Correlations between concentrations of air pollution and exercise-induced asthma (EIA) in the sample of children who had a clinical examination during the same week as air quality assessments (n=4643)
| Air pollutant | n | Correlation coefficient* | p Value |
| NO2 | 4254 | 0.022 | 0.1555 |
| PM2.5 | 4051 | 0.061 | <0.001 |
| Formaldehyde | 4374 | −0.018 | 0.2257 |
| Acetaldehyde | 4374 | −0.025 | 0.0945 |
| Acrolein | 3551 | 0.038 | <0.0253 |
↵* When less than 10 children were examined by the doctor in a classroom during a week, the median value of the concentrations of pollutants measured during the same week and the mean prevalence of EIA in the entire school were taken.
NO2, nitrogen dioxide; PM2.5, fine particles with aerodynamic diameter ≤2.5 μm.