Steer Clear of Exhaust When Exercising
Diesel fumes seem to put the heart at risk

(HealthDay News) -- Though exercise is undoubtedly good for you, when and where you pound out the miles might actually put your heart at risk.

Running or walking near urban traffic, in fact, has been shown to be problematic.

Scottish researchers found that men with stable heart disease who were exposed, even for a short time, to diesel exhaust fumes showed reduced blood flow to their hearts, which can increase the risk of various cardiovascular problems, including heart attacks and arrhythmias.

The levels of pollution involved in the Scottish study were similar to those generated by regular city traffic.

"Exercise reduces a person's lifetime risk of developing coronary heart disease," study co-author Dr. Nicholas Mills, a specialist registrar in cardiology at the Centre for Cardiovascular Sciences at the University of Edinburgh , told HealthDay . "We would suggest, however, that wherever possible, patients avoid exercising in heavy traffic."

Dr. Len Horovitz, a pulmonary specialist in New York City , said the study offered clear-cut advice to runners: "Don't jog behind a bus. Don't jog in heavy traffic," he told HealthDay . "If you're exercising outdoors, try to do it at a time when pollution and traffic are at their lowest level, so that would be very early in the morning or significantly into the evening when rush hour has passed."

Research has established a link between air pollution and dying from cardiovascular disease. One study found that long-term exposure to air pollution increased the risk of death from cardiovascular disease by 76 percent.

The Scottish study found that an interaction between the fine particles found in diesel exhaust and the fatty acids in low-density lipoprotein ("bad") cholesterol activates the genes that can cause inflammation in blood vessels, speeding up the process of atherosclerosis, which can lead to blockages.

It involved 20 men who'd had a heart attack but whose heart disease was stable. Participants were exposed to diluted diesel exhaust or filtered air for one hour while resting and while riding an exercise bike.

Heart rates increased similarly as a result of both the filtered air and the diesel exhaust sessions. But after the diesel exhaust session, the men had decreased blood flow to the heart. The diesel exhaust also reduced the release of endothelial tissue plasminogen activator, a "clot buster," the study found.

But no one yet knows how diesel exhaust creates this change in blood flow. It's also unclear which component of diesel fuel is responsible.

"We have for the first time identified ischemic and thrombotic mechanisms to explain why there are more admissions to hospitals with angina and heart attacks on days in which the levels of air pollution are increased," Mills said.

But with fumes adding to additional air pollution, the effects on the body may be even worse in the real world.

"In real life, you have diesel fuel exposure with a background of regular air pollution, the complicating ambient air pollution," Horovitz said.

On the Web

To learn more about air pollution and exercise, visit the American Lung Association.

SOURCES: HealthDay News ; Nicholas Mills, specialist registrar in cardiology, Centre for Cardiovascular Sciences, University of Edinburgh, Scotland; Len Horovitz, M.D., pulmonary specialist, Lenox Hill Hospital, New York City; Sept. 13, 2007, New England Journal of Medicine
Author: Anne Thompson
Publication Date: Aug. 31, 2008
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