Document 6bL0YYeR4x48OLLbddLeJQ93

wv, /W, t?y% r*w*'^nz3< rEnvponmental Contamination: Some Contemporary Issues persons who had been exposed in earlier years. There is no evidence that the presence or DOT in human fat is harmful at the levels reported in the general population. THE POLYCHLORINATED BIPHENYLS (PCBc) The PCBs are a family of chemicals known as chlorinated biphenyls and naphthalenes and wer: used in large quantities early in World War II to provide nonflammable insulation for electrical equipment. The products were sold under the trade name "Halowax," and a number of workers who were exposed to their vapors and dusts died from liver damage. The chlorinated naphthalenes proved to be so toxic to humans working with them that their use as insulating materials was voluntarily discontinued, but the chlorinated biphenyls now known as PCBs (poly chlorinated biphenyls) continued to be used in electrical equipment and for numerous other purposes. The PCBs comprise more than 200 chemical species, each distin guished by differences in the number of chlorine atoms and the position in which they have been incorporated into ringlike organic molecules known as "phenyls." Large-scale production of these compounds began around 1930 and reached a maximum in 1970, afterwhich production was voluntarily curtailed by the Monsanto Chemical Company, the principal manufacturer, because of develop ing concern about the effects of the PCBs on human health and wildlife. Sale of PCBs was thereafter limited to sealed systems from which environmental contamination could be minimized. During the many years in which they have been manufactured, the PCBs had been found to have remarkable properties that favored their use for many purposes. Because the compounds are excellent electri cal insulators and are not flammable, they have been used as dielec trics In transformers and large electrical condensers. These are sealed systems in which the PCBs can remain in place for the life of the equipment and can then be purified for reuse when the equipment Is crapped. However, tome leakage can be expected to occur during the lifetime of the equipment, and PCBs may eventually enter the environment via sewers or surface runoff to streams. PCBs are also used in small electrical capacitators, such as thdse in fluoreicent-lamp boosters, that have a relatively short life and ulti mately find their way to the scrap heap for incineration or land disposal. The compounds are also used in lubricating and cutting oils, as plasticizers in paints, in pesticides, in the manufacture of pnper. adhesives, and plastics, ns well as in heat transfer and hydraulic fluids. The many uses of the PCBs, plus the fact that they are highly HQNS 211231 The Organic Chemicals 237 stable chemicals, assured their role as ubiquitous environmental con taminants. The danger of PCBs to humans came to worldwide attention as a result of an accident in japan in 1968. in which rice oil was contami nated by PCBs leaking from a heating system.30 The first cases had unusual skin complaints, and upon investigation it was found that all patients had consumed rice oil that was contaminated by PCBs. The disease was soon found to involve more than skin complaints and was given the name "yusho'' (oil disease). The patients suffered from fatigue, nausea, swelling of the arms and legs, and liver injury. Babies born to mothers with yusho were smaller than normal. In addition, their subsequent growth and development were diminished, all of which indicated that the PCBs had caused fetal injury after being transported through the placenta. By 1973. about 1,200 cases of yusho had been reported as a result of this mishap.11 Shortly aher the yusho incident occurred, it became apparent that the analytical procedures used to detect DOT were being affected by the presence of another class of chlorinated organic compounds whose behavior in the analytical procedures was very similar to that of DOT. The results of tests for DDT were being biased by the presence of substances which were soon found to be PCBs. Thus, coincidentally with worldwide awareness of the human toxicity of PCBs, it was found that they, like DOT, were persistent in the environment and were present as contaminants of fresh water and marine organisms. Like DDT, the PCBs tend to accumulate in the fatty tissues of plants and animals. They are also capable of biomagnificatton: PCBs, at each step in the food chain, can be concentrated from ten to 100 times the concentration in the previous step. At the top of the food chain, in the sea birds and large carnivorous fish and sea mammals, the concentration can be 10 million times that in the surrounding water." As a result, although