Polychlorinated biphenyls are stable, lipophilic industrial compounds that are present in residue levels in human tissue, wildlife and freshwater sediment. They are toxic and are known to pass the placenta and intoxicate the fetus. Two large outbreaks of poisoning have occurred in Asia and women pregnant at or after the exposures had children who were developmentally impaired. Laboratory experiments in rhesus monkeys and rodents designed to assess neural or developmental neurotoxic effects show altered activity levels, impaired learning, and delayed ontogeny of reflexes. Children exposed transplacentally to PCBs in North America have been reported to display hypotonia and hyporeflexia at birth, delay in psychomotor development at 6 and 12 months of age and poorer visual recognition at 7 months. PCBs appear to be developmental neurotoxicants in both humans and animals and may pose a significant health risk, particularly to pregnant women and their offspring.

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