Relative contributions of dietary and drinking water pathways to PFAS exposure in the U.S. population: intake-based and biomonitoring analyses.

Per- and polyfluoroalkyl substances (PFAS) are persistent environmental contaminants widely detected in food and human serum, raising concerns about major exposure pathways in the general population. This study evaluated the relative importance of dietary and drinking water exposure pathways for seven legacy PFAS compounds consistently measured in NHANES using complementary intake-based and regression-based approaches. An intake-based model combined representative PFAS concentrations from U.S. monitoring studies with dietary intake data from the National Health and Nutrition Examination Survey (NHANES) to estimate population-average PFAS intake. A regression-based model used survey-weighted standardized regression coefficients to evaluate the contributions of dietary intake and drinking water consumption to interindividual variability in serum PFAS concentrations. The intake-based model estimated a total PFAS intake of approximately 17.4 ng/day from 2015 to 2020. Seafood was the largest contributor, with shellfish and finfish accounting for 43.2% and 9.2% of estimated intake, respectively. Drinking water contributed 15.5% of estimated intake despite its relatively low PFAS concentration, whereas dairy products, meat, and plant foods contributed 14.4%, 10.4%, and 7.4%, respectively. Regression analyses likewise identified shellfish as the largest contributor to variability in serum PFAS concentrations across survey periods, whereas drinking water contributed relatively little at the national level from 2015 to 2020. These findings identify seafood, particularly shellfish, as the largest contributor among the evaluated dietary and drinking water pathways for legacy PFAS and support continued monitoring of both legacy and emerging replacement PFAS in foods and drinking water to improve assessment of population exposure.