Environmental Decisions in the Face of Uncertainty (2013) / Chapter Skim
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Pages 1-18
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Similarly, advisory bodies commenting on the role of uncertainty in EPA risk assessments and regulatory decisions have focused on the health risk component. However, EPA takes many other factors -- economic and technological factors in particular -- into 1 Throughout this report the committee uses the term public health when referring to EPA's mission.
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Social factors, such as environmental justice, and the political context also play a role in EPA's decisions and can have inherent uncertainties that are difficult to quantify. This report strives to address this imbalance by giving attention to uncertainties in some of the factors that affect EPA's decision making in addition to the uncertainties in the estimates of human health risks.
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those decisions. The specific questions that EPA requested the committee to address are presented in Box S-1.2 Given that its charge is not limited to human health risk assessment and includes broad questions about managing risks and decision making, in this report the committee examines the analysis of uncertainty in those other areas in addition to human health risks.
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Deep uncertainty is uncertainty that is not likely to be reduced by additional research within the time period in which a decision must be 3 Although chemical risk assessors typically consider uncertainty and variability as separate and distinct, in the other areas uncertainty is seen as encompassing statistical variability and heterogeneity as well as model and parameter uncertainty. Because variability and heterogeneity can contribute to the uncertainty when a decision is being made, in this report the committee discusses them as a specific type of uncertainty.
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The task instead is to make decisions despite the presence of deep uncertainty using the available science and judgment, to communicate how those decisions were made, and to revisit those decisions when more information is available. UNCERTAINTY IN EPA'S ESTIMATES OF HEALTH RISK Uncertainty is inherent in the scientific information upon which health risk estimates are based.
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UNCERTAINTY: OTHER PUBLIC HEALTH SETTINGS Chapter 4 reviews the methods and processes used for uncertainty analysis at other public health agencies and organizations. Although a number of agencies conduct complex analyses that use probabilistic techniques to assess uncertainties in health risks, the tools and techniques that those 5 Statutory requirements and constraints in the nation's environmental laws shape the overall decision-making process, with general requirements relating to data expectations, schedules and deadlines, public participation, and other considerations.
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In all cases, decision makers should explain why and how uncertainties were taken into account in their decisions. Systematically considering uncertainties and their potential to affect a decision from the onset of the decision-making process will improve the decision, focus uncertainty analyses on the decision at hand, facilitate the identification of uncertainties in factors in addition to health risk estimates, improve the planning of uncertainty analyses, and
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In Box S-2 the committee provides BOX S-2 Implications of Uncertainty Analysis for Decision Making Health Uncertainties Uncertainty analyses in human health risk estimates can help decision makers to • evaluate alternative regulatory options; • assess how credible extreme risk estimates are and how much to rely on them in decision making; • weigh the marginal decrease in risk against the effort made to reduce it; • clarify issues within a decision by using scenarios to characterize very different worlds; and • in the case of scenario analyses for deep uncertainty, identify regulatory solutions that are effective over a broad spectrum of scenarios. Uncertainties About Technology Availability Uncertainty analyses in technology availability can help decision makers to • differentiate between well-established technologies with reasonably well-known costs, and those that have not been used for the purposes at hand; and • consider which technology may be considered "best practicable" or "best available" by providing information about both the likelihood of success of the unproven technologies, the time frame for success, and the effectiveness if successful.
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The success of a decision in the face of uncertainty depends on the analysts having a good understanding of the context of the decision and the information needed by the decision makers and also the decision makers having a good understanding of the evidence on which to base the decision, including understanding the uncertainty in that evidence. COMMUNICATING UNCERTAINTY IN DECISIONS Much of the research related to communicating uncertainty in environmental decisions actually focuses on communicating uncertainty in estimates of health risks.
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More communication is needed about the different sources of the uncertainty in EPA's decisions and about how those sources of uncertainty compare and affect a decision. For example, if the uncertainty in an estimate of health risks contributes to the uncertainty in a decision less than does the uncertainty in cost estimates, that should be communicated.
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decision documents and other communica tions to the public should systematically • include information on what uncertainties in the health risk assess ment are present and which need to be addressed; • discuss how the uncertainties affect the decision at hand; and • nclude an explicit statement that uncertainty is inherent in science, i including the science that informs EPA decisions. Uncertainty in Other Factors That Influence a Decision Finding 2 Although EPA decisions have included discussions and consideration of the uncertainties in the health risk assessment, the agency has generally given less attention to uncertainties in other contributors influencing the regulatory decision.
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EPA guidance contains appropriate advice about the conduct of these analyses, including the discussion of some uncertainties. However, the committee noted a lack of transparency regarding uncertainty analyses in the cost–benefit assessments in some EPA decision documents.
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Similarly, economists have explored the values people hold regarding specific health outcomes for the purposes of resource allocation or clinical guideline development. More research is needed into methods to appropriately characterize the uncertainty in those other factors and to communicate that uncertainty to decision makers and the public.
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The choice of uncertainty analysis depends on the context of the decision, including the nature or type of uncertainty, and the factors that are considered in the decision (that is, health risk, technological and economic factors, public sentiment, and the political context) , as well as on the data that are available.
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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.
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In summary, the committee was impressed by the technical advances in uncertainty analysis used by EPA scientists in support of EPA's human health risk assessments, which form the foundation of all EPA decisions. The committee believes that EPA can lead the development of uncertainty analyses in economic and technological assessment that are used for regulatory purposes as well as the development of ways to characterize and
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SUMMARY 17 account for public sentiment and political context. Leading in this way will require a targeted research program as well as disciplined attention to how those uncertainties are described and communicated to a variety of audiences, including the role that uncertainties have played in a decision.
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