Polybrominated diphenyl ethers (PBDEs) are widely used as brominated flame retardants and produce adverse effects on both ecological environment and human health. Therefore, monitoring the concentrations of PBDEs in cord serum and exploring the influencing factors can provide evidence for risk assessment in mother and infant populations.

The aim of this study is to evaluate PBDEs levels in newborn cord serum and explore associated influencing factors.

Between June 2009 and January 2010, 1 027 newborns from Sheyang Mini Birth Cohort Study (SMBCS) in Jiangsu Province were enrolled in this study. A questionnaire survey was conducted to collect the pregnant women's socio-demographic characteristics, living environment, and lifestyles. A total of nine PBDE congeners (BDE-28, BDE-47, BDE-99, BDE-100, BDE-153, BDE-154, BDE-183, BDE-207, and BDE-209) in the collected cord serum samples were determined using gas chromatography-negative chemical ionization mass spectrometry (GC-NCI-MS) and adjusted by total serum lipid concentrations. A multiple linear regression model was applied to explore the association between cord serum PBDEs concentrations and mother's socio-demographic characteristics.

Two or more PBDEs were detected in all cord serum samples. The positive rates of BDE-207 (97.27%), BDE-100 (92.99%), and BDE-209 (91.63%) were higher than 90%, followed by BDE-28, BDE-153, and BDE-154 with the positive rates ranging from 71.21% to 81.01%. The most abundant congener in cord serum was BDE-209, with a median concentration of 18.37 ng·g^-1 (calculated by lipid), followed by BDE-207 (1.14 ng·g^-1), BDE-28 (0.40 ng·g^-1), and BDE-100 (0.39 ng·g^-1). The results of multiple linear regression models indicated that mothers aged 25 to 30 years had a higher cord serum concentration of BDE-207 (b=0.21, 95% CI: 0.02-0.41; P=0.03) than those under 25 years old; mothers with insufficient weight gain had a higher BDE-154 concentration (b=0.18, 95% CI: 0.01-0.35; P=0.04) and mothers with higher weight gain had a lower BDE-209 concentration (b=-0.16, 95% CI: -0.30﹣-0.01; P=0.03) than those with normal gestational weight gain; cord serum concentrations of BDE-153 (b=0.18, 95%CI: 0.01-0.34; P=0.04) and BDE-154 (b=0.23, 95%CI: 0.12-0.34; P=0.01) were significantly positively associated with annual household income; the mothers who lived in suburban areas had a higher BDE-100 concentration (b=0.19, 95% CI: 0.01-0.38; P=0.04) and the mothers who lived in urban areas had a higher BDE-153 concentration (b=0.21, 95% CI: 0.02-0.40; P=0.03) than those living in rural areas. Additionally, seasonal differences were also observed in the cord serum PBDEs concentrations. The cord serum BDE-28 (b=-1.45, 95% CI: -1.68﹣-1.23; P=0.01) and BDE-100 (b=-0.60, 95% CI: -0.76﹣-0.43; P=0.01) concentrations collected in summer and autumn were lower than those in winter, while the BDE-153 (b=1.65, 95% CI: 1.45-1.84; P=0.01), BDE-154 (b=0.40, 95% CI: 0.27-0.53; P=0.01) and BDE-209 (b=0.60, 95% CI: 0.45-0.75; P=0.01) concentrations presented opposite seasonal pattern.

The selected newborns are extensively exposed to various PBDEs, among which BDE-209 is the most dominant congener. Their cord serum PBDEs concentrations are associated with maternal socio-demographic characteristics and birth season.