Background: Early-life exposure to traffic-related air pollution may decrease fetal growth and increase childhood obesity risk. Our objective was to evaluate the relationship of early-life exposure to traffic-related air pollution with birthweight in term newborns and obesity at age 7-8 years in two prospective birth cohorts in Cincinnati, OH (the Health Outcomes and Measures of the Environment (HOME) Study and Cincinnati Childhood Allergy and Air Pollution Study (CCAAPS)).
Methods: We estimated elemental carbon attributable to traffic (ECAT) exposure at residential addresses during pregnancy with a validated land use regression model. We assessed birthweight among term infants using birth records or parent report (HOME Study n= 333 and CCAAPS n=590). We measured children's weight and height at 7-8 years, and calculated age- and sex-specific BMI z-scores (HOME Study n= 198 and CCAAPS n=459). Using multivariable linear regression, we estimated the difference in term birthweight and BMI z-score per interquartile range (IQR) increase in ECAT concentrations in each cohort separately and in the pooled sample.
Results: In adjusted models, ECAT exposure was not associated with lower birthweight (pooled sample β: 30g; 95% CI: -6, 66), or with higher BMI z-score (pooled sample β: -0.04; 95% CI: -0.15, 0.08). Infant sex modified the association between ECAT and birthweight (p=0.05). Among male newborns, higher ECAT concentrations were associated with higher birthweight (β: 61g; 95% CI: 9, 113), but we observed no association among female newborns (β: -9g; 95% CI: -58, 41).
Conclusions: In contrast to some prior studies, early-life traffic-related air pollution exposure was not associated with lower birthweight or increased childhood adiposity in these two cohorts.