the concentration of PCBs in the ambient water might be only one part per billion, fish from the waters and bays of Europe, North America, and japan contain several parts per million. Concentrations as high as 800 parts per million have been found in the fish from some inland waterways." The higher levels tend to be found near centers of industrial activity, but worldwide contamination exists at levels on the order of one part per million. The toxicity of PCBs is variable, depending on the biological species and the particular molecular form of PCB to which they are exposed."'1* Some organisms are able to tolerate concentrations of PCBs that kill others. One of the most susceptible is the pink'Shrimp. among which complete mortality can be produced in water containing MO NS 211232 238 Environmental Contamination Some Contemporary Issues 100 parts per billion The stage of development is also important Many fish that can tolerate several parts per million as adults are seriously affected in earlier stHgcs of growth. Among the mammals, the mink has proved to be markedly sensitive, a fact that was discovcicd in 1967 when commercial mink ranchers fed their slock food prepared from Coho salmon contaminated by PCBs in a Lake Michigan tributary Subsequent laboratory experiments demonstrated that PCBs were extraoidmanly toxic to mink, and even more so to the embryos,31 The acme toxicity of PCBs to humans was demonstrated in the yusho incident, but in that instance the levels of exposures were high and therefore do not shed light on the toxicity of PCBs to humans at the levels "normally" found in the environment. The main source of PCBs for humans is the diet, and FDA market-basket studies since 1969 have shown that fish are the major source of PCBs.513* The daily intake of PCBs by the average teenage American male has dropped from 15 {nucrograms/day) micrograms per day in 1971 to about 8 7 in 1974 and 1975. This is due to reduced contamination in food other than fish and poultry, which have not changed significantly. Studies in Canada*0 and the United States*1 have shown that PCBs tend to concentrate in body fat and. because of the high fat content of human milk, can be passed in this way to breast-fed babies The actual PCB content of the fat in human milk is approximately the same as in other fatty tissues of the body and has averaged about 1.7 parts per million in North America during the period between 1969 and 1974. Samples containing as much as ten parts per million have been reported. People who eat fresh fish, particularly from lakes known to be contaminated with PCBs. tend to have the highest levels. There is reason to be concerned about these reports. Experiments with rhesus monkeys have showm that severe PCB intoxication occurs in the rhesus infants born to mothers fed PCB-contaminatcd food. The levels of PCBs in the rhesus milk are comparable to the highest values found in human milk in the United States and Canada. Nevertheless, the consensus among informed individuals is that the prescncc<oKPCBs in human milk docs not warrant changes in nursing jjtjicticcOuAowcvcr. an advisory committee tolTc"New York* Slate Health "Department recommended that tf mothers have been consum ing fish from waters known to be contaminated with PCBs on a regular basis, nursing should be discontinued after three months.*3 It has also been found that 2.5 to five parts per million of PCBs in the diet of rhesus monkeys caused toxic symptoms to develop within one to two months.** The rhesus monkey is a relatively scnsuive species, and is affected at concentrations as low as I percent of those HONS 211233 The Organu Chennuth 239 thai affect rats On the assumption that a teenager consumes 2,000 grams of food per day, his daily intake of PCBs is of the order of I percent of thai known to have caused toxic symptoms in monkeys This may seem to be a safe level, but it should be noted dial the market-basket esti mates are applicable to "average" people, and not to people who consume large quantities of fresh-water fish. Moreover, since PCBs are passed to breast-fed infants, infants may be relatively heavily exposed The infants of rhesus monkey mothers fed about 2 5 parts per million of PCB in their diet were undersized at birth, generally debilitated, and subject to frequent infections We cannot be certain that somewhere in the United Slates there arc not nursing mothers with a preference for fish contaminated with PCB. whose nursing babies are showing the effects of PCB toxicity The basic concerns about PCBs arc over the relative susceptibility of humans compared to rhesus monkeys, and to what extent there arc deviations from the national average There have been no reports of PCB