Air pollution is responsible for more deaths each year than malnutrition, malaria, AIDS, or alcohol and drug abuse.
And a spate of new studies suggest that our problems with unhealthy air are more pernicious and persistent than previously understood.
Today, the American Lung Association released its annual State of the Air report, finding that 43 per cent of U.S. residents — some 141 million people — now live in areas where poor air quality regularly risks damaging their health. That's seven million more people than in the group's last survey.
In places like California — the state that is home to seven of the nation's 10 smoggiest cities — the major driver of air pollution continues to be car and truck traffic, with the rapidly increasing population overwhelming even the most stringent environmental regulations.
And perhaps most worryingly, only six U.S. metro areas recorded no unhealthy smog or soot days: Bangor, Maine; Burlington, Vt.; Lincoln, Neb.; Wilmington, N.C.; Melbourne, Fla.; and Honolulu, Hawaii.
Overall, the World Health Organization now estimates that 75 per cent of the Earth's population — 5.5 billion people — live in areas where particulate pollution exceeds safety guidelines.