Update: PFAS in San Francisco Bay Water

A recent analysis of PFAS in the surface waters of SF Bay was conducted to understand the occurrence, fate, and potential risks to ecological and human health. Eleven of 40 PFAS were detected at part per trillions (ppt) concentrations in ambient water collected in 2021 from 22 sites in the Bay. Seven PFAS (PFPeA, PFHxA, PFHpA, PFOA, PFBS, PFHxS, and PFOS), were found in at least 50% of samples. Concentrations of PFAS in the Bay were generally consistent with similar studies globally for surface water. Sustained, multi-matrix monitoring of this important class of contaminants of emerging concern is a high priority for the RMP.

PFAS in San Francisco Bay 

Per- and polyfluoroalkyl substances (PFAS), a family of thousands of synthetic, fluorine-rich compounds commonly referred to as “forever chemicals,” are known for their thermal stability, non-reactivity, and surfactant properties. These unique compounds have widespread uses across consumer, commercial, and industrial products, resulting in widespread occurrence in the environment and wildlife across the globe. Long-chain PFAS, such as perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA), have been shown to be highly persistent, bioaccumulative, and toxic, leading to phase-out of production in the US. This has led to the emergence of a range of alternatives including short-chain PFAS and a range of polyfluoroalkyl compounds.Given the similarity in structure and preliminary testing conducted to date, researchers believe these compounds will exhibit similar toxicological responses, physical and chemical characteristics, and environmental persistence as better-studied long-chain compounds. Potential mixture and additive effects also pose a risk to human and ecological health.

The RMP has monitored PFAS in the San Francisco Bay for over a decade, and the class has been identified as a moderate concern according to the RMP’s tiered, risk-based framework that guides monitoring and management actions on emerging contaminants in the Bay.

Please contact Diana Lin ([email protected]) or Rebecca Sutton ([email protected]) for more information.

Key Materials

Bay Area Biota

PFAS are ubiquitous in Bay biota including fish, bird eggs, and harbor seals. Concentrations of PFOS in Bay harbor seals and bird eggs in 2004 and 2006 were some of the highest detected globally (here). Continued bird egg monitoring on a triennial basis has indicated decreasing levels in South Bay birds, though this still may pose a risk to hatching success (here).

In addition, sport fish are monitored on a recurring five-year basis, with the most recent study showing concentrations of PFAS, particularly in South Bay fish, exceeding thresholds that have been established by other states for the development of consumption advisories. SFEI is working with local community groups and stakeholders to build consensus on next steps to protect fishing communities (here). 

Bay Area Stormwater and Wastewater 

Stormwater and wastewater are two pathways for PFAS to enter the Bay. Studies of Bay Area stormwater and wastewater indicate that a significant fraction of the PFAS discharged are of unknown chemical composition. 

A recent regional study of influent, effluent, and biosolids on behalf of the Bay Area Clean Water Agencies (BACWA) detected various PFAS, though these concentrations were generally below many household consumer products. Further study is ongoing to evaluate the relative importance of residential and specific industrial sewershed sources to wastewater within the Bay Area.

Bay Area Surface Water and Sediment 

Studies of surface water and sediment have shown detectable levels of a variety of PFAS. Continued examination of PFAS in both media is ongoing as a part of the RMP’s Status and Trends monitoring as well as other special studies. Monitoring data provides critical information concerning the fate of PFAS in the Bay, and can inform predictive modeling efforts.

Additional Resources


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