Exposure to polycyclic aromatic hydrocarbons during maternal pregnancy: Effects of DNA damage on neural tube defects in offspring.

Prenatal polycyclic aromatic hydrocarbon (PAH) exposure may contribute to neural tube defects (NTD), but combined effects and underlying mechanisms remain unclear. We conducted a matched case-control study (128 pairs) in six high-risk counties in Shanxi Province, China (2004-2016). At delivery or pregnancy termination, placenta samples were collected. Sixteen placental PAHs and 11 hydroxylated metabolites were quantified by GC-MS/MS as biomarkers of fetal intrauterine exposure, alongside 16 DNA adducts measured by UPLC-MS/MS. Complementary ICR mouse experiments with benzoapyrene (BaP, 100 mg/kg) validated mechanistic findings. Statistical analyses used conditional logistic regression, WQS and BKMR (for parent PAHs and hydroxylated metabolites, respectively), followed by mediation analysis. Results showed that increased fresh vegetable intake and kitchen-living separation significantly reduced placental PAH concentrations. A dose-dependent increase in NTD risk was observed across tertiles of measured placental PAHs. The highest versus lowest tertile was associated with increased NTD risk for total PAHs (OR=5.04, 95%CI:1.96-12.96), phenanthrene (OR=4.96, 95%CI:2.05-11.97), and low-molecular-weight PAHs (OR=4.47, 95%CI:1.87-10.67) after adjustment for confounders. In subtype analyses, higher phenanthrene, low-molecular-weight PAH and total PAH related to anencephaly, whereas benzobfluoranthene, indeno1,2,3-cdpyrene, and 9-hydroxyfluorene were associated with spina bifida. Mixture models confirmed significant joint effects of multiple PAHs. Mediation analyses showed 5-HmdC changes explained 10.7% (phenanthrene) and 12.4% (total PAHs) of NTD risk. In mice, BaP increased NTD incidence (5.7% vs. 1.8%), stillbirths (1.8% vs. 0%), and fetal resorptions (3.6% vs. 1.8%) versus controls. BaP-exposed groups showed reduced 5-HmdC in fetal tissues, consistent with human findings. This study provides evidence that individual and mixed PAH exposures are associated with an increased risk of NTD. DNA damage, particularly 5-HmdC alterations, may partially contribute to this association. These findings further support preventive strategies, including dietary and household environmental modifications.