Document 7Op3k5gLMd78zMDXmM0e014JB

Member ni-Congress New York )i B. invMSON JUL28 *82 <n J&isfX' * 0 USE OF PESTICIDES A REPORT OF \ f ** /TH> PRESIDENT'S SCIENCE ADVISORY COM M UTEE . co CD in THE WHITE HOUSE Washington, D.C. M a / 15, 1963 For ulc bgr lhSuptiinirndcnt o( Document*. U.5. Govcinmini l'rinh't*K l'il'c* If ((PII u " km w . c:. i .. J / ' I / i `t \ I f t J> V rV I STATEMENT OF THE PRESIDENT ^ This'report on the use of pesticides has been prepared for me by rm ^Science Advisory Committee. u I have already requested the responsible agencies to implement the recom mendations in the report, including ihc preparation of legislative and tech nical proposals which I shall submit to the Congress. Because of its general public interest, I am releasing the rc|>ort foi publication. . T h e W hite H ouse, M a y 15, 1963 in ,< ii1 I >1 * .I \ I TABLE OF CONTENTS Statement of the President........................... I. Introduction............................ II. G ains................................................................................................ III. H azards............................................................................................ A. Classes of Compounds........................... ............................ B. Distribution and Persistence in the Environment........ C. Biological Effects on Man and Animals.......................... D. Toxicity of Specific Compounds....................................... IV. Pest Control Without Chemicals................................................ V. Role of Government in Pesticide Regulation......................... VI. Recommendations.......................................................................... Members of the President's Science Advisory Committee Panel on the Use of Pesticides................................ ........................... Members of the President's Science Advisory Committee. -- I 2 1 * 5 X 1 I 1' 1" -* ?' v ,t iI-; r'- , V. I. INTRODUCTION M an's primary concerns have always been (he struggle tor survival a*1 improvement .of his lot. As his numbers increased, he attained greati ability to manipulate his environment. In the process he sometiiues uilictcd damage on himself and on his surroundings. Advances have abv.n entailed a degree of risk which society must weigh and either accept, or iejeet, as the price of material progress. A major step in civilization was the domestication of food plants. With the birth of organized agriculture and (he resultant concentration of crops and animals, the stage was set for outbreaks of pests. Until that liuv man had to search for food as did the pests. Afterward neiihrr had (* search; instead, pest control became necessary. The welfare of an increas ing human population requires intensified agriculture. This in turn cnabh the pests to increase, which necessitates the use of pesticides with their m n comitant hazards. It thus seems inevitable that, as the population increase*so do certain hazards. In an effort to understand and evaluate these problems, the Panel iitulri took a review of the information relevant to pesticides, including rx p n i mental data and the various administrative procedures which arc design *1 for the protection of the public. The Panel could not have accomplished this review without the assistance it received from the Departments nl Agriculture, Interior, Defense, and Health, Education, and Welfare, as well as from many individuals throughout the country. The information provided to the Panel has demonstrated how rernarkahb effective the modern organic chemicals arc in facilitating both the roilin'' of insect vectors of disease and the unprecedented production of food, Icnl. and fiber. The use of pesticides associated with the production of nui food is carefully controlled by the growers and supervised by agricidiui specialists and the Food and Drug Administration. As a result, the reside levels measured, on foods, intended for interstate and foreign cnimurn arc low and rarely above Federal tolerance limits. The Panel believes that the use of pesticides must be continued if we . to maintain the advantages now resulting from the work of informed fond producers and those responsible for control of disease. On the ollu-r hand, it lias now become clear that the proper usage is not simple and (hat, whil*they destroy harmful insects and plants, pesticides may also be toxic beneficial plants and animals, including man. Their toxic effects in la*.