DALLAS — Air pollution in U.S. cities causes twice as many deaths from heart disease as it does from lung cancer and other respiratory ailments, a surprising new study suggests.
The statistical analysis was published Tuesday in Circulation, a journal of the American Heart Association.
"It certainly did surprise us when we first observed these results," said lead author C. Arden Pope III, an epidemiologist at Brigham Young University in Provo, Utah. "We just sort of anticipated that breathing particles into your lungs would most likely have a direct impact on your lungs."
Still, Pope stressed that the lungs are intricately involved. For example, lung inflammation from breathing polluted air can lead to heart disease.
The study analyzed data from a survey of 500,000 adults who enrolled in an American Cancer Society survey on cancer prevention in 1982.
It expands on a study by Pope and others published in the March 2002 issue of the Journal of the American Medical Association. Researchers said that study contained the strongest evidence yet linking air pollution with lung cancer deaths.
In this round of research, Pope and the others looked at the incidence of heart attacks and other cardiovascular diseases, and respiratory diseases. They then crunched those numbers with air pollution data for more than 150 cities kept by the Environmental Protection Agency.
Even after taking into account other risk factors, such as smoking, diet, weight and occupation, the scientists found that air pollution increased the chances of heart disease.
"This link was stronger for cardiovascular disease than respiratory disease," Pope said. "Substantially more than two-thirds of deaths due to air pollution are cardiovascular deaths, or heart diseases, if you will, versus respiratory deaths."
The pollution risk is from what scientists call combustion-related fine particulate matter — soot emitted by cars and trucks, coal-fired power plants and factories.
Pope said his findings are consistent with other research that suggests air pollution provokes inflammation and speeds up narrowing of the arteries.
Ralph Delfino, a University of California at Irvine epidemiologist, said the study is "quite important."
"I think it should serve not as the last word but as an encouragement to do more intensive investigations," he said.
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