PFOS and PFOA Updates: Proposition 65 and OEHHA’s PHGs

Posted on Behalf of  Catie Park

Proposition 65 and PFOA/PFOS

In November, 2017, Perfluorooctanoic Acid (PFOA) and Perfluorooctane Sulfonic Acid (PFOS) were listed as chemicals known to the state to cause reproductive toxicity (developmental endpoint) under Proposition 65 (OEHHA, 2017). In March, 2021, the Office of Environmental Health Hazard Assessment (OEHHA) published its intent to list PFOA under Proposition 65 as known to the state to cause cancer via the Authoritative Bodies Mechanism, based on the findings of the National Toxicology Program (NTP) 2020 report on PFOA carcinogenesis (OEHHA, 2021). Additionally, this December, OEHHA’s Carcinogen Identification Committee (CIC) plans to meet to discuss possibly listing PFOS under Proposition 65 for cancer endpoints (OEHHA, 2021).

Public Health Goals for PFOA/PFOS

During OEHHA’s public workshop on September 28, 2021, Public Health Goals (PHGs) and Health Protective Concentrations (HPCs) were proposed for PFOA and PFOS in drinking water (OEHHA, 2021) . PHGs correspond to the level of a chemical contaminant in drinking water that does not pose a significant risk to health over a lifetime, based on cancer risk. While not enforceable, these values form the basis for deriving enforceable drinking water standards, which are set as closely to advisory levels as feasible (OEHHA, 2021). The proposed PHGs and Health Protective Concentrations (HPCs) for PFOA and PFOS are as follows:


PHG (ppt)

PHG Effect

HPC (ppt)

HPC Effect



Kidney cancer (human data)


Increased liver enzymes  (human data)



Liver and pancreatic tumors (animal data)


Increased total cholesterol (human data)

The PHGs and and HPCs are among the most stringent state-level guidance values, if not the most stringent (e.g., for the PFOA PHG), released to date for any PFAS. As OEHHA notes, these values factor in assumptions regarding typical drinking water intake and its relative contribution to total daily PFAS exposure. OEHHA also incorporated several uncertainty factors to account for data gaps, inter- and intraspecies differences, and other considerations, thereby providing a substantial margin of safety.

Cardno ChemRisk scientists have historically monitored Proposition 65 listings for PFOS and PFOA, as well as their drinking water regulations (Cardno ChemRisk 6/8/2016; Cardno ChemRisk 1/21/2021; Cardno Chemrisk 2/2/2021; Cardno ChemRisk 5/6/2021). As discussion around these topics continues, so to do advances in assessing potential risks associated with PFOS and PFOA exposures. For more information about our PFAS capabilities, please reach out to Heather Lynch. For more information regarding our capabilities with Proposition 65, please reach out to Claire Mathis.