Table 3.
Number and percent of days fulfilling Condition 1 and Condition 2 a across each city-season, with the index pollutant as NO2 and PM2.5 separately
| Index pollutant: NO2 | Index pollutant: PM2.5 | ||||||
|---|---|---|---|---|---|---|---|
| Burbank No. (%) | Houston No. (%) | Pittsburgh No. (%) | Burbank No. (%) | Houston No. (%) | Pittsburgh No. (%) | ||
| Summer | Condition 1 | 10 (4.6) | 47 (17.7) | 17 (6.8) | 26 (11.9) | 46 (17.4) | 39 (15.6) |
| Condition 2 | 2 (0.9) | 17 (6.4) | 1 (0.4) | 8 (3.7) | 17 (6.4) | 14 (5.6) | |
| Winter | Condition 1 | 21 (10.6) | 63 (23.8) | 37 (15.4) | 32 (16.2) | 68 (25.7) | 30 (12.4) |
| Condition 2 | 5 (2.5) | 16 (6.0) | 4 (1.7) | 9 (4.5) | 13 (4.9) | 2 (0.8) | |
a
Condition 1 stipulates that the absolute value-daily differences of the index pollutant exceed the study period-IQR; Condition 2 requires Condition 1 as well as stipulating that the absolute value of the co-pollutant’s daily difference is in the lower tertile of daily difference absolute values (when NO2 is the index pollutant, PM2.5 is the co-pollutant and vice versa).
Abbreviations:
NO2, nitrogen dioxide; PM2.5, particulate matter with aerodynamic diameter ≤2.5μm