Human exposures to per- and polyfluoroalkyl substances (PFAS) and their biomonitoring

Abstract

Per- and polyfluoroalkyl substances (PFAS) are highly fluorinated organic compounds characterized by perfluoroalkyl chains such as CF₃- or -CF₂- groups. Perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) are the most studied PFAS, used in water/oil repellents, firefighting foams, and fluoropolymer production aid. Due to their chemical stability and resistance to biodegradation, PFAS persist in the environment and accumulate in wildlife and humans. Exposure occurs through contaminated water, air, food, and consumer products. Studies have shown regional differences in PFAS levels in Japan, with higher concentrations of drinking water in several locations of Kansai and Tokyo. Seafood is a substantial source of exposure, with PFNA and PFUnDA detected in fish and shellfish. Thus, blood levels of PFAS correlate with seafood intake and biomarkers like eicosapentaenoic acid. Human biomonitoring, especially via blood samples, is the most reliable method to assess PFAS exposure. PFOS and PFOA mainly distribute in blood and liver, with long half-lives (e.g., PFOA: 3.8 years). Since PFAS levels in urine and breast milk are low, blood plasma or serum is preferred for chemical analysis. Historical data show increasing PFAS levels in Japanese blood samples from the 1970s to 2000s, especially in Kyoto. Long-chain perfluoroalkyl carboxylic acids (e.g., perfluorononanoic acid, perfluoroundecanoic acid) are also prevalent and may affect lipid metabolism. Recent surveys in Okinawa, Osaka, and Gifu where local contaminations exist revealed high PFAS blood levels, exceeding guidance values recommended by German and U.S. agencies. These values were derived from epidemiological evidence on health risks of developmental effects, cholesterol elevation, and increased diabetes and cancer risks. The guidance recommends exposure reduction and clinical follow-up for individuals exceeding the threshold levels. Future efforts should focus on standardized analysis, identification of exposure sources, and comprehensive health risk assessments. Despite regulatory bans of selected PFAS, legacy contamination and ongoing exposure from other PFAS remain concerns.