Prenatal nitrate air pollution exposure and reduced child lung function: Timing and fetal sex effects

Background: Prenatal particulate air pollution exposure may alter lung growth and development in utero in a time-sensitive and sex-specific manner, resulting in reduced lung function in childhood. Such relationships have not been examined for nitrate (NO₃^-). Methods: We implemented Bayesian distributed lag interaction models (BDLIMs) to identify sensitive prenatal windows for the influence of NO₃^- on lung function at age 7 years, assessing effect modification by fetal sex. Analyses included 191 mother-child dyads. Daily ambient NO₃^- exposure over pregnancy was estimated using a hybrid chemical transport (Geos-Chem)/land-use regression model. Spirometry was performed at mean (SD) age of 6.99 (0.89) years, with forced expiratory volume in one second (FEV₁) and forced vital capacity (FVC) z-scores accounting for child age, sex, height and race/ethnicity. Results: Most mothers were Hispanic (65%) or Black (22%), had ≤ high school education (67%), and never smoked (71%); 17% children had asthma. BDILMs adjusted for maternal age and education and child's asthma identified an early sensitive window of 6–12 weeks gestation, during which increased NO₃^- was significantly associated with reduced FEV₁ z-scores specifically among boys. BDLIM analyses demonstrated similar sex-specific patterns for FVC. Conclusion: Early gestational NO₃^- exposure is associated with reduced child lung function, especially in boys.