EPA has done a great deal of highly skilled and scientific work on uncertainty analysis for estimates of human health risks. Although the committee was not tasked with reviewing the technical aspects of those uncertainty analyses, it did review the uncertainty analyses conducted in some risk assessments for context and as examples (see Chapter 2). It also reviewed a number of guidance documents, advisory committee reports, and advice from the National Research Council (NRC), all of which, as discussed above, focus on those uncertainties dealing with risk estimates, and not on other factors that affect EPA’s decisions. References to uncertainty in decision making typically discuss the uncertainty in estimates of human health risk (NRC, 1983, 1994, 1996, 2009, 2011).

The charge to the committee does not focus solely on uncertainty related to human health risk assessments but rather asks the committee to look more broadly at uncertainty in the decision-making process. For example, the charge asks how “uncertainty influence[s] risk management” and “other ways EPA can benefit from quantitative characterization of uncertainty (e.g., value of information techniques to inform research priorities),” and refers broadly to decision making. The committee was concerned that solely focusing attention—and resources—on reducing uncertainties in the risk assessment could lead to a false confidence that the most important uncertainties are addressed; extreme attention to reducing uncertainties in the human health risk assessment might not be sufficient without an attempt to characterize the other factors that are addressed in decision making and their uncertainties. The committee, therefore, examined the assessment of uncertainties in factors in addition to the risk to human health and the role of those uncertainties in the decision-making process (see Chapter 3). Although the uncertainty in the data and analyses related to the other factors cannot always be quantified, the report discusses the importance of being aware of those factors, potential uncertainties in those factors, and how they influence decisions, and communicating that information when discussing the rationale for EPA’s decision.

When approaching its charge, the committee was aware that the consideration of uncertainty by EPA in its regulatory decisions could be evaluated in a number of ways. The uncertainty in decisions could be evaluated solely on the standard that is set—that is, whether a standard limiting the amount of ozone in air or arsenic in drinking water or establishing remediation levels for a hazardous waste site is adequate or too protective. The decisions could also be evaluated by the quality of their technical and scientific support, such as risk assessments, costs and feasibility analysis, or regulatory impact analysis. They could also be evaluated on the basis of the process by which they were developed—for example, on the opportunities for public participation, the transparency in the decision-making process, and whether social trust was established through the process. Because each



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