The effect of ambient air pollution on exhaled nitric oxide in the Children's Health Study.

We assessed the effect of daily variations in ambient air pollutants on exhaled nitric oxide fraction (F(eNO)) using data from a cohort of school children with large differences in air pollutant exposures from the Children's Health Study. Based on a cohort of 2,240 school children from 13 Southern Californian communities, cumulative lagged average regression models were fitted to determine the association between F(eNO) and ambient air pollution levels from central site monitors with lags of up to 30 days prior to F(eNO) testing. Daily 24-h cumulative lagged averages of particles with a 50% cut-off aerodynamic diameter of 2.5 µm (PM₂.₅; over 1-8 days) and particles with a 50% cut-off aerodynamic diameter of 10 µm (PM₁₀; over 1-7 days), as well as 10:00-18:00 h cumulative lagged average of O₃ (over 1-23 days) were significantly associated with 17.42% (p<0.01), 9.25% (p<0.05) and 14.25% (p<0.01) higher F(eNO) levels over the interquartile range of 7.5 μg·m⁻³, 12.97 μg·m⁻³ and 15.42 ppb, respectively. The effects of PM₂.₅, PM₁₀ and O₃ were higher in the warm season. The particulate matter effects were robust to adjustments for effects of O₃ and temperature and did not vary by asthma or allergy status. In summary, short-term increases in PM₂.₅, PM₁₀ and O₃ were associated with airway inflammation independent of asthma and allergy status, with PM₁₀ effects significantly higher in the warm season.