Associations between PFAS in public water system drinking water and serum among Southern California adults
By Toki Fillman, Scott Coffin, Brandon Ta, Emily Beglarian, Wendy Linck, Hyoung-Gee Baek, Songmei Gao, Sabrina Smith, June-Soo Park, Nerissa Wu, and Kathleen Attfield
J Expo Sci Environ Epidemiol
October 30, 2025
DOI: 10.1038/s41370-025-00817-8
Background
Studies from areas with high level per- and polyfluoroalkyl substance (PFAS) contamination have reported significant contributions of drinking water to overall exposure but few studies have focused on general populations.
Objective
To examine the association between PFAS in public water system drinking water and concentrations in serum among a general population of California adults.
Methods
The CARE (California Regional Exposure) biomonitoring study measured PFAS in serum of Southern and Eastern California adults between 2018 and 2020. Participant addresses were geocoded and geographically assigned to public water systems (PWS). Between 2019 and 2022, the California State Water Resources Control Board issued investigative PFAS monitoring orders to potentially impacted PWS, focusing primarily on source wells. PFAS detections above the required reporting limit (4 ng/L for PFAS included in the final analysis) were used to assess associations with serum PFAS levels.
Results
Out of 563 participants in Southern California included in the final analysis, 314 (56%) lived in a PWS service area with at least one PFAS detected in their untreated source water and/or treated drinking water. Serum perfluorohexane sulfonic acid (PFHxS) geometric mean concentrations were 31.9% (95% CI: 11.1-56.6%) higher among participants whose PWS had at least one PFHxS detection compared to those without detectable levels. For participants with post-treatment drinking water data (n = 235), serum PFAS geometric mean concentrations were higher compared to those without detections for all modeled PFAS: PFHxS 79.9% (38.3-133.9%), perfluorooctanoic acid (PFOA) 30.4% (5.5-61.2%), perfluorooctane sulfonic acid (PFOS) 31.2% (0.7-70.9%), and ∑5 PFAS 42.0% (14.5-76.1%).
Impact
This study examined the association between public water system PFAS detections and serum concentrations among a general population of Southern California adults. We found that PFAS detections in public water systems were associated with higher serum PFAS concentrations. Our findings suggest PFAS contamination in drinking water may be a significant contributor to serum PFAS levels, even among communities without high level contamination from industrial manufacturing. These results support drinking water monitoring initiatives in California to understand PFAS contamination and mitigate exposure.
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