Perspectives on comparing risks of environmental carcinogens

In 1987, investigators (Ames et al.) concluded that the risks of man-made industrial carcinogens and pesticides (outside of the workplace) are trivial compared with the risks of naturally occurring carcinogens found mostly in the diet. They used a ranking system based on human exposure and rodent potency (HERP) data to arrive at this conclusion. As a result, they recommend that regulatory agencies, such as the Environmental Protection Agency and the Food and Drug Administration, base their priorities in this area on their HERP system. We analyzed the assumptions and data set upon which the HERPs were based, concluding that such a simplified approach to set public health policy is inappropriate given the underlying uncertainties. However, we note that when comparisons are consistently based on estimates of average daily exposure to common carcinogens, the HERP scores of many man-made pollutants are comparable to those of naturally occurring carcinogens in the diet.