Effect of moderate NO2 air pollution on the lung function of children with asthmatic symptoms

In the course of a 2 1/2-year longitudinal study, the influence of outdoor NO2 and of the heating device at home on lung function was investigated in 467 children of school age in the urban area of Freiburg. Data were gathered in three surveys using standardized interviews, lung function measurements, skin prick tests with inhalant allergens, and NO2 measurements from October to April near the child's home. Regarding the lung function of a subpopulation with asthmatic symptoms (n = 106) in the three consecutive surveys, multivariate regression analyses adjusted for confounders indicate negative associations between five dependent variables, FEV1%FVC (P = 0.004), FEV1% (P = 0.02), MEF75% (P = 0.038), MEF50% (P = 0.052), and MEF25% (P = 0.002), on the one hand, and outdoor NO2 for average NO2 concentrations exceeding 40 micrograms/m3 on the other. The use of individual room heaters is associated with decreased lung function and is significant only for FEV1%FVC (P = 0.033). Neither NO2 nor individual room heating is significantly associated with one of the lung function parameters in the subpopulation without asthmatic symptoms (n = 361). In conclusion, children with asthmatic symptoms are identified as being susceptible to having reduced lung function under outdoor air pollution where average NO2 concentrations exceed 40 micrograms/m3.