| Subgroup | PM2.5 μg/m3 | PM2.5 μg/m3 (FRMa) | ||||||||||||
| Mean | SD | Min | 5% | 95% | Max | N | Mean | SD | Min | 5% | 95% | Max | N | |
| Total | 10.9 | 5.0 | 0.0 | 3.6 | 19.7 | 88.0 | 1892 | 11.8 | 4.8 | 0.0 | 5.1 | 20.3 | 88.0 | 1580 |
| NWb | 7.4 | 4.6 | 0.3 | 2.1 | 16.5 | 50.5 | 201 | 8.8 | 5.0 | 0.8 | 3.7 | 19.3 | 50.5 | 134 |
| SWc | 9.8 | 6.9 | 0.0 | 2.2 | 23.8 | 69.5 | 224 | 11.3 | 6.9 | 0.0 | 4.3 | 25.5 | 69.5 | 165 |
| NCd | 8.0 | 4.2 | 0.3 | 2.2 | 14.9 | 88.0 | 198 | 8.8 | 4.0 | 1.2 | 4.0 | 15.4 | 88.0 | 161 |
| SCe | 10.0 | 3.9 | 0.5 | 3.8 | 16.5 | 82.5 | 353 | 10.6 | 3.7 | 0.7 | 5.0 | 17.0 | 82.5 | 280 |
| NEf | 12.7 | 4.4 | 1.6 | 6.3 | 20.7 | 68.4 | 621 | 13.0 | 4.3 | 1.6 | 6.8 | 20.8 | 68.4 | 577 |
| SEg | 12.4 | 4.1 | 1.8 | 6.8 | 20.0 | 48.0 | 295 | 12.6 | 4.1 | 2.5 | 7.1 | 20.2 | 48.0 | 263 |
| Mar-May | 9.8 | 4.1 | 0.0 | 3.6 | 16.7 | 48.0 | 1832 | 10.5 | 3.8 | 0.0 | 4.7 | 17.0 | 48.0 | 1535 |
| Jun-Aug | 12.3 | 5.5 | 0.0 | 4.4 | 21.8 | 88.0 | 1829 | 13.2 | 5.3 | 0.0 | 5.4 | 22.1 | 88.0 | 1524 |
| Sep-Nov | 10.5 | 4.8 | 0.0 | 3.6 | 18.7 | 82.5 | 1848 | 11.3 | 4.7 | 0.0 | 5.1 | 19.2 | 82.5 | 1543 |
| Dec-Feb | 11.1 | 5.3 | 0.0 | 2.4 | 19.8 | 65.3 | 1866 | 12.1 | 4.8 | 0.0 | 5.7 | 20.4 | 65.3 | 1562 |