** doses are well known and precautions can he taken to set?.Ihat humans " er* needlessly exposed. nut we must now also take measures to insure t.ctf.'itinurd exposures to small amounts of these chemicals in our environnt will not be harmful over long periods of time. levicw of pesticides brings into focus (heir great merits while suggesting l there are apparent risks. This is the nature of the dilemma that connts the Nation. The Panel lias attempted to stale the ease--the benefits, hazards, and the methods of controlling the hazards. can suggest y* of avoiding or lessening the hazards, Init in the end society must :idc, and to do so it must obtain adequate information on which to c its judgments. The decision is an uncomfortable one which can.never final hut must be constantly in (lux as circumstances change and nvlcdgc increases. II. GAINS FROM TH E USE OF PESTICIDES Due material standard of living lias been greatly elevated during the :h century by increased control over the environment. Few recent /rlopincnls have been so effective or have had application in such a :1c range of human endeavor as the pesticide chemicals. Although uicidcs have been used for centuries as adjuncts in pest control, the :at advances of the last 20 years resulting from the discovery, manu:ture, and application of new compounds have changed their rote in my instances to that of the principal and, frequently, sole control measure. Pesticide^ have made a great impact by facilitating the production and olcr.tion of food, feed, and fiber in greater quantity and quality; by iproving health; and by keeping in cheek many kinds of nuisance sects and unwanted plants. Agricultural needs have entailed the largest iplications of pesticides in this country. Productivity has been so in cased that famine is an unknown experience to the people of the dcdoped nations. Mechanization, improved fertilizers, and the breeding f productive and disease-resistant ciops have also contributed importantly, n addition, pesticides have made possible the economical production of tany crops which otherwise would be available only to a limited number f wealthy consumers. While reducing food losses, pest eonlrol has also resulted in foodstuffs f the highest quality. Today, for example, sweet corn, potatoes, cabage, apples, and tomatoes arc all available unman cd, and the American musewifr is accustomed to blemish-free products. Citrus fruits arc rhlnm damaged or lost because of scale inserts, fruitflics, or diseases, and he cost of animal protein is lower because large losses of cattle from tick ever and gnibs no longer occur. Modern agricultural efficiency is maintained not only through the use >f insecticides, but also by means of Jicibicidcs, fungicides, rndcnticidcs, icinatocidcs, plant-growth regulators, and other chemicals. T heir bencils extend beyond crops raised for direct human consumption. They icrinit efficient production of forage ami grains, which in mm are needed o 'fo r a productive livestock economy. Jn addition, they allow pmln yields of nonfood crops such as cotton, tobacco, and timber. fVsii- I- . have not, however, reached an optimum of effectiveness. More than 11 ' established pests have dcvclojied resistance to one or more previnm1, fcclive chemicals, and new pests arc occasionally introduced by ini . tional traffic. Rapid population growth and concomitant decrease in land avail 1 for agriculture necessitate greater crop yields per acre and reduction *>1 losses and spoilage in stored foods. Moreover, many products must In- j i>*> tcctcd during the process of manufacture and distribution. Besides enabling spectacular increases in agricultural production, j ti- cidcs have freed man from communicable diseases to an nnprrcrd* nt- il extent. In less developed areas of (he world, malaria, typhus, and si'lciv fever, previously controlled only with great difficulty, an; now limited "id in some locations eradicated. In each case, pesticides have facilitated trol of the insect vector. At some stage of their natural history a im' `--i of the major communicable diseases involve an intermediate Itost nr v< '- i Most successful disease-control programs have been directed at elin : ing this link in the chain of transmission, rather than treating nun ' e he has contracted the disease. However, control programs have not achieved disease eradication. Ma laria is still the disease responsible for the largest number of deaths in the world each year, although new eases are rare in the United States. Vi How fever, schistosomiasis, plague, and some rickettsial diseases are almo'i un known in the mainland of North America, but they still lake a large mil of human lives in the rest of the world. Furthermore, reservoirs of diM-.