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Study: Pollution and heart disease don't mix

WASHINGTON (CNN) -- People with heart disease may think they're doing their body good by exercising. But exercise isn't necessarily a good thing if it's being done in polluted air, according to a new study.

The new findings reveal the importance of avoiding outdoor exercise on hazy days.

Many researchers have previously reported a link between pollution and increased heart attacks and deaths.

The new study, reported in Monday's issue of Circulation: Journal of the American Heart Association, claims to be the first to examine heart strain during exercise --- showing decreased oxygen supply to heart muscle when air pollution is high.

People with heart disease were about three times more likely to have decreased oxygen supply to their heart muscle during exercise after periods of high level air pollution than when they were tested after periods of negligible air pollution, said Dr. Juha Pekkanen, a senior researcher at the National Public Health Institute, Unit of Environmental Epidemiology in Kuopio, Finland.

Pollution health tips

Avoid strenuous outdoor activity when ozone smog or other pollution levels are high. Highest levels typically occur in the afternoon.

Avoid congested streets and rush hour traffic, since motor vehicles are a primary source of air pollution.

Make sure teachers, coaches and recreation officials know about air pollution and offer alternative indoor activities for children.

Be aware of air quality. Pollution levels are often given with local weather reports and in newspapers.

Watch the calendar. Ozone smog tends to be worst during the May-to-October "smog season." Be especially conscious during hot weather.

Source: American Lung Association

The new study "highlights myocardial ischemia [oxygen deprivation to heart muscle] as a significant potential mechanism responsible for adverse cardiac outcomes associated with poor air quality," said an accompanying editorial by researchers at Beth Israel Deaconess Medical Center and Harvard Medical School in Boston.

Researchers analyzed data from 23 volunteers living in Helsinki, Finland, during the winter of 1998-99. Each was put on a bicycle ergometer for six minutes with while his or her heart was monitored.

Researchers reported an increased risk of decreased oxygen to the heart after periods of increased fine and ultra-fine particles in the air -- pollution mainly associated with emissions from factory smokestacks.

Ultra-fine particles have a diameter less than 0.1 micrometers. They are the type of pollutants that spew from exhaust pipes.

According to Dr. Murray A. Mittleman, director of cardiovascular epidemiology at Beth Israel, it's better for heart patients to exercise in air-conditioned settings compared to outdoors when pollution is high.