Studies confirm dirty air may cause disease

(CNN) -- Heart disease is the No. 1 killer in America. Lung cancer is the No. 1 one cancer killer. And asthma is the No. 1 chronic disease in children.

These diseases have a frightening element in common: Air pollution can make them worse.

And a study conducted by the American Cancer Society and others has reached a startling conclusion -- air pollution may be leading to deaths from lung cancer, heart attack, stroke and asthma.

"The bad news of the study is that we have confirmatory evidence of what we thought, that air pollution is causing death in the U.S. in excess of what we would have if there wasn't much air pollution," said George Thurston, associate professor of environmental medicine at New York University School of Medicine.

VIDEO CNN's Rhonda Rowland reports on how air pollution may lead to death (March 5) Play video (QuickTime, Real or Windows Media)

In the most polluted cities, lung cancer deaths were 20 percent higher than in clean cities -- a risk that is nearly equivalent of second-hand cigarette smoke.

"Many of the cities in the U.S. are above and well above the legal standard for the country. It shows that we have a lot of work to do in terms of cleaning up pollution," Thurston said.

Now there is new evidence that supports what many scientists have suspected for years -- dirty air may actually cause these diseases as well as lead to deaths from them.

A federally funded study conducted in the Los Angeles area and published last month found that children who played team sports outdoors on days with high ozone levels developed the most asthma.

"If you grow up in an area where the ozone is high, your lungs don't grow as well. So, we believe that chronic exposure, long-term exposure to ozone, may limit the growth of the lungs," said Dr. Gerald Teague, asthma researcher at Emory University in Atlanta, Georgia.

Escaping dirty air by leaving the big city is not an option. Summer heat can bring high ozone levels no matter where you live. And pollution -- from cars, trucks and power plants -- can be carried by wind and weather hundreds of miles away.