Practices and Empirical Insights from the National Research Program for Key Issues in Air Pollution in Beijing-Tianjin-Hebei and Surrounding Areas

1.Introduction The United States began implementing policies against air pollution in earnest starting in the early 1970s,taking several decades and an economic recession to achieve reductions in air pollution.In contrast,China has reduced its air pollution by the same amount in only seven years[1].Compared with foreign countries.