A Risk Management Framework for Decision-Making Under the Residual Risk Program. R. G. Hetes and K. A. Rimer, US EPA/OAQPS (MD-15), RTP, NC 27711; and D. A. Amaral, EC/R Inc., Chapel Hill, NC 27514
The determination to set residual risk standards is largely based on the magnitude of the estimated risks remaining to the exposed human population and ecosystems after the application of MACT standards. The CAA specifies that the Ample Margin of Safety Approach as outlined in the Benzene NESHAP will be used to guide regulatory decisions. As recommended by the Risk Assessment and Management Commission report, the determination will be made by an iterative process where screening level assessments will be applied to identify sources for further assessment via application of refined exposure assessments. Decisions of whether unacceptable risks remain after implementation of the MACT standards must typically be made after a refined analysis. Should unacceptable risks remain then EPA must develop risk-based standards to reduce these risks. Each decision of whether to regulate or not is a risk management decision. Furthermore, the types of data used and the uncertainty associated with any risk estimate will vary depending on the tier being assessed. These risk management decisions will be greatly improved if a framework is developed to serve as a guide, outlining the degree of uncertainty which is acceptable to make decisions at each tier — from decisions to remove from further analysis (essentially a decision not to regulate) or continue on to next tier to decisions that unacceptable risk remains and further regulation is needed.
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