Common names for PFOS are perfluoroctanesulfonic acid and perfluoroctylsulfonic acid. Some common PFOA names include perfluorocaprylic acid, perfluoroctanoic acid, and perfluoroheptanecarboxylic acid. PFOS and PFOA 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.

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. Although PFOS and PFOA do not have maximum contaminant levels (MCL), Cal Water has been monitoring for the presence of PFOS and PFOA for some time because they are constituents of interest to the U.S. Environmental Protection Agency (EPA).

All of Cal Water’s systems are compliant with the previous provisional health advisory (PHA) limit set by the EPA in 2009 for PFOS, which was 200 parts per trillion (we have no detections of PFOA in our systems, which had a previous PHA of 400 ppt). A provisional health advisory, while not a regulatory limit, sets a health-based threshold above which action should be taken to reduce exposure to an unregulated constituent. The EPA more recently finalized a new lifetime Health Advisory (HA), and response level, of 70 ppt combined for PFOS and PFOA.

Studies indicate that long-term exposure to PFOS and PFOA 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. The new HA has been set to reflect a margin of protection, including for the most sensitive populations. It is the level below which concentrations are not expected to result in adverse health effects over a lifetime of exposure.

Research into potential health effects evolves; knowing that these are constituents of emerging concern, we previously identified water sources and tested sites that would be more likely to have these compounds present. In our Chico, Visalia, and East Los Angeles districts, where we had one well (in each district) that exceeded the HA and response level of 70 ppt (combined for PFOS and PFOA), we have discontinued use of those sources.

If and when an MCL is established by the public health experts for these compounds, we will ensure our water sources are in compliance with any set standard.

More information on PFOS and PFOA is available at: