Fig. 3
The PM2.5 was explained by the principal air pollutants over China (2014), and graph a, b, c, and d represent SO2, CO, NO2, O3, respectively
Fig. 3 | BMC Public Health
The PM2.5 was explained by the principal air pollutants over China (2014), and graph a, b, c, and d represent SO2, CO, NO2, O3, respectively