Hormesis: policy implications

Protecting workers and the public from toxic chemicals, particularly carcinogens, has been a principal focus of public policy. Uncertainty regarding the toxicity of particular chemicals and their dose-response relationship has led to the use of the 'precautionary principle' in which regulators are willing to accept more costly regulation than necessary in order to prevent exposure and disease from these toxic chemicals. The Environmental Protection Agency's (EPA's) current policy of using 'mechanism of action' to set regulations means that hormesis could be used by the EPA without any change in policy if hormesis is accepted as scientifically valid. Hormesis could result in a qualitative change in regulatory policy. Because exposure to toxic chemicals conveys no health benefit in the current dose-response model, public risk aversion leads to a Delaney Clause-like 'no-risk' model for policy: ban toxic chemicals or lower exposure to trivial levels. Hormesis implies that individuals benefit from low exposure to toxicants. Although hormesis may not be relevant for individuals with compromised immune systems, it would be expected to help the vast majority of people. If so, permitting exposure levels that provided the greatest health benefit to most people would be balanced against these same levels hurting the most immune-compromised individuals. Public health routinely makes these trade-offs using a 'risk-risk' model. Thus, hormesis could transform the 'no-risk' approach into a 'risk-risk' approach that could tolerate much higher exposures to toxic chemicals than the current policy.