Document YGKMVOZ9NBENM814JMeJwy1DE

Chemical Pollution: Polychlorinated Biphenyls Polychlorinated biphenyls (PCBi) ire widely used industrial chemicals that were never intended for release into the environment, but they have nonetheless been found in rainwater, in human tis sue. and in many species of birds and fish. How PCBs tame to be widely distributed in the er ironment and what biological effec's they have are stilt largely unknown. But tike DDT, PCBs apparently degrade very slowly under natural conditions. They tend to accumulate in the food chain, and once ingested, they arc stored in the body's fatty tissues. As is true with many other chlorinated hydrocarbons, even small doses of PCBs can be toxic, although it is not clear that the amounts found in fish or birds have had detrimental elTects, The only epidemiological Infor mation about. PCBs' effects on man comes from an accidental poisoning incident in Japan in which some 1000 persons were affected. Polychlorinated biphenyls are rela tively inert compounds that hive low solubilities in water. The PCBs pro duced commercially are mixtures, in corporating some 50 or more of the 210 different PCD compounds that are theoretically possible from chlorinating biphenyi. The most common industrial mixtures average between 40 and 60 percent chlorine content, but their iso meric composition is only partially known, thus complicating the problems of sampling and analysis. Gas chroma tographic techniques are now most commonly used to determine the pres ence and the amount of PCBs ia sample. The method is not specific for identifying particular PCB compounds because or the lack of samples of the different isomers as reference standard*. 1 here appears to be some variability in biological and chemical activities among the compounds; highly chlorinated PCBs seem (o persist in the environ ment the tongesl and are less toxic than the mors rapidly degraded low chlorine forms. There is also evidence that some cornu treiat PCB mixtures, especially those manufactured in Eumpe or Jspan, may contain trace amounts of dibenzofurans or other ex tremely toxic impurities, which may be the i ..use of sonic of the toxic effects ascribed to PCBs themselves. The major uses of PCBs derive from their nonflammability, high dielectric constant, and plasticizing abilities. These uses include applications ss dielectric fluids in capacitors and transformers, as hydraulic fluids, and at heat transfer fluids; also PCBs have been widely used as plasticizers and solvents in adhesives, sealants, paints, tnd printing inks. Some 95 percent of the large phase correction capacitors used in transmitting electric power, for exam ple, contain PCBs--amounting in 1968 to almost 2.5 million gallons in the United Slates alone*; replacement of PCBs by other dielectric fluids, accord ing to Martin Broadhurst of the Na tions! Bureau of Standards, would re quire that the capacitors be rebuilt ind that they be 50 percent larger. Alter nate materials for plasticizer applica tions of PCBs, on the other hand, are readily available. Industrial usa of PCBs has grown steidily since their introduction In 1930. U.S. sales In 1970 ctme to about 34,000 tons, with cumulative produc tion over the years amounting to an estimated 4x 10* tons, (By compart-, son, U.S. production of DDT in recent yean has been about 70.000 tons.) Leu, in fact almost nothing, is known about the quantities produced world wide; in addition to the production in the United Slates, PCBs are made in Europe, Japan, and the U.S.S.R. The only U.S, producer of PCBs, the Mon santo Chemical Corporation, refused until recently to release production fig ure*. but the company hat taken the unusual step of refusing to sell any mm PCBs for plasticizer applications and those heat transfer applications in volving food preparation. Current an nual U.S. sales, as a result, have fallen to about 20,000 tons per year, although exports have continued to increase. How PCBs are released into (he en vironment is not known, but several scientists believe (hat sewage outfalls and industrial disposal into waterways are major sources. Rivers and streams may be the primary means of transport * More 6rL*ll4 t*f*p**6i lo muy of fur*tJon4 Kgrt c*t be ftwtd Jn Iha lorlfrcemJAi hrliM tuwt of MrafrA frrtpttttvn, JourMi io b pwOUih4 bjr the NaHonal liuik lute ft EitviromiMmil Mnwi, JUitlrtft Triartfk North CipoUm, for PCBs within (he environment, a]> though the atmosphere also appears to be s means of dispersal. Adel 5arofim of the Massachusetts Institute of Tech