Document 5k2n9r3EGrbq8MXONRVnyDBNV

i. I PESTICIDE POLLUTION C? OUR tWIRCvUEST? C E. Harris, Research Institute, CDA, London, Ontario. The furor which has arisen in recent years over "pollution11 of our environment by pesticides io rather difficult to comprehend. It developed largely as a re cult of a book called "Silent Spring" by Rachel. Carso* This book served a purpose in that it stimulated an appraisal of the adequacy of infor nation ca pooticido residues and their persistence in the environment, but uany of the rrbatcr-ents in it were inaccurate and the conclusions based on caution rather than true facto. Heedless to say sene segments of the pesticide industry responded tdth salvo after salvo In an atter.pt to refuto lliss Careen. The end result has been that the book rv.de a groat deal of money; that industry has boon hampered in the development of more effective, less persistent pesticides by restrictive end often ill-iciviced legislation; and that the public has become utterly confused as to the asset3 and liabilities of pesticide use. This confusion is best demonstrated by the fact that the urban duellers, who on the one hand question the use of pesticides in agriculture, are on the other hand, responsible for the huge consiurpticn of theca sane materials for home and garden use * In 1945 a corpomd, no*./ famous, by the nave of DX/f became available for general use* It was the first of a series of highly effective, breadspectrum; poisons, commonly known as the chlorinated hydrocarbons. Others in tMs category include aldrin, dieldrin, heptachlor,_and er.ivin. These materials wore fantastically effective against nearly all specieo of insect leasts and naturally they wore used extensively, often at excesedvo rates'or by methods of application v;h.ich wore both v;asteful. and detrimental0 Uo . needlessly ceatavdunted huge sections of our environment. More recently, two other major groups of compounds Imve become available for use - the organophoephorns raid carbamate insecticides. These materials are generally loss persistent, but also 3ocs effective than the organocbloriueco Oar major coiicern with regard to environmental pollution at present is with DET, aldrin, dieldrin, and hoptachlor. In ono way or another insecticide residues generally end up in the soil regardless of whether they are applied directly to tho coil or to crops from which they are washed down into the soil by rainfall. The pored.ctcnco of the so materials in soil has been examined quite extensively. Both.aldrin and heptachlor are relatively^ volatile and disappear quite rapidly from the coil. Uriortiwuvtely, soii__rmi.croorgam.cv3 ccnvort rmall amountsiof altirih"and hoptachlor to dioldrin end heptachlor epo:ddo, both of which _are tonic, persistent compounds. l)UT_.iq_also_ highly_ persistent in coil, but is elewly degraded by rmicroorganicmie to DDE. Tho peroicteiico and . degradation of all these insecticides'is iimTlimnced by coil, type, noictvrs, tccporc&ura, method of cultivation, turd crop cover* From the cvail.nble ` evidence, it would amveer that residue a of dioldrin and DPI will p.ersi.qt in soil for rv-ny yoarn0 ' ,' . . DSW 255459 STLCOPCB4061138  . DDT, aldrin, and to a lesser extent, heptachlor have been used extensively in Ontario. Soils in many of our agricultural areas are contaminated with residues of these materials or their breakdown product's. In most cases, the degree of contamination is not great,-with total chlorinated hydrocarbon residues in the top six inches of soil being ' approximately 2 ppm or less. However, in tobacco and vegetable soils the residues average 3 and 10 ppm respectively while in orchard soils they average 62 ppm. `............ _. . . Although residues are present in our soils, this does not necessarily mean that they constitute a pollution problem. This will depend entirely on the side-effects which are occurring as a result of this residue buildup. .Without going into great detail I would like to discuss some of these possible side-effects and the data which we have at present. Side-effects may be of two types - direct and indirect. The direct side-effects are primarily those relating to the soil organisms them selves. Indirect side-effects may result from movement of the insecticide from one sector of the environment to another. ' " What of the effects of insecticides on the soil organisms? The first to be considered must be the soil microorganisms' which are of major importance, in maintaining soil fertility. Extensive evidence obtained in our own laboratory and at numerous other laboratories tliroughout the world clearly indicates that the chlorinated hydrocarbon insecticides have little, if any, effect on soil microorganisms, as a natter of fact, the opposite appeal's to be- the case, i.e. the soil microorganisms play a major role in the degradation of pesticides. In some cases the pesticides are degraded to even more toxic metabolites, as is the case with aldrin to dieldrin. In other cases, they are degraded to less toxic compounds. Soil animals also comprise an extremely important part of the soil ecosystem. The major Phyla include the