Associations between prenatal exposure to environmental phenols and child neurodevelopment at two years of age in a South African birth cohort

Objective: Evidence suggests that prenatal environmental phenol exposures negatively impact child neurodevelopment, however there is little research on the effects of mixtures of multiple phenol exposures. We analyzed associations between prenatal exposure to phenol mixtures and cognitive neurodevelopment at two years of age among 545 mother-child pairs from the South African Drakenstein Child Health Study. Material and methods: We measured maternal urine environmental phenol concentrations once during the second trimester of pregnancy. We used the Bayley Scales of Infant and Toddler Development III to assess cognitive development at two years of age. We used linear regression models adjusted for maternal HIV status, maternal age, ethnicity, prenatal tobacco exposure, child sex, and socioeconomic status (SES) to examine individual associations. We compared four mixture methods: self-organizing maps (SOM), Bayesian kernel machine regression (BKMR), quantile-based G-computation (qgcomp) and weighted quantile sum (WQS) regression to explore joint effects of the exposure mixture. We assessed effect modification by SES, sex, prenatal tobacco exposure, and ethnicity. Results: Across all methods, we found no association between individual phenol exposures or the joint exposure mixture with the cognitive score. Prenatal tobacco exposure modified the association between pentachlorophenol (PCP) and cognitive neurodevelopment (interaction p-value = 0.012), with higher PCP concentrations associated with lower cognitive scores among non-smokers (beta = − 2.17; 95% CI: −3.83, −0.51). Sex modified the association between bisphenol A (BPA) and cognitive neurodevelopment (interaction p-value = 0.021), with males having a significant adverse association (beta = −1.39; 95% CI: −2.54, −0.23). SES modified the association between bisphenol S (BPS) and cognitive neurodevelopment (interaction p-value = 0.003), with individuals of moderate-high SES having a significant adverse association (beta = −1.84; 95% CI: −3.26, 0.06) Conclusion: While we found no main effects of prenatal phenol exposure on cognitive neurodevelopment, the associations with PCP, BPA, and BPS were more pronounced among certain subgroups.