Determinants of Serum PFOA Concentrations Among Residents in the Industrially Contaminated Area 11 Years After PFOA Production Cessation in Osaka, Japan

Background: In 2023, community-initiated biomonitoring was conducted among residents near the Daikin Industries Yodogawa Plant (DIYP), where PFOA contamination had previously been identified. Methods: Serum PFOA and questionnaire data were analyzed in 1174 participants; 1084 had complete data for 15 prespecified variables. Log10(PFOA) was modeled using multivariable regression, with model selection by AIC and Bonferroni correction. A sensitivity analysis excluded six consumers of self-grown agricultural products. We also theoretically examined the relationship between serum concentration and time-weighted average exposure using a one-compartment model with a lognormal Ornstein–Uhlenbeck exposure process. Results: Residence, age, fish consumption, drinking habit, laxative use, and tap-water use were significant determinants. Residents nearest DIYP had a geometric mean PFOA concentration of 5.95 ng/mL and adjusted concentrations 18–21% higher than other areas. Predicted and observed stratum means were strongly correlated (r = 0.927). Results remained significant in sensitivity analysis. The theoretical analysis showed that the white-noise limit provides a global lower bound for the serum–exposure correlation; for averaging over three biological half-lives, ρ ≥ 0.858. Conclusions: Elevated PFOA near DIYP suggests that local exposure may have persisted after production ceased in 2012. Continued biomonitoring is warranted.