May 7, 2020
SFEI senior scientist, Dr. Rebecca Sutton, published a new study in the journal Chemosphere that modeled long-term trends of perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) over time in San Francisco Bay. This study was a collaboration with Francisco Sanchez-Soberon (first author) of the Universitat Rovira I Virgili in Tarragona, Spain. PFOS and PFOA are the most widely studied per- and polyfluoroalkyl substances (PFAS), and are in the Moderate Concern category of the Regional Monitoring Program tiered risk-based framework for contaminants of emerging concern (CECs). These compounds have been widely used as water and stain repellents, such as in nonstick coatings; however, their presence in the environment is concerning because they are harmful to humans (causing liver damage, endocrine disruption, fertility decrease, and cancer) and to wildlife.
A model was developed to simulate concentrations of PFOA and PFOS in Bay water and sediment. This Bay model was linked to another model that estimated accumulation in shiner surfperch, a popular sport fish species. The model predicts that it will take approximately 100 years for PFOS in South Bay fish to decline by 75%. Concentrations of PFOS and PFOA were highest in the South Bay compared to fish from North and Central Bay. At present, California does not have guidance on safe levels of fish consumption for PFOA and PFOS.
Concentrations of both compounds showed exponentially decreasing trends over time, which is expected as use of these compounds has been phased out in the US. Nearly stable PFOA concentrations in water were reached after 50 years, but the model showed that PFOS concentrations would not stabilize in sediment and fish for 500 years. The simulations in this study were generated using one year of data (2009) as the base case scenario. Because of this, there is inherent uncertainty in these results from a lack of input data for water, wastewater, and stormwater, which highlights the need for additional monitoring in these areas.
Programs and Focus Areas:
Clean Water Program
Bay Regional Monitoring Program
Related Projects, News, and Events:
RMP Technical Report: Per and Polyfluoroalkyl Substances (PFAS) in San Francisco Bay: Synthesis and Strategy (News)
Perfluoroalkyl and polyfluoroalkyl substances (PFAS) are a broad class of fluorine-rich specialty chemicals. More than 4,700 PFAS are used in consumer, commercial and industrial applications. Well-studied members of the perfluoroalkyl family, including perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA), have been shown to be highly toxic. Use is shifting to alternatives to PFOS and PFOA, including shorter-chain perfluoroalkyl chemicals and polyfluoroalkyl chemicals.
Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS) (Project)
Perfluoroalkyl and polyfluoroalkyl substances (PFAS) are a broad class of fluorine-rich specialty chemicals. More than 4,700 PFAS are used in consumer, commercial and industrial applications, including food packaging materials, waterproof textiles, stain-resistant carpets and furniture, fire-suppression foams, processing aids for the production of fluoropolymers like Teflon, mist suppressants in metal-plating, and hydraulic aviation fluids. Perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) have been shown to be highly toxic and have been phased out of production in the US.