SOME IMPLICATIONS FOR QUANTITATIVE RISK ASSESSMENT IF HORMESIS EXISTS

The existence of hormesis should impact quantitative risk assessment i n at least seven fundamental ways. (1) The dose-reponse models for bio assay and epidemiological data should have greater flexibility to fit the observed shape of the dose-response data and no longer be forced t o always be linearly increasing at low doses. (2) Experimental designs should be altered to provide greater opportunity to identify the herm etic component of a dose-response relationship. (3) Rather than a life time average daily dose or its analog for shorter time periods, dose s cales or metrics should be used that reflect the age or time dependenc e of the dose level. (4) Low-dose risk characterization should include the likelihood of beneficial effects and the likelihood that a dose l evel has reasonable certainty of no appreciable adverse health effects . (5) Exposure assessments should make greater efforts to characterize the distribution of actual doses from exposure rather than just upper bounds. (6) Uncertainty characterizations should be expanded to inclu de both upper and lower bounds,and there should be an increased explic it use of expert judgement and weight-of-evidence based distributional analyses reflecting more of the available relevant dose-response info rmation and alternative risk characterizations. (7) Risk should be cha racterized in terms of the net effect of a dose on health rather than a dose's effect on a single factor affecting health - for example, ris k would be better expressed in terms of mortality from all causes comb ined rather than a specific type of fatal disease.