Table 1. Overall statistics of environmental factors in 100 Japanese cities, April 2012 to March 2015.
| Environmental factors, daily mean | Number of cities |
Mean (SD) | Percentile | ||
| 25th | 50th | 75th | |||
| PM2.5, µg/m3 | 100 | 14.6 (8.3) | 8.6 | 13.1 | 18.8 |
| Coarse PM, µg/m3 a | 77 | 6.4 (5.1) | 2.9 | 5.6 | 8.9 |
| Ox, ppbb | 95 | 42.3 (15.2) | 31.8 | 40.6 | 51.7 |
| NO2, ppb | 99 | 12.4 (6.1) | 7.9 | 11.2 | 15.7 |
| SO2, ppb | 91 | 2.1 (1.2) | 1.3 | 1.9 | 2.7 |
| Ambient temperature, °C | 100 | 15.7 (8.5) | 7.7 | 16.0 | 23.0 |
| Relative humidity, % | 100 | 67 (13) | 58 | 68 | 76 |
NO2, nitrogen dioxide; Ox, photochemical oxidants; PM, particulate matter; SD, standard deviation; SO2, sulphur dioxide.
aConcentrations of coarse PM were calculated by subtracting PM2.5 concentrations from those of suspended particulate matter.
bDaily maximum 8-h mean concentrations.