Figure 2
From: Meta-analysis of adverse health effects due to air pollution in Chinese populations
Air pollution concentration in Chinese cities. Only the annual mean concentrations of the latest publication for each city were shown to avoid over-representation. The years of the study period were indicated after the city names. Dotted lines for PM10 and NO2 were WHO annual Air Quality Guidelines [23]. Dotted lines for SO2 and O3 were annual limits derived from WHO short-term Air Quality Guidelines [24].