Fluorine Mass Balance, including Total Fluorine, Extractable Organic Fluorine, Oxidizable Precursors, and Target Per- and Polyfluoroalkyl Substances, in Pooled Human Serum from the Troms(sic) Population in 1986, 2007, and 2015

Of the thousands of per- and polyfluoroalkyl substances (PFAS) known to exist, only a small fraction (<= 1%) are commonly monitored in humans. This discrepancy has led to concerns that human exposure may be underestimated. Here, we address this problem by applying a comprehensive fluorine mass balance (FMB) approach, including total fluorine (TF), extractable organic fluorine (EOF), total oxidizable precursors (TOP), and selected target PFAS, to human serum samples collected over a period of 28 years (1986, 2007, and 2015) in Tromso, Norway. While concentrations of TF did not change between sampling years, EOF was significantly higher in 1986 compared to 2007 and 2015. The S12PFAS concentrations were highest in 2007 compared to 1986 and 2015, and unidentified EOF (UEOF) decreased from 1986 (46%) to 2007 (10%) and then increased in 2015 (37%). While TF and EOF were not influenced by sex, women had higher UEOF compared to men, opposite to target PFAS. This is the first FMB in human serum to include TOP, and it suggests that precursors with >4 perfluorinated carbon atoms make a minor contribution to EOF (0-4%). Additional tools are therefore needed to identify substances contributing to the UEOF in human serum.

Automated summary

A comprehensive study on per- and polyfluoroalkyl substances (PFAS) in human serum samples was conducted, revealing that only a small fraction of PFAS are commonly monitored, which may lead to underestimation of human exposure. The study applied a fluorine mass balance approach and observed that total fluorine (TF) concentrations remained stable over time, while extractable organic fluorine (EOF) decreased. Furthermore, sex was found to influence the levels of unidentified EOF (UEOF) in a different way compared to target PFAS.