concerns of stakeholders, and it will help define analytic endpoints and identify population subgroups and heterogeneity and other uncertainties.

The committee believes that quantitative uncertainty analyses should only be undertaken when they are important and relevant to a given decision. Whether further quantitative uncertainty analysis is needed will depend on the ability of these analyses to affect the environmental decision at hand. One way to gauge this is to inquire whether perfect information would be able to change the decision, for example, whether knowing the exact dose–response function would change the regulatory regime. Clearly, if an environmental decision would stay the same for all states of information and analysis results, then it would not be worth conducting the analysis.


Although some analysis and description of uncertainty is always important, how many and what types of uncertainty analyses are carried out should depend on the specific decision problem at hand. The effort to analyze specific uncertainties through probabilistic risk assessment or quantitative uncertainty analysis should be guided by the ability of those analyses to affect the environmental decision.


Finding 8

A structured format for the public communication of the basis of EPA’s decisions would facilitate transparency and subsequent work with stakeholders, particularly community members. EPA decision documents should make it clear that the identified uncertainties are in line with reasonable expectations presented in EPA guidelines and other sources. This practice would facilitate the goals of the first recommendation of the committee in this report—that EPA decision documents should make it clear that uncertainty is inherent in agency risk assessments. The committee intends that the recommendations in this report support full discussion of the difficulties of decision making, including—and possibly particularly—when social factors (such as environmental justice and public values) and political context play a large role.


U.S. Environmental Protection Agency (EPA) senior managers should be transparent in communicating the basis of the agency’s decisions, including the extent to which uncertainty may have influenced decisions.

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