When comparing the estimated PFOS isomer pattern of the total exposure based only on direct PFOS exposure (Fig. 4A and B, red line) relative to Enzalutamide in vitro PFOS and precursor exposure (blue line), only a small deviation is seen, indicating that direct PFOS exposure dominates the overall PFOS isomer pattern or that both pathways (direct and indirect exposure) lead to a similar PFOS isomer pattern. Additional uncertainties in estimating the PFOS isomer pattern of the total exposure are differences in uptake and biotransformation rates between linear

and branched precursor isomers. Both in vivo and in vitro experiments have shown that branched precursor isomers are degraded faster relative to the linear isomer ( Benskin et al., 2009b, Peng et al., 2014 and Ross et al., 2012), however, no isomer-specific biotransformation factors have been provided. In the intermediate-exposure scenario in the present study, the biotransformation fraction of precursors to PFOS is estimated at 0.2 for both branched

and linear isomers. However, the influence of a potentially higher percentage biotransformation of branched precursors to branched PFOS is further investigated with the assumption that the PFOS and precursor isomer pattern in dust and air are 70/30 linear/branched and equal uptake for all isomers ( Fig. 4C). With biotransformation Proton pump inhibitor factors of > 0.2 for the biotransformation of branched precursors to branched PFOS (relative to 0.2 for the linear precursor isomers), the isomer pattern in total PFOS exposure intake reflects the isomer pattern found in human serum. However, human serum isomer patterns cannot be explained even when complete biotransformation of branched precursors to branched PFOS is assumed. For both PFOS and its precursors, faster uptake of branched isomers relative to the linear isomers was observed in rats and fish (

Benskin et al., 2009a and Peng et al., 2014). In the intermediate-exposure scenario in the present study, the uptake fractions of PFOS and its precursors are estimated at 0.8 for both branched and linear isomers. The influence of a potentially higher uptake efficiency for branched isomers Docetaxel purchase compared to linear isomers is further investigated with the assumption that the PFOS and precursor isomer pattern in dust and air are 70/30 linear/branched and biotransformation fractions are 0.2 ( Fig. 4D). Greater uptake of branched PFOS and precursors (> 0.8) compared to the linear isomers had little impact on the isomer pattern of total PFOS intake. Completely efficient uptake of branched isomers (relative to 0.8 for linear isomers) only changed the isomer pattern of total PFOS intake from 84% to 81% linear PFOS.