Protozoa, Annelida, and Arthropoda. . Little is known about the soil Protozoa. However, there has been a con siderable amount of work done on earthworms. The results clearly indicate that with one or two exceptions (heptachlor,j_chlordane),_the_chlorinated hydrocarbon jlnsecticides_ have little effect__on e arthworsn populations. Unfortunately, earthworms are capable of absorbing relatively large amounts of the chlorinated hydrocarbons from soil. When these contaminated worms are fed on by birds in sufficient quantities, it can result in serious side- effects. As would be expected, the soil Arthropods are more seriously effected by the chlorinated hydrocarbons. In addition, to controlling pest species of insects, other beneficial species are also effected, including the parasites and predators of the pests. However, this broad-spectrum effect is not confined to the chlorinated hydrocarbons - the organophosphorus and carbamate STLCOPCB4061139 insecticides may be even more toxic to the beneficial soil animals. It hag also been shorn that in some cases, DDT. cm liavej beneficial effect in so far as soil fertility is concernsdr"^^iLj-^-V4^e.ljgdnate" the predatory mites in soil which prey on beneficial__^ilenibola. As a result, the -beneficial Collembola will increase in soils contaminated vrith DDT. Aldrin and the other cyclodiene insecticides appear to have a greater detrimental effect on soil Arthropods than DDT. However, some interesting v/ork in England has shovm that the effect of aldrin on beneficial soil Arthropods is of less iraportance than normal soil cultivation. One serious side-effect which has occurred as a result of the buildup o'f residu.es of the cyclodiene insecticides in soils has been the development of insecticidal.re sistance by soil insects. If insect populations v/ere uniformly susceptible to insecticides, the residues in soil v/ould resuJ.t in complete elimination of the insect populations, and the ultimate in insect control vrould be attained. Unfortunately, this is not the. case, since the individuals in any insect population will vary in their degree of susceptibility to an insecticide. In many cases, there are a few- individuals in the population which are highly resistant to insecticides. As the insecticide concentration increases in soil to toxic levels, the susceptible Individuals are eliminated for generation after generation. Finally the population becomes totally resistant. This is what has happened v/ith many soil insects. In_Caxiada "ths_rootjnaggots hare become resistant to all the cyclodiene insecticides. Elsewhere, wirevrarms, corn rootv;orms, and grubs havejalso_ bo come jresistant to the cyclodiens insecticides .or DDT, In Canada, none of the soil insects have become resistant to DDT - indicating that residu.es of DDT in the soil have not yet reached a sufficient level to result in constant selection pressure on the soil insect populations. The search for alternative materials to control these cyclodiene-resistant soil insects has been both expensive and time-consuming, and in some instances, we still have not found satisfactory alternative control measures. ' In^ay discussion on the effect of pesticide residues in soil on the coil organisms one cannot ignore the plants grovm in the soil. Studies conducted in our own laboratory and elsev/here clearly indicate that residues of dieldrin and heptachlor epoxide, but not DDT, are absorbed from soils by some crops. Generally spealdng root crops are the greatest ''absorbers." Other vegetable crops also absorb dieldrin and heptachlor epoxide from the soil. However, the residus3in these crops are not exceeding the tolerances for direct human consumption vrhicli have been established by the Food and Drug Directorate of the Department of National Health and Welfare. . . . A potentially more serious aspect of this problem, howeverj involves the absorption of residues of the cyclodiene insecticides by crop3 used for animal feed. Here v:e become involved with the problem of "magnification." Wien small amounts of dieldrin, for example, are absorbed by crops which arc in turn fed in large quantities, continuously, to animals, the animals tend to store the insecticide in. their fatty tissue. V/ith continuous feeding of a contaminated crop, perhaps. 10~2;5[_x_ the^^concentration of_ dieldrin found in the plant nay be found in milk or other animai products. Thus a residue of 20 ppb in feed may result in. a resiciue~bf" 0J2 ppm in milk - an unacceptable DSNN 255461 STLCOPCB4061140 level.' We have found that crops such as alfalfa, oats, corn, sugar beets, potatoes, and turnipsjsill absorb ;dieldrin_and..;heptaclilpr. epoxide."from 'soil. . Information rfrom various areas in Canada indicates that we have fairJy extensive low-level contamination of milk and to a lesser extent, other animal products with residues of dieldrin and other chlorinated hydrocarbons. Ho1.;ever, residues of the chlorinated hydrocarbon insecticides in milk and ^ animal products, are, in the vast-majority of cases, well within the acceptable V/ limits recognized by Federal Agencies. The evidence indicates that insecticide residues in our crops, milk, and other animal products do not constitute a hazard to human health. From the discussion so far, it is apparent that the direct side- . effects resulting from the accumulation of chlorinated hydrocarbon insecticide .d residues in soil are not sufficiently serious to merit major concern. Those problems which do exist, e.g. toxicity to earthworms, insecticide resistance, and absorption and translocation of residues by crops are limited to some ^ cyclodiene insecticides. DDT has caused remarkably few direct side-effects when one considers the amount of material which has been used over the past . 