How SDWA Governs PFAS Standards
The Safe Drinking Water Act (SDWA) authorizes EPA to establish national primary drinking water regulations (NPDWRs) for contaminants that may cause adverse health effects and are known or anticipated to occur in public water systems. The SDWA requires EPA to set maximum contaminant level goals (MCLGs) at the level at which no known or anticipated health effects occur, and enforceable MCLs as close to MCLGs as feasible.
For PFOA and PFOS — which EPA determined are carcinogenic with no safe threshold — the MCLGs were set at zero, while the enforceable MCLs were set at 4 ppt (the practical limit of measurement and treatment technology). This non-zero MCL despite a zero MCLG reflects the feasibility constraints built into SDWA.
Limitations of the Current SDWA Framework
The SDWA regulatory process is slow and resource-intensive. From initiating a regulatory determination to finalizing an MCL typically takes 5–10 years, during which health effects evidence accumulates faster than standards can be updated. The PFAS MCL — first formally proposed in 2023 and finalized in 2024 — came decades after PFAS health risks were identified.
The SDWA’s substance-by-substance approach has historically allowed PFAS manufacturers to substitute unregulated compounds for regulated ones — the ‘regrettable substitution’ problem that drove replacement of PFOA with GenX (HFPO-DA) and other next-generation PFAS. The EPA’s grouping approach in the 2024 rule (covering PFNA, PFHxS, and HFPO-DA alongside PFOA and PFOS) partially addresses this.
Proposed Legislative Reforms
Congressional proposals to reform SDWA for PFAS include authorizing EPA to regulate PFAS as a chemical class rather than compound by compound, providing additional funding for small system compliance assistance, and requiring manufacturers to fund treatment technology development. The PFAS Action Act, passed by the House but not the Senate in previous Congresses, incorporated several of these elements.
States frustrated with federal pace have enacted their own PFAS drinking water standards, sometimes more stringent than federal MCLs. Vermont’s 20 ppt combined standard for five PFAS compounds preceded the federal MCLs and remains stricter for the mixture. The interaction between state and federal SDWA standards creates a layered regulatory system that utilities must navigate.