Energy use and air pollution have been synonymous in China for decades, especially in urban areas.【66】Fifteen or 20 years ago in China's northern cities, such as Shenyang, air pollution was characterized by decreased visibility caused by high levels of particulates and sulfur dioxide (SO2). Although conditions have improved in modern cities, such as Beijing and Shanghai, China still has three of the ten most polluted cities in the world and hundreds of cities that are not in compliance with the World Health Organization (WHO) air quality guidelines. 【67】More than 120 cities have populations of more than one million, and by the end of the twenty-first century, 10 to 20 cities will have populations of more than 10 million. Rapid urbanization will challenge governments at all levels, not only to provide basic services to growing urban populations, but also to modernize, to continue to develop economically, and to address environmental concerns, particularly air pollution, that result from rapid economic growth. Chinese planners now recognize that the choice of energy supply affects not only public health, but also land use, the environment, infrastructure, services, and economic growth.【68】Because China has an overabundance of coal and a scarcity of oil and gas, planners must continually balance the public good (i. e. , public health and quality of life) against the easy availability of polluting coal and the high cost of importing oil and natural gas. Fundamentally, the Chinese policy community must address ambient air quality concerns by integrating energy supply and use for all economic sectors--industrial, power generation, residential, commercial, and transportation. 【69】The national averages for emissions of SO2 and particulate matter (PM) have decreased, mostly as a result of stepped up enforcement of existing standards by national, provincial, and municipal governments. However, because of the increase in vehicle pollution and the continued prevalence of fine-particle pollution, the government passed a second amendment in 2000 to the 1987 Law of Air Pollution Prevention and Control.【70】When the new law is fully implemented over the next decade, it will greatly strengthen environmental laws and standards.