Presentation on theme: "ENT 5009, S 2011 Vera Krischik Entomology, U Minnesota"— Presentation transcript:
1ENT 5009, S 2011 Vera Krischik Entomology, U Minnesota The history of DDTENT 5009, S 2011Vera KrischikEntomology,U Minnesota
2DDT is moderately to slightly toxic to mammals The history of DDTDDT is moderately to slightly toxic to mammalsby the World Health Organization as Class IIDDT oral toxicity.acute oral LD 50mg/kg in ratsmg/kg in mice300 mg/kg in rabbitsmg/kg in dogsand >1,000 mg/kg in sheep and goatsDDT dermal toxicity: DDT is less toxic exposed via the skin.acute dermal LD502,510 mg/kg in ratsDuring the 30 years prior to its cancellation in 1973, a total ofapproximately 1,350,000,000 pounds of DDT was used domestically.
3The history of DDT DDT Regulatory History: A Brief Survey (to 1975) [EPA report, July 1975,DDT (Dichloro-diphenyl-trichloroethane), for many years one of the mostwidely used pesticidal chemicals in the US, was firstsynthesized in Its effectiveness as an insecticidewas only discovered in Shortly thereafter, duringWorld War II, the U.S. began producing large quantities ofDDT for control of vector-borne diseases such as typhus andmalaria abroad.After 1945, agricultural and commercial usage of DDT becamewidespread in the U.S. The popularity of DDT, a member of thechlorinated hydrocarbon group, was due to its reasonable cost,effectiveness, persistence, and versatility.During the 30 years prior to its cancellation,a total of approximately 1,350,000,000 pounds of DDT wasused in the US.
4The history of DDT DDT Regulatory History: A Brief Survey (to 1975) [EPA report, July 1975,After 1959, DDT usage in the U.S. declined greatly, dropping from apeak of approximately 80 million pounds in that year tojust under 12 million pounds in the early 1970s.Of the quantity of the pesticide used in , over80 percent was applied to cotton crops, with the remainderbeing used predominantly on peanut and soybean crops.The decline in DDT usage was the result of(1) increased insect resistance;(2) the development of more effective alternative pesticides;(3) growing public concern over adverse environmental side effects(4) increasing government restrictions on DDT use.
5Silent Spring by Dr. Rachael Carson was published in 1962. The history of DDTDDT Regulatory History: A Brief Survey (to 1975)[EPA report, July 1975,The Federal Government was aware of the hazards of DDT1. In 1957, the Forest Service (USDA), prohibited the spraying of DDTin specified protective strips around aquatic areas on lands under itsjurisdiction.2. In 1958, after having applied approximately 9-1/2 million poundsin its Federal-State control programs since 1945, USDA began to phaseout its use of DDT. Spraying of DDT was reduced from 4.9 million acres in1957 to just over 100,000 acres in The major uses of DDT by theForest Service have been against the gypsy moth and the spruce budworm.Silent Spring by Dr. Rachael Carson was published in 1962.3. In 1964, the Secretary of the Interior issued a directive statingthat the use of chlorinated hydrocarbons on Interior landsshould be avoided unless no other substitutes were available.In June 1970, the use of 16 types of pesticides, including DDT,was banned on any lands managed by the Department..
6The history of DDT DDT Regulatory History: A Brief Survey (to 1975) [EPA report, July 1975,4. Between November 1967 and April 1969, USDA canceled DDTregistrations for use against house flies and roaches, on foliageof more than 17 crops, in milk rooms, and on cabbage and lettuce.5. In August 1969, DDT usage was sharply reduced in certain areas ofUSDA's cooperative Federal-State pest control programs following areview of these programs in relation to environmental contamination.6. In November 1969, USDA initiated action to cancel all DDT registrationsfor use against pests of shade trees, aquatic areas, the house andgarden and tobacco. USDA further announced its intention to discontinueall uses nonessential to human health and for which there were safe andeffective substitutes.
