polychlorinated biphenyl (redirected from Chlorinated biphenyl)

polychlorinated biphenyl or PCB, any of a group of organic compounds originally widely used in industrial processes but later found to be dangerous environmental pollutants. Polychlorinated biphenyl is a fat-soluble, water-insoluble hydrocarbon containing chlorine. It is extremely stable, withstanding temperatures of up to 1,600°F; (870°C;), is fire-resistant, and has been used as a heat-transfer and insulating fluid in cooling systems and electrical equipment; it has also been used in sealants, rubber, paints, plastics, printing ink, and insecticides. The chemical has entered the environment largely as a pollutant from equipment leaks, the weathering of many materials that contain PCB, and through interaction with food products. PCBs are not readily biodegradable. Production has been banned in several industrialized countries; the United States stopped producing PCBs in 1977.

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PCB

 in full polychlorinated biphenyl

Any of a class of highly stable organic compounds prepared by the reaction of chlorine with biphenyl, a two-ring compound. The commercial product, a mix of several PCB isomers, is a colourless, viscous liquid that is almost insoluble in water, does not degrade under high temperatures, and is a good electrical insulator (see dielectric). PCBs became widely used as lubricants, heat-transfer fluids, and fire-resistant dielectric fluids in transformers and capacitors in the 1930s and '40s. In the mid 1970s they were found to cause liver dysfunction in humans and came under suspicion as carcinogens; their manufacture and use were consequently restricted in the U.S. and many other countries, though illegal dumping by manufacturers continued. They persist in the environment and have entered the food chain, causing great harm especially to invertebrates and fish.