PCB metabolism, persistence, and health effects after occupational exposure: implications for risk assessment.

Analysis of the kinetics and congener selectivities for PCB metabolism in occupationally exposed workers shows that the lipid PCB concentrations required for the induction of P4502B cytochromes must be > 20 mg/kg; for inducing P4501A and the associated toxic effects, > 600 mg/kg. The observed kinetic behavior indicates that the reported statistical associations between serum PCB levels and certain disease states in the general population (lipid PCBs generally 0-2 mg/kg) probably arise from correlations with the factors that control steady-state xenobiotic levels in human serum (notably, P450 activity and serum lipids) rather than from novel toxic activities of the PCBs.