The concentration of air pollutants was very similar among the prefectures with mean values ranging 22.2 μg/m3 to 24.5 μg/m3 for SPM. The mean daily average temperature ranged from 13.6 °C to 16.4 °C, while the mean relative humidity (RH) ranged from 65.3% to
74.4%, reflecting the humid subtropical climate of the Kanto area.