Mass Fractions, Congener Group Patterns, and Placental Transfer of Short- and Medium-Chain Chlorinated Paraffins in Paired Maternal and Cord Serum

Multiple studies have demonstrated the occurrences of short-chain chlorinated paraffins (SCCPs) and medium-chain chlorinated paraffins (MCCPs) in environmental matrixes, but human internal exposure to them has been studied rarely. Mass fractions and congener group patterns of SCCPs and MCCPs in paired maternal and cord serum were studied for the first time to investigate the placental transport mechanism and prenatal exposure risks of CPs. Samples were collected in Beijing, China, and analyzed using two-dimensional gas chromatography coupled to time-of-flight mass spectrometry. SCCP and MCCP mass fractions in maternal serum were 21.7–373 and 3.76-31.8 ng/g ww, respectively. They were 8.51–107 and 1.33–12.9 ng/g ww, respectively, in cord serum. Significant positive correlation between SCCP and MCCP levels in maternal serum was found (p < 0.01), suggesting SCCPs and MCCPs may undergo similar accumulation, transfer, and transformation pathways. The predominant congener groups for SCCP and MCCP in maternal serum were C10–11Cl6–7 and C14Cl7–8. The homologue profiles of CPs in cord serum were similar but with varied contribution percentage compared with those in maternal serum. By calculating and comparing cord-maternal serum ratios for each individual congener group, passive diffusion was recognized to be the possible placental transport form. The relationships between CP and thyroid hormone concentrations (THs) indicated that exposure to CPs might affect circulating TSHs. C9-CPs were also detected, improving our understanding of CPs in human serum.