**- in animals, and insects which can transmit them, will remain with us h** ihe predictable future both in this country and in other parts of the wmld. ih-is requiring a continued effort to control (hern. An additional complication in disease control is that the insert m *. ;>. such as mosquitoes that transmit malaria, may produce resistant p*- lions capable of transmitting their resistance to pesticides from griui.-pon to generation. In order to keep up with the successive threats nl m eel vectors as they develop resistance to one chemical after another, it i> im portant to enlarge and improve our capability for controlling pests, Pesticides also have made control of many nimanrr insects and pi mis financial])' feasible. Were the cost higher, the funds for their eontiol \ -uld he used by other more critical demands on the economy. For ex.in-i ! it might be loo expensive to control the varieties of mosquitoes licit !> 1 in marshes and estuaries which do not transmit disease, but limit man - menl of some of the most desirable recreational areas. Similaily, ! tion of roaches from kitchens, aphids from roses, and fungi in- '* greens arc very desirable but n<inessential benefits. Kflicient agricultural production, protection of health, ami elimin *1 nuisances arc now required and expected by modern man. I lie i- .Is rs 0*1 3 if ' ''' scd* to,accomplish these ends must continue to improve, although their resent scope'and magnitude far exceed the few examples included here, t is certain (hat coining years will witness sophistication of methods and cw uses for which pesticides were not originally conceived. III. THE HAZARDS OF USING PESTICipES Evidence of increasing environmental contamination by pesticide elicminls has generated concern which is no longer limited to citizens of affected reas or members of special-interest groups. During two decades of inensive technical and industrial advancement we have dispersed a huge 'olumc of synthetic compounds, both intentionally and inadvertently, tfnny, such as detergents, industrial wastes, and pesticides, arc now found ar from the point of initial dispersal. Today, pesticides arc detectable in many food items, in some clothing, in man and animals, and in various parts of our natural surroundings. Carried from one locality to another by air currents, water runoff, or living or ganisms (either directly or indirectly through extended food chains), pesti cides have traveled great distances and some of them have persisted for long periods of lime. Although they remain in small quantities, their variety, toxicity, and persistence arc affecting' biological systems in nature and may eventually affect human health. The benefits of these substances are apparent. We arc now beginning to evaluate some of their less obvious effects and potential risks. Precisely because pesticide chcmirals arc designed to kill or mctaboli cally upset some living target organism, they arc potentially dangerous to other living organisms. Most of them arc highly toxic in concentrated amounts, and in unfortunate instances they, have caused illness and death of people and wildlife. Although acute human poisoning is a measurable and, in some cases, a significant hazard, it is relatively easy to identify ; control by comparison with potential, low-level chronic toxicity which been observed in experimental animals. The Panel is convinced that we must understand more completely the properties of these chemicals and determine their long-term impact on biological systems, including man. The Panel's recommendations arc di rected toward these needs, and toward more judicious use of pesticides or alternate methods of pest control, in an effort to minimize risks and maxi mize gains. They arc offered with the full recognition that pesticides constitute only one facet of the general pmblcm of environmental pollution, but with the conviction that the hazards resulting from their use dictate rapid strengthening of interim measures until such lime as we have realized a comprehensive program for controlling environmental pollution. A. Cl.ASSr.S OF COMI'OUNUS The term pesticide hi oat11y includes compounds intended for a variety nf purposes. '1 hey arc used to control insects, mites, ticks, fungi, nematodes, rodents, pest birds, predatory animals, rough fish, plant discasr*, anil wei U; and also to act as regulators of plant growth, as defoliants, and as dixitr.wnv As of June 19G2, almost 500 compounds incorporated in more than 5IT"il formulations were registered for use in the United States. 