U.S. Environmental Protection Agency
EPA-815-R-24-010
April, 2024
Background and Purpose
Section 1412(a)(3) of the Safe Drinking Water Act (SDWA) requires the Administrator of the U.S. Environmental Protection Agency (EPA) to finalize a Maximum Contaminant Level Goal (MCLG) simultaneously with the publication of a National Primary Drinking Water Regulation (NPDWR). The MCLG is set, as defined in Section 1412(b)(4)(A), at “the level at which no known or anticipated adverse effects on the health of persons occur and which allows an adequate margin of safety.” Consistent with SDWA 1412(b)(3)(C)(i)(V), in developing the MCLG, the EPA considers “the effects of the contaminant on the general population and on groups within the general population such as infants, children, pregnant women, the elderly, individuals with a history of serious illness, or other subpopulations that are identified as likely to be at greater risk of adverse health effects due to exposure to contaminants in drinking water than the general population.” Other factors considered in determining MCLGs for drinking water contaminants include health effects data, toxicity values, cancer classifications, and potential sources of exposure other than drinking water. MCLGs are not regulatory levels and are not enforceable.
The purpose of this document is to provide a summary of the relevant health effects information, and to describe the derivation of the EPA’s final individual MCLGs for perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) used in the Per- and Polyfluoroalkyl Substances (PFAS) NPDWR (USEPA, 2024f). The individual MCLGs are based on the final toxicity assessments for PFOA or PFOS, which were developed and finalized to support the PFAS NPDWR (USEPA, 2024d, e). The toxicity assessments underwent both external peer review through the EPA Science Advisory Board (USEPA OOW, 2023) and public comment (USEPA, 2024c). This document summarizes the key elements (e.g., cancer classifications) that the agency used as the basis for determining the individual MCLGs for PFOA and PFOS and provides the final MCLGs for PFOA and PFOS used in the PFAS NPDWR. It is not intended to be an exhaustive description of all health effects information or quantitative analyses provided in the final human health toxicity assessments (USEPA, 2024d, e), nor is it a drinking water health advisory.
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