Superfund

The Environmental Protection Agency (EPA) is required to assess the risks to human health posed by each of the Superfund program's hundreds of hazardous waste sites. Because EPA uses these risk assessments to determine whether and how sites should be cleaned up, they are a source of considerable scrutiny and controversy. For example, both industry and environmental groups have criticized risk assessment for inconsistently estimating the amount of contamination that persons living near the Superfund sites may have been exposed to. This report reviews 20 of the approximately 70 risk assessments EPA did in 1992. GAO provides information on (1) whether the risk assessments adhered to EPA guidance, (2) whether they varied among the regions and sites, and (3) how EPA monitors the quality and consistency of risk assessments. GAO focused particularly on how risk assessments measured human exposure to hazardous contaminants and calculated the resulting risk. GAO also provides data on the sources of contamination described in these risk assessments and the risks associated with these sources.

GAO found that: (1) most of the 20 risk assessments reviewed generally adhered to EPA guidance, were prepared consistently among the 10 EPA regions, identified which contaminants were present, and used similar assumptions in measuring human exposure to hazardous contaminants; (2) some risk assessments were not completely accurate and did not follow EPA guidance for estimating contamination levels, adequately describe the assumptions' inherent weaknesses, or calculate the total risk of exposure; (3) EPA has used many different assumptions in estimating exposure, future site uses, residual contamination amounts, and the ways people absorb contaminants through their skin; (4) although EPA has conducted annual quality assurance reviews to monitor the quality and consistency of risk assessments, these reviews produce only summary descriptive information and do not analyze inconsistencies among risk assessments; (5) EPA could improve its risk assessments and better meet regional staff needs by analyzing assessment inconsistencies; and (6) identifying assessment inconsistencies would not require significant additional funding, since EPA already collects the necessary information in its annual reviews.

Recommendations

Our recommendations from this work are listed below with a Contact for more information. Status will change from "In process" to "Open," "Closed - implemented," or "Closed - not implemented" based on our follow up work.

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