1. The chlorinated hydrocarbons containing carbon, hydrogen, ' and chlorine arc tiic pesticides used in greatest tonnage, 'flic most f.uni1' arc DDT, dicldrin, aldrin, endrin, toxaphrnc, lindane, niechnxyi l*` * chlordanc, and hcptachlor. Among those used extensively as her hi* : arc 2,4-D ajid 2,4,5-_T_for_control.of broad-leaved weeds in lawns, p;wuivs.cereal crops, and brush growth jdong highways and fences. 2. The organic phosphorus compounds, composed of phnsphoni*. i*\ygen, carbon, and hydrogen, are used principally as insecticides ami iniliei ! Paralh'ton, malathion, phosdrin, and tetraethyl pyrophosphate ( T U T ) are examples. 3. Other organic compounds include the caibamates, diuitmpl...... . organic sulfur compounds, organic mercurials, and such natuial pmh** is as rotenone, pyrethrum, nicotine, strychnine, and the anticoagulant i* * I poisons. 4. Inorganic substances with a long hisloiy of use include copper m. arsenate of lead, calcium arsenate, compounds of chlorine and Ihr zinc phosphide, thallium sulfate, and sodium fluoroacelate. B. D istrioution and Persisten c e in t h e E n v ir o n m en t The worldwide use of pesticides has substantially increased since the !*-. velopment of DDT and other chlorinated hydrocarbons in the early I!11"**. United States production,and use arc illustrated in figures 1 and 2. h is estimated that 350 million pounds of insecticides alone were used in the United States during 19G2. They arc distributed annually over nrnilv ''0 million acres (about 1 acre out of 20 within the 48 contiguous St.in-*). These acreages arc composed of farmlands, forests, and iusccl-bierdiiig areas, including wetlands. Wccdkillcis arc distributed on approxim *i- ly the same number of acres, with some overlap of areas covered by ir *i 'ietdes. Thus the land area treated with pesticides is approximately I .* le of 12 within the 48 Slates. About 45 million pounds are used each ir in urban areas and around homes, much of this by individual hnmenv. <<is. The annual sale of aerosol ``bug bombs'' amounts to' irtoie (ban on* ter household. Other compounds, Mich as fungicides, aho are used ->stamial tonnage. In recent years vve have recognized the wide distribution and per-i-i* *'* of DDT. It has been delected at great distances (tmn the place u* plication anti its concentration in certain living organism* ha* In ' served. DDT has been found in oil of fish that live lar at sea and caught ofT the coasts of eastern and western North A m erica, Smith A Europe, and Asia. Observed concentrations have varied hmu Irpart per million (ppm) to more than 300 ppm in oil. ,* U .s. Production of Syntuf.tic O rganic P esticides COMPOSITION A/IO DISPOSITION OF 961 PRODUCTION Source : USDA. 1062. Figure 1 Residues of DDT and certain oihcr chlorinated hydrocarbons have been Irlcctcd in most of our major rivers, in ground water, in fish from our fresh raters, in migratory birds, in wild mammals, and in shellfish. Small amounts >fDDT have been delected in food from many parts of the world, including iroresscd daily products from the United States, Europe, and South tmrrica. The amounts arc rarely above Food and Drug Administration FDA) tolerance limits, but these have probably contributed to tlic buildup .f DDT tve now observe in the fat of the people of the United States, Janada, Ccimany, and England. In the United Stales, DDT and its uctaholitcs have been found in the fat of persons without occupational rxposttre at an average of 12 ppm (approximately 100 to 200 mg. of DDT )cr adult) for the past 10 years. In England and Germany, recent studies cvcalcd an average concentration of 2 ppin in human fat. Data ahoul zhildren arc not available. An important characteristic of several commonly used pesticides is their persistence in the environment in toxic form. The chemical half life of liable cldorinatrd hydrocarbons in soils, and the lime they remain active ligaimt some soil insects, air measuicd in years. Tin: organic phosphorus 00 compounds are more rapidly degraded although, under certain ri* " i- stances, they have persisted iioin one growing season to ifte next foil* : routine application. Pyrcthnim, rotenone, and nicotine an- d** 1 relatively rapidly after application, but compounds incoi pointing i. lead, and arsenic arc persistent. The distribution and persistence of