Last week the EPA released a final National Primary Drinking Water Regulation establishing Maximum Contaminant Levels, or “MCLs,” for six PFAS. National Primary Drinking Water Regulations, or “NPDWR,” are legally enforceable standards that apply to public water systems and thereby limit the legally allowable levels of specific contaminants in public drinking water supplies.
The final rule establishes MCLS for five individual PFAS:
- PFOA – 4 ppt
- PFOS – 4 ppt
- PFHxS – 10 ppt
- PFNA – 10 ppt
- HFPO-DA (GenX) – 10 ppt
In addition to those single-PFAS MCLs, the final rule establishes a “Hazard Index” designed to account for the cumulative health effects of different sources of PFAS. The Hazard Index calculations are too cumbersome to reproduce here, but the Hazard Index applies to combinations of PFHxS, PFNA, HFPO-DA and PFBS. The important takeaway from the EPA’s new approach is that public water sources that contain more than one of the regulated PFAS may violate the NPDWR even where no single PFAS is present in excess of the MCLs.
The final rule also establishes a Maximum Contaminant Level Goal of 0 ppt for both PFOA and PFOS. Although Maximum Contaminant Level Goals are not enforceable standards, they are the first step in establishing enforceable MCLs in the future, so public water providers should be prepared to reach these levels in the future.
Practical Takeaways
Public water systems will now have to monitor for these PFAS and provide public reports on the levels of these PFAS in their water. Water systems will have three years to complete initial monitoring for these PFAS and will then have ongoing monitoring obligations. If monitoring reveals regulated PFAS in excess of the MCLs, public water systems must make capital improvements and reduce the levels of regulated PFAS by 2029. From that year forward, public water systems that have the above-noted PFAS in excess of the MCLs must act to reduce those levels and provide notice to the public.
To assist with these new obligations, the EPA is making available nearly $1 billion in funding to public water systems. Funding can be used for initial PFAS testing and treatment at both public water systems and homes served by private wells.
The effects of the NPDWR may be felt beyond public water systems. Public water systems may seek to defray the costs of complying with these new regulations by suing those potentially responsible for PFAS in their source water.
