On October 3, 2025, California’s Office of Environmental Health Hazard Assessment (OEHHA) announced the development of a public health goal (PHG) for perfluorohexane sulfonic acid (PFHxS) contamination in drinking water. PFHxS is a manmade chemical used in commercial products for its water- and stain-repellent properties and in firefighting foam.
A PHG is the level of a chemical contaminant in drinking water that does not pose a significant risk to health. The development of a PHG for PFHxS is a precursor to an enforceable drinking-water standard for the chemical. This development comes in the wake of the Trump Administration’s decision to rescind federal drinking-water standards for PFHxS.
California’s move to establish a PHG demonstrates that it will continue to pursue stringent PFAS regulation, even when the federal government signals some change in its approach.
Federal Action
In April 2024, the Environmental Protection Agency (EPA) under the Biden Administration issued the first national, legally enforceable drinking-water standard for certain PFAS. The enforceable maximum contaminant levels (MCLs) set by the rule are 4.0 parts per trillion (ppt) for PFOA and PFOS individually, and 10 ppt for PFNA, PFHxS, and GenX chemicals. A separate health-based guideline for mixtures containing two or more of PFHxS, PFNA, GenX, and PFBS substances uses a hazard index calculation.
In May 2025, after several industries pointed to significant compliance challenges, the EPA under the Trump Administration announced it would delay the compliance deadline for the Biden-era PFOA and PFOS standards while rescinding and reconsidering limits for the other PFAS, including PFHxS.
State Action
In 2022, OEHHA recommended a notification level for PFHxS at 2 ppt based on thyroid toxicity. The California State Water Resources Control Board set the notification level at 3 ppt, due to laboratory reporting limits, and a response level of 20 ppt. According to the water board, there are 1,609 sample points with detections of PFHxS at or above 2 ppt, which means 130 public water systems serving a population of approximately 9.7 million people are affected by PFHxS.
On May 27, 2025, the water board announced that it intends to promulgate an enforceable MCL for PFHxS and requested that OEHHA establish a PHG for the chemical. OEHHA’s development of a PHG is a prerequisite to the water board’s subsequent development of an MCL, since California law requires that an MCL be established at a level as close to its PHG as is technologically and economically feasible.
To set the PHG for PFHxS, OEHHA must first compile all relevant scientific information available, including studies of the chemical’s effects on laboratory animals and studies of humans who have been exposed to the chemical. OEHHA uses data from these studies to perform a health risk assessment, in which they determine the levels of the contaminant in drinking water that could be associated with various adverse health effects.
Implications for Stakeholders
Once OEHHA establishes a PHG, large California water agencies must report PFHxS contamination every three years, which may incentivize investments in treatment and detection technology and create pressure to raise rates.
Although PHGs are not regulatory standards, they are a legally required and foundational step in setting OEHHA’s enforceable MCL. The MCL may ultimately be used in lawsuits filed by public water systems against companies potentially responsible for groundwater contamination. These lawsuits may seek to recover the costs incurred to clean up PFHxS contamination and bring the water suppliers into compliance with the MCL.
Given the number of public water systems potentially impacted by PFHxS, industry groups may file legal challenges to the PHG or any derived MCL. For example, there have been legal challenges to OEHHA’s PHG for perchlorate (a chemical found in rocket fuel), which was unsuccessful, and MCL for hexavalent chromium, where the court invalidated the MCL for failure to properly consider the economic feasibility of compliance.
Looking Ahead
OEHHA is accepting public comments on the proposal through November 3, 2025. The agency will release a draft assessment, followed by public comment and peer review, before adopting a final PHG.
The PHG development may take years, with drinking-water standards taking potentially several more. In the meantime, stakeholders can prepare by continuing to monitor and engage in the rulemaking processes to share their perspectives with the state.
Alston & Bird continues to track ongoing litigation, legislative actions, and regulatory shifts in the evolving PFAS landscape. To stay on top of these developments, please visit our PFAS Primer or contact an attorney on our PFAS Team.
If you have any questions, or would like additional information, please contact one of the attorneys on our Environment, Land Use & Natural Resources team.
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