In the 25 Chinese cities, and, the averaged concentrations of TSP during 1991e2000 and PM10 during 2001e2006 were 382 and 104 mg/m3, respectively (Table 2).
The annual concentrations declined 25% for TSP from 1991 to 2000, suggesting that particulate air pollution had been substantially improving in 1990s in China; however, the annual concentrations of PM10 did not change much during 2001e2006 (Fig. 2).
The correlation coefficient between TSP (1990e2000) and PM10 (2001e2006) was 0.45 (p < 0.01) (Fig. 3).