Persistent Chemicals: Information on EPA's Analysis of Costs for its PFAS Drinking Water Regulation
Fast Facts
Chemicals called per-and polyfluoroalkyl substances—PFAS—have been found in water and are associated with health risks like cancer. The Environmental Protection Agency recently issued a regulation setting maximum levels for some PFAS in drinking water. EPA was required to estimate the costs of the regulation.
The quality of EPA’s cost analysis is being challenged in court. Due to the litigation, this Q&A report focused on whether EPA published and sought public comment on various elements of its cost estimate, as required by law. We described the cost estimate and found that EPA did publish and seek public comment on it as required.
Highlights
What GAO Found
In March 2023, the Environmental Protection Agency (EPA) proposed a drinking water regulation for six types of per- and polyfluoroalkyl substances (PFAS). It also published an accompanying analysis of costs and benefits, as required by the Safe Drinking Water Act (SDWA). EPA’s analysis included the initial cost estimate of compliance with the proposed regulation. EPA then collected public comments and, in April 2024, published its response to the comments along with a revised, higher cost estimate to accompany the final regulation. See figure 1 for a timeline of these events in EPA’s regulatory process.
Figure 1: Timeline of Certain Events in the Environmental Protection Agency’s (EPA) Regulatory Process for the Per- and Polyfluoroalkyl Substances (PFAS) National Primary Drinking Water Regulation as of July 2025
Note: On May 14, 2025, EPA announced its intent to rescind and reconsider parts of the regulation.
aPFAS National Primary Drinking Water Regulation Rulemaking, 88 Fed. Reg. 18,638 (Mar. 29, 2023).
bIn addition to the Safe Drinking Water Act requirement that EPA seek public comment on its Health Risk Reduction and Cost Analysis, the Administrative Procedure Act requires agencies to consider all relevant and timely submitted comments and respond to all significant comments received during the public comment period. 42 U.S.C. § 300g-1(b)(3)(C); 5 U.S.C. § 553(c).
cPFAS National Primary Drinking Water Regulation, 89 Fed. Reg. 32,532 (Apr. 26, 2024).
dAmerican Water Works Ass’n. v. U.S. Envtl. Prot. Agency, No. 24-1188 (D.C. Cir., filed June 7, 2024).
As required by SDWA, EPA published estimates of the quantifiable costs associated with the maximum contaminant levels the agency proposed, as well as three less expensive alternatives. According to EPA, the agency made changes to the initial cost estimate in response to public comments and newly available data. For example, based on the comments, EPA increased the estimated costs public water systems could incur to conduct pilot studies of installed treatment media.
EPA also published descriptions of potential nonquantifiable costs. For example, EPA stated that co-occurring PFAS could create additional nonquantifiable costs as public water systems might have to replace treatment media—such as granular activated carbon—more frequently.
Finally, EPA published descriptions of sources of uncertainty that could either increase or decrease actual costs relative to EPA’s cost estimate.
Why GAO Did This Study
Under SDWA, EPA is authorized to set National Primary Drinking Water Regulations. Such regulations are meant to protect public health by limiting levels of contaminants in drinking water. When EPA proposes a drinking water regulation that includes a maximum contaminant level, SDWA requires EPA to also conduct an analysis for the regulation that includes estimates of both costs and benefits.
In March 2023, EPA proposed a drinking water regulation for six types of PFAS. EPA finalized the regulation in April 2024. PFAS have been found in drinking water, and certain PFAS have been associated with a variety of negative health effects, including cancer.
Some stakeholders have asserted that EPA’s analysis of costs for the PFAS drinking water regulation does not adequately represent the costs that public water systems will incur to comply with the regulation. In June 2024, three lawsuits were filed challenging the regulation. Among other issues, the quality of EPA’s analysis of the costs of the regulation is being challenged. As of July 23, 2025, the litigation is ongoing.
On May 14, 2025, EPA announced its intent to make a number of changes to the PFAS drinking water regulation, including rescinding the maximum contaminant levels for three individual PFAS and a mixture of those three PFAS plus one additional PFAS. EPA subsequently repeated this intention as part of a filing in the litigation over the regulation.
The joint explanatory statement accompanying the Consolidated Appropriations Act, 2024 (170 CONG. REC. S1105, S1682 (daily ed. March 5, 2024)) includes a provision that GAO review the cost estimates supporting EPA’s PFAS drinking water regulation. Because this issue is the subject of ongoing litigation, GAO’s work focused on whether EPA sought and published public comment on various elements of the analysis of costs, as required by SDWA.
For more information, contact J. Alfredo Gómez at gomezj@gao.gov.