SDWA Framework and PFAS
The Safe Drinking Water Act (SDWA) of 1974 established EPA authority to regulate contaminants in public water supplies. The regulatory process for establishing Maximum Contaminant Levels (MCLs) requires EPA to complete health-effects assessments, determine feasibility of treatment to achieve proposed standards, and evaluate economic impacts — a process that historically took many years or decades. PFAS did not appear on any federal drinking water contaminant list until 2016, when PFOA and PFOS were included in the Unregulated Contaminant Monitoring Rule (UCMR 3) as unregulated contaminants requiring monitoring data.
Health Advisories as a Stopgap
In 2016, EPA established lifetime health advisories (LHAs) for PFOA and PFOS at 70 parts per trillion — intended as non-enforceable guidance while the formal rulemaking process proceeded. The 2022 interim updated health advisories revised these to 0.004 ppt for PFOA and 0.02 ppt for PFOS — levels below current analytical detection limits, effectively indicating that no safe level had been identified. These advisories spurred water system action but had no enforcement mechanism.
The 2024 MCL Rulemaking
EPA’s April 2024 final rule establishing MCLs for six PFAS compounds — PFOA, PFOS, PFNA, PFHxS, HFPO-DA (GenX), and PFBS — represented the completion of the formal SDWA rulemaking process for these compounds. The rule set PFOA and PFOS limits at 4 ppt and established hazard index calculations for the other four. Public water systems have until 2027 for initial monitoring, 2029 for compliance. The rule was immediately challenged in federal court by water utilities and chemical industry groups.
Future PFAS Regulatory Expansion
The 2024 MCL rule covers six PFAS but leaves thousands of other compounds unregulated. EPA has announced intent to pursue regulatory action on additional PFAS compounds through both SDWA rulemaking and other regulatory authorities. States maintaining PFAS lists covering dozens to hundreds of additional compounds provide a preview of potential future federal action. The legal and policy trajectory of PFAS regulation under SDWA is expected to expand significantly over the next decade as additional health-effects assessments are completed.