Comments: implications of hormesis for industrial hygienists

Quantitative health risk assessment is based on extrapolating from the high-dose end of the dose–response curve to points close to the origin or the threshold where the dose levels are closer to the lower environmental or occupational exposures. Hormesis is demonstrated in chronic toxicological studies where the animals treated at the lowest experimental dose appear to be healthier than the controls, as evidenced by longer life spans, less disease and/or increased body weight. If the occupational exposure limit (OEL) or environmental exposure limit (EEL) is in the range of the hormetic effect, or lower than the hormetic effect, then a case could be made that exposure at the OEL or EEL is `safe.’ This idea is controversial because it challenges some of the basic assumptions of quantitative health risk assessment as it has been practiced during the past 50 years. De-emphasis of the dose–response curve in determining OELs and EELs will occur not because of hormesis, but because the emerging sciences of genomics and proteomics will shift the focus from statistical methods to individuals as genetic and protein engineering becomes more sophisticated and powerful.