poisoning in nursing infants, but there had been no epidemiolog ical studies ns of the end of 1977 Only by careful and sufficiently extensive studies can assurances be gamed that occasional eases of PCB poisoning are not occurs ing in the infant population The fact that these studies have not been done ts an example of the inetTectivencss of the means for epidemiological research for environmental health in the United States. The PCBs are a particularly difficult class of compounds to evaluate from the toxicological point of view. As noted earlier, their chemical complexity is such that they exist in more than 200 forms (isomets), and the toxicity of a particular isomer, as well as the rale at which it will degrade in the environment, depends on the chemical species involved. A further complication arises because PCBs can be trans formed into a class of highly toxic impurities, polychlorinated dtbenzofurans (PCDFs). These KTDFs can be formed In the process of manufacture or by subsequent degradation processes. It is known that the contaminated nee oil that caused yusho in Japan contained high levels of dibcn7oftirans. and it has been suggested that because the PCBs were used as a heat-transfer medium, the high temperatures may have degraded the PC Bs to produce PCDFs The toxicity of PCBs may thus depend, not only on their particular chemical identity, but also on the extent to which they are contaminated with dibeu/ofuntns," The role of PCDFs in the epidemiology of PCB poisoning is not well understood. Unfortunately, ihc PCDFs are extremely dif ficult to mca.xuic in trace amounts and very few studies on the effects HONS 211234 240 Environmental Contamination. Some Contemporary Issues of PCDFs have been reported In 1973. the FDA issued regulations that banned the industrial uses of PCBs in establishments manufacturing, handling, or storing human food, animal feeds, and paper food-packaging materials.,T The regula tions also proposed temporary limits on PCHs in food. The most important limitation was that pertaining to fish, a maximum of five parts per million in the edible portions The Canadian authorities subsequently reduced the permissible PCB concentration in fish to two parts per million, following which the United Stales FDA pro posed a similar change."1 The PCB content of a fish depends to a large extent on its feeding habits For example, the American shad spends most of its life in the open ocean but comes to the estuaries to spawn Since the shad are usually caught for market on their way to their spawning grounds, they have relatively low levels of PCBs. Catfish and eels, which tend to feed among the sediments of the estuaries. arc among the fish that contain the highest concentrations. ft is ironic that, at the very time when benefits were being expected from the enormous expenditures for the clean waters programs of many states, the PCB and other similar problems have developed and. for some time to come, wilt deny the use of important waterways for some of the very purposes for which billions were spent for pollution control. As an example, the total expenditures by local, state and federal governments for water-pollution control in the Hudson River estuary were in excess of 3 billion dollars by 1976, However, the new sewage-treatment plants were not designed to remove toxic substances that accordingly are allowed to enter the lakes, rivers, or bays along with the treated sewage. Because of the high concentrations of PCBs m Hudson River fish, it was decided to ban commercial fishing for an indefinite pciiod starling late in 1973. The principal species affected was the striped bass, which is highly prized by both sports and commercial fishermen. Sports fishing was allowed, but the fishermen weie cautioned not to eat more than one fish meal per week and were forbidden to sell the catch. Eels were not allowed to be taken by either sportsmen or commercial fishermen. An exception to the ban on commercial fishing was made in the case of shad which, for the reasons noted, proved not to be excessively contaminated. The main sources of PCB contamination of the Hudson were believed to be two General Flee trie Company plants at Fort Kdward and Hudson Falls, located in the upper reaches of the nver. A prolonged hearing resulted from charges by New Yoik State that the company polluted the waters of the river to such an extent as to be HONS 211235 The Organic Chemicals 241 injurious to wildlife, and that the company should eliminate its dis charge of PCBs and "restore the health of the Hudson River and other natural resources to the extent that PCB discharges have despoiled them. . . The hearing that followed illuminated the history of PCB discharges