California Revises Drinking Water Notification and Response Levels for PFAS

New state health advisory levels for PFAS inch closer to federal maximum contaminant levels 

On Oct. 29, the California State Water Resources Control Board revised notification and response levels previously set in 2022 for several per- and polyfluoroalkyl substances (PFAS) in drinking water. These changes to California's drinking water guidance values for regulated PFAS and inconsistency among states and the U.S. Environmental Protection Agency present challenges for municipalities.

Following human health toxicity recommendations from the state's Office of Environmental Health Hazard Assessment (OEHHA), the California State Water Board issued new and revised notification and response levels for perfluorooctanoic acid (PFOA), perfluorooctanesulfonic acid (PFOS), and perfluorohexane sulfonic acid (PFHxS), which are currently more in line with EPA. The board also issued notification and response levels for perfluorohexanoic acid (PFHxA), a "short-chain" PFAS with no federal drinking water guideline. 

The table below shows the new notification and response levels for these four PFAS. 

The notification and response levels for perfluorobutane sulfonic acid (PFBS) did not change and remain 500 ng/L and 5,000 ng/L, respectively. 

California's PFAS notification and response levels are not regulatory compliance standards but health advisory levels for contaminants in drinking water issued under the authority of the Deputy Director of the State Water Board's Division of Drinking Water (DDW).

Requirements for notification and response levels under DDW

Notification levels represent health advisory levels that, according to the state, would pose no significant health risks to individuals consuming the water daily. Notification and response levels are precautionary measures for contaminants that could be candidates for maximum contaminant levels (MCLs) but haven't yet completed a regulatory standard-setting process. Importantly, California has not yet issued state MCLs for any PFAS.

Under Health and Safety Code 116378, if a public water system finds one of these PFAS above the set notification level, it must report this to the DDW. Any confirmed detection of these chemicals during required testing must also be included in the public water system's annual Consumer Confidence Report.

If a water system has average annual concentrations of PFOA, PFOS, PFHxA, or PFHxS or a single confirmed detection of PFBS above the chemical-specific response level, it must do one of the following:

• Take the water source out of service right away
• Treat or blend the water
• Notify the public about the exceedance within 30 days

The exceedance must also be reported in the annual Consumer Confidence Report.

How these notification and response levels compare to federal and other state drinking water values 

These changes make California's PFAS notification levels numerically consistent with the federal MCLs for PFOA and PFOS. However, there are important differences in how California response levels and federal MCLs are implemented.

California's response levels of 10 ng/L for PFOA and 40 ng/L for PFOS are higher than the federal MCLs, which are 4.0 ng/L for either compound, and trigger different implementation responses. This inconsistency over when mitigating action is required for PFOA and PFOS is further complicated by differences in risk communication from each agency. California defines 4.0 ng/L as the level in drinking water that does not pose a significant health risk for PFOA and PFOS, yet EPA states that there is no safe level of exposure and sets the federal MCLs at the level they claim is the lowest level feasible for effective implementation, meaning at the analytical practical quantitation level.

EPA does not yet have a drinking water health advisory or MCL for PFHxA; however, the OEHHA notification level recommendation is similar to toxicity values reported in EPA's 2023 PFHxA assessment. Other states have drinking water guidance values or standards for PFHxA that are several orders of magnitude higher, based on toxicity assessments conducted between 2019 and 2021. EPA has not stated when or whether it will initiate rulemaking for a national drinking water standard for PFHxA. 

Overall, these new notification levels will affect water providers across the state, who will need to provide analytical results to the DDW and the public in Consumer Confidence Reports. The results of those tests could trigger more notifications and remediation efforts across the state.