Even among communities without high level contamination from industrial manufacturing
California, 30 October 2025 — A new study of California’s general adult population reveals that per- and polyfluoroalkyl substances (PFAS, commonly known as “forever chemicals”) in public water systems are significantly associated with elevated PFAS concentrations in residents’ blood serum.
The study, conducted by the California Regional Exposure (CARE) biomonitoring program, tested serum PFAS levels in 563 adults from Southern and Eastern California between 2018 and 2020. Researchers geographically matched participants’ residential addresses to public water systems (PWS) and analyzed data from the California State Water Resources Control Board’s monitoring of potentially contaminated water sources from 2019 to 2022.
Key Findings:
- 56% of participants (314 individuals) lived in water system service areas where at least one PFAS was detected
- Residents whose water systems detected perfluorohexane sulfonic acid (PFHxS) had serum PFHxS concentrations 31.9% higher on average (95% CI: 11.1%–56.6%)
- Among 235 participants with post-treatment drinking water data, serum concentrations were significantly elevated for all PFAS measured:
- PFHxS: 79.9% higher
- Perfluorooctanoic acid (PFOA): 30.4% higher
- Perfluorooctane sulfonic acid (PFOS): 31.2% higher
- Sum of 5 PFAS: 42.0% higher
Study Significance:
This research demonstrates for the first time that even in general communities without high-level industrial contamination, PFAS in drinking water may be a significant contributor to serum PFAS levels in residents. The findings support California’s ongoing drinking water monitoring initiatives and highlight the importance of understanding PFAS contamination levels and reducing public exposure risks.
PFAS are a class of man-made chemicals that persist in the environment and have been linked to various adverse health effects. This study underscores the urgent need to strengthen PFAS monitoring and treatment in public water systems.
The study was published in the Journal of Exposure Science & Environmental Epidemiology: Fillman, T., Coffin, S., Ta, B. et al. Associations between PFAS in public water system drinking water and serum among Southern California adults. J Expo Sci Environ Epidemiol (2025). https://doi.org/10.1038/s41370-025-00817-8
