EPA Finalizes Standards for Six PFAS

Abstract

On April 10, 2024, the US Environmental Protection Agency (EPA) announced the final rule setting standards for six per- and polyfluoroalkyl substances (PFAS). Water systems will have three years to conduct initial monitoring requirements and prepare to issue public notifications annually.

The new standards for PFAS include five MCLs and MCL goals (MCLGs), for a total of six PFAS. For perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS), EPA set each of the MCLs at 4.0 ng/L and the MCLGs at 0 ng/L, based on a determination that PFOA and PFOS are carcinogenic. EPA also set individual MCLs and MCLGs for perfluorohexanesulfonic acid (PFHxS), perfluorononanoic acid (PFNA), and hexafluoropropylene oxide dimer acid (HFPO-DA) acid at 10 ng/L. Finally, EPA set an MCLG and MCL using a hazard index of 1 (note the significant figures) for PFHxS, PFNA, HFPO-DA, and perfluorobutanesulfonic acid (PFBS).

The NPDWR also establishes monitoring requirements for compliance and to determine eligibility for reduced monitoring using EPA's Standardized Monitoring Framework. Initial and ongoing compliance monitoring must be conducted quarterly for any large system serving more than 10,000 people and for small systems that do not rely on groundwater sources. Compliance with the MCLs is based on the running annual average (RAA) of the monitoring results for each entry point to the distribution system (EPTDS), where monitoring results below the practical quantification limits for the six PFAS will be treated as zero for the purposes of calculating RAA.

Similar to the Standardized Monitoring Framework, EPA has established requirements for a system to be eligible for a reduced monitoring schedule at an EPTDS if PFAS levels are below one-third of the corresponding MCL (2.0 ng/L PFOA, 2.0 ng/L PFOS, and a hazard index of 0.5 for PFBS, PFNA, PFHxS, and HFPO-DA). EPTDSs that are eligible for reduced monitoring will be required to sample triennially (one sample per three-year period). If a triennial sample exceeds the trigger level, the system must revert to quarterly monitoring.

Water systems are required to issue public notifications using consumer confidence reports (CCRs) and in response to violations, consistent with previous NPDWR. Violations of the MCL(s) will require a Tier 2 notification to the public within 30 days of the system learning of the violation as well as a Tier 3 notification through the CCR. The CCR must also include information relevant to detections of any of the six PFAS.

Water systems will need to begin conducting initial monitoring of these PFAS in accordance with the requirements and determine whether next steps, such as installing PFAS drinking water treatment facilities, will be necessary. The rulemaking does not limit the types of treatment technologies systems may use to comply with the MCLs, but the most used treatment technologies for PFAS, including powder and granular activated carbon, ion exchange resin, and membrane filtration (e.g., reverse osmosis, nanofiltration). Water systems will also need to begin preparing public education and reporting materials for potential detections of PFAS in finished water supplies.

While not yet proposed, EPA is also working toward listing certain PFAS-containing wastes as hazardous under the Resources Conservation and Recovery Act. On Feb. 8, 2024, EPA proposed listing nine PFAS as hazardous constituents, including the six PFAS covered by the NPDWR. While no rulemaking timeline is yet scheduled, the listing could affect PFAS treatment residuals and increase waste management costs. AWWA continues to support its members through legislative advocacy to ensure congressional support with infrastructure funding and through technical resources on PFAS.