Assessment of haze-related human health risks for four Chinese cities during extreme haze in January 2013

To evaluate the human health risks (premature death risk as an indicator) in Beijing, Shanghai, Guangzhou and Xi'an during extreme haze in January 2013. The daily average particulate matter ≤ 2.5 µm in aerodynamic diameter (PM2.5) concentrations of Beijing, Shanghai, Guangzhou and Xi'an in January 2013 were collected and their characteristics explored. The populations and mortality rate of four cities in 2010 were collected from the statistical yearbook, the exposure-response relationships selected from the reference and then the premature death calculated according to the proportion risk model of Poisson regression. In January 2013, the 24 h mean concentrations of PM2.5 in Beijing, Shanghai, Guangzhou and Xi'an were (240 ± 165) , (83 ± 27), (94 ± 49) and (210 ± 98) µg/m(3) respectively and they were all above the secondary level of Ambient Air Quality Standards (GB 3095-2012). The 24 h mean concentrations of PM2.5 in Beijing and Xi'an were much higher than those in Shanghai and Guangzhou. Approximately 86.4%