Abstract
Studies have highlighted the increasing fraction of unidentified organofluorine (UOF) compounds in human blood, whose health effects are not known. In this study, 130 whole blood samples from the Swedish general population were analyzed for extractable organofluorine (EOF) and selected per- and polyfluoroalkyl substances (PFAS). Organofluorine mass balance analysis revealed that 60% (0–99%) of the EOF in female samples could not be explained by the 63 monitored PFAS; in males, 41% (0–93%) of the EOF was of unidentified origin. Significant differences between both age groups and gender were seen, with the highest fraction of UOF in young females (70% UOF, aged 18–44), which is contrary to what has been reported in the literature for commonly monitored compounds (e.g., perfluorooctane sulfonic acid, PFOS). Increasing the number of monitored PFAS did not lead to a large decrease of the UOF fraction; the seven highest PFAS (C8–C11 PFCAs, C6–C8 PFSAs) accounted for 98% of sum 63 PFAS. The high fraction of UOF in human samples is of concern, as the chemical species of these organofluorine compounds remain unknown and thus their potential health risks cannot be assessed.
Highlights
The most studied per- and polyfluoroalkyl substances (PFAS), perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS), have been linked to various negative health outcomes
To the best of our knowledge, this is the first study showing a statistically significant (p < 0.05) difference in the percentage of unidentified organofluorine (UOF) between genders and age groups, with females having a higher UOF fraction that was especially pronounced for the youngest females
Combined with females having consistently higher extractable organofluorine (EOF) concentrations (Figure 1), these results indicate that females have a higher UOF internal exposure than males
Summary
The most studied per- and polyfluoroalkyl substances (PFAS), perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS), have been linked to various negative health outcomes. One of the main producers, 3M phased out PFOS and PFOA production in the United States after 2002,11 and both PFOS and PFOA have been included in the Stockholm convention since 2009 and 2019, respectively.[12] As a result, production has shifted to other PFAS, for example, shorter (C4 and C6)-chained PFAS13 and perfluoroether compounds.[14] While PFAS with shorter perfluorinated carbon backbones were considered to have a lower health and environmental impact due to lower bioaccumulative potential,[15] recent studies have indicated that at higher concentrations the PFAS with shorter carbon backbones have toxicities similar to their longer-chained analogues.[16,17] Human biomonitoring studies have already detected other ether compounds (6:2 chlorinated polyfluorinated ether sulfonate (6:2 Cl-PFESA) and 4,8-dioxa3H-perfluorononanoic acid (ADONA)).[18,19]
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