Air Pollution Can Hamper the Heart
Study finds that traffic, especially, holds risks after a heart attack

(HealthDay News) -- Pollution from cars and trucks and industrial plants has been shown to trigger heart attacks, but experts had been at a loss to explain why.

Until now.

Researchers from Harvard University found that the tiny particles in air pollution cripple the heart's ability to conduct electrical signals, and this affects people with coronary artery disease.

According to the American Heart Association, air pollution is a toxic soup that can contain carbon monoxide, nitrates, sulfur dioxide, ozone, lead, secondhand tobacco smoke and particulate matter that is composed of solid and liquid particles within the air. It can be generated from vehicle emissions, tire fragmentation and road dust, power generation and industrial combustion, metal processing, construction and demolition activities, windblown soil, pollens and molds.

For the study, Dr. Diane R. Gold, an associate professor of medicine and environmental health, led a team that collected data on 48 people who had coronary artery disease and were from the Boston area.

The researchers monitored the participants for 24 hours using portable electrocardiograph machines, looking for changes in the electrical conductivity of the heart, which is called ST-segment depression. This break in the heart's normal rhythm can mean the heart isn't getting enough blood or the heart muscle is inflamed.

All participants had been in a hospital because of a heart attack, unstable angina (the chest pain or discomfort that occurs when the heart doesn't get as much blood and oxygen as it needs) or worsening symptoms of coronary artery disease. Forty percent had suffered heart attacks; 25 percent had diabetes.

Gold's group also looked at the average levels for all pollutants in Boston and found that these levels were below accepted or proposed National Air Quality Standard thresholds.

The researchers found that increased levels of fine particulate matter (less than 2.5 micrometers in diameter) and black carbon, which is found in traffic exhaust, were associated with an increase in ST-segment depression. Sulfur dioxide, which is the product of combustion, but not from cars, was also associated with an increase in ST-segment depression.

Increases in ST-segment depression were much higher in people recovering from a heart attack than in others, the researchers reported.

"We found that elevation in fine particles from non-traffic as well as traffic sources and black carbon, a marker for traffic, predicted depression ST-segment levels," Gold told HealthDay. "Effects were greatest within the first month after hospitalization and for patients with heart attack during hospitalization or with diabetes."

The American Heart Association and the American College of Cardiology both suggest that people who have just been discharged from a hospital after a heart attack should avoid traffic because of the stress of driving, Gold said.

"Our study provides additional rationale to avoid or reduce heavy traffic exposure after discharge, even for those without a completed myocardial infarction, since traffic exposure involves pollution exposure as well as stress," Gold said.

On the Web

To learn more about air pollution and health, visit the U.S. Environmental Protection Agency's AirNow program.

SOURCES: HealthDay News ; Diane R. Gold, M.D., M.P.H., associate professor, medicine and environmental health, Harvard University, Boston; Sept. 9, 2008, Circulation, online ; American Heart Association (www.americanheart.org)
Author: Dennis Thompson
Publication Date: September 30, 2009
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