7The history of DDT DDT Regulatory History: A Brief Survey (to 1975) [EPA report, July 1975,7. In August 1970, in another major action, USDA canceled Federalregistrations of DDT products used as follows:(1) on 50 food crops, beef cattle,goats, sheep, swine, lumber, finished wood products and buildings;(2) around commercial, institutional, and industrial establishmentsincluding all nonfood areas in food processing plants and restaurants,(3) on flowers and ornamental turf areas.
8Environmental Defense Fund (EDF), EPA issued notices of The history of DDTDDT Regulatory History: A Brief Survey (to 1975)[EPA report, July 1975,EPA Regulatory Actions1. Federal regulation of pesticides was transferred to the USEPA.In January 1971, under a court order following a suit by theEnvironmental Defense Fund (EDF), EPA issued notices ofintent to cancel all remaining Federal registrations of productscontaining DDT. The principal crops affected by this action were cotton,citrus, and certain vegetables.2. In March 1971, EPA issued cancellation notices for allregistrations of products containing TDE, a DDT metabolite.The EPA further announced that no suspensionof the registration of DDT products was warranted becauseevidence of imminent hazard to the public welfare was lacking.Suspension, in contrast to cancellation, is the more severeaction taken against pesticide products under the law.
9The history of DDT DDT Regulatory History: A Brief Survey (to 1975) [EPA report, July 1975,3. Because of the decision not to suspend, companies were able tocontinue marketing their products in interstate commerce pendingthe final resolution of the administrative cancellation process.After reconsideration of the March order, in light of a scientificadvisory committee report, the EPA later reaffirmedrefusal to suspendDDT registrations.4. The report was requested by Montrose ChemicalCorporation, sole remaining manufacturer of the basic DDT chemical.In August 1971, upon the request of 31 DDT formulators,a hearing began on the cancellation of all remainingFederally registered uses of products containing DDT.When the hearing ended in March 1972, the transcripts of9,312 pages contained testimony from 125 expert witnesses and over300 documents.
10The history of DDT DDT Regulatory History: A Brief Survey (to 1975) [EPA report, July 1975,5. On June 14, 1972, the EPA Administrator announcedthe final cancellation of all remaining crop uses of DDTin the U.S. effective December 31, The order did not affect publichealth and quarantine uses or exports of DDT.The Administrator based his decisionon findings of persistence, transport, biomagnification,toxicological effects and on the absence of benefits of DDTin relation to the availability of effective and less environmentallyharmful substitutes.The effective date of the prohibition was delayed for six monthsin order to permit an orderly transition to substitute pesticides.
11It took 11 years to ban DDT from agricultural use in the US. The history of DDTDDT Regulatory History: A Brief Survey (to 1975)[EPA report, July 1975,6. In conjunction with this transition, EPA and USDA jointly developed"Project Safeguard," a program of education in the useof highly toxic organophosphate substitutes for DDT.7. Immediately following the DDT prohibition by EPA,the pesticides industry and EDF filed appealsontesting the June orderwith several U.S. courts. Industry filed suit to nullify the EPA ruling whileEDF sought to extend the prohibition to those few usesnot covered by the order.8. The appeals were consolidated in the U.S. Court of Appealsfor the District of Columbia. On December 13, 1973, the Courtruled that there was "substantial evidence" support the EPA ban on DDT.It took 11 years to ban DDT from agricultural use in the US.Silent Spring by Dr. Rachael Carson was published in 1962.
121936 The chemist, Dr. Paul Herman Mûller, an employee THE DEADLY DUST: DDT***parts found in Davis, K.R American Heritage Magazine22(2)1936 The chemist, Dr. Paul Herman Mûller, an employeeof the great dye-manufacturing firm of J. R. Geigy, S.A., of Basel.He invented two new insecticides, trade-named Gesarol and Neocid;their specific toxic ingredient, however, remained mysterious to him.In 1939, in search of this specific compound, he synthesized achlorinated hydrocarbon whose unabbreviated chemical name isdichlorodiphenyltrichloroethane or DDT.He also soon learned that he was not the first man to make it.Back in 1874 a German student named Othmar Zeidler,working toward a doctor’s degree, had synthesized it as anexercise in pure chemistry. But Zeidler had no notion how,if at all, the new compound could be used.
