Haze pollution is not a local environmental issue. Both local emission and regional transport contribute to haze formation. Due to the East Asian monsoon, air pollutants can be transported far away and impact greatly on the air quality of those downstream areas (Hsu et al„ 2009). Along with the regional transport of air pollutants, haze pollution can be geographically extended even to those areas with few local pollution emissions (Zhao et al„ 2013c).