Air pollution is considered the world’s current single greatest environmental hazard, responsible for one in eight premature deaths globally according to the World Health Organization (WHO). Descriptions are given in this chapter of the major sources of outdoor ambient air pollution, followed by the prevalence of air pollution in the U.S., EU, China, and India. Attention is paid to the problem of unhealthy indoor air quality in many Asian countries. Data are provided about the morbidity and mortality of air pollution on human and ecological health. The adverse impact of polluted air on the health of children is emphasized. The history and provisions of the U.S. federal Air Pollution Control Act of 1955 are described. Discussed is the struggle to integrate greenhouse gases into regulatory actions by the EPA under provisions of the Clean Air Act. Global air pollution policies in the EU, China, and India are presented, concluding with the global economic impact of air pollution.