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WEDNESDAY, Jan. 21, 2009 (Health.com) — Americans are living longer because the air they breathe is getting cleaner, a new study suggests. The average drop in air pollution seen across 51 metropolitan areas between 1980 and 2000 appears to have added nearly five more months to people’s lives, according to a study published Wednesday in The New England Journal of Medicine.

Residents of cities that did the best job cleaning up air pollution showed the biggest jump in life span; for example, Pittsburgh’s clearer air meant its citizens could expect to live nearly 10 months longer.

“Here’s a situation where we say we think that improving our air quality should improve health and life expectancy, and so we did it, in many cities more so than others,” says lead researcher C. Arden Pope III, PhD, of Brigham Young University in Provo, Utah. “We wait a couple of decades and see if it really helps, and the answer is that it did, and that’s good news.”

Long-term exposure to dirty air—specifically, the tiny specks known as fine-particulate air pollution—shortens lives and contributes to cardiovascular and lung disease. Particulate matter is inhaled almost like a gas and is thought to hike blood pressure, heart attack risk, and the chance of heart disease–related death.

The American Heart Association and the American College of Cardiology recommends that heart patients avoid driving for two to three weeks after leaving the hospital due to pollution (and stress). Other research has suggested that a nonsmoker living in a polluted city has about the same risk of dying of heart disease as a former smoker.

Gas and diesel engines, coal-fired plants, steel mills, smelters, refineries, and other industrial processes involving burning at high temperatures produce these particles, which are no bigger than 2.5 microns across—or about one-fortieth the diameter of a human hair. “Those are the ones that can penetrate deeply into the lungs and cause most of the health problems,” says Pope.

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