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Persistent Pollutants

California considers advisory level for PFHxS in drinking water

Recommended concentration for this PFAS is lower than any other state regulatory level

by Cheryl Hogue
March 23, 2022


California regulators are recommending that each utility in the state notify its customers if it finds perfluorohexane sulfonic acid (PFHxS) at a level greater than 2 parts per trillion in drinking water.

Chemical structure of perfluorohexane sulfonic acid (PFHxS)

"If 2 ppt is below the PFHxS detection limit of currently available and appropriate technology, our recommendation is to set the notification level at the lowest level that can reliably be detected," a spokesperson for the California Office of Environmental Health Hazard Assessment (OEHHA) tells C&EN in an email.

The OEHHA calculated the recommended 2 ppt level based on published data linking PFHxS exposure to thyroid, liver, and developmental toxicity and to additional adverse health effects other than cancer.

PFHxS is a member of the large family of per- and polyfluoroalkyl substances (PFAS) and is a persistent pollutant. Biomonitoring studies have found it in the blood of almost all people in the US who were tested.

3M formerly manufactured PFHxS in the US but phased out production of the molecule two decades ago. PFHxS was used in stain-resistant fabrics, in fire-fighting foams, in food packaging, and as an industrial surfactant. The substance also can form in the environment from transformation of some other PFAS.

Before California’s PFHxS notification level for drinking water can take effect, the State Water Resources Control Board must approve it.


This article was updated on March 24, 2022, to reflect an amended comment from the California Office of Environmental Health Hazard Assessment spokesperson. The spokesperson says the recommendation is to set the detection limit to the strictest level of detection if 2 parts per trillion can’t be detected with available and appropriate technology. The original statement was that 2 ppt is below current technologies’ detection limit.



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