Background: Prenatal and early life periods represent critical windows for oxidant pollutant-induced lung remodeling. The objective of this study was to examine the association of prenatal and lifetime exposures to air pollutants with pulmonary function in a cohort of children with asthma.

Methods: Prenatal and lifetime exposure to several air pollutants was reconstructed for 232 children with asthma from the San Joaquin Valley of California, USA. Prenatal and lifetime residences were geocoded. We obtained data on monthly average ozone (O₃), carbon monoxide (CO), nitrogen dioxide (NO₂), and particulate matter with a median aerodynamic diameter <10 μm (PM₁₀) concentrations. Metrics were created for key developmental periods. Predictive models were developed for 8 pulmonary function measures. A newly-developed stepwise model selection procedure-the Deletion/Substitution/Addition algorithm-was implemented and results were compared with those obtained using traditional stepwise methods.

Results: Second-trimester exposure to NO₂ negatively affected forced vital capacity (FVC) and forced expiratory volume in 1 second (FEV₁), and first trimester exposure to PM₁₀ negatively affected peak expiratory flow (PEF) rate. Exposure to CO in early years of life also had a negative effect on FEV₁/FVC and forced expiratory flow between 25% and 75% of FVC (FEF_25-75)/FVC. Second trimester exposure to PM₁₀ and exposure to CO in the first 6 years of life had negative effects on forced expiratory flow at 25% of FVC. Prenatal, but not trimester-specific, exposure to CO was negatively associated with FEF_25-75. Effects were limited to subgroups, such as children who were African American, those diagnosed with asthma before the age of 2 years, and those exposed to maternal smoking during pregnancy.

Conclusion: Prenatal and early-life exposures to CO, PM₁₀, and NO₂ have a negative effect on pulmonary function in subgroups of asthmatic children.