PFAS in San Francisco Bay Water

Scientists with the San Francisco Bay Regional Monitoring Program (RMP) detected PFAS, also known as “forever chemicals,” at parts per trillion concentrations in the waters of the Bay. A recent report finds the contaminants present in Bay water including the well-studied PFOS and PFOA, as well as their replacements.

These compounds are persistent and toxic; levels in Bay water do not appear to pose risks to wildlife. However, measured concentrations do suggest possible concern for people who eat fish from the Bay regularly. PFAS have been detected in Bay sport fish, bird eggs, and harbor seals, and in wastewater and stormwater discharges. Bay Area wastewater agencies are partnering with the RMP on a study of the sources of PFAS to wastewater treatment plants. Preliminary results point to the importance of dealing with PFAS as a class, as well as the importance of source control to reduce human exposure to PFAS.

PFAS have many uses, including as cosmetic ingredients, paint additives, stain resistant textile coatings, grease resistant food packaging, and many others. Industrial uses include oil and gas fracking and specialized foams for suppressing fuel fires. The state of California has passed bans on PFAS in some specific products to reduce harmful exposures. For example, California will become the first state in the U.S. to ban the use of PFAS chemicals on apparel and textile products, starting January 2025. Other recent actions cover PFAS in cosmetics, children’s products, carpets and rugs, paper-based food packaging, and fire-fighting foams.

Earlier this week, California Attorney General Rob Bonta filed a lawsuit against PFAS manufacturers for endangering public health, causing irreparable harm to the state's natural resources, and engaging in a widespread campaign to deceive the public.

The RMP study analyzed ambient surface water in San Francisco Bay for 40 PFAS to discern the occurrence, fate, and potential risks to ecological and human health. Eleven of 40 PFAS were detected in ambient surface water collected in 2021 from 22 sites in the Bay. Concentrations of PFAS in the Bay were generally consistent with similar studies globally for surface water. 

Results from this study support the continued classification of PFAS as Moderate Concern for the Bay. Concentrations of individual PFAS and their sums across sites in ambient surface water remain below available ecotoxicity thresholds, though these thresholds do not consider potential bioaccumulative effects. However, the 90th percentile concentrations of PFOA and PFOS in water exceed available human health screening levels for seafood ingestion, consistent with a recent RMP sport fish study indicating potential concern. Sustained, multi-matrix monitoring of this important class of contaminants of emerging concern is a high priority for the RMP.

Future monitoring of San Francisco Bay can be used to track the impacts of state PFAS restrictions on our environment.