A STANDARDIZED BENCHMARK APPROACH TO THE USE OF CANCER EPIDEMIOLOGY DATA FOR RISK ASSESSMENT

worker level months. Clarity and scientific validity are two criteria for assessing the qual-ity of communications between scientists and risk managers. Regu-lating permissible exposures on the basis of very-low-dose risk extrapolation uses scientific information that may not meet either criterion. With regard to clarity, it is difficult for an individual to conceive of the meaning of risks on the order of 1 in 1,000,000 life-time excess. With regard to scientific validity, the uncertainties of extrapolating risks at very low doses are evident in the wide varia-tion in results produced depending on the statistical and pharmaco-kinetic assumptions made. An alternative approach is to fix benchmarks from which safety factors are chosen (Gaylor, 1983). For epidemiological data, we propose a benchmark of that exposure which would cause 1 % cancer excess with 10 yr of exposurefol-lowed by 30 yr of further followup. These values have been chose