Concentrations and isomer profiles of perfluoroalkyl carboxylates in house rats (Rattus norvegicus) and human blood: Implication for human exposure sources.

In humans, perfluoroalkyl acids (PFAAs) are derived from direct external exposure and subsequent degradation of their precursors, but the contribution of the sources remains unclear. Here, we examined PFAA concentrations and isomer profiles in house rat (Rattus norvegicus; n = 29, a similar source of human exposure to PFAAs) and human blood (n = 194), and explored the sources of PFAAs in humans. Perfluorooctane sulfonate (PFOS, 19-49 %) was the predominant PFAA in rat tissues, with the highest concentrations of ΣPFAAs in the liver (sum of PFAAs, mean 20-212 ng/g wet weight (ww)). Perfluorooctanoate (PFOA, mean 2.6 ng/mL) was the major PFAA in human blood. Differences in composition profiles of PFAAs indicate that distribution behaviors of the compounds is different among different tissues. In addition, the average percentage of branched PFOA and PFOS in rat tissues was 3.1-6.7 % and 20-37 %, respectively, compared to 4.1 % and 25 % in human blood. Our study suggests that perfluoroalkyl carboxylates in house rats and humans may be primarily due to atmospheric degradation of fluorotelomer alcohol-based chemicals.