Issues in risk assessment and modifications of the NRC health effects models

A report, Health Effects Models for Nuclear Power Plant Accident Consequence Analysis, was published by the US Nuclear Regulatory Commission, in 1985, and revised in 1989. These reports provided models for estimating health effects that would be expected to result from the radiation exposure received in a nuclear reactor accident. Separate models were given for early occurring effects, late somatic effects, and genetic effects; however, this paper addresses only late somatic effects, or the risk of cancer expected to occur in the lifetimes of exposed individuals. The 1989 revision was prepared prior to the publication of the BEIR V, 1988 UNSCEAR, and ICRP 60 reports. For this reason, an addendum was needed that would provide modified risk models that took into account these recent reports, and, more generally, any new evidence that had appeared since the 1989 publication. Of special importance was consideration of updated analyses of the Japanese A-bomb survivor study data based on revised DS86 dosimetry. The process of preparing the addendum required thorough review and evaluation of the models used by the BEIR V, UNSCEAR, and ICRP committees, and also required thorough consideration of the various decisions that must be made in any risk assessment effort. This paper emphasizes general issues and problems that arise in risk assessment, and also indicates areas where additional development and application of statistical methods may be fruitful