Although levels of poly- and perfluoroalkyl substances (PFASs) in human maternal and neonatal blood have been widely reported in the literature, relationship of maternal-fetal transmission of PFASs with carbon chain length is presently not well understood. In this study, 11 PFASs were analyzed in matched samples, including not only maternal blood (MB, n = 31) and cord blood (CB, n = 30), but also placenta (n = 29) and amniotic fluid (AF, n = 29). Except for perfluorohexanoic acid (PFHxA), the detection frequencies of PFASs were similar among placenta, MB, and CB (>80% for 8 PFASs, nondetectable for 2 PFASs). Though only perfluorooctanoic acid (PFOA) was frequently detected (>90%) in AF, with a median concentration of 0.043 ng/mL, other 5 PFASs were also detectable in AF samples with low concentrations (mean: 0.013-0.191 ng/mL). This suggests that in addition to blood-borne in utero exposure, the fetus is also exposed to low levels of PFASs through AF. Concentrations of PFOA in AF were positively correlated with those in MB (r = 0.738, p < 0.01) and CB (r = 0.683, p < 0.001), suggesting that AF concentration could reflect fetal PFOA exposure during pregnancy and can be used as a biomarker. To clarify the effects of carbon chain length on maternal transfer of PFASs, we calculated maternal transfer efficiencies of PFASs from MB to CB (TMB-CB). A U-shaped trend in TMB-CB of C7-C12 perfluoroalkyl carboxylic acids (PFCAs) with increasing carbon chain length was found in this study for the first time. The U-shaped TMB-CB of PFCAs with carbon chain length is an integrated result of opposite trend of the ratios between MB/placenta and placenta/CB based on carbon chain length. This is the first study to report the occurrence of PFASs in human placenta. The results reported here enable better understanding of the maternal-fetal transmission of PFASs.

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Phthalic acid esters (PAEs) are readily metabolized to phthalate metabolites (mPAEs) in the human body. The occurrence of mPAEs in adult human samples is well documented; however, the maternal-fetal transmission of mPAEs has seldom been studied. In this study, 78 paired maternal-fetal samples, including maternal urine (MU), maternal serum (MS), cord serum (CS), and amniotic fluid (AF), were collected from pregnant women in Tianjin, China. Seven mPAEs were detected in MS, CS, and AF, whereas all 11 investigated mPAEs were found in MU. The median concentration of ∑mPAEs was the highest in MU (128 ng/mL, with a range of 20.2-973 ng/mL), and proceeded in the order of CS (44.9, 13.9-315 ng/mL), MS (24.6, 3.75-156 ng/mL), and AF (10.4, 7.69-79.8 ng/mL). The values of ∑mPAEs and several individual mPAEs were significantly correlated between MU and MS, with generally higher concentrations in MU, which indicated that urinary mPAEs is a good indicator of PAEs' exposure in adults. Notably, the median CS:MS ratios of ∑mPAEs (1.58) were higher than 1, indicating that fetuses were exposed to mPAEs before birth. Significant correlations were also observed between MS and CS, which suggested that mPAEs in MS provide an indication of the fetal exposure. This study presents the first systematic analysis of the distribution and transmission of various mPAEs between mothers and fetuses.

Although levels of perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) in human blood are well documented, information on elimination of these chemicals is limited. In this study, PFOS and PFOA were analyzed in 81 whole blood-urine paired samples from general adults and pregnant women in Tianjin, China. PFOS and PFOA were detected in 48 and 76% of adult urine (AU) samples, with geometric mean (GM) concentrations of 0.011 and 0.008 ng/mL, respectively; whereas relatively low PFOS and PFOA concentrations were found in maternal urine (MU) samples, with GM concentrations of 0.006 and 0.003 ng/mL, respectively. For PFOA, the coefficients of Pearson's correlation between whole blood concentrations and creatinine-adjusted and creatinine-unadjusted urinary concentrations were 0.348 (p = 0.013) and 0.417 (p = 0.002), respectively. The GM urinary elimination rates of PFOS (PFOSUER) and PFOA (PFOAUER) were 16 and 25%, respectively, for adults. These results indicate that urine is an important pathway of excretion of perfluoroalkyl substances (PFASs). The partitioning ratios of PFAS concentration between urine and whole blood (PFASU/B) in pregnant women (PFOSU/B, 0.0004; PFOAU/B, 0.0011) were significantly lower (p = 0.025 for PFOSU/B, p = 0.017 for PFOAU/B) than the ratios found in non-pregnant women (PFOSU/B, 0.0013; PFOAU/B, 0.0028). Furthermore, our results suggest a clear gender difference in the urinary elimination of PFOA, with male adults (31%) having significantly higher PFOAUER than that of female adults (19%). PFOSUER was significantly inversely correlated with age (r = -0.334, p = 0.015); these findings suggest that urinary elimination of PFOS is faster in young adults than in the elderly.

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