Challenges of probabilistic assessment of operator and residential non-dietary exposure.

There are several challenges in the area of probabilistic exposure assessment of operator and residential non-dietary exposure: the proper uses of the available data and how to adequately understand and characterize the uncertainty in the assessment. The adequacy of the data can be assessed either qualitatively or quantitatively. If a qualitative assessment were deemed acceptable, then expert judgement would be the primary methodology. However, in most instances a quantitative assessment of adequacy will be possible and will provide more pertinent information. In that case statistical techniques should be used. Understanding and characterizing uncertainty is a separate challenge, which is often ignored. Instead risk assessors present characterizing the variability in the assessment as a characterization of both uncertainty and variability. This can lead to misinterpretation of the outputs of the assessment. Interpretation of outputs can be discussed on two levels - familiarizing the risk managers and the policy makers with the types of outputs resulting from a probabilistic assessment (graphs and/or matrices of values) as well as explaining the meanings and implications of the values. The burden is placed on the assessor to clearly reflect to the risk managers and policy makers the way on which variability and uncertainty were handled in the assessment. In advising the risk managers and policy makers, it is important to remind them of the purpose of conducting a probabilistic risk assessment: the probabilistic assessment allows a means to characterize the degrees of uncertainty and variability in terms of probabilities.