Study finds foul air can trigger heart attacks

From Rhonda Rowland
CNN Medical Unit

ATLANTA, Georgia -- Studies already suggest that bad air can contribute to a number of health threats, including asthma attacks and lung and heart disease.

Now there's evidence that as pollution increases, so do your chances of a heart attack, according to a study in the American Heart Association journal Circulation.

Within just two hours of breathing in fine particles from a city's bad air -- caused by vehicle exhaust and smokestacks, among other factors -- the risk of a heart attack increased 44 percent. A full day after exposure, heart attacks increased overall by one-third.

"We were able to look at an hour-by-hour basis and what we found, as a result, was that in fact the risk of a heart attack seems to go up very shortly after high increased levels of fine particles," said Dr. Murray Mittleman, director of cardiovascular epidemiology at Beth Israel Deaconess Medical Center in Boston, Massachusetts.

Researchers interviewed 772 Boston-area heart attack survivors a few days after they were admitted to the hospital, to determine when their symptoms began, then compared the data to air pollution measurements.

"I was surprised that with such a relatively small sample of individuals they were able to see this kind of effect that they did see, which says to me that we are probably measuring something real," said Dr. Frank Spiezer of Harvard Medical School.

High-risk people should take precautions

Researchers used air-quality measurements collected from monitoring stations throughout the Boston area.

"We now know for very low concentrations, concentrations below the national air quality standards, we still can detect effects of air quality on humans," said Petros Koutrakis of the Harvard School of Public Health.

Because they're so small, the particles can bypass the body's normal defense mechanisms and go deep into air sacs in the lungs, triggering an inflammatory response, researchers told Reuters.

This bad air is not just found in big cities. Weather patterns can send it hundreds of miles away, and it can vary dramatically from day to day.

While the conditions may not pose a big threat to young, healthy people, those who are at high risk for heart disease should avoid spending a lot of time outdoors on those hot, humid, hazy days, researchers say.

And when indoors, people should try to keep the bad air out by using air conditioning and making sure air filters are clean.