Polychlorinated biphenyls: an overview of metabolic toxicologic and health consequences

Polychlorinated biphenyls (PCBs) are complex mixtures of chlorinated aromatic hydrocarbons which are classified as lipophilic xenobiotics in vivo. Because of their unusual thermal and insulating properties, widespread use in industry was commonplace. They eventually gained entry into the biota, and their diffuse distribution represents both a potential and actual risk to humans and animals due to their bioconcentration in the food chain and toxicity secondary to accidental occupational or environmental exposure. Experimental poisoning in various animal models demonstrates that PCBs are potent inducers of hepatic microsomal enzyme systems, transmitted transplacentally and produce reproductive dysfunction. They alter immune function by decreasing the cell-mediated response and, in addition to producing myriad manifestations, are tumorigenic. Human exposure to PCBs has been associated with similar abnormalities, but because of limited data their chronic toxicity has not been well established. This is the key problem to evaluating possible untoward health effects in humans.