Board hears proposed PFAS notification‑response changes: PFOA/PFOS NLs aligned to 4 ng/L, PFHXS RL set to 10 ppt running annual average; OEHHA recommends 1 µg/L

The State Water Resources Control Board on Aug. 6 discussed proposed revisions to notification and response levels for several PFAS chemicals and received a health‑policy recommendation from the Office of Environmental Health Hazard Assessment (OEHHA) to set a notification level for PFHXA at 1 microgram per liter (1 µg/L).

The discussion was informational; staff said the deputy director will follow the statutory notice and comment process before issuing final notification/response levels. Board members and several water‑sector associations provided public comments raising concerns about funding, monitoring points, and public understanding.

What notification and response levels are

Deputy director staff reminded the board that notification and response levels (NRLs) are statutory, advisory values derived under Health and Safety Code procedures (see HSC sections noted by staff). They are not maximum contaminant levels (MCLs) but are intended to prompt public notification and, in some cases, system response actions while the regulatory process continues. Under Health and Safety Code section 116378, when a water system detects PFAS under a DDW monitoring order it must follow statutory notification requirements or remove the source from service.

Proposed changes described by staff

- PFOA and PFOS notification levels: Staff proposed reducing the notification levels to 4 ng/L for both PFOA and PFOS. That value aligns with the current U.S. EPA MCL for each compound. Staff proposed no change to the existing response levels for those analytes (the response‑level approach remains in place while federal MCL schedules proceed).

- PFHXS: Staff proposed changing the treatment of PFHXS from a single confirmed sample at 20 ppt to a running annual average response level of 10 ppt. The change is intended to align with U.S. EPA’s approach and reduce operational complications for water systems that would otherwise face a different sampling/response cadence for PFHXS.

- PFHXA (new NRL recommendation): OEHHA senior toxicologist Chris Banks presented OEHHA’s notification‑level recommendation for PFHXA at 1 microgram per liter (1 µg/L, equivalent to 1 part per billion). “The notification level recommendation that we had derived is for 1 microgram per liter, which is equivalent to 1 part per billion,” Dr. Banks said.

How OEHHA derived the PFHXA recommendation

OEHHA staff reported a systematic literature review that yielded roughly 1,200 PFHXA publications; however, human epidemiology evidence was judged insufficient for a direct human‑based derivation. OEHHA selected two critical animal studies (Loveless et al. and National Toxicology Program rat data) and identified the most sensitive endpoints as nasal cavity degeneration (female rats) and reduced thyroid hormone (male rats). OEHHA used benchmark‑dose modeling to derive points of departure, adjusted for interspecies kinetics, and applied a composite uncertainty factor of 300 (square‑root factors and factors of 10 to address animal‑to‑human extrapolation, human variability, chronic‑exposure extrapolation and database deficiencies). OEHHA applied a default relative source contribution (RSC) of 20% (portion of total exposure attributable to drinking water) and used infant drinking rates for the thyroid endpoint because infants are particularly sensitive to small thyroid perturbations. The combined calculations produced a health‑protective concentration of about 0.8 µg/L, which OEHHA rounded to 1 µg/L as the recommended notification level.

Staff timeline and implementation notes

Deputy director staff said they will accept public comment from the board hearing and written submissions and anticipate issuing the revised NRLs after review of comments; staff suggested an issuance timeline in September unless significant new issues arise. Staff cautioned that many of the worst‑case estimates of impacted systems are based on single historic maximum samples and that a running annual average will reduce the number of systems that ultimately must take action. Using a worst‑case single‑sample approach, staff estimated an upper bound of affected systems/wells (e.g., tens of systems and wells) for some of the changes but cautioned that these counts are conservative and likely overstate the number of systems that would need to act under a running annual average or updated monitoring data.

Public comments at the hearing

Several water‑sector groups provided comments during the item:

- Megan Murphy, senior regulatory advocate, California Municipal Utilities Association (CMUA), urged that state funding be provided to support monitoring, treatment and infrastructure so costs do not fall onto ratepayers; she also urged that monitoring be at the point of entry rather than only at source samples and that state feasibility assessments reflect California’s operational realities rather than relying solely on EPA’s economic assumptions.

- Nick Blair, senior policy advocate, Association of California Water Agencies (ACWA), said some members will be implicated and urged consideration of timing and costs, noting some utilities are already upgrading treatment to meet current response levels.

- Sue Mossberg, executive director, California‑Nevada Section, American Water Works Association (AWWA C‑N), cautioned that NLs/RLs are poorly understood by the public and can prompt actions by utilities that are costly and may divert funds from known public‑health priorities; she urged caution about rapidly lowering advisory levels and requested adequate time and funding for compliance planning if MCLs follow.

Board discussion

Board members asked staff to clarify monitoring points (source vs. point of entry) and how blending or treatment would affect notification obligations. Staff said California’s practice is to obtain source‑level data to understand contributor wells and to then allow point‑of‑entry monitoring to demonstrate compliance where blending or treatment is in place; staff said orders and permits will document how systems must operate and respond if a contributing well is lost.

Staff also noted that U.S. EPA has indicated it may revisit some PFAS MCL decisions on economic grounds; staff said that, as of the hearing, the proposed state changes are aligned with EPA’s current MCLs for PFOA and PFOS and that PFHXA is not on EPA’s reconsideration list.

Why this matters

NRLs and RLs guide early public‑notification and system‑response steps before enforceable MCLs are in place. Changes to those advisory levels can trigger public notice obligations, planning for treatment or source removal, and requests for state funding — items that utilities and regulators raised during public comment.

Next steps

Staff will accept written comments, consider board input and proceed through the statutory notification process. Staff said it expects to issue revised NRLs in the near term (staff noted September as an approximate target if no major new issues arise).