The distribution of one day lag ambient air pollutants in the 44 schools during the study period was presented in Fig. 2. The fluctuation of levels of pollutants was smaller in the three-month mean than in the single-day mean. For sub chronic exposure, the level of air pollution was highest in the southern part of Taiwan, followed by the middle and northern parts, and lowest in the eastern part. The means, standard deviations, minimum and maximum values, and IQRs of the concentration of each air pollutant were shown in Table2. Both with in and between districts correlation coefficients of air pollutants revealed that PM2.5 was highly associated with PM10, but the correlation with PM2.5–10 has been weaker. Besides, NO2 was significantly associated with CO (Table3). Furthermore, there was significant with in district correlation between PM2.5 and CO, yet the between district correlation was trivial.