Associations between Typical Environmental Factors and the Risk of Fetal Neural Tube Defects in North China

Background: The relationship between the levels of various environmental chemicals and the high prevalence of neural tube defects (NTDs) in north China remains unclear. This study aimed to classify the associations of maternal exposure to polycyclic aromatic hydrocarbons (PAHs), passive smoking, and widely concerned trace metal elements with NTD risk. Methods: Our case-control study recruited a total of 828 subjects: 285 women who delivered a fetus with NTDs (cases) and 543 women a healthy newborn without NTDs (controls). We measured the concentrations of PAHs, nicotine/cotinine, and various trace metal elements in two hair sections grown near the early pregnancy. Findings: Overall, no significant associations were found between the risk of any NTD subtypes and the hair levels of PAHs, nicotine/cotinine, and some metals (i.e., Cd, Sb, Pb, Cr, Mn, Fe, Ni, Co, and Cu). According to the cross-validation results for the two hair sections, hair concentrations of Mo and Sn were inversely associated with anencephaly risk, and the hair concentration of Zn was inversely associated with the risk of spina bifida. Interpretation: We concluded that maternal exposure to either PAHs or passive smoking was not a significant risk factor for NTDs, whereas the maternal less intake of certain trace metal elements may contribute to the high NTD prevalence in north China. It suggested that much effort should be spent to improve the dietary quality of various essential trace metal elements to reduce NTD risk for population living in North China. Funding: This research was supported by grants from the National Key Research and Development Program, P.R. China (Grant No. 2016YFC1000501) and the National Natural Science Foundation of China (No. 41771527 and 81373014). Conflict of Interest: The authors declare they have no actual or potential competing financial interests. Ethics Approval Statement: The study protocol was approved by the Institutional Review Board of Peking University (PU-IRB) and the signed consent was obtained from all subjects.