other chlorinated liydioeaihoii' hm : been studied in less detail, although some of these chemicals have Invn widely applied. One of these, dirldrin, resembles PI) I* in stahilifi. jr- sistcncc, and in solubility. Recently, it has been found in the fat of i 'drills of southern England. It has also been found in many wild birds, IMi .ml mammals in tlic United States. These facts led the Panel to nniirij* ii.it surveys will discover dicldrin and other persistent rhloiinalcd liytln* ' 'is in man and wildlife throughout most of the United States. , . * * i 1. V ' ` >  ' C .1Biological E ffects on M an and A nimals /:.v/ioinriT of nidii Tlir extent of hazard associated with use of a pesticide is determined by c degree of exposure and the compound's toxicity. Exposure depends on rsistener, the amount applied, the method of application, and availability die chemical in a biologically active form. Pesticides canjcntcr the body ' (a) ingestion, (6) absorption through the intact skin, and (c) inhalation, (a} When examining the potential hazards to man from extensive use prsiiridcs, an early consideration should he the possible effects of chemical sidurs in tiic Nation's food supply. The Panel has received evidence that, fore pesticides arc rcconunrnded for registration, considerable research is been performed on the extent and nature of their residues on foods, and int safeguards exist which can permit pesticide usage without danger to the msumcr. These include proper controls over manufacture, commercial istribution, and techniques of pesticide application to crops; strict cstabslinicnt of tolerance limitations; inspection for residues in produce; and llicr precautions. When measured in foods entering interstate or foreign Dinmcrcc, and in total diet studies, residue levels have been very low and ircly above the legal tolerance limits. If illegal residues arc found, the lods containing them arc removed from the market. Residues arc not so consistently low for food items marketed within their talc of origin. Some Stale authorities sample food for pesticide residues, lata from certain States have shown residues well above the Federal tolcrnce on 3 percent of the fresh fruits and vegetables offered for sale in diotesale markets. (Many States do not perform systematic sampling for L'siducs in the produce and dairy products intended for consumption within lie State. Residues of several chlorinated hydrocarbons have been measured in amc birds and game fish at levels above Federal tolerance limits. Re mise few wildlife meals arc consumed, this is not an important source for rsiduc accumulation in man. By contrast, household use of pesticides with ladvcrienl contamination of dishes, utensils, -or food may well produce nnre significant residues in man. () Most insecticides arc readily absorbed through the intact skin. Skin r-ntanunalion ran he an important source of exposure for persons who inislandle pesticides in their foiuuiialion or commercial application. FurtherMore, since householders usually take few precautions in their home and anlru uses of these chemicals, they may receive extensive skin contact loth from successive applications and from continuing exposure to residues. I lie rale of absorption through the skin depends on the chemical nature rf the pesticide and on its fm nuilaliou. In general, compounds in solution n oils or in organic solvents arc absorbed more readily than those in iqurous preparations or in dry powder. Skin absorption can occur from pesticide aerosols, from dusts, from clothing or blankets im prrgnnln' h chlorinated hydrocarbons, and from contaminated soil or lawn gr.is The rales of skin absorption have not been adequately studied in m--i. It is particularly important to determine the rates at which nmilipi" I -tg insecticides arc absorbed through human skin in contact with im pire' red clothing or blankets. Such impregnation is performed dining the r - ufacturc of mothproofed garments and materials, and routinely tlmiti du'i cleaning. Many of these articles, such as sweaters and blankets, m.n ' in direct contact with the skin for prolonged periods. Clearly, stud'* o r needed to understand possible sensitization and allergic rrspomes. (c) Man's exposure to pesticides can also occur through inli-d "it. Airborne insecticides arc sources of exposure when rrlrased during l<; -mg operations directed against nuisance inserts in public areas, lmilduu-. "id homes. Pesticides may be inhaled in dusts from treated sod, fmiii 1 "i-e dusts contaminated by applications for household pests, or from iii*-th proofed rugs and blankets. 