polychlorinated biphenyls (PCBs) /-klôr″inā′tid/ , a group of more than 30 isomeric compounds used in plastics, insulation, and flame retardants and varying in physical form from oily liquids to crystals and resins. All are potentially toxic and carcinogenic. The toxicity varies with the type of PCB and concurrent exposure to other substances, such as carbon tetrachloride. Mild exposure may cause chloracne; severe exposure may result in hepatic damage.
