Table 1.
Season-stratified study-period distribution daily difference distribution for ambient NO2 and PM2.5 in three US cities, 2010 – 2012
| NO2 (ppb) | PM2.5 (μg/m3) | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Summer | Burbank (n=218 days) | Houston (n=265 days) | Pittsburgh (n=250 days) | Burbank (n=218 days) | Houston (n=265 days) | Pittsburgh (n=250 days) | |||||||
| SP | Diff. | SP | Diff. | SP | Diff. | SP | Diff. | SP | Diff. | SP | Diff. | ||
| 25th percentile | 14.4 | −3.5 | 8.4 | −1.9 | 6.2 | −1.8 | 16.3 | −2.3 | 9.6 | −2.2 | 9.5 | −3.5 | |
| Median | 19.8 | −0.6 | 10.5 | −0.4 | 8.9 | 0.3 | 19.1 | 0.5 | 11.7 | 0.0 | 12.9 | −0.1 | |
| 75th percentile | 25.3 | 3.4 | 13.1 | 2.3 | 11.9 | 2.5 | 22.8 | 2.9 | 15.6 | 2.3 | 17.3 | 3.0 | |
| IQR | 11.0 | 6.9 | 4.7 | 4.2 | 5.7 | 4.3 | 6.5 | 5.2 | 6.1 | 4.5 | 7.8 | 6.5 | |
| SP IQR: diff. IQR ratioa | 1.60 | 1.11 | 1.32 | 1.25 | 1.34 | 1.20 | |||||||
| Winter | Burbank (n=198 days) | Houston (n=265 days) | Pittsburgh (n=241 days) | Burbank (n=198 days) | Houston (n=265 days) | Pittsburgh (n=241 days) | |||||||
| SP | Diff. | SP | Diff. | SP | Diff. | SP | Diff. | SP | Diff. | SP | Diff. | ||
| 25th percentile | 20.5 | −5.3 | 12.0 | −5.1 | 9.2 | −4.2 | 11.5 | −4.5 | 8.4 | −2.8 | 7.0 | −3.8 | |
| Median | 26.9 | 0.6 | 16.5 | −0.1 | 13.8 | −0.3 | 15.8 | 0.6 | 10.9 | 0.1 | 10.7 | 0.2 | |
| 75th percentile | 32.7 | 4.6 | 20.5 | 4.8 | 19.0 | 4.0 | 22.0 | 4.5 | 13.4 | 2.8 | 15.0 | 3.6 | |
| IQR | 12.2 | 9.9 | 8.5 | 9.9 | 9.7 | 8.2 | 10.6 | 9.0 | 5.1 | 5.6 | 8.0 | 7.4 | |
| SP IQR: diff. IQR ratioa | 1.23 | 0.86 | 1.19 | 1.17 | 0.90 | 1.08 | |||||||
a
SP IQR: diff. IQR ratio expresses the ratio of the study period IQR to the daily difference IQR within each city-season
Abbreviations:
SP, Study period distribution; Diff., Daily difference distribution; IQR, interquartile range; NO2, nitrogen dioxide; PM2.5, particulate matter with aerodynamic diameter ≤2.5μm; ppb, parts per billion; μg/m3, micrograms per cubic meter