Polychlorinated Biphenyls: Still Prevalent, but Less of a Problem

The presence and danger of polychlorinated biphenyls (PCB's) in the environment is not yet a dead issue, but it is one that appears to be dying quite rapidly. Despite mounting evidence of both the omnipresence and toxicity of this widely used chemical, governmental and industrial curbs on its use have largely halted its influx to the environment, and the potential for ecological damage appears to have been averted. PCB's have been detected in fish, wildfowl, foods, and highly polluted waterways (Science, 14 January, p. 155). New evidence presented at the 164th national meeting of the American Chemical Society, however, suggests that PCB's have pervaded the environment to a much greater extent than was previously suspected. Gerald W. Bowes of the Canadian Wildlife Service, Ottawa, Ontario, for example, has found PCB's in tissues of polar bears and seals captured throughout northern Canada, including locations well within the Arctic Circle. In these nonmigratory bears, he notes, the concentration of PCB's was greater than the combined concentrations of the organochlorine pesticides DDT and DDE. In the United States, the U.S. Geological Survey has found PCB's in water and sediment samples from 17 of 39 states examined. Hans J. CrumpWiesner of the USGS says that concentrations of PCB's in water samples ranged from 0.1 to 4.0 parts per billion (ppb), and that such residues were detected even in newly developed real estate lakes and at two USGS field stations far removed from industrial sources. Bottom sediment samples contained PCB concentrations as great as 3.2 ppm. The Food and Drug Administration has detected PCB's in nearly 20 percent of some 3500 samples of fish, milk, eggs, and cheese examined during the past 18 months, according to Albert C. Kolbye, Jr., deputy director of FDA's Bureau of Foods. More than 54 percent of fish samples contained detectable amounts of PCB's, as did 29 percent of egg samples. Only 6 percent of cheese samples and 7 percent of milk samples contained detectable amounts, however. The average PCB concentrationin a normal U.S. diet, Kolbye adds. is only about 10 percent of FDA's interim safety level of 5 ppm. More important, Anne R. Yobs of the Environmental Protection Agency's Office of Pesticides Programs, Chamblee, Georgia, reported that PCB residues were found in 54.3 percent of 2189 human adipose (fatty) tissue samples collected in 18 states and the District of Columbia. More than twothirds of the positive samples contained at least 1 part per million (ppm). PCB levels greater than I ppm, she says, were found in approximately twice as many males as feniales, and in three times as many whites as nonwhites but statistical evaluation of the results has not been performed because the study is still in its preliminary stages.