25 years, and the residue levels present in the soil. But what of the indirect side effects? Are the organochlorine insecticide residues in soil being transferred by one method or another to other sectors of the environment? On preliminary examination it would appear that this is highly unlikely. The_so~-called uhard" insecticides, DDT, dieldrin, and . heptathlor_epoxide are virtually non-volatile and Insoluble irT water,r~'They are strongly adsorbed by soil and' do" hot move to any significant extent through ` the, soil to the ground water. Yet^ it _i"s_bec6mihg'apparent that relatively small amounts of these materials are indeed being transported from soil to water and air. Presumably this is occurring because of very limited volatili zation, and because of erosion of topsoil by both v/ind and water. Because of , its widespread use, the major offenders are DDT and its degradation product .DDE. Although the extent of contamination of water or silt with these materials my only be at the ppb or even ppt level, these rainute concentrations can, because of magnification, result in serious effects on the upper levels of the biological chains in the ecosystem. For example minute concentrations of DDT~DDE adsorbed on suspended colloids in water can be absorbea_and concentrated by juderoqrganisns. The microorganisms" are conajmsef^y planktoiv^eating.. fish, which are in turn consumed by larger predatory ^ish, which are then consumed in turn by..predatqry_bird3_such as cormorants, mergansers, and ospreys. In one situation in Long Island Sound it is claimed that the concentration of DDT increased froa 3 ppt in water to 25 ppm inThe~predatory birds - ah astounding . 8.3 .million fold increase oust the original amount. YJhile such a concentration': , might not'be toxic to the birds there is evidence that DDT interferes with h^ calciurn jr.etabolisn_and hence the_j'thin-shell" phenomenon which is apparently j / common in predatory birds. More recently,-the"research results liave indicated ,r)l that it is not DDT which is so much responsible for the upset in calcium meta- w ( bolisa in birds or the toxicity to fish embryos, but..rather its_degradation product DDE, which for many years v;as considered a "harmless" residue. DS\N 255462 STLCOPCB4061141 ' ' - Vlliile the evidence that DDT-DDE can result in serious side-effects in the ecosystem is generally accepted it is difficult at present to quantitatively estimate its importance relative to other pollutants. Unfortunately, much of the data on fish and vri.ldli.fe- is subject to question. Analysesi.by_gas liquid chromatography which.is. the generaljmethqd_nqw_in use is a difficult, exacting , task. Interpretation of the data is extremely important and, unless one is nv careful, artifacts or _conteri.nant_s_can_ often_be_ mistaken for DDT or DDE. However, because it seems like such a simple technique, virtually every biologist arid conservationist has purchased a gas chromatograph and is busily injecting extracts of everytlung under the sun into his machine. Consequently, it is an almost impossible task to separate the good data from the bad, the fact from fiction, vrith regard to DDT and vrildLife. Complicating the picture is a group of common industrial pollutants, related to DDT, which, it is nov; reco&nxreei, are j.n l'--" themselves highly toxic(i'.ore so than DDT-DDE) and produce similar physiological ] effects, qn_.fish and vfildl-ife. _'Those pollutants, known as PCD5 c-p (polychlorinated biphenyls)| occur commonly in industrialized areas. The picture vrith regard to these materials is not yet clear, but it seems likely that future work mill show that the PCBTs are pollutants of equal or even greater_jjnportance_than DDT-DDE. .............. . ... ......................... : ~............ . .......