Table 3.
Risk ratios, 95% confidence intervals and chi-square values for associations between lag 1 air pollution metrics and respiratory emergency department visits
| Pollutant | N | Metric | IQR a | RR (95% CI) per IQR | Standard unit | RR (95% CI) per std unit | Χ2 | P value |
|---|---|---|---|---|---|---|---|---|
| CO (ppm) | 3486 | 1-hr maximum | 1.40 | 1.014 (1.009, .1.019) | 0.5 | 1.005 (1.003, 1.007) | 30.6 | <0.001 |
| 24-hr average | 0.45 | 1.015 (1.010, 1.019) | 0.5 | 1.016 (1.011, 1.021) | 39.4 | <0.001 | ||
| Commute (7–10am, 4–7pm) | 0.43 | 1.007 (1.003, 1.011) | 0.5 | 1.008 (1.003, 1.013) | 10.6 | 0.001 | ||
| Day-time (8am–7pm) | 0.30 | 1.004 (0.999, 1.008) | 0.5 | 1.006 (0.998, 1.014) | 2.0 | 0.156 | ||
| Night-time (12am–6am) | 0.62 | 1.011 (1.008, 1.015) | 0.5 | 1.009 (1.007, 1.012) | 46.8 | <0.001 | ||
| NO2 (ppb) | 3635 | 1-hr maximum | 23.0 | 1.011 (1.006, 1.016) | 10 | 1.005 (1.003, 1.007) | 22.1 | <0.001 |
| 24-hr average | 13.3 | 1.012 (1.007, 1.017) | 10 | 1.009 (1.005, 1.013) | 21.8 | <0.001 | ||
| Commute (7–10am, 4–7pm) | 13.8 | 1.008 (1.003, 1.013) | 10 | 1.006 (1.002, 1.010) | 11.1 | 0.001 | ||
| Day-time (8am–7pm) | 11.5 | 1.003 (0.998, 1.008) | 10 | 1.002 (0.998, 1.007) | 1.2 | 0.282 | ||
| Night-time (12am–6am) | 22.2 | 1.016 (1.011, 1.021) | 10 | 1.007 (1.005, 1.009) | 42.4 | <0.001 | ||
| O3 (ppb) | 2883 | 8-hr maximum | 28.9 | 1.020 (1.012, 1.028) | 25 | 1.017 (1.010, 1.024) | 23.9 | <0.001 |
| 1-hr maximum | 31.0 | 1.018 (1.010, 1.025) | 25 | 1.014 (1.008, 1.020) | 22.7 | <0.001 | ||
| 24-hr average | 16.2 | 1.007 (0.999, 1.015) | 25 | 1.011 (0.999, 1.024) | 3.4 | 0.067 | ||
| Commute (7–10am, 4–7pm) | 21.3 | 1.006 (0.998, 1.015) | 25 | 1.007 (0.998, 1.017) | 2.2 | 0.139 | ||
| Day-time (8am–7pm) | 26.7 | 1.018 (1.010, 1.026) | 25 | 1.017 (1.009, 1.025) | 18.3 | <0.001 | ||
| Night-time (12am–6am) | 19.0 | 0.991 (0.985, 0.997) | 25 | 0.988 (0.980, 0.996) | 8.6 | 0.003 | ||
| PM2.5 (μg/m3) | 1660 | 1-hr maximum | 17.4 | 1.004 (0.999, 1.009) | 10 | 1.002 (1.000, 1.005) | 2.9 | 0.089 |
| 24-hr average | 10.9 | 1.004 (0.998, 1.010) | 10 | 1.004 (0.998, 1.010) | 1.9 | 0.171 | ||
| Commute (7–10am, 4–7pm) | 11.5 | 1.005 (0.999, 1.011) | 10 | 1.004 (0.999, 1.009) | 2.5 | 0.113 | ||
| Day-time (8am–7pm) | 10.8 | 1.003 (0.997, 1.009) | 10 | 1.003 (0.997, 1.008) | 0.8 | 0.380 | ||
| Night-time (12am–6am) | 13.6 | 1.004 (0.999, 1.010) | 10 | 1.003 (0.999, 1.007) | 2.3 | 0.133 | ||
a
IQR=interquartile range of pollutant metric