Exposure characteristics of legacy PFAS, and their precursors and alternatives among children and adolescents of Korea.

Among children and adolescents, exposure to per- and poly-fluoroalkyl substances (PFAS) and their substitutes remains poorly characterized. This study analyzed major PFAS and their substitutes in serum samples from 257 children (6-12 years) and 283 adolescents (13-18 years) using the Korea Ministry of Food and Drug Safety biospecimen archive. Eleven compounds, including PFHpA, PFOA, PFNA, PFOS, and 9Cl-PF3ONS, were detected in over 70 % of the participants, with several legacy PFAS detected at levels exceeding those reported elsewhere. Among the study population, PFOA, PFHxS, and PFOS exhibited the highest concentrations, and children generally showed higher levels than adolescents. Notably, 85 % and 4 % of participants showed PFOA levels that exceeded HBM-1 and HBM-2 values, respectively. Among the substitutes, 9Cl-PF3ONS was detected in all participants, while 6:2FTS, a precursor, was present in more than half of the participating subjects (>55 %). PFAS levels, particularly those of PFOA and PFOS, were significantly higher among individuals consuming tap water compared to those relying on bottled water (p < 0.05). This likely reflects the higher contamination levels of surface water, the primary source for tap water, compared to groundwater, which is commonly used for bottled water in South Korea. Additionally, dietary intake, particularly seafood and meat consumption, was associated with elevated PFAS levels. The present findings highlight the high and widespread exposure to PFAS among Korean youth, emphasizing the need for further research to identify exposure sources and implement mitigation strategies to reduce PFAS exposure.