Environmental Protection Agency:

Use of Precautionary Assumptions in Health Risk Assessments and Benefits Estimates

GAO-01-55: Published: Oct 16, 2000. Publicly Released: Oct 16, 2000.

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Some of the Environmental Protection Agency's (EPA) regulations set standards that limit environmental contaminants to levels that are determined, in large part, on the basis of the health risks they pose. When EPA assesses the health risks of contaminants, however, the agency is faced with uncertainties and gaps in scientific knowledge and data. This report summarizes GAO's findings on whether EPA's benefits estimates for major environmental regulations that establish health-based standards reflect precautionary assumptions about health risks. Three key factors influence EPA's use of precautionary assumptions in assessing health risks. First, EPA is influenced by its mission to protect human health and safeguard the natural environment. Second, EPA is influenced by the nature and extent of relevant data. Finally, EPA is influenced by the nature of the health risk being evaluated.

Recommendation for Executive Action

  1. Status: Closed - Implemented

    Comments: GAO recommended that EPA take two actions in issuing its cost-benefit report developed to help the agency set an appropriate limit for arsenic in public drinking water systems. In its report, EPA implemented one, but not the other, of the recommended actions. Specifically, as GAO had recommended, EPA's cost-benefit analysis for the final rule disclosed the precautionary assumptions GAO identified, leading to more informed decisionmaking. Although EPA did not implement the part of GAO's recommendation about providing sensitivity analysis on these assumptions, the agency went beyond GAO's recommended action in one case. EPA adjusted the estimate of the lower bound of cancer risk from arsenic to redress the impact of one of the assumptions. EPA adjusted its lower bound risk estimate to take into consideration the relatively high arsenic concentration in food consumed in Taiwan (where the risk studies were conducted) as compared to the U.S. (where the results of the studies were being used to estimate risks to the U.S. population).

    Recommendation: To better inform decisionmakers about the effects of precautionary health assumptions on EPA's estimates of the benefits associated with the arsenic rule, the Administrator, EPA, should ensure that EPA's cost-benefit report for the final rule fully disclose the precautionary assumptions used and provide sensitivity analysis on the key precautionary assumptions included in the agency's benefits estimate.

    Agency Affected: Environmental Protection Agency


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