Your life depends on good air. Every year, air pollution causes the premature deaths of between 5.5 million and 7 million people, making it more deadly than HIV, traffic accidents and diabetes combined. The majority of these deaths—about 4 million—are caused by indoor air pollution, primarily in developing countries. But it takes a toll in developed countries as well. In Europe, for example, air pollution shortens the average life expectancy by nearly one year. Worldwide, more than 80 percent of people living in urban areas breathe air that exceeds pollution limits advised by the World Health Organization (WHO).