A probabilistic framework for non-cancer risk assessment

Risk assessment involves an analysis of the relationship between exposure and health related outcomes to derive an allowable exposure level or to estimate a low-dose risk. Acceptable levels of human exposure for non-cancer effects generally are derived by dividing an experimental no-observed-adverse-effect-level or a lower confidence limit benchmark dose by a product of several uncertainty factors. This paper presents a hierarchical modeling framework for a probabilistic approach to non-cancer risk assessment. The hierarchical model integrates the distributions of uncertainty factors and the distribution of the actual exposure level to construct the dose–response model for the proportion of population at risk and the dose–response model for the expected proportion of population at risk for a given exposure distribution. The proposed approach is based on the use of the BMDL (lower confidence limit on the benchmark dose) as a POD (point of departure) for risk assessment of non-cancer effects.