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

Further evaluation of the impact of long-term exposure to the gaseous air pollutants nitrogen dioxide (NO) and ozone (O) on child lung function and of NO or O on eosinophilic airway inflammation is needed. To determine whether NO and O are associated with lung function and fractional exhaled nitric oxide (Fe) in children. We measured lung function (forced expiratory volume in 1 second [FEV] and forced vital capacity [FVC]) at midchildhood (mean age, 7.9 yr;  = 703), early teens (13.2 yr;  = 976), and midteens (17.6 yr;  = 624) study visits, and Fe at the early and midteens study visits in Project Viva, a cohort of mother-child pairs in the Boston area. Long-term exposure to NO and O was estimated at the home address using geospatial models. We examined associations of home address NO and O exposure and proximity to roadway with lung function and Fe 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. Median exposure to NO was 33.1 ppb (interquartile range [IQR], 10.4 ppb) and to O was 35.3 ppb (IQR, 3.4) in the first year of life. Exposure to NO was associated with lower FEV and FVC across all age groups and exposure time intervals: For example, an IQR increment of NO exposure from birth through the early teen visit was associated with 189.9 ml lower FEV (95% confidence interval, -273.3, -106.5) at the midteen visit. Lifetime NO exposure at was associated with higher Fe at the early teen visit: for example, 16.2% higher Fe (95% confidence interval, 7.1-26.4%) per IQR of lifetime NO through the early teen visit. O exposure was not associated with lung function or Fe. Aeroallergen sensitization (measured in a subset of participants) modified associations of NO and O with Fe. Exposure to NO was associated with lower lung function and higher Fe among generally healthy children and teenagers. Because NO 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.