Risk (OR† (95% CI)) of asthma, bronchial hyper-reactivity (BHR) and both conditions by quartile (relative to first quartile) for NO, NO2 and PM2.5
| Asthma | BHR (PC20 ≤2) | Asthma and BHR | |
| NO | |||
| ≤27.7 | 1 | 1 | 1 |
| 27.7–32.4 | 0.8 (0.2 to 3.3) | 1.0 (0.4 to 2.4) | 2.1 (0.3 to 15.1) |
| 32.4–40.3 | 1.4 (0.4 to 5.2) | 1.1 (0.5 to 2.6) | 1.8 (0.2 to 12.8) |
| >40.3 | 1.8 (0.5 to 6.1) | 1.0 (0.4 to 2.2) | 3.3 (0.5 to 20.5) |
| NO2 | |||
| ≤28.4 | 1 | 1 | 1 |
| 28.4–32.2 | 1.9 (0.3 to 5.7) | 0.8 (0.3 to 2.0) | 0.9 (0.1 to 7.7) |
| 32.2–35.6 | 3.4 (0.8 to 14.0) | 0.8 (0.3 to 1.9) | 2.3 (0.4 to 15.1) |
| >35.6 | 2.1 (0.5 to 8.4) | 0.7 (0.3 to 1.7) | 3.1 (0.5 to 19.3) |
| PM2.5* | |||
| ≤3.70 | 1 | 1 | 1 |
| 3.70–5.11 | 2.3 (0.4 to 13.4) | 0.7 (0.3 to 1.7) | – |
| 5.11–7.79 | 3.4 (0.6 to 18.7) | 1.5 (0.6 to 3.5) | 4.9 (0.8 to 29.5) |
| >7.79 | 7.0 (1.4 to 36.0) | 1.4 (0.6 to 3.5) | 11.7 (2.1 to 65.5) |
NO, nitric oxide; NO2, nitrogen dioxide; PM2.5, particulate matter of mean aerodynamic diameter ≤2.5 μm.
↵* Analysis performed based on lnPM2.5 given skewed distribution of PM2.5; equivalent quartiles presented here.
↵† ORs adjusted for intervention group, atopy at 12 months, ethnicity, gender, mother, father or sibling history of asthma, and maternal post-secondary education.