Technical experts often communicate uncertainties to decision makers in aggregate. However, aggregate estimates of uncertainty do not necessarily provide the decision makers with an understanding of the uncertainty and its implications for a decision. Information about the type and sources of uncertainty can help decision makers decide whether further research is warranted to decrease the uncertainty or whether to refine the decision to reduce the effects of the uncertainty. Descriptions of where there are uncertainties can also indicate which groups or stakeholders might bear the burden of a higher-than-anticipated health risk or cost because of the uncertainty. Knowing who is likely to be affected by the uncertainty in the costs and benefits would allow decision makers to design the initial proposed regulations to address or prepare for those potential outcomes in advance. If the individual sources of uncertainty that contribute to the overall uncertainty can be determined, then uncertainty analyses in, for instance, cost–benefit analyses or cost-effectiveness analyses could incorporate graphic representations displaying the relative importance of the different sources of uncertainty sequentially so as to provide an easily interpretable graphic display of the sources of uncertainty (Krupnick et al., 2006).

Audience Characteristics

Level of Technical Expertise

The audience for the communication of uncertainty in environmental decisions, such as those made by the EPA, will have a broad array of backgrounds and roles (Wardekker et al., 2008). EPA’s scientific and technical staff communicates about uncertainty in health risk estimates, economic analyses, and other factors with agency decision makers. The agency discusses the uncertainties in its decisions with stakeholders, including individuals who might have little to no technical knowledge, as well as with industry specialists and others with high levels of technical expertise. The uncertainty that affects decisions should be discussed with all stakeholders, but the strategy used for those discussions might vary with the technical expertise of the audience. For example, agency decision makers will often have strong technical backgrounds and might need to see specific numbers to best understand the extent of uncertainty and how it affects their decisions. Industry and advocacy group scientists similarly might prefer specific numbers, as such numbers might provide them with a complete picture and the data needed for them to conduct their own independent analyses. Members of the public without strong technical backgrounds might benefit more from graphic representations of the uncertainties along with discussions about how those uncertainties will be considered in a decision, the potential consequences of those uncertainties, and whether and how EPA

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