Bisphenol A Metabolites and Bisphenol S in Paired Maternal and Cord Serum

Human studies show associations between maternal bisphenol A (BPA) exposure and developmental effects in children, yet biomonitoring of BPA metabolites in maternal and fetal serum remains limited, and less is known for BPA alternatives. BPA-glucuronide, BPA-sulfate, and bisphenol S (BPS) were quantified in 61 pairs of maternal and cord sera from Chinese participants. Total BPS was only detectable in four maternal (<0.03-0.07 ng/mL) and seven cord sera (<0.03-0.12 ng/mL), indicating low exposure but providing the first evidence that BPS crosses the human placenta. Total BPA metabolites in cord serum were significantly higher than in maternal serum (p < 0.05), suggesting that these may be formed in the fetus or cleared more slowly from the fetoplacental compartment. Unlike the pharmacokinetic results from controlled oral exposure studies in which BPA-glucuronide is the major BPA metabolite, here, BPA-sulfate was the dominant metabolite (GM: 0.06 and 0.08 ng/mL), significantly higher than BPA-glucuronide (GM: 0.02 and 0.04 ng/mL) (p < 0.01) in both maternal and cord sera. Moreover, the proportion of BPA-sulfate increased with total BPA. These are the first human data for BPA metabolites in paired maternal and cord serum, and results suggest that the human fetus and pregnant mother have unique exposure to BPA metabolites. Direct analysis of BPA metabolites in serum provides complementary information for evaluating early life-stage exposure and risks of BPA.