EPA Proposes National Primary Drinking Water Regulation for PFAS

After several years of per- and polyfluoroalkyl substances (PFAS) making news headlines, the United States Environmental Protection Agency (EPA) announced on March 14, 2023, its proposed National Primary Drinking Water Regulation (NPDWR) for six PFAS compounds. This proposal includes federal maximum contaminant levels (MCLs) for PFOA and PFOS individually, and for a combined concentration approach (referred to as a hazard index) for PFHxS, PFNA, HFPO-DA (GenX), and PFBS. Tuesday’s announcement comes just nine months after the EPA released revised drinking water health advisories for PFAS.

What this means for water suppliers

This proposal sets the MCL for PFOA and PFOS at 4 nanograms per liter (ng/L, or parts per trillion), based on achievable laboratory detection limits.

Additionally, the EPA is proposing a hazard index approach for the four other compounds. This approach reflects the combined (or additive) potential for toxic effects resulting from the compounds individually and as mixtures. The hazard index is determined by dividing the concentration of each of the four analytes (PFHxS, PFNA, HFPO-DA, and PFBS) by the calculated health-based water concentrations for each compound individually. The summed value of the quotients is the hazard index. The EPA lists the health-based water concentrations as:

  • 9.0 ng/L for PFHxS
  • 10.0 ng/L for HFPO-DA
  • 10.0 ng/L for PFNA
  • 2,000 ng/L for PFBS

This leads to the proposed MCL of a hazard index equal to or less than 1.0 for these four compounds.

The EPA is proposing these regulations under the authority of the Safe Drinking Water Act. If promulgated, it would require all public water systems monitor for PFAS, notify the public of any PFAS levels detected, and treat water to reduce PFAS to levels below the regulatory standard. Public comment on the proposal is being accepted and a public hearing is slated for May 4, 2023.

How we can help

To date, Woodard & Curran’s engineers and environmental consultants have partnered with clients across the country to address the presence of PFAS in both drinking water and the environment. Our experts are reviewing the details of the science underlying MCLs and calculation of the health-based water concentrations and associated hazard index. We expect to learn more as other industry representatives do the same and provide comments on the proposal.

Meanwhile, we have been working with communities and water agencies for years in anticipation of federal regulatory measures. In many cases this work has been driven by states that set their own limits for PFAS in the absence of an enforceable federal standard. In Hudson, Massachusetts, our drinking water experts implemented a treatment system to work in conjunction with the existing water treatment plant. Similarly, we partnered with the water department in Mansfield, Massachusetts, to pilot test and implement PFAS treatment systems at two existing sources. Our experts have also helped to develop innovative treatment techniques to remediate PFAS chemicals where they are found in groundwater aquifers, and have conducted studies to determine the PFAS concentrations found in soil as a result of aerial transport and precipitation, which influence background concentrations.

Our environmental services team is also working to better understand how PFAS interacts with the water cycle and navigating an evolving regulatory landscape with our clients to address PFAS in soil and groundwater.

Regardless of where PFAS is found, we understand the potential ramifications that arise with new regulatory measures. Our experts are positioned to not only assist in mitigation projects, but also support public agencies’ pursuit of funding resources to protect public health.


Rob Little Practice Leader Drinking Water

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