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PCBs Polychlorinated Biphenyls Polychlorinated biphenyls are a family of man-made chemicals that contain two hundred and nine individual compounds with varying toxicity Many different combinations are possible In chemical terminology phenyl denotes a ring structure of six carbon atoms attached to something else biphenyl results when two such rings are attached to each other Polychlorinated biphenyl PCB is any molecule having multiple chlorine atoms attached to the carbon atoms of a biphenyl nucleus Chlorine atoms can be placed at any or all of ten available sites PCBs have been used widely as coolants and lubricants in transformers capacitors and other electrical equipment The manufacture of PCBs stopped in the United States in October 1977 because of evidence that PCBs accumulate in the environment and may cause health hazards for humans Although PCBs are no longer manufactured human exposure still occurs Many older transformers and capacitors still contain fluids that contain PCBs The useful lifetime of these transformers can be thirty years or more Prior to 1977 certain occupational settings had and may still have higher levels of human exposure Animal experiments have shown that some PCB mixtures produce adverse health effects that include liver damage skin irritations reproductive and developmental effects and cancer With these observations it is most considerably dangerous for humans The US Department of Health and Human Services has determined that PCBs may reasonably be expected to be carcinogens Human studies to date show that irritations such as acne-like lesions and rashes can occur in PCB-exposed workers Other studies of people with occupational exposure suggest that PCBs might cause liver cancer Reproductive and developmental effects may also be related to occupational exposure and eating of contaminated fish While the role in producing cancer reproductive and developmental effects can not be clearly determined the suggestive evidence provides an additional basis for public health concerns about humans who might be exposed to PCBs It has also been suggested that chemicals such as PCBs
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