WA11 Governance & Law: Global Perspectives
E145-146
8:00 AM - 12:00 PM, Wednesday
() Hormesis: How low a dose is too high?
Williams, B1, Nedoff, J2, Kennedy, L2, 1 Kennedy/Jenks Consultants, Portland, Oregon, USA2 Kennedy/Jenks Consultants, San Francisco, California, USA
ABSTRACT- Hormesis (positive responses to low doses of stressors) has gained increased attention from scientists and regulators in the last several years. Often, very low doses of a contaminant can result in a positive effect, rather than the expected adverse effect. Many authors have suggested that this phenomenon is actually a short-lived physiological stimulus to stress-response systems. In fact, the positive effect(s) can change to adverse effect(s) at some point as the concentration of contaminant is increased. Because of the narrow range of concentrations typical of the transition from positive to adverse effects, it is important to evaluate the potential impact of these low levels of contaminants in the context of regulatory assessment. Currently, hormesis is rarely considered in risk assessments and in some instances, the effects of contaminants at low levels confound regulatory decisions. This presentation will compare current and proposed regulatory thresholds for contaminants that appear to exhibit hormesis and concentrations of these contaminants at the effects transition points. It is likely that some regulatory guidelines should be reviewed regarding the occurrence of hormesis and the range of concentrations where positive effects are extinguished or become adverse effects. The range of the dose response curve where positive effects begin to decrease will also be compared to doses considered to be toxic. The hormesis phenomenon challenges the public and (often) regulatory perception that even very low doses of a contaminant causes adverse effects. The discontinuity of effects documented in many laboratory dose-response tests (first positive effects then adverse effects) should be considered in assessing the environmental effects of contaminants.
Key words: adverse effects, hormesis, positive effects, regulatory