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.

Associated Staff: 
Programs and Focus Areas: 
Clean Water Program
Bay Regional Monitoring Program
Emerging Contaminants