Probabilistic exposure assessment of operator and residential exposure; a Canadian regulatory perspective.

An overview of the considerations central to selection of probabilistic versus deterministic approaches to assessment of operator and residential exposure are provided. From a regulatory perspective, the decision to use probabilistic over deterministic assessments should include consideration of factors such as the nature of the populations being assessed, including the expected duration and frequency of their exposures, as well as an understanding of the toxicity endpoints that the exposure assessment will be linked to during risk assessment. In situations where there is an identifiable need to characterize variability and uncertainty and/or quantify the exposure that will represent most of the exposed population, and where there are adequate data to characterize input parameters, probabilistic assessments may be appropriate. Issues with respect to probabilistic assessments for which detailed, harmonized guidance are required are outlined. These issues are discussed within the context of a tiered approach to exposure and risk assessment.