Long-Term Exposure to Nitrogen Dioxide and Ozone and Respiratory Health in Children

Rationale: Further evaluation of the impact of long-term exposure to the gaseous air pollutants nitrogen dioxide (NO₂) and ozone (O₃) on child lung function and of NO₂ or O₃ on eosinophilic airway inflammation is needed. Objectives: To determine whether NO₂ and O₃ are associated with lung function and fractional exhaled nitric oxide (Fe_NO) in children. Methods: We measured lung function (forced expiratory volume in 1 second [FEV₁] and forced vital capacity [FVC]) at midchildhood (mean age, 7.9 yr; n = 703), early teens (13.2 yr; n = 976), and midteens (17.6 yr; n = 624) study visits, and Fe_NO at the early and midteens study visits in Project Viva, a cohort of mother-child pairs in the Boston area. Long-term exposure to NO₂ and O₃ was estimated at the home address using geospatial models. We examined associations of home address NO₂ and O₃ exposure and proximity to roadway with lung function and Fe_NO using linear regression models, adjusting for age, sex, height, weight, season, relative humidity, temperature, parental smoking, and measures of socioeconomic status. We examined for effect modification of the midteen associations by blood eosinophil concentration, physical activity, aeroallergen sensitization, and parental atopy. Results: Median exposure to NO₂ was 33.1 ppb (interquartile range [IQR], 10.4 ppb) and to O₃ was 35.3 ppb (IQR, 3.4) in the first year of life. Exposure to NO₂ was associated with lower FEV₁ and FVC across all age groups and exposure time intervals: For example, an IQR increment of NO₂ exposure from birth through the early teen visit was associated with 189.9 ml lower FEV₁ (95% confidence interval, -273.3, -106.5) at the midteen visit. Lifetime NO₂ exposure at was associated with higher Fe_NO at the early teen visit: for example, 16.2% higher Fe_NO (95% confidence interval, 7.1-26.4%) per IQR of lifetime NO₂ through the early teen visit. O₃ exposure was not associated with lung function or Fe_NO. Aeroallergen sensitization (measured in a subset of participants) modified associations of NO₂ and O₃ with Fe_NO. Conclusions: Exposure to NO₂ was associated with lower lung function and higher Fe_NO among generally healthy children and teenagers. Because NO₂ exposure levels were within the annual U.S. Environmental Protection Agency standard, these findings suggest a need to reduce exposure to this pollutant to optimize child respiratory health.