by the company in a manner that was neither a credit to the company nor to the state and federal govern ments As stated in the opinion of the hearing examiner, "these unlawful consequences are the product of both corporate abuse and regulatory failure: corporate abuse in that G.E. caused the PCBs to be discharged without exercising sufficient precaution and concern; regu latory failure in that G.E. informed the responsible federal and state agencies of its activities, and they too exercised insufficient caution and concern. . , ." The General Electric Company had purchased more than 41.000 tons of PCBs of various types from the Monsanto Chemical Company since 1966. The material was used in the manufacture of electrical condensers, and during much of the time it used them, the compjny had been discharging an average of about 30 pounds per day of PCBs to the river. As a result of the 1972 amendments to the Federal Water Pollution Control Act, the states were required to adopt control programs based on effluent limitations. As a result. New York State required that a certificate be obtained that authorized the discharge of individual pollutants. A federal discharge permit was required following certifi cation by the state. General Electric applied for such a permit in late 1971. Two years later, the slate certified that no effluent standards were applicable to the proposed discharges, and the U.S. Environ mental Protection Agency regional office issued a draft permit that proposed to authorize a daily average discharge of 30 pounds from the two plants. The draft permit also proposed that the chlorinated hydrocarbon discharges be reduced to zero within 21 months of the permit's issuance.** A requirement for zero discharge is unrealistic. Large industrial plants can reduce their discharges to any desired level shorl of zero. The discharge of 30 pounds per day could have been reduced to three pounds per day, .03, ,003 pounds, or lower, but some finite discharge would remain that could be detected. In practice, a waste-discharge limit should be based on the risks to human health a/id wildlife, technical feasibility, the characteristics of the receiving body of water, and cost. If the plant is to operate, the permissible discharge must be expressed in finite terms. It can be reduced to whatever level required, but not to zero When the permit was finally issued in December of 1974, it ordered HONS 211236 242 Environmental Contamination. Some Contemporary Issues that the discharge of PCBs be reduced to 3 5 ounces by mid-1977, The position that General Electric look at the hearing rested substantially on the premise thai since ihc Department of Environmental Conserva tion and the Environmental Protection Agency were fully aware of the PCB discharges, the discharges could not be illegal, The hearing examiner commented that "G E's argument has more than superfi cial appeal/' '' ' By 1972 it was well known by the State Department of Environ mental Conservation that PCBs were present in striped bass in concentrations ten tintes or more the FDA's limit of five parts per million- The high levels persisted through 1977, despite the fact that G.E quickly reduced its releases. The PCBs were deposited in the sediments, where they have served as a reservoir for pollution of the biota, and it is not known how long it will take for the river to cleanse itself. t lltc stale had the power all along to correct the problem, the existence of which was known six years before the matter received public attention. Since the matter of PCB pollution was a national problem, the staie looked to Ihc federal government for policy, but received only a guideline for the maximum permissible PCB conient of fish, and no detailed instructions as to how the guideline should be interpreted. The federal government had the power to stop (he sale of fish in interstate commerce, but failed to do so. The company pre sumably thought the dtobtem-oouM -aoi-hg a criftUS P9C because l^yy applied for and received permission to discharge PCBs in the staled amount. However, the laigc companies that manufactured and used the PCBs had the means to evaluate Ihc impact of PCB discharges to Ihc estuary. They did not do so on the assumption that generic questions of this kmcTfiavc been dealt with traditionally by govern ment. Problems similar to those created by PCBs and DDT have been caused by other chlorinated organic compounds. These include kepone, and nurex. Most of the offending organic chemicals have been chlorinated hydrocarbons that arc both toxic and persistent in the environment. ' The episodes of pollution by chlorinated hydrocarbons served to emphasize the need for a National Toxic Substances Control