Updating California’s PFAS Notification & Response Levels

PFHxS now has Notification and Response Levels; which PFAS are next?

In California, per- and polyfluoroalkyl substances (PFAS) regulations are rapidly evolving. While there are still no enforceable maximum contaminant levels (MCLs) for PFAS in California, there have been recent updates to notification levels (NLs) and response levels (RLs) for publicly supplied drinking water. Although not enforceable standards, these values serve as health-based advisories and often indicate chemicals of concern that are being considered for an MCL. California NLs and RLs for PFAS are generally in the parts per trillion (ppt) range, signifying potential human health impacts at trace levels in drinking water.

The State Water Resources Control Board (State Board) recently proposed a NL and RL for perfluorohexane sulfonic acid (PFHxS) at 2 parts per trillion (ppt) and 20 ppt, respectively. These values were updated to 3 ppt and 20 ppt in their official issuance as of 31 October 2022. PFHxS is a common replacement for PFOS and used in commercial products such as food packaging and cleaners for its stain and water-resistant properties, as well as in industrial applications such as aqueous film forming foams (AFFF) and metal plating. PFHxS has been detected throughout California’s groundwater. A summary of current California NLs and RLs is provided below.

Compound NL (ppt) RL (ppt)
Perfluorooctanoic acid (PFOA) 5.1 10
Perfluorooctane sulfonic acid (PFOS 6.5 40
Perfluorohexane sulfonic acid (PFHxS) 3 20
Perfluorobutane sulfonic acid (PFBS) 500 5000

Beyond these four PFAS, the State Board has requested that NLs and RLs be developed for the following PFAS:

  • Perfluorohexanoic acid (PFHxA);
  • Perfluoroheptanoic acid (PFHpA);
  • Perfluorononanoic acid (PFNA);
  • Perfluorodecanoic acid (PFDA); and
  • 4,8-Dioxa-3H-perfluorononanoic acid (tradename ADONA), commonly served as a PFOA replacement in industrial processes.

While MCLs, NLs, and RLs may continue to be announced for one PFAS compound at a time, it is rare that PFAS are ever detected in isolation in the environment. PFAS are often used in complex mixes and, consequently, are detected together in groundwater and municipal water samples (e.g., wastewater treatment plants often contain a suite of sulfonic acids, carboxylic acids, as well as PFAS precursors). Therefore, although only PFOA and PFOS have California MCLs on the horizon (in addition to being covered under ), it may be recommended to treat all detected PFAS present to avoid future possible regulatory violations.

While the United States Environmental Protection Agency aims to finalize federal MCLs for PFOA and PFOS by late 2023, the agency states it will also be evaluating “additional PFAS and considering regulatory actions to address groups of PFAS.”

For more information on how EKI can assist with your PFAS needs, visit our PFAS webpage, or email our PFAS team leaders at PFAS@ekiconsult.com.

About the Authors:

Corey Carpenter, PhD

Environmental Engineer

Dr. Carpenter’s doctoral research focused on emerging contaminant (including PFAS) measurement and treatment as well as chemical fate and transport in surface waters. His recent work includes leading a PFAS impacted groundwater treatment study and providing technical support for detection of PFAS in a municipal groundwater supply. Dr. Carpenter is published in peer-reviewed journals related to emerging contaminant identification, monitoring, and treatment as well as other surface water investigations.

Emily Cook, PhD

Environmental Engineer

Dr. Cook has gained extensive expertise in the properties, transformation, and applied treatment strategies of per- and polyfluoroalkyl substances (PFAS) during graduate school. For her dissertation, she investigated the biotransformation of PFAS precursors with various source zone co-contaminants, activated persulfate chemical oxidation and mineralization of PFAS subclasses in the context of in situ treatment, and the toxicity of PFAS on in situ bioremediation processes.