Every year, the American Lung Association releases a report on the quality of the air in the United States. Every year, the results are frightening.
The 10th annual State of the Air report was released on April 29th and it contains bad news for more than half of all Americans. According to the report, over 186 million people live in areas where air pollution levels are high enough to represent a significant health risk.

While the report acknowledges that there have been some improvements in air quality in recent years, the almost every major urban center in the nation is still operating under clouds of polluted air. Although some of the nation’s largest cities have actually improved their air quality in recent years (including New York City, Los Angeles, Atlanta and Washington, D.C.), in some cities the air quality continues to worsen year after year.

"This should be a wake-up call," warned Stephen J. Nolan, the National Board Chair of the American Lung Association. "When 60 percent of Americans are left breathing air dirty enough to send people to the emergency room, to shape how kids’ lungs develop, and to kill, air pollution remains a serious problem."

Not only is air pollution a health threat in the sense that it increases the risk of respiratory illnesses, it also contributes to global warming. Many of the main sources of air pollution – cars, factories and cargo ships – release greenhouse gases into the atmosphere.

Cleanest Cities (in terms of long-term particle air pollution)

1. Cheyenne, Wyoming
2. Santa Fe-Espanola, New Mexico
3. Honolulu, Hawaii
4. Great Falls, Montana
5. Flagstaff, Arizona

Dirtiest Cities (in terms of long-term particle air pollution)

1. Bakersfield, California
2. Pittsburgh-New Castle, Pennsylvania
3. Los Angeles-Long Beach-Riverside, California
4. Visalia-Porterville, California
5. Birmingham-Hoover-Cullman, Alabama