Transplacental transfer of polycyclic aromatic hydrocarbons in paired samples of maternal serum, umbilical cord serum, and placenta in Shanghai, China

Prenatal exposure to polycyclic aromatic hydrocarbons (PAHs) is a high-priority public health concern. However, maternal to fetal transplacental transfer of PAHs has not been systematically studied. To investigate the transplacental transfer of PAHs from mother to fetus and determine the influence of lipophilicity (octanol-water partition coefficient, K_OW) on transfer process, in the present study, we measured the concentrations of 15 PAHs in 95 paired maternal and umbilical cord serum, and placenta samples (in total 285 samples) collected in Shanghai, China. The average concentration of total PAHs was the highest in maternal serums (1290 ng g⁻¹ lipid), followed by umbilical cord serums (1150 ng g^-1 lipid). The value was the lowest in placenta samples (673 ng g^-1 lipid). Low molecular weight PAHs were the predominant compounds in the three matrices. Increases in fish and meat consumption did not lead to increases in maternal PAH levels, and no obvious gender differences in umbilical cord serums were observed. The widespread presence of PAHs in umbilical cord serums indicated the occurrence of transplacental transfer. The ratios of PAH concentrations in umbilical cord serum to those in maternal serum (F/M) and the concentrations in placenta to those in maternal serum (P/M) of paired samples were analyzed to characterize the transfer process of individual PAHs. Most F/M ratios on lipid basis were close to one (range: 0.79 to 1.36), which suggested that passive diffusion may control the transplacental transfer of PAHs from maternal serum to the fetal circulation. The P/M and F/M values calculated on lipid basis showed that PAHs with lower K_OW were more likely to transfer from mother to fetus via the placenta. - Highlights: • PAHs in paired samples of maternal and umbilical cord serum, and placenta were study. • Low molecular weight PAHs were the predominant compounds in the three matrices. • PAHs can transfer from maternal serum to the fetal circulation. • Passive diffusion may control the transplacental transfer process of PAHs. • PAHs with lower K_OW were more likely to transfer from mother to fetus via placenta. - Polycyclic aromatic hydrocarbons can transfer from maternal serum to the fetal circulation and passive diffusion may control the process.