Uncertainty Analysis in Exposure Assessment-Relevance for Toxicological Risk Assessment

Abstract

Within the last decade the documentation of uncertainty has become mandatory as a necessary part of any exposure and risk assessment. A key document that is used as a framework in many regulatory approaches is the guidance document published by the WHO (IPCS) in 2008. The structure of this chapter follows the guiding principles described there, adding information from various regulatory documents. The process of an exposure assessment is structured by the definition of the scope of analysis, the selection of appropriate exposure scenarios for the population under concern, and the choice of conceptual and mathematical models with appropriate parameters. The evaluation of the resulting exposure calculation should support conclusions about the likelihood of exceeding health-based guidance values. The choice of parameters must cover the existing variation of all influence factors. The process should start with simplified approaches and repeated iteratively until the level of residual uncertainty can be tolerated with respect to the purpose. Each uncertainty may be analyzed at one of three tiers: qualitative, deterministic, or variance based. The identification and evaluation of the different kinds and sources of inherent uncertainty is part of the overall analysis and documentation. By this, uncertainty analysis strongly supports informed decision-making and risk communication under uncertainty.