title: Characterizing multi-pollutant air pollution in China: Comparison of three air quality indices.
abstract: Multi-pollutant air pollution (i.e., several pollutants reaching very high concentrations simultaneously) frequently occurs in many regions across China. Air quality index (AQI) is used worldwide to inform the public about levels of air pollution and associated health risks. The current AQI approach used in China is based on the maximum value of individual pollutants, and does not consider the combined health effects of exposure to multiple pollutants. In this study, two novel alternative indices--aggregate air quality index (AAQI) and health-risk based air quality index (HAQI)--were calculated based on data collected in six megacities of China (Beijing, Shanghai, Guangzhou, Shjiazhuang, Xi'an, and Wuhan) during 2013 to 2014. Both AAQI and HAQI take into account the combined health effects of various pollutants, and the HAQI considers the exposure (or concentration)-response relationships of pollutants. AAQI and HAQI were compared to AQI to examine the effectiveness of the current AQI in characterizing multi-pollutant air pollution in China. The AAQI and HAQI values are higher than the AQI on days when two or more pollutants simultaneously exceed the Chinese Ambient Air Quality Standards (CAAQS) 24-hour Grade II standards. The results of the comparison of the classification of risk categories based on the three indices indicate that the current AQI approach underestimates the severity of health risk associated with exposure to multi-pollutant air pollution. For the AQI-based risk category of 'unhealthy', 96% and 80% of the days would be 'very unhealthy' or 'hazardous' if based on AAQI and HAQI, respectively; and for the AQI-based risk category of 'very unhealthy', 67% and 75% of the days would be 'hazardous' if based on AAQI and HAQI, respectively. The results suggest that the general public, especially sensitive population groups such as children and the elderly, should take more stringent actions than those currently suggested based on the AQI approach during high air pollution events. Sensitivity studies were conducted to examine the assumptions used in the AAQI and HAQI approaches. Results show that AAQI is sensitive to the choice of pollutant irrelevant constant. HAQI is sensitive to the choice of both threshold values and pollutants included in total risk calculation.
authors.affiliation: Jiangsu Key Laboratory of Atmospheric Environment Monitoring and Pollution Control, Jiangsu Engineering Technology Research Center of Environmental Cleaning Materials, Collaborative Innovation Center of Atmospheric Environment and Equipment Technology, School of Environmental Science and Engineering, Nanjing University of Information Science & Technology, 219 Ningliu Road, Nanjing 210044, China.
authors.forename: Jianlin
authors.initials: J
authors.lastname: Hu
authors.affiliation: Zachry Department of Civil Engineering, Texas A&M University, College Station, TX 77843, USA.
authors.forename: Qi
authors.initials: Q
authors.lastname: Ying
authors.affiliation: Environmental Resources Management (ERM), Walnut Creek, CA 94597, USA.
authors.forename: Yungang
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Department of Civil and Environmental Engineering, Louisiana State University, Baton Rouge, LA 70803, USA. Electronic address: hlzhang@lsu.edu.
authors.forename: Hongliang
authors.initials: H
authors.lastname: Zhang
mesh_terms: D000368:Aged; D000388:Air / Q000032:analysis / Q000592:standards; D000393:Air Pollutants / Q000032:analysis*; D000397:Air Pollution / Q000032:analysis* / Q000706:statistics & numerical data; D002648:Child; D002681:China; D002947:Cities; D005260:Female; D015386:Hazardous Substances / Q000032:analysis*; D006305:Health Status Indicators; D006801:Humans; D010316:Particle Size; D052638:Particulate Matter / Q000032:analysis*; D012306:Risk
chemical_list: D000393:Air Pollutants; D015386:Hazardous Substances; D052638:Particulate Matter
keywords: Air quality index; China; Health risk; Multi-pollutant air pollution; PM(2.5)