13controlling Colorado potato beetles on crops, THE DEADLY DUST: DDTBy 1939 when World War II had begun, and during its opening months Müller, having already proved DDT’s effectiveness incontrolling Colorado potato beetles on crops,found it equally effective in destroying lice on war refugees.They became convinced that he had discovered the most powerfulsynthetic insecticide then known, fatal on contact in extremely minutequantities to an incredibly wide range of insects,yet apparently wholly nontoxic to man.In 1940 Geigy quickly patented the formula as a general insecticide,and the manufacture of DDT began. The patent descriptions were sent to Geigy’s branches in Britain and the United States.
14malaria (carried by Anopheles mosquitoes), THE DEADLY DUST: DDTIn early 1942 the immediate concern of British and Americanentomologists was the millions of Allied army and navy personnelspread around the world, and theuse of DDT’s for control ofmalaria (carried by Anopheles mosquitoes),epidemic typhus (carried by body lice), anddysentery and typhoid fever (carried by houseflies).With growing desperation they had been searching for a substitute forpyrethrum, a contact insecticide extracted from aflower and, before the war, imported chiefly from Japan.War with Japan cut off the major source of supply justas the demand for pyrethrum soared.Allied doctors and sanitation engineers began to havenightmares about losing the war to germs thatcould kill more people than all the bombs and bullets.
15three million pounds a month by the time it THE DEADLY DUST: DDTUrgently needed by Allied Forces was a synthetic contact insecticidethat was easy and safe to handle and capable of being economicallymass-produced, which DDT seemed to be.British and American scientists were quick, therefore, to begin testing.Geigy’s claims, which had at first seemed wildly excessive,were soon verified.All DDT was allocated to the armed services save a few hundredthousand pounds for further experiments. With the War ProductionBoard encouraging its manufacture, DDT production was approachingits wartime maximum ofthree million pounds a month by the time itwas placed on Army supply lists in May, 1943and on Navy lists in January, 1944.
16For the first time in history, typhus is a well-advanced epidemic THE DEADLY DUST: DDTAmong these were field tests in which DDT in powder form wassuccessfully used, in 1943, to arrest small typhus epidemics in Mexico,Algeria, and Egypt. The Egyptian work was done under the supervisionof the AmericanBrigadier General Léon Fox, a field director of theTyphus Commission headquartered in Cairo.It was Fox who was summoned to newly captured,refugee-swollen Naples in late 1943, where Allied medical authoritiessaw that a major typhus epidemic was in the making. New typhus casesin the city approached sixty a day, and people were dying by the scoreeverywhere, even in the gutters. Predictions were as many as 250,000fatalities. In mid-December, the general and his men began a systematicdusting of the entire Neopolitan population with DDT and by mid-Februarythere were no new cases at all.For the first time in history, typhus is a well-advanced epidemicwas not only arrested but, in a few weeks, totally eliminated.This was the beginning of DDT’smarch to glory.
17By the war’s end, DDT had become the most publicized THE DEADLY DUST: DDTSoldiers and sailors by the million carried small cans of DDT powderto protect themselves against bedbugs, lice, and mosquitoes.Millions of DDT aerosol bombs were used to spray theinteriors of tents, barracks, and mess halls.Through European refugee camps, along the Burma Road, across jungle battlefields of Southeast Asia, on Saipan and dozens of South Sea isles infested by stinging, biting insects, DDT spread its beneficent mist.By the war’s end, DDT had become the most publicizedsynthetic chemical in the world. One American newspaper clipping service accumulated nearly 21,000 items about it in an eighteen-month period in Most were glowingly enthusiastic;only a few questioned the unmixed blessings of DDT.
