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Definition |
Polychlorinated Biphenyls (PCBs) are a family of more than 200 chemical compounds (congeners) with 1 to 10 chlorine atoms attached to biphenyl and a general structure of C12H10-xClx. PCBs were commercially produced as complex mixtures of congeners at different degrees of chlorination for a variety of applications. Their use was based on their chemical stability, and desirable physical properties. According to WHO, several congeners are now considered to be "dioxin-like" because of their toxicity and certain features of their structure similar to 2,3,7,8-tetrachlorodibenzo-p-dioxin. PCBs are not readily biodegradable, their use declined and was essentially terminated because of environmental concerns. USA stopped producing PCBs in 1977. (NCI)
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