Pollution can be hard on the heart

People with severe coronary artery disease need to stay inside on high pollution days, which pose an increased and immediate risk of heart attack or unstable angina, according to research by Brigham Young University and LDS Hospital.

The researchers linked images and data taken in the cardiac catheter lab at LDS Hospital with date-specific pollution levels collected by BYU to reach the conclusion. Their study will be published Tuesday in Circulation, the journal of the American Heart Association.

"On the days with higher concentrations of PM2.5, there's increased risk of having one of these ischemic heart disease events — specifically heart attack and related types of events," says C. Arden Pope, a BYU epidemiologist and lead author on the study. Pope is widely published and quoted on the health effects of air pollution.

The excessive risk applies only to those with diseased coronary arteries, but it's a sobering fact that many people do not know they have coronary artery disease until such an event occurs, say Benjamin D. Horne, director of cardiovascular epidemiology at the hospital, and Dr. Joseph "Brent" Muhlestein, director of the cardiac catheterization lab there. He is also a professor of medicine at the University of Utah. Heart disease is the No. 1 killer in America.

The researchers note that other studies show elevated exposure to the type of pollution called small particulate matter 2.5 (PM2.5) increases risk of developing heart disease. PM2.5 is fine pieces of soot smaller than 2.5 microns, or less than five one-hundredths the width of a human hair. It is generated by combustion, most often from vehicles, manufacturing and coal-fired power plants.

The EPA says that the annual average level of such particles in the air should not exceed 15 micrograms per cubic meter. The study shows that a daily increase of 10 micrograms per cubic meter in PM2.5 air pollution is accompanied by a 4.5 percent increased risk of having unstable angina or a heart attack. In winter inversions, Pope says, Utah may see 100 micrograms per cubic meter or more.

The researchers linked BYU's detailed daily air pollution measures, taken from monitoring sites in northern Utah, with LDS Hospital's registry of more than 12,000 heart patients, controlling for other factors that contribute to heart disease and heart attack, such as diabetes, smoking, obesity and high blood pressure. They also controlled for two pollution-related factors: temperature and relative humidity, Pope says.

While they hope the study will be a springboard to more research and to efforts to further improve air quality, Muhlestein says he thinks some impact will be immediate. "If the air outside is bad, I want my patients to call and say they're not coming in. They need to stay out of that air on the days it's bad."

Horne and Muhlestein both advocate preventive measures such as improving public air-quality warning systems, educating the public about the need for those at risk to take it easier and stay indoors and teaching the public to improve filtration of indoor air. Muhlestein's hoping the study will spark increased effort to improve air quality overall.

Other co-authors on the study were Dr. Jeffrey Anderson, associate chief of cardiology at LDS Hospital and professor of internal medicine at the U.; Dr. Dale G. Renlund, who has joint appointments at the hospital and the U.; and Heidi T. May of LDS Hospital.

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