Polychlorinated Biphenyls

Polychlorinated biphenyls (PCBs) were widely used industrial formulations noted for their lipophilicity and stability, and these properties contributed to their use as solvents and dielectric fluids for transformers and capacitors. PCBs were first identified in the environment in the 1960s, and their subsequent detection in almost every component of the global ecosystem including fish, wildlife, and humans resulted in a ban on their manufacture and use in most countries during the 1970s. PCBs are complex mixtures of congeners, which include several nonortho-substituted compounds such as 3, 3′, 4, 4′, 5-pentachlorobiphenyl which bind and activate the aryl hydrocarbon receptor (AhR). The potential adverse effects of individual PCB congeners and defined mixtures on laboratory animals have identified multiple effects and toxicities. Major human health concerns are focused on neurodevelopment effects of PCBs; however, the observed effects are highly variable and require further investigation. Risk assessment of individual PCBs that are AhR agonists utilize an additive toxic equivalency factor approach; however, risk and hazard assessment of PCB mixtures and their interactions is not well defined.