Use of epidemiology and clinical toxicology to determine human risk in regulating polychlorinated biphenyls in the food supply.

Polychlorinated biphenyls (PCBs) became a national problem in 1971 when several accidental contaminations of foods were reported. Extensive efforts were successfully undertaken by FDA to reduce the residues of PCBs in food. However, the PCB levels in several species of freshwater fish have raised concern about PCB residues from environmental contamination. This concern prompted a reassessment of the human risk involved in consumption of such fish. The best evidence that a chemical may produce adverse health effects in humans is provided by adequate epidemiologic data confirmed or supplemented by data from valid animal tests. Traditionally, where the regulatory agencies have used results of animal toxicology experiments to evaluate hazard and predict hypothetical safety for humans, "safety factors" such as 1 to 10 or 1 to 100 have been used. The size of the safety factor and the potential exposure to a chemical are established by properly informed scientific judgment. More recent efforts have involved use of a combination of human and animal data and a variety of mathematical models to determine risk. The human epidemiology data and the animal toxicity data of PCB exposure are reviewed, as well as risk assessment in general. Specific examples of risk assessment are presented in which animal data are extrapolated to humans, based on several levels of human exposure to PCBs in fish.