18THE DEADLY DUST: DDTAs experiment conducted by the USDA Bureau of Entomology on May 23,1945, was reported not only in scientific journals but also in general-circulation magazines. At the rate of five pounds per acre an oil solution of DDT was sprayed over a gypsy-moth-infested 1,200 acre oak forest near Moscow, Pennsylvania. It was terrifyingly effective. Every gypsy moth caterpillar in the forest died within hours and at least 4,000 birds within eight days.DDT’s killed ladybug beetles which resulted in a tremendous multiplication of aphids, which are not affected by DDT butare naturally controlled by ladybugs.The forest was on the way to being completely defoliated when rainshalted the outbreak; aphids are shortlived in wet weather.
19In few if any other tests was the rate of DDT application as THE DEADLY DUST: DDTIn few if any other tests was the rate of DDT application ashigh as in the Pennsylvania oak forest.One pound per acre was found sufficient to kill gypsy moth caterpillarsin a nearby forty-acre wood, a rate of application thatseemed not to harm birds but was still disastrous for aquatic life,according to Dr.Rachel Carson of the US Fish and Wildlife Service.And when DDT in this lesser amount was sprayedover peach orchards to kill caterpillars of the Oriental fruit moth, it wasfound to be considerably more destructive of aparasite that attacked the moth than it was of thecaterpillars themselves.In other instances, fruit trees were turned literally bloodred with spider mites, after DDT killed the insects that normally fed on them.
20Research reports noted the amazing persistence of DDT’s THE DEADLY DUST: DDTResearch reports noted the amazing persistence of DDT’seffectiveness, due to its chemical stability and insolubility in water.Pyrethrum as then used in ordinary household sprays washighly poisonous to insects for the first few hours afterapplication but gradually lost all power within a day or two.DDT, sprayed upon an interior wall, was fatal to flies and mosquitoesfor as long as three months;a treated mattress was a fatal resting place for bedbugsfor as long as nine months;a DDT-sprayed blanket could be laundered a half dozen times,even dry-cleaned two or three times, and stilled kill every moth.This was an obvious advantage to the Army and Navyas well as to future civilian consumers, but among biologicalscientists it raised further questions as to the wisdom ofreleasing DDT for mass sprayings of fields and orchards,forests and pastures, city parks and tree-lined streets, year after year.
21In early April, 1945, a report was released by the USDA on THE DEADLY DUST: DDTIn early April, 1945, a report was released by the USDA ontwo years of nationwide testing of DDT by department entomologists.The report spoke of DDT as a “two-edged sword,”at once the “most promising insecticide ever developed and themost menacing". Obviously a great deal more needed to be knownabout it before it could be deemed “safe for general use”said Time magazine on April 16, 1945.Nevertheless, DDT was released for general use barely fourmonths later. On August 31,1945, three days beforethe end of World War II, the War Production Boardrevoked its allocation order reserving the insecticidefor military use. DDT was given certification by governmentagencies for almost unrestricted agricultural, household, andother uses swiftly followed.The Food and Drug Administration, for example, established as“safe” a DDT content of up to 7 ppm (parts per million), althoughno research was done on chronic affects.
22Once DDT was released from wartime federal controls, THE DEADLY DUST: DDTOnce DDT was released from wartime federal controls,the government’s power over its production, distribution,and use was diminished, probably more than a trustingpublic was aware.USDA's limited control over pesticide manufactureand marketing derived from an Act of Congress in 1910primarily intended to protect the farmer against fraud;lacked any requirement for registering a pesticide before marketing it.Not until 1947, when Congress, facing a flood of chemical poisons in thewake of DDT, passed an Insecticide, Fungicide, and RodenticideAct (FIFRA) of 1947 that incorporated and strengthened majorprovisions of the 1910 law. Consumer protection was broadened to includeregulations for proper labeling and detailed instructions for safe use.The quintessential problem of the broad environmental effects ofpesticide use was not even considered in the legislation, orin the debate preceding its passage.
