The evaluation reports will qualitatively describe the inherent and site-specific uncertainties of the process and the potential effects on the evaluation of health protectiveness. Uncertainties associated with data evaluation and identification of COPCs, the exposure assessment, toxicity assessment, and risk characterization will be presented. The uncertainty analysis is performed as a final step for these components of the risk evaluation process. Probabilistic techniques to quantify uncertainties are not included in the analysis.

Generally, uncertainties are associated with the multitude of assumptions characteristic of each step of the calculations used to derive the PCLs. These assumptions are characteristically conservative which, when compounded in the process, tend to overestimate potential risk. Types of information to be evaluated in the reports include a description of uncertainties associated with sample collection and analyses (e.g., objectives of sampling, quality of data), the likeliness of pathway completion, selection of exposure parameters (e.g., amount of exposed skin surface area), and the fate and transport of contaminants (and modeling assumptions). Inherent uncertainties in the toxicity assessment (e.g., derivation of toxicity values) and risk characterization steps (e.g., dose additivity for multiple substance exposure) will also be noted.

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