~ " In recent months the opponents of pesticide .use have mounted a tremendous campaign to have the chlorinated hydrocarbon insecticides banned in Forth America as v:ell as other areas of the world, This group which comprisoo an unlikely combination of a) conservationists v.'ho are genuine dy concerned about the environment; b) individuals out for personal gain; and c) out-and-out screwballs, has already succeeded in having DDT banned or restricted for use in several States in the U.S. and in Ontario. The common cyclodiene insecticides vrith the exception of endrin are also banned in Ontario. Unfortunately these "instant experts," do not have any concept of the new problems v/hich they themselves are creating. As_the_persistent chlorinated hydrocarbons are , discarded, organophospherus and carbamate insecticides__are_.being.,substituted, ( ^ $ on the questionable assumption that these materials will .have less, soriou.3 side | effects. I am willing to predict that in time we will bs^ encountering far ) more serious problems vrith seme of these substitutes them vre have with the organochlorir.es at the present time. I say this for a number of reasons. First, there is a popular misconception that the newer materials are_less psrsistent in soil than the so-called "hard" chlorinated hydrocarbons and this is_ not ' necessarily_ths_case. Second, while most chlorinated hydrocarbons have limited solubility in water, many of the newer materials are slightly to moderately soluble, and we run the risk of contaminating ground water as well as streams and lakes. Third, in many instances these newer materials are being applied at 5-6 x the rate that vre applied the chlorinated hydrocarbons. Fourth, these materials are more toxic to handle, and can be as, or more toxic, to beneficial . soil animals, fish, and vri.idJJ.fe. 'With some of these new materials we run a risk of sterilizing the environment? ' .. The dismaying aspect of this problem of pesticide pollution is that, at present, it is only the radicals on each side who are being heard. The press and communications media, with their well-known weakness for shocking headlines such as "Zoologist claims DDT causes cancer" encourage such radical DSW 255463 STLCOPCB4061142 -6 } approaches, Tlie progress which the opponents of pesticide use have made in the- past few months is terrifying. With each new blast from "Pollution Probe" the Provincial Government seems to react by banning another pesticide. In the midst of this controversy the voice of the moderate majority is seldom heal'd.. .'- . What can we as .individuals, and as professional groups do, to bring some sanity to the situation? Obviously we must make our voices heard above the anguished screams of the radicals. In doing so it is necessary to recognize that both the Federal and Provincial governments are involved in tlie regulation of pesticide use, and we must be heard at both levels. What should we say? The following are just a few suggestions: 1) Research: YJe cannot do without pesticides; at the same time vie do not. want to use materials 'which will result in serious environmental pollution. There is a drastic requirement for expan si. on of cur . research programs on pesticide application, efficacy, and persistence and degradation in the environment. Research programs on integrated control should also be expanded. More research requires more funds both at federal and provincial levels. . 2) Legislation: Tlie requirements for registration of pesticides at the Federal level should be tightened. In addition to information on . efficacy and hazurd to human health.,, much more emphasis should be placed on the effects of pesticides on environmental quality. Once a material is registered it should be mandatory that in-depth reviews of the registered uses be conducted periodically. Sufficient qualified staff should be provided to enable the CDA to conduct these reviews. As a general principle, registrations (Federal) and recommendations (Provincial) should be in agreement. At the present time provincial recommendations are not worth the paper they are printed on since a material can be used If it is registered for vise, regardless of whether it is recommended for use! . - At the Provincial level the Government should ensure that qualified staff are available to administer the Pest Control Act, At present the number of qualified pesticide specialists within the provincial civil service is shockingly small. The Provincial Govern ment should consider appointment of a highly qualified pesticide coordinator responsible for coordination of pesticide work within the Provincial Government and for lidson v.ith the Federal Government. 3) Control of Pesticide Use: At present, as long as a material is registered for use, there is little further control over its use. As a result, much of our problem of pesticide pollution arises from pestlcido misuse. Drugs are sold by prescription; surely pesticides should be handled in a similar fashion. Unless the moderates begin to make themselves heard in this pesticide controversy, the voice of the radicals will result in restrictions on pesticide use willch will be a serious detriment to agriculture, and will at the sam3 time result DSW 255464 STLCOPCB4061143 -7~ 1 in even more serious environmental pollution. Much of the uproar over pesticide use in the p?.'ess today is resulting from hysterical accusations made by an illinformed public, politicians, and other publicity seekers v;ho have few facts and even less knowledge on which to base their obviously prejudiced comments. Hysterical accusations based on fiction rather than fact, have no place in science. Perhaps it vrould be wise to substitute caution in place of hysteria, prudence in place of politics, and sound research in place of press conferences to determine the best approaches to pest control. DSW 255465 STLCOPCB4061144