23Worldwide, there was a desperate need for all the food and fiber THE DEADLY DUST: DDTWorldwide, there was a desperate need for all the food and fiberthat could be produced, and DDT could do more to increase productionthan any other insecticide.In Greece, where a third of the work force had been losingtwo to three months of work time annually to malaria,and where malarial infant mortality in many villagesapproached 100%, the disease was virtuallyeliminated from some 6,000 villages by a massiveDDT-spraying campaign under the auspices ofUNRRA, the United Nations Relief andRehabilitation Agency.At the same time, through the use of DDT against insect pests,farm production was reportedly increased by as much as 40%.In Egypt and India, equally remarkable results were achieved.It was reliably estimated that by 1950 DDT had saved five millionlives over the world through destruction of malarial mosquitoes.
24DDT was by far the most widely and THE DEADLY DUST: DDTDDT was by far the most widely andheavily used chemical pesticide through the 1950’sThe U.S.D.A. has estimated that, without chemical pesticides,some 30 per cent of America’s protein supply and 80 % of cropswould be lost to insects.Though he held no medical degree and had never engaged inmedical research, Dr. Paul Herman Müller was awarded a Nobel Prize in Medicine for DDT in 1948.In early 1946 U.S.D.A. entomologists through selectivebreeding in a laboratory, created a strain of housefly much moreresistant compared to houseflies found in the field.Rachael Carson published an article in Science,on March 12, 1946, “In view of the increasing use of DDT forhousefly and mosquito control it seems possible that, in time,a similar increase in resistance may occur under naturalconditions.”
25The evidence that DDT was poisoning the environment multiplied THE DEADLY DUST: DDTThe evidence that DDT was poisoning the environment multipliedthroughout the iggo’s. There were increasingly frequentreports of direct poisoningsof birds, of fish, of small game,sometimes after applications in excess of prescribed amountsbut often, too, when the prescriptions were precisely followed.One day in January, 1958, Olga Huckins wrote a long, eloquentlyangry letter to her friend Rachel Carson, describing the deadlyeffect of DDT spraying for mosquito control over theHuckinses’ private two-acre bird sanctuary at Powder Point,in Duxbury, Massachusetts.Not long afterward Miss Carson was a house guest at Powder Pointwhen, late in the afternoon, the spraying plane came over.The next morning she went through the estuary with theHuckinses in their boat. She was sickened by what she saw—dead and dying fish everywhere, crayfish and crabs dead orstaggering as their nervous systems were destroyed.“You ought to write about this,” the Huckinses kept saying.“You’ve got to.…”
26For as the stubbornly persistent DDT enters a food chain that THE DEADLY DUST: DDTFor as the stubbornly persistent DDT enters a food chain thatbegins with herbivores and runs through small to large and thenlarger carnivores, including man, the process known as“biological magnification” occurs.An early instance was recorded on the East Lansing campus ofMichigan State University. Annual spraying of elms with DDTbegan there in 1954 to control the beetle that spreads Dutch elm disease.For the first year or so there were no apparent side effects.But then people noticed that there were no more robins on the campus.Earthworms feeding on elm leaves with tiny amounts of DDTon them accumulated the stuff in their body fat until a level toxic torobins was reached. Robins that ate those worms died—and robins unfortunate enough to visit the campus eventwo years after spraying had been discontinued also died.
27the mud was found to contain 0.014 ppm. of DDT; THE DEADLY DUST: DDTIn other studies the magnification rate in specific food chains was measured in the bottom of Lake Michigan’s Green Bay:the mud was found to contain ppm. of DDT;crustaceans absorbing DDT from the mud,concentrated it in their bodies to 0.41 ppm;fish feeding on the crustaceans, concentrated DDT in their bodies to from 3 to 6 ppm;Herring gulls feeding on the fish accumulated DDT to the level of 99 ppm. This concentration, though not immediately fatal to individual gulls, reduces normal reproduction.The eggs of these herring gulls were abnormally thin and contained 227 pp. of DDT.
