Distribution of per- and poly-fluoroalkyl substances and their precursors in human blood

Many studies have examined per-and poly-fluoroalkyl substances (PFASs) in human blood. However, the dis-tribution of PFASs in human blood remains not well known, especially for perfluorooctane sulfonate (PFOS) precursors. In this study, human blood samples (n = 162) were collected from general Chinese population, and then the isomer-specific partitioning of PFASs between human plasma and red blood cells (RBCs) were inves-tigated. Perfluorooctanoate (PFOA) and PFOS were consistently the predominant PFASs in both human plasma and RBCs. In human blood, among C-4-C(7 )perfluoroalkyl carboxylates (PFCAs), the calculated mean mass fraction in plasma (Fp) values increased from 0.76 to 0.82 with the increasing chain length. C-7-C-13 PFCAs exhibited a trend of gradually decreasing mean F-p with chain length. Among PFAS precursors, 6:2 fluorotelomer phosphate diester had the highest mean F-p value (0.87 +/- 0.11). Calculated F-p values of N-methyl per-fluorooctanesulfonamide (N-MeFOSA) and N-ethyl perfluorooctanesulfonamide (N-EtFOSA) were 0.66 & PLUSMN; 0.13 and 0.70 +/- 0.12, respectively. Individual branched isomers consistently had greater F-p values than their corresponding linear isomers for PFOA, PFHxS, and perfluoroctane sulfonamide. To our knowledge, this study first reports the distribution of N-MeFOSA and N-EtFOSA in human blood, contributing to the better understanding of the occurrence and fate of PFASs in humans.