nology has estimated that from 1000 lo 2000 tons per year escaped into ihe atmosphere in past years from plasti cized materials containing PCBs. and that about 4000 tons per year entered waterways from dumping and leakage of lubricants, hydraulic fluids, and hest transfer fluids. Other sources may in clude leaching from dumps and landAlls, where, Sarofim believes, about half of the PCBs produced eventually end up. Although measurements of PCBs in air and water are scant, the general pattern from these measure ments and from more extensive mea surements of PCB residues in biotas is consistent, according to Sarofim, with the hypothesis that discharge*of PCBs into the environment occurs mainly naar industrial areas. A similar pattern was found by Oilman Veith of the Uni versity of Wiscoosin in his studies of Lake Michigan watersheds; he siso de lected PCBs in the sewage of all mu nicipalities studied. Once in the environment, PCBs ap pear to persist for a long time. Labora tory studiet by O. Hutziogcr of Ihe National Research Council of Canada In Halifax and others have indicated that PCBs can be dechlorinated by ultraviolet light and lead to the forma tion of hydroxyl derivativea and other polar compounds that are more readily degraded by microorganisms, but the extent to-which this occurs under nat ural conditions is not known. In many areas, however, PCB residues in fish are equivalent to or higher than DDT and other pesticide residues. David Stalling of the Bureau of Sport Fish eries and Wiidlifa, Columbia, Missouri, found PCB residues as much as i 00 times larger than DDT residues io fiih from heavily industrialized areas, with roughly equal residues of both sub stances in fish from many other regions. The highest PCB residues in fish seem to occur in highly polluted coastal waters--like Tokyo Bay and Long Is land Sound--and In some inland water ways--such as the Orest Lakes--where coho salmon have been found wish PCB concentrations in excess of j parts U JANUARV 1*11 t HONS 206054 per million, (he limit *1 which the U S. Food .ind Drug Administration attempts to seize ront.immntcd fish and ponilry sold in interstate commerce. More typir.il concentrations, in most species of fish in the North Atlantic, range from 0.01 to 1.0 ppm. Fish taken from mijkiurhcd arctic Inkes have been found tn contain comparable residues. Both surface-feeding fish and those that dwell at greater depths contain PCB*. Lven higher concentrations are found in birds that feed on fish, reach ing 300 to 1000 ppm in cormorants and ospreys. According to Robert Risebrough of the University of Ca'-iornia's Bodega Marine Laboratory residues are generally highest in bird specimens from the North Atlantia or from along the California coast, and generally lower in birds front the South Atlantic and Central Pacific Oceans, Residues appear to be lowest in wildlife from the Antarctic region. Most U.S. inhabitants apparently have some residues, if only traces, of PCBs in their bodies. Preliminary data from nationwide monitoring program being coordinated by the Environ* mental Protection Agency show that 33 percent of more than 600 samples of human adipose tissue contained PCB residues of it least 1 ppm. One individual, an old man with no known industrial exposure to PCBs, was found by the Michigan Department of Health to hove 100 ppm in his fatty tissues. The source of PCB residue* in hu man tissue is presumably food. Studies in Sweden have indicated that Rah arr the primary source of PCDs for most Swedes, with average intake of PCBs from all sources estimated to be about 1 microgrtm per kiEogrem of body weight'per day. Individuals who ata large amounts of fish consumed about ten times as much PCB*. Babies re ceived the highs at doses per kilogram of body weight, iartaiy from milk. Realdues of PCBs in food were somewhat smaller than thorn of DDT and metabo lites of eklormeiad pesticides. In the United States, the pattern appears so be the same, with PCBs common in freshwater fish such as coho salmon and lake trout. Small residues in cereals have been traced to the recycled paper used in packag ing and thence to the ink in e brand of carbonless carbon paper, among other somccs. The ink no longer contain* PCBs. and efforts are being made to separate out old stocks of the carbon paper in the manufacture of recycled paper. Several batches of poultry and i* ' eggs With high PCB residues have been traced to contamination of the poultry feed by [caking heat exchangers, ex cept in one instance where the source of the PCBs remains