Ambient Water Quality Criteria Methodology Revisions. D. Borum, J. Du, J. Donohue, Y. Patel, K. Sappington, R. Cantilli, C. Abernathy, W. Morrow, and S. Gilbertson, Office of Water, U.S. Environmental Protection Agency, 401 M Street, S.W., Washington, DC 20460
EPA published draft revisions to the Methodology for Deriving Ambient Water Quality Criteria (AWQC) for the Protection of Human Health pursuant to Clean Water Act requirements. States and Tribes may use the revised methodology to develop water quality standards. The revisions will substantially enhance science policy guidance for setting water quality criteria by incorporating scientific advances that have occurred during the past 18 years since the original guidance was published and, thus, increase the scientific defensibility of recommended criteria. It also provides more flexibility for decision-making at the State, Tribal and EPA Regional level. EPA is promoting greater involvement by States and Tribes in making risk assessment decisions and in adapting criteria to local conditions. The revisions recommend consideration of the Agency’s guidance on assessing noncarcinogenic effects of chemicals, including integrating reproductive/developmental, immunotoxicity, and neurotoxicity data. EPA also recommends the use of quantitative dose-response modelling for RfD derivations. For cancer risk assessments, more sophisticated methods to comprehensively determine the likely mechanism that causes human carcinogenicity are recommended, consistent with EPA’s 1996 proposed revised cancer guidelines. In the area of exposure assessment, the use of local studies on fish consumption is encouraged and EPA provides default values for the general population, recreational fishers and subsistence fishers. The methodology can also account for other sources of exposure when setting criteria to ensure that an individual’s total exposure does not exceed a threshold level. The revisions also emphasize the use of bioaccumulation factors for estimating potential exposure to contaminants via the consumption of contaminated fish and shellfish, since they reflect the accumulation of chemicals by aquatic organisms from all surrounding media (water, food, sediment).
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