March 14, 2023 EPA Update

On March 14, 2023, the United States Environmental Protection Agency announced a proposed National Primary Drinking Water Regulation (NPDWR) for six PFAS including PFOA, PFOS, PFNA, HFPO-DA (GenX), PFHxS, and PFBS.

What we currently know about the proposed Maximum Contaminant Levels (MCLs):

The EPA is proposing MCLs as follows:

  • PFOA: 4 ppt (ng/l)
  • PFOS: 4 ppt (ng/l)
  • A hazard index approach for any mixture of PFNA, HFPO-DA (GenX), PFHxS, and PFBS equal to "1 unit"

To determine the Hazard Index for the additional four PFAS, water systems would monitor and compare the amount of each PFAS in drinking water to its associated Health-Based Water Concentration (HBWC), which is the level at which no health effects are expected for that PFAS. Water systems would add the comparison values for each PFAS contained within the mixture. If the value is greater than 1.0, it would be an exceedance of the proposed Hazard Index MCL for these four PFAS. A FAQ sheet on how to calculate the hazard index is available here.

The proposed HBWC for these four PFAS are:

  • PFHxS: 9 ppt
  • HFPO-DA (GenX): 10 ppt (same as the previously issued Federal Health Advisory Level (HAL))
  • PFNA: 10 ppt
  • PFBS: 2000 ppt (same as the previously issued HAL)

The full news release can be found here on the EPA website.