2. Effects on man There have been few systematic studies of people occupationally c\pi'M*d to pesticides. In one such investigation, a small group of voluntm - with an intake up to 35 mg. of DDT per day over a period of month' was reported to show no apparent ill effects during 18 months of gross cl* i ca tion. DDT and its metabolites averaged 270 ppm in their fat, mm1d>-m 20 times the average level found in adults sampled In this eountty. I.b ' d groups of adults occupationally exposed to the more toxic prslicid1 m- also being studied, and there is evidence of neurologic impaiimcnt. ; - lly reversible, in those individuals heavily exposed to certain chloim and Iim Iio - carhons and organic phosphates. Unfortunately, possible long-irun 1ll*cls of other compounds cannot be predicted on the basis of cxpci inn -'iili DDT, or even predicted for DDT itself, on the basis of the limited <li*;\l studies available. Accidental acute poisoning in man has been earned by a k 1 `h. pesticides, including at least 1 compound from each major rl.m. 1 u h year, approximately 150 deaths arc attributed to misuse of pruiridi* he United States. About half of these occur in children who were a " nv exposed at home. The number of nonfatal poisonings can only he v-- A Special Committee on Public Policy Regarding Agricultural Cl appointed by Gov. Edmund G. Brown on June 15, I`WO, reprutn* i California, which uses 20 percent of the nationally omimiiim iI u- : 3,000 children per year ingest various amounts of these compound' In that State during 1959 there were also 1,100 eases of orcupational *h msc due to agriculture chemicals, mostly among agricultural woikeis. Ihi-se figures include acute illnesses, whether the reaction was very n r 1! >r severe enough to require hospitalization. One difficulty in estini.i" 'lit* incidence of poisoning is that the symptoms caused by pesticide lo*: little different from those of many common illnesses. . ,. I.ihlc -is known about the consequences to man when he accumulates tore than onc^pesticide in his body. Synergism, or potentiation, is the tint action of two agents which results in an effect which is greater thari ic sum of their individual effects. Some combinations of two organic hosphates have produced effects 10 times those observed when either com ound was fed separately. Preliminary FDA data show only additive ci vets from mixtures of chlorinated hydrocarbons included in diets of cx- criincntal animals. Physicians arc generally unaware of the wide distribution of pesticides, licir toxicity, and their possible effects on human health. Diagnosis of icsticidc toxicity is apparent when a patient with acute asthma has to he csuscitatcd in the middle of the night following exposure to commercial ogging. However, diagnosis is difficult in patients with nonspecific ymptoms that may result from unsuspected contamination with pesticides. The Panel was unable to find any federally sponsored research in this area of potential medical importance. 3. Effects on wildlife Many kinds of insect-control programs have produerd substantial mor talities among birds and other wildlife. Some fatalities have been the result of carelessness or nondircclcd use; others-have followed programs carried out exactly as planned. Mortalities among birds have approached 80 percent in areas heavily treated with DDT for Dutch elm disease control, with heptachlor for imported fire ant control, and with aldrin or dicldrin for controlling the Japanese beetle. Fish losses have been extensive even with lower rates of application in programs such as spruce bud worm control using DDT. Losses following agricultural operations are more scattered and less well documented. Most insecticides arc toxin to a wide range of animals, and certain classes arc consistently more susceptible than others. Insecticides tend to be more toxic to invertebrates than vertebrates, because the target insects arc more closely related to other invertebrates. For example, pink shrimp have been experimentally poisoned by 0.9 parts per billion of heptachlor. Other marine organisms arc also highly sensitive. The growth of young oysters has hern inhibited by concentrations as low ns 3 parts per 100 million of cblordane, bcptarblor, or rotcnoiu:. Five other rouunonty used pesticides inhibit oyster growth in cnncciiirations of 1 part per 10 million. An entire year's production of young salmon was nearly eliminated in the Mirainirhi River in New Hnmswirk in I9.VI, and again in lDf>5. This rrsulted from DDT applications of one-half pound per acre for control of the spruce hudwoim. Stream meets, which arc. a most important food for young salmon, disappeared and failed to return within 2 years. Surviving young salmon were very thin. In (lritish Columbia, mortality of coho salmnn approached 100 prrceiit in at least four major streams after the Miimumliiu; forests were sprayed with 1 pound of DDT per acre for control oi liic black-headed budworm. This mortality occurred despite piev*nf; measures to avoid treating the streams themselves. Among vertebrates, fish arc generally more sensitive than birds, ami !