Prenatal exposure to organochlorine pesticides and early childhood neurodevelopment: A prospective birth cohort study

Organochlorine pesticides (OCPs), banned decades ago due to their environmental persistence and toxicity, countinue to be detected as residual DDTs and HCHs in human populations. Previous studies suggest that prenatal exposure to OCPs may impair neurodevelopment in offspring, but the evidence remains inconsistent, especially regarding specific isomers, such as α-HCH and γ-HCH, which have rarely assessed in humans. This study investigated the association between prenatal OCP exposure and early childhood neurodevelopment, and explored the potential sex-specific effects. We measured HCH isomers (α-HCH, β-HCH, γ-HCH), DDT isomers (p,p'-DDT, o,p'-DDT), and DDT metabolites (o,p'-DDD, o,p'-DDE, p,p'-DDD, p,p'-DDE) in cord serum from 447 mother-child pairs in a birth cohort study in Wuhan, China (2014-2015). Neurodevelopment was assessed at age 2 with the Bayley Scales of Infant Development, which generated mental development index (MDI) and psychomotor development index (PDI) scores. Associations were evaluated using linear regression and weighted quantile sum (WQS) regression, with analyses stratified by sex. Most OCPs were detectable in over 50 % of samples, with median concentrations of 39.5 ng/g lipid for ∑DDTs and 10.8 ng/g lipid for ∑HCHs. Higher cord serum OCP concentrations were associated with lower MDI scores. An interquartile range (IQR) increase in γ-HCH was linked to a 2.45-point decrease in MDI (95 % CI: -4.76, -0.14) in all children, although this association did not remain significant after FDR correction. In girls, inverse associations were observed for α-HCH (-4.54 points; 95 % CI: -7.55, -1.53), γ-HCH (-5.20 points; 95 % CI: -8.04, -2.36), and p,p'-DDD (-5.25 points; 95 % CI: -9.97, -0.53). In mixture analyses, each quartile increase in OCP mixture was associated with a 6.10-point decrease in MDI and a 6.46-point decrease in PDI in girls, with γ-HCH (51.2 %) and p,p'-DDT (35.6 %) identified as the largest contributors. The results indicate that prenatal exposure to certain OCPs, particularly γ-HCH and p,p'-DDT, is associated with poorer neurodevelopment in early childhood, especially in girls. The findings highlight the need to address persistent OCP exposure and its developmental impacts.