Health Impact of Outdoor Air Pollution in China: Current Knowledge and Future Research Needs

Guest Editorial Outdoor air pollution is one of China's most serious environmental problems. Coal is still the major source of energy, constituting about 75% of all energy sources. Consequently, air pollution in China predominantly consists of coal smoke, with suspended particulate matter (PM) and sulfur dioxide (SO 2) as the principal air pollutants. In large cities, however, with the rapid increase in the number of motor vehicles, air pollution has gradually changed from the conventional coal combustion type to the mixed coal combustion/motor vehicle emission type. Currently, inhalable particles (PM <10 µm in aero dynamic diameter; PM 10), SO 2 , and nitrogen dioxide (NO 2) are the criteria pollutants of concern in China. Generally, PM levels in cities in the north are higher than those in the south, whereas SO 2 and NO 2 levels do not differ much. In 2004, the annual average PM 10 concentrations for major Chinese cities were 102 µg/m 3 in southern cities, 140 µg/m 3 in northern cities, and 121 µg/m 3 in cities nationwide. The annual average concentrations of SO 2 and NO 2 nationwide were 66 µg/m 3 and 38 µg/m 3 , respectively (China State Environmental Protection Agency 2005). Although its ambient air quality has improved substantially, China is still facing the worst air pollution problem in the world. Outdoor air pollution has become a major concern for public health. The World Bank (2007) estimated that the total health cost associated with outdoor air pollution in urban areas of China in 2003 was between 157 and 520 billion Chinese yuan, accounting for 1.2–3.3% of China's gross domestic product. Health end points studied in China in association with air pollution include all-cause mortality, mortality and morbidity due to cardio pulmonary disease, and numbers of outpatient and emergency department visits (Chen et al. 2004). Changes in respiratory and other clinical symptoms, lung function, and immune function are also studied. Dozens of time-series studies have been conducted in large Chinese the association of short-term exposure to air pollution with mortality or morbidity (Chen et al. 2004). Mortality or morbidity risk estimates per unit increase in air pollution level among Chinese populations are generally similar in magnitude to risks estimated in other parts of the world. A recent multi city time-series analysis in Hong Kong, Shanghai, and Wuhan provided further evidence of short-term risks (Wong et al. 2008), with significant health effects detected at …