28By the late 1950’s it was clear to Dr. Carson, and THE DEADLY DUST: DDTBy the late 1950’s it was clear to Dr. Carson, andother knowledgeable observers, that DDT’sincreasingly massive invasion of the food chain waslargely responsible for the fact that bald eagles wereceasing to breed on the East Coast between Florida and Maine(large concentrations of DDT residues were found in the brainsof prematurely dead eagles); that eagles in the Great Lakes regionfaced extinction because their egg shells were growing too thin(the physiological mechanism by which DDT inhibits calciumproduction would soon be discovered); that peregrine falcons weredisappearing as breeding birds in the whole eastern half of the U.S.;that ospreys would disappear from Connecticut by the early 1970's ifpresent rates of decline continued.Nor was DDT’s invasion of the food chain limited to land or tooffshore waters. Oceanic food chains werebeing similarly contaminated, and ocean currents were spreading DDTresidues to the most remote corners of the earth.
29Predictable in a general way by the pattern of events was the THE DEADLY DUST: DDTPredictable in a general way by the pattern of events was thesad case of the Bermuda petrel, a carnivorous bird thatfeeds solely on oceanic life far from any area where DDT is used.The bird comes to Bermuda for only a few hours, at night, to lay its eggs.It eats nothing there. Yet its eggs in the late 1960’s contained6.44 ppm of DDT on the average, and its reproduction wasdeclining at a rate which, if continued, must end incomplete reproductive failure by 1978.Even Antarctica’s Adélie penguins, Weddell seals, and skua gulls,carnivores all, were soon found to carry trace amounts of DDTin their fat, though they live thousands of miles from thenearest area of DDT use.Undoubtedly they ingest DDT residues in their food.
30But DDT was also found, in the 1960’s, in Antarctic snow, THE DEADLY DUST: DDTBut DDT was also found, in the 1960’s, in Antarctic snow,indicating that the food chain is not the only means bywhich the poison spreads.Studies conducted in Maine and New Brunswick, Canada,in the 1950's showed that approximately half the DDT sprayedover forests at treetop level hung suspended in the atmosphereto be spread worldwide on the wind. DDT attached to erosiondebris also travels in irrigation water, rivers, and ocean currents.Some 2,400 tons of it have been estimated to have accumulated bynow in Antarctica’s snows.
31In 1968Charles F. Wurster, Jr., of the State University of New York at THE DEADLY DUST: DDTIn 1968Charles F. Wurster, Jr., of the State University of New York atStony Brook found in the laboratory that very low concentrations of DDTmeasurably reduced photosynthesis in cultures of four species of coastaloceanic phytoplankton representing four major classes of algae.Furthermore, the same had been found true of a natural phytoplanktoncommunity (as distinct from a laboratory culture) at Woods Hole.“I’ll tell you what we worry about most,” said David M. Gates,director of the Missouri Botanical Garden in St. Louis, to a reporter in 1969,"—an irreversible catastrophe.A number of pesticide spills, for example, in those areas of the ocean where… much of the world’s oxygen [is produced]. If you plot the frequency ofthis kind of event, they’re getting closer and closer.”Much of this kind of fear has been allayed by recent scientificfindings that suggest that no significant interchange ofoxygen occurs between ocean and atmosphere, and, in addition,that some phytoplankton are considerably less sensitive topesticides than others. Such findings, of course, do not alterthe fact that any large-scale interference with ocean life wouldhave serious repercussions.
32her book aroused even before its formal publication date in 1962. THE DEADLY DUST: DDTDr. Rachael Carson was not surprised by the storm of controversyher book aroused even before its formal publication date in 1962.But with scientific colleagues, with the general public, and withmany governmental policy makers, Silent Spring was enormouslypersuasive. In 1964 Rachel Carson, aged fifty-six, died of cancer.Today DDT is increasingly suspected of direct injury to man.Evidence of the carcinogenic effects of DDT have multiplied since 1962.Indeed, in the very year following publication of Silent Spring,Dr. William C. H. Hueper of the National Cancer Institute reportedDDT to be “cancer producing according to presently availableevidence” and incriminated DDT in the “production of benignand malignant tumors of the liver, cancers of the lung, and leukemias. .
