General information on PFAS is below. Details about Cal Water’s position are available on the Leadership on PFAS page.


Commonly found substances within the per- and polyfluoroalkyl substances (PFAS) family of compounds are PFOS, PFOA, PFNA, PFBS, PFHxS, and GenX. These are manmade compounds that have been used to make carpets, clothing, fabrics for furniture, paper packaging for food, and other materials (e.g., cookware) that are resistant to water, grease, or stains. They are also used for firefighting at airfields and in a number of industrial processes.

In March 2023, the U.S. Environmental Protection Agency (EPA) announced a proposed national primary drinking water regulation for these types of PFAS. The proposed regulation calls for a maximum contaminant level (MCL) for PFOS and PFOA of 4 parts per trillion (ppt) each. PFNA, PFHxS, PFBS, and GenX would have a combined hazard index limit of 1.0; the hazard index calculation would determine if the levels of these PFAS as a mixture pose a potential risk.

Previously, in June 2022, EPA announced reduced Health Advisory (HA) levels of 0.02 parts per trillion (ppt) for PFOS and 0.004 ppt for PFOA. The prior HA level was 70 ppt for PFOS/PFOA combined. EPA also established HAs for PFBS of 2,000 ppt and GenX of 10 ppt.

HAs are non-enforceable, non-regulatory guidelines under which there is no expected risk to health to all people, including sensitive populations, over a lifetime of exposure. The advisories, which offer a margin of protection, also take into account exposure through other sources beyond drinking water. However, they do not take into account technological and economic feasibility of testing and treatment.

Additionally, in October 2022, the California State Water Resources Control Board’s Division of Drinking Water (DDW) issued a notification level of 3 ppt and response level of 20 ppt for PFHxS. DDW has not changed its response levels for the other PFAS compounds (PFOA: 10 ppt; PFOS: 40 ppt; PFBS: 5,000 ppt) and notification levels (PFOA: 5.1 ppt; PFOS: 6.5 ppt; PFBS: 500 ppt).

How Cal Water is Protecting Our Customers

Protecting our customers’ health and safety is our highest priority, and Cal Water is committed to complying with all standards set by the public health experts. We are currently evaluating the impact of the proposed regulation on our systems and any treatment required should the regulation be adopted as proposed. We have long followed recommendations from DDW, and even went beyond by testing every active source in our systems. Although not required by the state, we believed it was the right thing to do. In cases where detections were above the levels at which state public health experts have recommended water suppliers take action (the response level), we took the affected sources out of service until treatment was/can be installed.

Studies indicate that long-term exposure to PFAS over certain levels could have adverse health effects, including developmental effects to fetuses during pregnancy or breastfed infants; cancer; or liver, immunity, thyroid, and other effects. Potential health impacts related to PFAS from all sources (which also include food wrappers, firefighting foam, and non-stick cookware, for example) are still being studied, and research is still evolving on this issue.

We believe a comprehensive approach is needed to properly address the situation. We’ve encouraged the EPA to establish a consistent, science-based standard as quickly as feasible, and strongly supported state legislation that will prohibit the sale and use of certain products that contain PFAS, require the certification of accurate testing methods for PFAS, and establish a publicly accessible database that houses the sources of PFAS entering water supplies. We have also filed a lawsuit to hold the manufacturers of the compounds responsible and prevent our customers ultimately from having to bear the costs of treatment, to the extent possible, and are seeking grants to help further offset treatment costs.

This does shed light on the importance of protecting our water resources. While we are doing our part to treat the water and meet the standards the public health experts have set, it’s important that our population as a whole focuses on being good stewards of the environment and takes steps to prevent impacting the water supply.

More information on EPA’s proposed regulation is available in its March 14, 2023 press release.

Common Names

PFOS: perfluoroctanesulfonic acid and perfluoroctylsulfonic acid

PFOA: perfluorocaprylic acid, perfluoroctanoic acid, and perfluoroheptanecarboxylic acid

PFNA: perfluorononanoic acid

PFBS: perfluorobutane sulfonic acid and potassium perfluorobutane sulfonate (together)

PFHxS: perfluorohexane sulfonic acid

GenX: hexafluoropropylene oxide dimer acid & its ammonium salt