Polychlorinated biphenyls

Polychlorinated biphenyls (PCBs) are a group of man-made chemicals that were widely used in the past, particularly in the United States, as a fire preventive and insulator in the manufacture of transformers and capacitors due to their ability to withstand exceptionally high temperatures.

History

PCBs were first synthesized in the lab in 1881. Commercial production started in 1929 but their harmful effects were not known until the 1960s. The U.S. Environmental Protection Agency (EPA) banned the production of PCBs in 1979 due to evidence of environmental accumulation and health effects.

Chemical Structure

PCBs are a class of organic compounds with 2 to 10 chlorine atoms attached to biphenyl, which is a molecule composed of two benzene rings. The number of chlorine atoms and their location on the biphenyl molecules determines the physical and chemical properties of each PCB congener.

Health Effects

Exposure to PCBs can lead to skin conditions such as acne and rashes. Studies in workers exposed to PCBs have shown changes in blood and urine that may indicate liver damage. In addition, PCBs are classified as probable human carcinogens.

Environmental Impact

PCBs have been shown to degrade very slowly in the environment and can remain for long periods cycling between air, water and soil. PCBs can be carried long distances and have been found in snow and sea water in areas far from where they were released into the environment.

Regulation

In the United States, PCBs are regulated by the EPA under the Toxic Substances Control Act (TSCA) and by the Food and Drug Administration (FDA). Other countries have also established limits for PCBs in air, drinking water, and food.

See Also

• Dioxin
• Persistent organic pollutant
• Toxic Substances Control Act

Polychlorinated biphenyls Resources
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