Act that would prevent potentially cittiisirophic pollution with chemical wastes. A law finally was signed by President Ford in 1976. It requires that before they can be approved for use, all new chemicals must be tested for their human toxicity and ecological effects. Ihis is a law thiit was long ovetduc and. if wisely administered, can greatly reduce, if not eliminate entirely. Ihc danger that a new chemical will HONS 211237 The Organic Chemicals 243 damage human health or wildlife However, if it is administered too zealously, the world may be denied the use of new chemicals that could be of great benefit to mankind Great administrative wisdom will be needed to provide the kind of balance that will give (he protection needed, while at (he same time assuring that the incentives to produce beneficial new chemicals will not be destroyed. NOTES l. Carson. Rachel. "Silent Spring," Houghton Mifflin Co . Bosion. Mass (l%2). 2 Kilgore, W. W, and M Li. "The Carcinogenicity of Pesticides." in' "Residue Reviews: Residues or Pesticides and Other Coniaminunls in the Total bnviionment" (F. A Gunther. ed.). Springcr-Verlag, New York) Hcidclbcrg/Bcrlin (1973). Vol 48. p 141 3. U.S. Environmental Protection Agency. "Report of the DDT Advisory Committee." Washington. D.C. (1971) 4. National Academy of Sciences "Pest Control An Assessment of Present and Allcrnative Technologies " Vol V. "Pcs( Control and Public Health." National Research Council, Environmental Studies Board. Washington, D C. (.1976). 5. Deichmann, W B. "Liver Cancer Deaths in the Continental USA from 1930 to 1972,** Am. Indus. Hyg Assn. J. (September (976), p. 495-498 6. Hayes. W. L. "Mortality in 1969 from Pesticides. Including Aerosols." Arch. Env. Health (March-April. 1976). pp. 61-72 7. World Health Organization "Health Hazards of the Human Environ ment.** B. Carcinogens. Geneva (1972). pp. 219-228. 8. Bevenue. A. "The `Bioconcentration- Aspects of DDT in the Environ ment,*' tn: ''Residue Reviews. Residues of Pesticides and Other Con taminants in the Total Environment" (F. A. Gunther ed > Springer* Verlag, New York/HeidelbergtBcilm (1976). Vol. 61, p, 37 9. Woodwctt. G M "Tome Substances and Ecological Cycles " Scientific American 2!6<3):24-3l (t%7). 10. Ware, G. W. "Effects of DOT on Reproduction in Higher Animals." in "Residue Reviews. Residues of Pesticides and Other Contaminants in the Total Environment'* (F. A. Gunther, ed ). Springcr-Verlng. New York) Hekteibctg/Bcrlm (1975). Vol. 59. p 119. It. Cooke. A. S "Shell Thinning in Avwn Eggs by Environmental Pollui* anil.** Environmental Pollution 4 85-1'2 (1973). 12. *`U.S. Department of Health. Education and Welfare Report Of the Secretary's Commission on Pesticides'* (December. 1969). p, 50 13 Robinson, J. "Orgunochlonnc insecticides and Bird Populations in Brit ain," in: "Chemical Fallout Current Research on Persistent PistiLidcs" (M. Miller and G. Berg, eds ). (. h.nies C. Thomas. Spiingfield HE (t%9). p. 113. HQNS 211238 244 Environmental Contamination: Some Contemporary Issues 14. Devlin, R M. "DDT A Renaissance''" Environmental Science and Technology 8 322-325 (1974) 15. Wursicr, Charles F "DDT Reduces Photosynthesis by Marine Phyto plankton." Science 159 1474 (1968) 16. Wagner. R H "Environment and Man," W. W. Norton. New York (1971). 17. Commoner. Barry "The Closing Circle." Knopf. New York (1971) |8. Massachusetts Institute of Technology "Man's Impact on the Global Environment. Report of the Study of Critical Environmental Problems ` (SCEP) (1970). 19. "DDT Residues in Marine Phytoplankton." in: "Residue Reviews- Resi dues of Pesticides and Other Contaminants in the Toial Environment" (F. A Gunther, ed ), Springcr-Vcrlag. New York/Heidelberg/Bcrhn (1972), Vol. 44. p. 23. 20. National Academy of Sciences, '`pest Control: An Assessment of Present and Alternative Technologies." Vol. 1. "Contemporary Pest Control Practices and Prospects The Report of the Executive Committee." Naiional Research Council, Environmental Studies Board, Washington. DC. (1975). 21. Wursicr. Charles F. "DDT Goes to Trial in Madison," BioSaence 19,809-813 11969). 22. Wurster, Charles F. "American Scientists Take Legal Action to Improve Pesticide Regulation." presented at the International Conference on The Responsibility of Science in Modern Society, Florence, Italy (October 4, 1976). 23. Federal Register. "Environmental Proteciion Agency. Consolidated DDT Hearings." Federal Register 37 (I3I):I3369-I3375 (July 7 1972). 24. Council on Environmental Quality. "Sixth Annual Report." U S Gov ernment Printing Office. Washington, D.C. (1975), p 368 25. Johnsion, D. W "Decline of DDT Residues in Migratory Songbirds," Science 186.841-842(1974). 