Table 3

ORs* and 95% CIs for associations between the cumulative effects of ambient air pollutants over 0–3 days (per IQR increase) and emergency department visits for COVID-19

CharacteristicsPM2.5NO2O3
Age (in years)
 <651.016 (1.007–1.026)
I2=50.6% (<0.01)
1.024 (1.016–1.033)
I2=21.9% (0.15)
1.002 (0.996–1.009)
I2=16.1% (0.22)
 ≥651.012 (1.001–1.023)
I2=25.9% (0.11)
1.034 (1.018–1.050)
I2=46.7% (<0.01)
0.994 (0.989–1.000)
I2=23.8% (0.13)
 P value for effect modification0.72
I2=43.4% (<0.01)
0.99
I2=44.6% (<0.01)
0.52
I2=52.6% (<0.01)
Sex
 Male1.013 (1.003–1.022)
I2=37.7% (0.03)
1.037 (1.022–1.053)
I2=50.4% (0.01)
1.001 (0.994–1.009)
I2=56.9% (<0.01)
 Female1.017 (1.008–1.026)
I2=41.5% (0.01)
1.014 (1.006–1.023)
I2=87.1% (<0.01)
1.003 (0.996–1.009)
I2=54.2% (<0.01)
 P value for effect modification0.49
I2=41.4% (<0.01)
0.34
I2=41.4% (<0.01)
0.51
I2=41.4% (<0.01)
COVID-19 case status
 Confirmed1.012 (1.004–1.021)
I2=47.2% (<0.01)
1.028 (1.021–1.036)
29.1% (0.08)
1.000 (0.994–1.006)
70.5% (<0.01)
 Suspected1.010 (1.000–1.021)
I2=0.0% (0.68)
0.985 (0.969–1.000)
0.0% (0.52)
1.009 (1.005–1.013)
30.4% (0.07)
 P value for effect modification0.84
I2=41.9% (<0.01)
0.27
I2=30.6% (0.02)
0.31
I2=60.3% (<0.01)
Pneumonia status
 Yes0.995 (0.978–1.013)
I2=43.8% (<0.01)
1.017 (1.001–1.033)
I2=33.8% (0.05)
0.998 (0.991–1.004)
I2=20.4% (0.18)
 No1.015 (1.011–1.019)
I2=32.1% (0.06)
1.029 (1.021–1.037)
I2=34.1% (0.04)
1.001 (0.995–1.008)
I2=65.2% (<0.01)
 P value for effect modification0.64
I2=43.1% (<0.01)
0.84
I2=37.3% (0.01)
0.41
I2=50.0% (<0.01)
Hospital
 Yes1.023 (1.015–1.031)
I2=44.2% (0.01)
1.020 (1.008–1.032)
I2=41.5% (0.02)
1.005 (0.998–1.011)
I2=64.1% (<0.01)
 No0.992 (0.980–1.004)
I2=37.5% (0.03)
1.027 (1.020–1.034)
I2=21.3% (0.16)
0.993 (0.988–0.998)
I2=34.7% (0.04)
 P value for effect modification0.04
I2=47.7% (<0.01)
0.84
I2=41.4% (0.00)
0.01
I2=52.7% (<0.01)
  • I2: The variance due to heterogeneity estimated by the I²-statistic for the strata models and the models when calculating the p value for effect modification. In parentheses, the p values for the statistical significance of heterogeneity are reported.

  • Models represent pooled health region-specific estimates derived using two-stage random effects meta-analysis and meta-regression.

  • ORs reflect a 6.2 µg/m3 change in PM2.5, a 7.7 ppb change in NO2 and a 10.8 ppb change in O3

  • *Models represent pooled health region-specific estimates derived using two-stage random effects meta-analysis and meta-regression. ORs reflect a 6.2 µg/m3 change in PM2.5, a 7.7 ppb change in NO2 and a 10.8 ppb change in O3. Models adjusted for daily mean ambient temperature, relative humidity, the effective reproduction number, the OxCGRT Government Response Index and population density and percentage of the population self-identified as Black as meta-predictors.

  • NO2, nitrogen dioxide; O3, ozone; OxCGRT, Oxford COVID-19 Government Response Tracker; PM2.5, particulate matter with diameter less than 2.5 μm.