EPA Releases Proposed PFAS National Primary Drinking Water Regulation

By Robert Hollander, P.E.

On Wednesday, March 29, 2023, the United States Environmental Protection Agency (EPA) published, in the Federal Register, a Proposed PFAS National Primary Drinking Water Regulation (NPDWR) (88 FR 18638). The proposal includes Maximum Contaminant Level Goals (MCLGs) and Maximum Contaminant Levels (MCLs) for six per- and poly-fluoroalkyl substances (PFAS) found in drinking water. Key elements of the rulemaking are as follows:


  • MCLG of 0 parts per trillion (ppt) for both Perfluorooctanoic acid (PFOA) and Perfluorooctane sulfonic acid (PFOS) based on potential carcinogenicity. MCLG is the maximum level of a contaminant in drinking water at which no known or anticipated adverse effect on the health of persons would occur, allowing an adequate margin of safety.
  • PFAS Mixture Hazard Index (HI) MCLG of 1.0 (unitless) for a combination of four other PFAS chemicals specifically, perfluorohexane sulfonic acid (PFHxS), hexafluoropropylene oxide dimer acid (HFPO–DA) and its ammonium salt (also known as a GenX chemicals), perfluorononanoic acid (PFNA), and perfluorobutane sulfonic acid (PFBS) based on non-cancer health effects.
  • Enforceable MCL of 4.0 ppt for both PFOA and PFOS.
  • Health-Based Water Concentrations (levels protective of health effects over a lifetime of exposure, including sensitive populations and life stages) for four other PFAS. HBWCs are as follows: HFPO – DA = 10 ng/L, PFBS = 2000 ng/L, PFNA = 10 ng/L, PFHxS = 9 ng/L.
  • Enforceable PFAS Mixture HI MCL for HFPO, PFBS, PFNA, and PFHxS of 1.0 (unitless). The HI is calculated by dividing the concentration of each of these chemicals in collected samples by the HBWC (HQ = concentration in water samples ÷ HBWC) and summing the resulting Hazard Quotients, as follows:
  • Compliance for both MCLs and the HI MCL is based on a running annual average of compliance samples.
  • Initial monitoring (frequency dependent on type of system, population served, and source of raw water) must be completed within three years of the publication date of the final rule. The proposal includes provisions for grandfathering monitoring data from the Unregulated Contaminants Monitoring Rule 5 (UCMR5) to satisfy initial monitoring.
  • Compliance monitoring (frequency dependent on population served and results from initial monitoring) would officially commence starting with the first monitoring period after the effective date of the rule (i.e. three years after the publication date of the final rule).
  • Trigger levels are proposed to establish reduced compliance monitoring frequency for averages of PFOA and PFOS of <1.3 ppt and HI <0.33. If future averages meet or exceed the trigger levels, initial compliance monitoring frequencies must be restored.
  • Approved analytical methods for the PFAS chemicals in this rulemaking are Method 533 and Method 537.1, with Practical Quantitation Levels (PQLs) of 4.0 ppt for PFOA and PFOS, 5.0 ppt for HFPO-DA, 3.0 ppt for PFHxS, 4.0 ppt for PFNA, and 3.0 ppt for PFBS.
  • The proposed rule identifies granular activated carbon (GAC) and Ion Exchange (IX) as Best Available Technologies for removing PFAS chemicals from water. Point-of-Use (POU) treatment is not considered adequate, at this time, to comply with proposed MCLs.
  • Violations of the MCLs require Tier 2 notifications (PN within 30 days of the public water system becoming aware of the violation, and including information in future Consumer Confidence Reports).
  • PLEASE NOTE that this is a proposed rule and EPA is still soliciting comments from the public until May 30, 2023. All areas are open for comment, but some specific areas EPA is requesting comment include:
    • Maximum Contaminant Level Goals
    • Maximum Contaminant Levels (e.g. PFOA/PFOS MCL of 4.0 ppt and HI of 1.0; PFOA/PFOS MCL 4.0 ppt with no HI, PFOA/PFOS MCLs of 5.0 ppt or 10 ppt with no HI)
    • Monitoring and Compliance Requirements (e.g. should EPA allow use of UCMR5 monitoring results for compliance with initial monitoring requirements; Trigger Levels)
    • Analytical Methods (e.g. PQLs, laboratory capacity)
    • Designation of violations of proposed MCLs as Tier 2
    • Treatment Technologies
    • Economic Analysis

The public is encouraged to review the rule at Per- and Polyfluoroalkyl Substances (PFAS) | US EPA,  scrolling down to Supporting Materials. Comments may be submitted to the Federal eRulemaking Portal: identified by Docket ID No. EPA-HQ-OW-2022-0114 (more easily accessed via the link included in the e-version of the Federal Register Notice (88 FR 18638) by May 30, 2023.



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