26. Nickerson, P R. and K. R. Barbehenn "DDT Residues in Starlings, 1974." Pest. Moult. J. 9( 1): l (1975). 27. Anderson, D. W. J. R Jchl, R. W, Risebrough, L, A. Woods, L. R. Dcwees and W. G, Edgecomb, "Brown Pelicans: Improved Reproduc tion off the Southern California Const." Sciente 190.806-808 (1975), 28. Woodwelt, G. M.. P. P Craig and H. A. Johnson. "DDT in the Bio sphere: Where Docs It GoT'Sr/eme 1974:1101-1107 (1971), 29. Ware, G- W., B. J, bstesen and W. P. Cahill. "DDT Moratorium in Arizona--Agricultural Residues after 4 Years." Rett. Momt. J, 8(2) 98 (1974). 30. Higuchi. Keataro (cd.). "PCB Poisoning and Pollution." Kodansha Ltd., Tokyo and Academic Press, New York (1976). fP. It, Kuratstmc, Mnsnnort. "Epidemiologic Studies on Yusho," id: "PCB + Poisoning and Pollution" (K Higuchi. cd ). Kodansha Ltd , Tokyo and Academic Press. New York (1976), HONS 211239 The Organic Chemicals 245 32. Nisbct, I. C T and A. F Sarofim "Rates and Routes of Transport of PCBs in the Environment," Environmental Health Perspective. Experi mental Issue No. I (April. 1972), 33, Panel on Hazardous Trace Substances. Report of Panel on Hazardous 1 race Substances to Ad Hoc Committee on Environmental Hcalih Re search (David P. Rail. Chairman), Environ Res. 3:249-362 (1972) 34 Peakalj, D B. "Polychlorinated Biphenyls. Occurrence and Biological Effects." in "Residue Reviews Residues of Pesticides and Other Con taminants in IhcTolnl Environment" (T, A Gunther, ed ), Springer-Vetlag. New York/Hcidelberg/Berlin (1972), Vol 44 p I. 35 l.nvironmen/al Health Perspectives* Experimental Issue No I (April, 1972). 36. Environmental Protection Agency Proceedings of the National Confer ence on Polychhninated Biphenyls (November 19-21. I97J). Chicago, III., EPA*S6OI6'?i*O0d, Environmental Protection Agency. Office of T oxic Substances, Washington. D.C (March 1976) 37 Kornreich. M., ei al. "'Environmental Impact of Polychlorinated Biphenyls" MITRE Technnal Report 7006 The MITRE Corpoialion, McLean. Va. (May, 1976). 38 Kolbye. A. C. "Food Exposures to Polychlorinated Biphenyls." En vironmental Health Perspeiuvcs. Experimental Issue No. I (April, 1972) 39. Jclmck. C. and P. F.. Corndiussen "Levels of PCB's in the U S Food Supply," in: Proceedings of the National Conference on Polychlorinated Biphenyls (November 19-25, 1975), Chicago. Ill , EPA-S6OI6-`7S-004, U S Environmental Protection Agency, Office of Toxic Substances Washing ton. D C. (March, 1976). 40. Grant. D.. J. Mes and R. Frank "PCB Residues in Human Adipose Tissue and Milk," in; Proceedings of the Notional Conference on Polychlorinated Biphenyls (November 19-21. 1975), Chicago, 111. tPA- 56045-75-004, U.S, Environmental Protection Agency, Office of Toxic Substances, Washington, D.C (1976). p 144. 41. Kutz, F, W. and S. C. Slrassman. "Residues of Polychlorinated Biphenyls in the General Population of the United States," in' Proieed- lags of the Nnfiowif Conference on Polychlorinated Biphenyls (November 19-21. 1975), Chicago, 111., EPA-560)6-76-004, U S En vironmental Protection Agency. Office of Toxic Substances. Washington. D.C. (1976). p 139. TjXMiller. R. W. "Pollutants in Breast Milk." Journal of Pcdtntries 90(3):5I0-.M2 (1977), 43. N.Y. State Health Planning Commission "Report of the Ad Hoc Com mittee on the Health Implicitturns of PCBs in Mothers' Milk," Albany, N.Y. (January, 1977). , 44. Allen, J. R, "Response of the Ncmhumnn Primate to Polychlorinated Biphenyl Exposure." Research Activities at Regional Primate Centers. Federation Prmeediugs. Vol. 34. No 8, pp. 1675-1679 (1975). 45. McNulty. Wilbur P. Pnrteatings ttf the National Confererne on Poly- HONS 211240 246 Environmental Contamination: Some Contemporary Issues chlorinated Biphenyls (November 19-21, t975), Chicago, 111.. EI'A-560/675*004. U.S Environmental Protection Agency. Office of Toxic Substances. Washington, D C. (1976). p 347 <6 Kuratsunc. M . Y Masuda. and J, Nagayama. "Some of the Recent Findings Concerning Yusho." in; Proceedings of the Notional Confer ence on Polyi Marinated Biphenyls (November 19-25. I97J), Chicago, III . fcPA-56016-75-004. U.S Environmental Piotection Agency. Office of Toxic Substances. Washington, 0 C U976) 47. Environmental Protection Agency. Proceedings af the National Conference on Polychlorinated BipArnyfs, (November 19-25, 1975). Chicago. Ill , /M-.56016*7.3-004, U.S Environmental Protection Agency, Office of Toxic Substances. Washington. D.C. (1976). 48. Department of Health. Education and Welfare. Food and Drug Adminis tration. '`Polychlorinated Biphenyls (PCB's),'' Federal Wcgiifer 42(63) 17487-17494 (April 1. 1977). 49. State of New York, Department of Environmental Conservation, Interim opinion and order. File No 2833 (February 9. 1976). MOMS 21124*1