No. 1370. U.S. Government Printing Office, Washington, D.C. 86 p.
• Wallace, G. J. 1959. Insecticides and birds. Audubon Mag. 61(7): 10-12, 35.
• Wallace, G. J. 1962. The seventh spring die-off of robins at East Lansing, Michigan. Jack-Pine Warbler; 40(1): 26-32.
• Weaver, L., C. G. Gunnerson, A. W. Breidenbach, and J. J. Lichtenberg. 1965. Chlorinated hydrocarbon pesticides in major U.S. river basins. Publ. Health Rep. 80: 481-493. [PMC free article: PMC1919592] [PubMed: 14299201]
• Wurster, C. F., Jr. 1968. a. Chlorinated hydrocarbon insecticides and avian reproduction: How are they related? In First Rochester Conference on Toxicity, Chemical Fallout, Current Research on Persistent Pesticides. University of Rochester, Rochester, New York.
• Wurster, C. F., Jr. 1968. b. DDT reduces photosynthesis by marine plankton. Science 159(3822): 1474-1475. [PubMed: 5732488]

Footnotes

*

As used here, the term “pesticides” includes chemicals employed to kill living organisms that are considered pests. The major groups of pesticides considered here are insecticides, fungicites, and herbicides. The term “pesticide” may also include chemicals used against pests to repel, attract, or interrupt a vital function such as reproduction (sterilants). Other chemicals sometimes considered as pesticides are plant growth regulators, desiccants, and defoliants.

*

World Health Organization, Vector Biology and Control. 1969. The present place of DDT in world operations for public health. Statement presented at the symposium “The Biological Impact of Pesticides in the Environment,” at Oregon State University, Corvallis, August 19, 1969.

*

LD₅₀—Lethal dose for 50 percent of the test populations (a computed, not observed, figure) reported in milligrams toxicant per kilogram body weight of test species (mg/kg).