Hormesis: implications for public policy regarding toxicants

Protecting workers and the public from toxic chemicals, particularly carcinogens, has been a principal goal of public policy. In the absence of knowing by what mechanism of action a toxicant harms people, regulatory toxicology assumes that even tiny doses can cause harm. Risk aversion has led to legislation and regulation that seek to ban toxic chemicals or lower exposure to trivial levels. Contradicting this policy, many studies show health benefits from low-level exposure to toxicants, including some carcinogens. This is known as hormesis. Thus, hormesis could lead to a fundamental change in the policy for regulating toxic substances. In particular, all toxicants that benefit health at low-level exposures should face similar change in regulations for low-dose exposure. The result would be the dissolving of the source of differences in policy for carcinogens and noncarcinogens at low doses. Two questions must be answered before hormesis can be incorporated into regulatory policy. (a) Are there sensitive individuals who would be harmed at doses that would help most people? (b) Is the hormetic effect toxicant specific or would exposure to just a few toxicants achieve the full benefit from hormesis?