undetermined. Residues arc present in dairy milk in some localities. Officials of the Pood and Drug Ad ministration characterise PCBs as a "potential but not immediate health hazard," and claim, on the basis of their monitoring programs, that except for his eating of fish the American consumer receives no systematic ex po--are to PCB*. However, FDA au thority extends only to interstate sales of food, and FDA guidelines tend to reflect only the average consumer. It seems likely, because of the localized nature of PCB sources and variations in individual diet, that heavy fish eaten and some other individuals experience more substantial exposures. The only clinical experience with human illness that is directly trace able to PCB consumption occurred in 1968 in southern Japan. More than 1000 person* who hid eaten rice oil contaminated with PCBs that leaked from a heal exchanger during manu facture developed darkened skins, eye discharge, severe sene, end other symp toms of what came to be called Yusho, oil disease. Patients were found to have consumed sn average of 2 grams of PCB, with symptoms appearing at a minimum dose of about 0.3 g. The PCBs can readily cross the placental barrier, and several Infants ware born with Yusho symptoms, some to ap parently unaffected mothers. Recovery appears to be difficult, according to Masanori Kuralsune of Kyushu Uni versity in Fukuoka, Japan, with symp toms still present In many cases 3 years later; no methods of treatment are known. It it not dear whether any of the subsequent deaths among the pa tients can be attributed to scute PCB poisoning, and H is still not known whether the commercial PCB mixture Involved contained traces of dibenrofursits or other impurities. Although PCBs have been In use for more than 30 years, detailed studies of their toxic properties have only recent ly been undertaken. The studies are complicated by variability in the tox icity of different commercial samples of PCBs. Experiments in the Netherlands by J. O. Vos of the University of Utrecht showed liver damage and edema in chickens and skin lesions in rabbits. The wont effects seemed to be caused by an impurity in the European PCB mixture, which Vo* bcltevej i0 t,e dibenzofuran. The results of a 2-year study funded by Monsanto showed liver dxmxge and some difference in weight gain in rah and dogs whose feed contained 100 ppm of PCBs, but no teratogenic or mutagenic cffcctl. At a dose rate of 10 ppm, there were apparently no ef fects of any kind, except for some im pairment to the hitching of chicken eggs. Reproduction was affected most hy tow-chlorine PCB mixtures, but long-term damage to the liver seemed So be due to high chlorine mixtures. By contrast, in one of the field occurrences Of PCB contamination, the htichabilily of eggs at Holly Farms in North Caro lina was noticeably decreased, even though the concentration of PCBs in the feed was less thsn the no-effect levels reported in the Monsanto study Although most birdl and mammals appear to be relatively resistant to PCBs, some species, such as mink, seem to be more susceptible. Fish are also more susceptible; Stallings found that bluegil) and catfish died when exposed for several weeks to concentrations be tween 20 tnd 30 parts per biiiion. that trout died at about 8 ppb, and that let he) doses for shrimp were as low as I ppb. The biologietl actions of PCBs in side the body are also relatively un known, PCBs have been shown to alter liver tissue, inhibit the growth of cul tured celis, and affect s variety of en zyme systems; but in most instances the mechanism of action is still uncer tain. Paul Lichtenstein of the Univer sity of Wisconsin has shown that PCB' interact with DDT and other chlori nated pesticides; nontoxic amounts of PCBs in Insects increased the toxicity of DDT and some organo phosphate pesticides by as much st 100 percent. Much of the research on PCBs has pointed to the similarity of PCBs and DDT in their environments! effects. They are both widely distributed in the environment, they both affect the re productive system of birds, and they enter the human diet primarily through residues in fish. But PCBs, unlike DDT, wens seldom deliberately released into the environment. Their presence and persistence there reemphasize thr ,1k, lihood that tny widely used industrial chemical may become in environmental pollutant, and increase the responsibil ity for public disclosure of production quantities tnd use patterns when similar situations occur in the future. --Allen L. Hammond scitNce. vol. ns HONS 206055