Congener-SpecificMother–Fetus Distribution,Placental Retention, and Transport of C 10–13 andC 14–17 Chlorinated Paraffins in Pregnant Women

Short-chain chlorinated paraffins (SCCPs) and medium-chain chlorinated paraffins (MCCPs) are high production volume persistent and toxic industrial chemicals, found ubiquitously in various environmental matrices. However, information is scarce regarding human internal exposure. The congener-specific SCCP and MCCP levels in matched maternal serum (n= 31), umbilical cord serum (n= 31), and placenta (n= 31) were studied to investigate the maternal-placenta-fetus distribution and the placental transport mechanisms of SCCPs and MCCPs. The results indicated that lower chlorinated and shorter carbon-chain CPs were efficiently transported across placenta compared to highly chlorinated and longer carbon chain CPs. Meanwhile, ∑MCCP concentration followed the order of maternal sera > placentas > cord sera. The cord/maternal concentration fraction ratios (R_(CM)) of CPs exhibited similar values from C_(10) to C_(14), and then from C_(15), a decreasing trend was observed with increasing carbon chain length. The log-normalized maternal SCCP concentrations were positively correlated (P < 0.01) with that in the cord, suggesting fetus exposure to SCCPs during pregnancy. Furthermore, the placenta/maternal concentration fraction ratio (R_(PM)) values for MCCPs were relatively higher than those for SCCPs, demonstrating that MCCPs were not efficiently transported and effectively retained in placenta tissues. These findings provide a better understanding of the maternal-fetal transmission and neonatal exposure to CPs.