A history of PCB biodegradation

Polychlorinated biphenyls (PCBs) are a group of related chemicals (congeners) which were produced during the middle of this century as chlorinated derivatives of biphenyl. There are 209 congeners distinguished by the number and position of chlorine atoms on a biphenyl backbone, although many of these congeners are not found in the commercial PCB mixtures (marketed under the tradename 'Aroclor' in the U.S., 'Clophen' in Europe, and 'Kaneclor' in Japan) (Ballschmiter & Zell, 1980; Hutzinger et al., 1983; Erickson, 1992). The chemical and thermal stability of these compounds formed the basis for the widespread use of PCBs as the fire-retardant fluid in electrical equipment, heat exchangers, hydraulic fluids, and compressor fluids. However, this chemical stability also carried with it a degree of biological stability that has resulted in the accumulation of PCBs at sites of its manufacture, use, storage, and disposal.