The most rigorous study of its kind to link pollution and heart disease finds women are at much greater risk of developing and dying from cardivovascular disease who live in areas with higher levels of pollution, according to the New England Journal of Medicine.
While doctors have known known air pollution can be bad for the heart, they didn't know it was this bad.
"The magnitude of the findings are substantially higher than what's been seen in prior research on long-term effects of air pollution," said Dr. Joel Kaufman at the University of Washington.
The study monitored the health of more than 65,000 post-menopausal women for up to nine years and tracked the air quality near their homes, checking the level of tiny particles spewed from cars, trucks and power plants.
Their tracked through pollution meters which are scattered in virtually every metropolitan area in the country to continously measure the amount of particles in the air, with the results compiled by the Environmental Protection Agency.
This latest study suggests women living in cities with the highest levels of air particles, such as Los Angeles, Atlanta and New York, were 76 percent more likely to die from a heart attack or stroke than women breathing the cleaner air of Honolulu or Tucson, Arizona.
"Not only were the effects higher in polluted cities, but within a city," Kaufman said. "The more polluted areas were places where there were higher rates of heart disease."
And these findings were consistent regardless of a woman's weight or smoking history, blood pressure or cholesterol levels.
"The particles effect the lining of the blood vessels which makes it easier for cholesterol plaque to form, and also it makes the blood stickier so clots are more likely to form," said Dr Leslie Cho of the Cleveland Clinic.
Air particles are harmful to both women and men, but women may be more vulnerable, in part, because they have smaller coronary arteries.
While no one is suggesting they move out of pollution "hot spots", doctors say women should focus on those heart disease risk factors they can control.
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