-'* ' arc /norc sensitive than mammals. Reptiles and amphibians vary gr' **` from species to species, but their susceptibilities usually fall between lb*- of fish and birds. Variations in sensitivity may result in tbe rliiuin.ii',*ii of certain forms from the food chain. While some organisms may I* decimated, resistant organisms which suivivc exposure may concentrate and store pesticides at levels higher than those found in the environment. Su* I: biological magnification on the part of resistant species may nliim.ii U damage more sensitive organisms which arc higher in the fond chain. \* Clear Lake, Calif., for example, waters containing 0.02 ppm of 'I ' *' produced plankton containing 5 ppm, which in turn produced fish with ' containing hundreds to thousands of parts per million. Grebes that fr. tbe fish died although their fat contained somewhat smaller residue llic fish. Robin populations declined drastically after Dutch elm disease spr.iv . in certain communities in Wisconsin and Michigan. Earthworms, resist mi to DDT, fed on fallen elm leaves and accumulated substantial amounts *<l the pesticide. Robins, for whom worms arc a principal food, fed on ihworms and died. The process of biological magnification has less impact on man hrr.m human food is produced by a two- or three-link chain in which the pro --w. if recognized, can be controlled. For example, residues are permitted m feeds for domestic animals only in amounts that will not ultimately vi* I 1 unacceptable levels in meat, in milk, or in other animal pioducis. 'll* , excessive levels of pesticide residues in agricultural piodurts used human food result only from accident or misuse, while damaging levels in '** food of wild animals may be unwanted cfTccis resulting from irroiiiinrn***-I practices. When contaminated fish and shellfish are harvested <mcrcially, any residues they may contain are of concern to the fidu-n .' and the consumer. Yet the commercial fisherman rammi control 'h" sources of such contamination. Wild animal populations arc affected differently by prstirides ivm*' than arc domestic animals and man. Unlike the latter, wild atiimah not be kept from treated areas long enough for the'chemical irdilui degrade or otherwise dissipate, because birds am! mammals air 1 range over relatively large arras, they arc exposed to a varirtv of dil1 compounds. Insectivorous birds are likely to he attracted to a* .dense insect populations, and may be exposed when chemicals ate -*| Furthermore, birds reoccupy a depleted area very rapidly; thus a ti* I area may constitute.a trap into which successive waves of birds mm< "d arc killed. Fish in streams are generally less mobile than biids and ntals, but they, loo, may be subject to imilliple cxpnMiii' <*, j1' ng waters* contaminated by accidental drifts or run-offs can affect isl liven though they do not move into treated atcas. D. T oxicity of S pecific C o m po u n d s hlorinated hydrocaibons very small doses (some eases less than I ppm) chlorinated hydro ins have caused liver damage to experimental animals, and in large i they have caused acute central nervous system effects, occasionally .vcd hy death. The mechanisms leading to these effects arc unknown, ir biological effects of DDT have been studied more fully than those her pesticides. Its toxicity to man and other mammals is low. Pcoigesling laigc amounts of DDT usually sulicr no apparent ill effects, ironic feeding experiments with rats, 5 ppm produced characteristic inalcd hydrocarbon changes in the liver, but no evidence of tumor :tion. Reproduction studies in rats showed that 50 ppm reduced lumber of young that survived the nursing period. There was no l on reproduction at 10 ppm. However, many useful insects and r valuable invertebrates such as shrimp, crayfish, and crabs arc highly ptiblc to DDT. Decimation of these useful populations