Table 4.
Associations Between Prenatal Exposure to Air Pollution and Asthma Incidence in the Nationwide Cohort in Single- and Two-Pollutant Models of 1,060,154 Children Born in Denmark, 1998–2016 a
| Pollutant | Single-Pollutant Models | Two-Pollutant Models | |||
|---|---|---|---|---|---|
| Copollutant Adjusted for PM2.5 | PM2.5 Mutually Adjusted | Copollutant Adjusted for NO2 | NO2 Mutually Adjusted | ||
| HR (95% CI) | HR (95% CI) | HR (95% CI) | HR (95% CI) | HR (95% CI) | |
| PM2.5 | 1.06 (1.04–1.08) | – | – | 1.05 (1.03–1.08) | 1.01 (0.99–1.03) |
| PM10 | 1.05 (1.04–1.06) | 1.04 (1.01–1.07) | 1.01 (0.98–1.05) | 1.06 (1.04–1.09) | 0.99 (0.96–1.01) |
| NO2 | 1.04 (1.02–1.05) | 1.01 (0.99–1.03) | 1.05 (1.03–1.08) | – | – |
| NOx | 1.01 (1.01–1.02) | 1.00 (0.99–1.01) | 1.06 (1.04–1.08) | 0.97 (0.95–1.00) | 1.09 (1.04–1.13) |
| EC | 1.03 (1.02–1.03) | 1.01 (1.00–1.02) | 1.05 (1.02–1.07) | 1.02 (1.01–1.03) | 1.01 (0.99–1.03) |
| OC | 1.08 (1.06–1.10) | 1.08 (1.06–1.10) | 1.01 (0.99–1.03) | 1.08 (1.06–1.09) | 1.01 (1.00–1.03) |
| SO2 | 1.02 (1.01–1.03) | 1.01 (1.00–1.02) | 1.05 (1.03–1.07) | 1.01 (1.00–1.03) | 1.03 (1.02–1.05) |
| O3 | 0.98 (0.96–0.99) | 1.00 (0.98–1.02) | 1.06 (1.04–1.08) | 1.01 (0.99–1.04) | 1.05 (1.02–1.07) |
| SO42- | 1.04 (1.01–1.08) | 0.94 (0.90–0.99) | 1.08 (1.05–1.10) | 1.03 (1.00–1.07) | 1.04 (1.02–1.05) |
| NO3- | 1.02 (1.00–1.03) | 0.97 (0.95–0.99) | 1.09 (1.06–1.11) | 1.01 (1.00–1.03) | 1.04 (1.02–1.05) |
| NH4+ | 1.01 (0.99–1.03) | 0.92 (0.89–0.95) | 1.11 (1.08–1.13) | 1.00 (0.98–1.03) | 1.04 (1.02–1.05) |
| SOA | 1.02 (1.01–1.04) | 1.01 (1.00–1.03) | 1.05 (1.04–1.07) | 1.02 (1.01–1.04) | 1.04 (1.02–1.05) |
| Sea salt | 0.99 (0.97–1.00) | 1.01 (0.99–1.02) | 1.06 (1.04–1.08) | 0.99 (0.98–1.01) | 1.04 (1.02–1.05) |
a Hazard ratios (HR) and the 95% CIs from Cox regression models per fixed increments of the interquartile range (μg/m3) of the time-weighted average exposures to ambient air pollutants for the full prenatal period of 2.4 for PM2.5, 2.7 for PM10, 8.7 for NO2, 13.4 for NOx, 0.3 for EC, 0.5 for OC, 2.7 for SO2, 8.5 for O3, 0.9 for SO42-, 0.6 for NO4-, 0.4 for NH4+, 0.1 for SOA, and 0.2 for sea salt with age as the time dimension adjusted for birth year, sex, household income, maternal education, parity, season of birth, smoking during pregnancy and municipality.
The total number of children is 1,060,154 and the number of asthma cases is 65,143.