33In 1963, in direct response to the public concern aroused by THE DEADLY DUST: DDTIn 1963, in direct response to the public concern aroused bySilent Spring, President Kennedy’s Science Advisory Committeerecommended a reduction of DDT use with a view to its totalelimination as quickly as possible, along with other “hard”pesticides.Soon thereafter Secretary of the Interior Stewart Udall issued anorder banning the use of DDT on Interior-controlled lands“when other chemicals can do the job.” Wisconsin, Michigan,California, Massachusetts, and other states began to movetoward state prohibitions of DDT.Finally, in November of 1969, acting on the recommendation of aspecial study commission on pesticides,Robert H. Finch, Secretary of Health, Education, and Welfare,announced that the federal government would “phase out” all but“essential uses” of DDT within two years.Many Americans assumed that this phasing out means the end of DDT. But not so.
34Even though, belatedly, the search has been intensified for THE DEADLY DUST: DDTEven though, belatedly, the search has been intensified forsafe alternatives to persistent pesticides, the worldwidedemand for DDT increases as underdeveloped countriesface the immediate desperate problems of feeding andprotecting the health of exploding populations.The U.N.'s World Health Organization and the Food and AgriculturalOrganization have strongly opposed any prohibition or evenreduction of DDT’s use, arguing that it is the cheapest effective pesticide(it costs about fifteen cents a pound as compared with a dollar or morefor other chemicals), that poor countries cannot afford substitutes,and that without the kind of crop protection and disease control providedby DDT, millions must surely and quickly die.
35How could it be removed from sprayed fruits and vegetables since, THE DEADLY DUST: DDTHow could it be removed from sprayed fruits and vegetables since,unlike earlier poisons, it would not wash off?Would it persist and build up in soils to a levelpoisonous to warm-blooded animals?And just how toxic was it to such creatures, including man?Harmless to man when absorbed in small doses over the short run,might it not build up in fatty tissues(experiments with dogs in 1944 and ’45 proved itdid concentrate in fatty tissues) with harmful long-term effects?Would it be carried by soil erosion into streams and lakes and seas,with deadly effects on aquatic life?And, in general, what effect would its widespread usehave upon the ecological balance?
36DDT is moderately to slightly toxic to mammals THE DEADLY DUST: DDTDDT is moderately to slightly toxic to mammalsby the World Health Organisation as Class IIDDT oral toxicity.acute oral LD 50mg/kg in rats;mg/kg in mice;300 mg/kg in rabbits;mg/kg in dogs;and >1,000 mg/kg in sheep and goats.DDT is less toxic to test animals exposed via the skin.acute dermal LD502,510 mg/kg in rats
37THE DEADLY DUST: DDTCancer The evidence relating to DDT and carcinogenicity provides uncertainconclusions. It has increased tumour production, mainly in the liver andlungs, in test animals such as rats, mice and hamsters in some studies.In rats, liver tumours were induced in three studies at doses of12.5 mg/kg/day over periods of 78 weeks to life, andthyroid tumours were induced at doses of 85 mg/kg/day over 78 weeks.Tests have shown laboratory mice were more sensitive to DDT.Life time doses of 0.4 mg/kg/day resulted in lung tumours in thesecond generation and leukaemia in the third generation, andliver tumours were induced at oral doses of 0.26 mg/kg/dayin two separate studies over several generations(19).The US Environmental Protection Agency (EPA) hasdetermined that DDT and DDE are probable human carcinogens(20).Work carried out by the US National Cancer Institute correlates breast cancerin women with increased levels of DDE in blood serum. From 14,290 womenmonitored in the New York University Women's Health Study,researchers selected 58 women who had developed breast cancer and171 matched controls without cancer. After adjusting for participants'childbearing and breast feeding histories, and for family history of breast cancer,researchers found a four-fold increase in relative risk of breast cancer forwomen with elevated levels of DDE in the blood.