Conjugated bisphenol S metabolites in human serum and whole blood.

Studies have shown that bisphenol S (BPS) is mainly present as its conjugated metabolites in human blood. However, the distribution of conjugated BPS metabolites in different human blood matrices has not been characterized. In this study, paired human serum and whole blood samples (n = 79) were collected from Chinese participants, and were measured for the occurrence of BPS and 4 BPS metabolites. BPS was detectable in 49% of human serum (<LOD-1.7 ng/mL) and 78% of whole blood (<LOD-2.1 ng/mL) samples. In both human serum and whole blood, BPS-sulfate (BPS-S; 74% and 86%, respectively) and BPS-glucuronide (BPS-G; 68% and 84%, respectively) had higher detection frequency than BPS. Consistently, BPS-S was the predominant BPS metabolite in human serum (mean 0.39 ng/mL) and whole blood (0.41 ng/mL), significantly higher than BPS-G (mean 0.13 and 0.13 ng/mL, respectively). This is contrary to the data from controlled oral exposure studies on model animals and humans, in which BPS-G was the dominant BPS metabolite in serum. BPS-S (mean ± SD, 0.99 ± 0.35) had the highest partitioning coefficient between human serum and whole blood, followed by BPS-G (0.89 ± 0.27) and BPS (0.81 ± 0.28), suggesting their preferential accumulation in the red blood cell fraction. These results represent the first human data on conjugated BPS metabolites in paired human serum and whole blood, which help to elucidate of the occurrence of conjugated BPS metabolites in humans.