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Press Release

EPA Releases Final Drinking Water Standards for PFAS Chemicals

By Miranda Henning, BCES, Managing Principal, Business Director, Health and Ecology
Avram Frankel, P.E., Managing Principal, Business Director, Investigation and Remediation

On April 10, 2024, U.S. Environmental Protection Agency (EPA) announced its final National Primary Drinking Water Regulations for the following six per- and polyfluoroalkyl substances (PFAS): perfluorooctanoic acid (PFOA), perfluorooctane sulfonic acid (PFOS), perfluorohexane sulfonic acid (PFHxS), hexafluoropropylene oxide dimer acid (HFPO-DA) and its ammonium salt (also known as GenX chemicals), perfluorononanoic acid (PFNA), and perfluorobutane sulfonic acid (PFBS). PFOA, PFOS, PFHxS, PFNA, and GenX are regulated individually. Additionally, mixtures containing two or more of PFHxS, PFNA, GenX, and PFBS are regulated as a group.

Maximum Contaminant Levels 

Maximum contaminant levels (MCLs) are developed by EPA, under the Safe Drinking Water Act, based on consideration of potential health effects, treatment feasibility, and cost. EPA set MCLs of 4 parts per trillion (ppt) for PFOA and PFOS. EPA also set MCLs of 10 ppt each for PFHxS, PFNA, and GenX. MCLs are enforceable drinking water regulations and represent the maximum amount of chemical that is permitted in the public drinking water supply.

For PFHxS, GenX, PFNA, and PFBS, EPA established a hazard index (HI) MCL based on a Health Based Water Concentration (HBWC) established for each of these compounds. The HBWCs for each compound in the HI are 10 ppt for PFHxS, PFNA, and GenX, and 2000 ppt for PFBS. The HI MCL applies to drinking water containing at least two of the four PFAS included in the HI. The regulations include a weighted average calculation for evaluating the HI MCL. The calculated HI must be less than 1 to comply with the proposed HI MCL.

Maximum Contaminant Level Goals 

EPA also set maximum contaminant level goals (MCLGs) for PFOA, PFOS, PFHxS, PFNA, and GenX. An MCLG is a chemical-specific guidance value and represents the maximum concentration of a chemical in drinking water at which no adverse health effects are expected to occur. MCLGs are non-enforceable health-based values that do not consider treatment feasibility or cost. For both PFOA and PFOS, the final MCLG is zero ppt based on EPA’s determination that PFOA and PFOS are “likely to cause cancer.” For PFHxS, PFNA, and GenX, the MCLGs are 10 ppt.

For PFHxS, GenX, and PFNA, EPA established MCLGs identical to the MCLs, and the HI MCLG equal the HI MCLs. This reflects EPA’s determination that treatment to the MCLGs is feasible and cost effective.

Comparison to Previously Proposed or Promulgated Criteria 

The final MCLs and MCLGs for PFOA and PFOS are the same as the draft values proposed by EPA in March 2023. Individual MCLs and MCLGs for PFHxS, PFNA, and GenX were not previously proposed, nor was an MCLG for PFBS. The final MCLs are lower than EPA’s 2016 lifetime health advisories of 70 ppt for PFOA and PFOS and the MCLGs are below EPA’s interim lifetime health advisories for PFOA and PFOS of 0.004 ppt and 0.02 ppt respectively, issued in June 2022.The final MCLs reflect EPA’s conclusion that potential health effects from exposure to PFOA and PFOS occur at lower concentrations than previously indicated.

Implications and Challenges Ahead  

Over time, water providers across the country will be required to comply with the new MCLs. EPA is requiring water systems to complete monitoring of PFOA, PFOS, PFHxS, PFNA, GenX, and PFBS by 2027. Public water systems have until 2029 to comply with the MCLs. Currently, 12 states have enforceable drinking water criteria and 6 have some form of non-enforceable criteria. These criteria are not aligned with the new MCLs.

In addition, the new MCLs will present challenges to many drinking water providers, regulators, and industries as they navigate increased costs of compliance, monitoring, and, potentially, treatment or development of new water sources.

Notably, EPA released a proposal in February 2024 to list nine PFAS compounds, including the six PFAS regulated here, as hazardous constituents under the Resource Conservation and Recovery Act. EPA may also soon finalize its designation of PFOA and PFOS as hazardous substances under the Comprehensive Environmental Response, Compensation, and Liability Act of 1980, which would allow EPA more oversight of PFAS remediation currently overseen by states.

Expert PFAS Regulatory and Scientific Support  

Integral’s team is at the forefront of technical and regulatory PFAS developments. Our multidisciplinary experts can guide you through the evolving PFAS regulatory landscape and evaluate associated risks. Please reach out to us for support in navigating upcoming regulatory actions including implications for water treatment and site remediation. To speak with one of our experts, please contact Miranda Henning, BCES, or Avram Frankel, P.E. For more information, check out Integral’s PFAS page:  Per- and Polyfluoroalkyl Substances (PFAS) | Integral Consulting (


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