On October 29, 2025, the California State Water Resources Control Board’s Division of Drinking Water (State Water Board) issued new and revised notification levels and/or response levels for four per- and poly- fluoroalkyl substances (PFAS):
- Perfluorooctanoic acid (PFOA)
- Perfluorooctanesulfonic acid (PFOS)
- Perfluorohexane sulfonic acid (PFHxS)
- Perfluorohexanoic acid (PFHxA)
The State Water Board now has notification and response for five PFAS. The compounds and limits that are bolded are new as of October 29, 2025.
*Parts Per Trillion (PPT)
**Running Annual Average - Based on the average concentration calculated from quarterly (4) samples.
***EPA has announced plans to rescind these MCLs
California’s notification and response levels are non-regulatory, health-based advisory levels established for contaminants in drinking water for which State MCLs have not been established. These are established as precautionary measures for contaminants that may be considered candidates for the establishment of MCLs. MCLs, in contrast, are legally binding limits that public water systems are required to meet.
Although the notification and response levels are health-based advisory levels, exceeding either of the notification level or the response level requires the agency to take specific actions as articulated in the Health and Safety Codes sections 116378 and 116455. With an exceedance of the notification level, these provisions require notification of the governing board and notification of any water systems that are directly supplied water. In the context of the response level exceedance, community members may need to be notified, or the source must be taken offline.
Federal PFAS Regulations
The U.S. Environmental Protection Agency (EPA), has established MCLs for certain PFAS. On April 10, 2024, the EPA issued a final National Primary Drinking Water Regulation (NPDWR) setting MCLs for six PFAS compounds with an initial compliance deadline of 2029.
As previously reported by BBK, EPA has indicated that it will be proposing modifications to the NPDWR, including extending the compliance deadline for the PFOA and PFOS MCLs to 2031, and aims to rescind the MCLs for PFHxS, GenX, PFNA, and the Hazard Index. EPA intends to have a final rule with these modifications in Spring 2026.
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