may be a y side effect of extensile applications. cldrin and aldrin are many limes more t ixic to vetebrates than DDT. : aldrin is converted to dieldrin in man and in the environment, a dison of dieldrin applies to both. cldrin is present in the body fat of residents of England (average 0.2 ) and is probably also present in tbc fat of the U S. population as a t of extensive applications of the chemical in this country. There been many eases of acute poisoning in pcojile exposed to dieldrin in work. Signs of intoxication involve the central nervous system, and include clcctrocncephalographic changes, muscle tremors, and conons. Individuals have suffered recurrences of these symptoms after have been free of them for more than a month following their last SIIIC. ur knowledge of toxicity at lower doves comes chiefly from FDA feeding riinents in which mice were fed varying concentrations of dieldrin and n in their diet. Chronic exposure to as little as 0.5 ppm produced iogiial liver damage while incicasc to 10 ppm caused a fourfold asc in the frequency of liver tumors. There are virtually no data on the tson cnihiyonic development. In one of the few experiments known to *anel, the feeding of dicldiin (at O.b mg./kg. of body weight) to several nanl dogs resulted in 100 pciccnl mortality of 11 nursing puppies. 'Flic icrs were fcil the pesticide during pregnancy but none during lactation, nother study, rats fed dieldrin at 2.5 ppm in the diet showed a signifireduction in number of pregnancies and an increased mortality in ling young. Although most insecticides do not kill wild mammals in the field even whi n they kill birds and fish, 1 to 3 lbs. per acre of dieldrin or aldrin produces hit'll mortality among mammals in the treated ar. as. Dieldrin is also highly toxic to many birds, amphibia, reptiles, and fish. It reduces the reproduction of captive quail by decreasing egg production, decreasing the pcricnlngr of eggs that hatch, and increasing the mortality of chicks. Many beneficial and useful invertebrates arc very susceptible. Other chlorinated hydrocarbons in common use have shown marked acute toxicity to rats in feeding experiments. Chronic effects have been noted with chlordane and hcptachlor at the lowest level fed to experimental animals. Chlordane at 2.5 ppm produced liver damage and 0.5 ppm of hcptachlor epoxide produced liver damage and increased moit.ility in the laboratory mice. Field use also suggests high toxicity to birds and mammals. Although these substances arc used in large quantities, there have been no studies to determine whether they accumulate in the human population, nor are there adequate studies of their genetic, tuinorigcnic, teratogenic, or re productive effects in mammals or birds. 2. Organic phosphorus compounds Among their effects, the organic,phosphorus compounds inhibit cholin esterase activity and thereby interfere with transmission of impulses from nerve to ganglion and nerve to muscle. Most organic phosphorus insecticides have relatively high acute toxic itirs and have caused many fatal and nonfatal poisonings in man. In casts of poisoning, removal from exposure to the compound usually permits rapid recovery. Many of them are degraded rapidly and thus seldom persist in the environment, but some, such as parathion, have persisted for months in soils and have recently been found in trace amounts in water drawn from deep wells. IV. PEST CONTROL W ITHOU T CHEMICALS Methods for controlling [rests without the use of pesticides we re known to farmers even in ancient times. Crops were planted in airas least liable to [rest damage; crops were moved to virgin territory to leave the |>si* behind; rotation was practiced and crops that were less prone to disease wenplanted; if the pests came late in the season, crops were planted rally, an' vice versa. Many of these methods arc used today. 'I lie environment can also be modified indirectly; for example*, we um screens on windows to keep out mosquitoes, and flood or diain marshes to destroy their breeding aicas. In criiain eases parasites, predators, and diseases control the pests without chemicals. In the United States and mans other countries of the world parasites and predators have been sucrcssfnlls introduced to combat scale insects on citrus fruits, apples, and sugarcane: and in Australia the myxomatosis virus was introduced to kill rabbits. Entomologists have long been interested in the use of insect enemies ,fii pest control. The U.S. Department of Agriculture has been at live in