Since the 1980s, a number of studies examining the relationship between ambient air pollution and health effects in China have been conducted. It is important to remember that although the studies measured only ambient air pollution levels, in reality people are exposed to a combination of indoor and outdoor air. One of most definitive of these studies examined the relationship between air pollution and mortality in two residential areas of Beijing. According to this study, the risk of mortality was estimated to increase by 11 percent with each doubling of SO2 concentration, and by 4 percent with each doubling of TSP. When the specific causes of mortality were examined, mortality from COPD increased 38 percent with a doubling of particulate levels and 29 percent with doubling of SO2. Pulmonary heart disease mortality also increased significantly with higher pollution levels. Levels of air pollution measured often exceeded WHO guidelines, particularly in winter when ambient air pollution was exacerbated by indoor fuel burning and climatic conditions. Yet, what was striking is that excess mortality was associated with pollutant levels below WHO guidelines, suggesting that the guidelines cannot be perceived as a safe limit .
Respiratory diseases, hospitalization, or doctor visits are often a more sensitive measure of the impact of air pollution on human health than mortality. One recent study confirmed that as concentrations of SO2 and TSP rose in Beijing, so did visits to the emergency room. This increase in unscheduled hospital visits occurred both when air pollution levels were extremely high (primarily in the winter) and when the levels were below WHO’s recommended guidelines, bolstering studies in developed countries that have shown excess respiratory disease and mortality at lower doses . Although Beijing has been the focus of many studies, it has no monopoly on bad air. Chongqing, the largest and most recently declared autonomous zone, has a higher concentration of SO2 than any of China’s five other largest cities . A recent study found that several symptoms of compromised health, including reduced pulmonary function and increased mortality, hospital admissions, and emergency room visits, were correlated with higher levels of air pollution in Chongqing . A study conducted in another of China’s largest cities, Shenyang, estimated total mortality increased by 2 percent with each 100 micrograms per cubic meter increase in SO2 concentration, and by 1 percent for each 100 micrograms per cubic meter in TSP .
Respiratory diseases are not the only health impacts of concern associated with air pollution. Lead exposure, for instance, leads to neurological damage, particularly in children. China has no comprehensive national data on blood-lead levels, a reliable biomarker of exposure, but some studies show that blood-lead levels are far above the threshold associated with impaired intelligence, neurobehavioral development, and physical growth. (The U.S. standard is 10 micrograms per deciliter.) Between 65 and 100 percent of children in Shanghai have blood-lead levels greater than 10 micrograms per deciliter. Those in industrialized or congested areas had levels averaging between 21 and 67 deciliters . In Shanghai, prenatal exposures to lead from urban air were associated with adverse development in the children during their first year of life .
References and notes
44. Xu Xiping et al., “Air Pollution and Daily Mortality in Residential Areas of Beijing, China,” Archives of Environmental Health, Vol. 49, No. 4 (1994), pp. 216<196>222.
45. Xu Xiping, Li Bauluo, and Huang Huying, “Air Pollution and Unscheduled Hospital Outpatient and Emergency Room Visits,” Archives of Environmental Health, Vol. 103, No. 3 (1995), pp. 286<196>289.
46. China Environment Yearbook, China Environment Yearbook, 1996 (China Environment Yearbook Press, Beijing, 1997), p. 193 (Chinese language edition).
47. Op. cit. 12, p. 18.
48. Xu Zhaoyi et al., “The Effect of Air Pollution on Mortality in Shenyang City,” Journal of Public Health in China, Vol. 15, No. 1 (1996), p. 61.
49. Op. cit. 12, p. 20.
50. Shen Xiao-Ming et al., “Prenatal Low-Level Lead Exposure and Infant Development in the First Year: A Prospective Study in Shanghai, China,” paper presented to the International Society for Environmental Epidemiology, University of Alberta, Edmunton, Canada, August 1996.