Organophosphorus Flame Retardants in Pregnant Women and Their Transfer to Chorionic Villi

The potential for prenatal exposure has recently raised concerns over the health risks of endocrine disruptors; however, knowledge about human prenatal exposure to organophosphorus flame retardants (OPFRs) is lacking. In this study, 2-ethylhexyl diphenyl phosphate (EHDPP), tributyl phosphate (TBP), triphenyl phosphate (TPHP), and tris(2-chloroethyl) phosphate (TCEP) were detected in the majority of chorionic villus samples, with median concentrations of 13.6, 18.8, 11.1, and 0.51 ng/g of dry weight (dw), respectively, significantly higher than those in the matching maternal decidua samples (5.96, 10.8, 1.44, and 0.26 ng/g of dw, respectively). The ratios of concentrations in chorionic villi (containing embryos) to those in maternal deciduae (CMRs) were 4.17, 3.82, 2.81, and 2.00 for EHDPP, TPHP, TBP, and TCEP, respectively, which correlated with their log Kow values (p = 0.003). The results of transthyretin (TTR) binding assays indicated that the stronger the binding ability to TTR, the higher the CMRs. The median concentrations of the metabolites diphenyl phosphate (DPHP), dibutyl phosphate (DBP), and bis(2-chloroethyl) phosphate (BCEP) were 4.11, 429, and 157 ng/g of dw in chorionic villi, higher than those in deciduae (1.64, 181, and 25.4 ng/g of dw, respectively). The ratios of DPHP/TPHP and DPHP/EHDPP were 0.20 and 0.43 in chorionic villi and 1.24 and 2.03 in deciduae, respectively, much lower than those of DBP/TBP and BCEP/TCEP (20.9 and 165.6 in chorionic villi and 13.1 and 35.3 in deciduae, respectively), suggesting that the difference in metabolism between the deciduae and chorionic villi would affect their maternal transfer.