Hormesis: Implications for public policy regarding toxicants

Protecting workers and the public from toxic chemicals, particularly carcin ogens, has been a principal goal of public policy. In the absence of knowin g by what mechanism of action a toxicant harms people, regulatory toxicolog y assumes that even tiny doses can cause harm. Risk aversion has led to leg islation and regulation that seek to ban toxic chemicals or lower exposure to trivial levels. Contradicting this policy, many studies show health bene fits 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 t hat benefit health at low-level exposures should face similar change in reg ulations for low-dose exposure. The result would be the dissolving of the s ource of differences in policy for carcinogens and noncarcinogens at low do ses. Two questions must be answered before hormesis can be incorporated int o regulatory policy. (a) Are there sensitive individuals who would be harme d at doses that would help most people? (b) Is the hermetic effect toxicant specific or would exposure to just a few toxicants achieve the full benefi t from hormesis?