(EPA) guidance for human health and ecological risk assessment (EPA 1997b, 1999) is generally consistent with the commission’s framework and is commonly used in conducting ERAs at PCB-contaminated-sediment sites. This guidance is limited to human health and ecological risk assessment and needs to be extended to explicitly include social, cultural, and economic impacts.

This chapter provides an overview of the ERA process and discusses the use and limitations of scientific information in each of the steps of a risk assessment of PCB-contaminated sediments. The steps that are described include exposure assessment to PCBs; ecological effects and human health effects from PCB exposure; PCB risk characterization; social, cultural, and economic impacts of PCB contamination; and comparative risk assessment. A summary of findings and specific recommendations for conducting ERAs at sites with PCB-contaminated sediments are given at the end of this chapter.

ENVIRONMENTAL RISK ASSESSMENT

ERA provides a process to evaluate the probability that adverse effects are occurring or might occur in the future because of the presence of contamination (see Box 6-1). The framework for this assessment is designed to follow a flexible, tiered approach beginning with a screening-level assessment followed by more detailed evaluations of the site. In this approach, initial or screening-level assessments are used to identify the issues and possibly rebut the presumption of risk. This assessment is typically based on minimal data and very protective assumptions. Three outcomes are possible from this screening-level assessment. First, the screening assessment might indicate that the degree or extent of contamination is sufficiently small to pose no significant risk. Second, the risk might be predicted to be relatively great, but the extent of contamination is sufficiently small to make effective management technically feasible and relatively cost-effective. In such cases, the decision to initiate a particular risk-management strategy or not may be taken without further refinement of the risk assessment. Third, if potential risks cannot be rebutted and the extent of contamination is such that a rapid and effective risk-management strategy cannot be easily identified and applied, a more refined ERA should be conducted. A refined ERA should begin with a baseline assessment to quantify the existing and potential risks associated with PCB contamination as described in this chapter. The baseline risk assessment should be followed by an examination of potential risk-management options (Chapter 7), the development of a risk-management strategy (Chapter 8), the implementation of the risk-management strategy (Chapter 9), and a short- and



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