Concentrations of per- and polyfluoroalkyl substances (PFAS) in private well drinking water and serum of individuals exposed to PFAS through biosolids: The Maine Biosolids Study.

Per- and polyfluoroalkyl substances (PFAS) are synthetic and persistent chemicals that can contaminate food and water systems and have lasting negative implications for human health. We described paired residential well water and serum PFAS concentrations among adults residing where PFAS-contaminated biosolids were historically applied to farmland as fertilizer. In 2023, we measured 7 PFAS in serum from 145 participants who had up to 28 PFAS measured in their well water within the 3 prior years due to proximity to a biosolids application site. Participants were median(interquartile range) 63(15) years, 58 % were female, 71 % lived less than a mile from a site of biosolids application, and 58 % had well water PFAS levels exceeding the Maine Interim Drinking Water Standard (∑6 legacy PFAS ≥20 ng/L). In well water, PFOA, PFOS, PFHxA, PFHpA, PFPeA, PFBA, PFHxS, and PFNA were detectable in >50 % of wells, and 21 unique PFAS were detected. Well water concentrations were highest for PFOA [GM(GSD) 13.6(20.1) ng/L]. In serum, detectable PFAS included PFOA [GM(GSD) 6.1(4.9) ng/mL)]; PFOS [8.3(4.1) ng/mL], PFHxS [1.4(2.5) ng/mL], PFNA [1.3(3.8) ng/mL], PFDA [0.40(4.1) ng/mL], and PFUnDA [0.17(2.8) ng/mL]. Of PFAS measured and highly detectable in both serum and water, PFOA had the strongest inter-matrix correlation (0.72); other PFAS had moderate correlations (0.32-0.33). In conclusion, individuals living in an area with historic application of PFAS-contaminated biosolids had elevated and highly correlated PFOA concentrations in water and serum. Other serum PFAS were elevated but moderately correlated with water concentrations, suggesting potential non-water exposure pathways.