Traffic soot linked to heart attacks

Proximity of exhaust is said to triple risk in susceptible people

October 21, 2004|By Jonathan Bor | Jonathan Bor,SUN STAFF

Fighting traffic can triple the risk of heart attack in people who are already susceptible. But don't blame the stress that comes with stalled freeways and missed appointments.

The likely culprit, scientists said yesterday, is the hefty dose of particulate air pollution - or soot - that people breathe when they spend time surrounded by exhaust pipes.

The problem isn't limited to car-choked areas, according to German scientists who studied heart attacks in Augsburg, a city of 265,000 that they described as moderately congested.

Annette Peters, lead author of a study appearing in today's New England Journal of Medicine, said she was surprised to find that the risk was about the same whether people sat behind the wheel or in buses or streetcars.

If stress were the trigger, Peters said, she would expect to see a greater problem among people who had just finished driving than those who had taken public transportation.

"It's surprising because it points more toward air pollution rather than the stress of driving, though we can't exclude that there is an interaction between stress and pollution," said Peters, an epidemiologist with the GSF-National Research Center for Environment and Health in Neuherberg.

Though the findings remain to be confirmed, the study suggests that traffic ranks alongside anger, strenuous exercise, and use of cocaine and other drugs as factors that can trigger attacks in people with underlying heart disease.

"It certainly supports what many of us have suspected, that air pollution is not good for the heart," Dr. Roger S. Blumenthal, director of preventive cardiology at the Johns Hopkins School of Medicine, said of the study.

"Trying to cut back on your exposure to some of this noxious stimuli is probably going to be good for you in the long run," he said. One simple method might be recirculating the airflow in your car rather than drawing outside air.

Though the cause is not certain, experts speculated that the arteries feeding heart muscle constrict in reaction to a sudden dose of air pollution. In people with underlying disease, this might cause fatty plaques - which cling to the inner lining of these blood vessels - to break off and form clots that can disrupt the flow of blood.

Other factors might work differently to trigger attacks. Emotional stress, for instance, sets off a harmful rush of adrenaline.

In the German study, researchers used a tracking system that collects information on nearly all heart attack victims in the Augsburg region. Besides gathering medical histories, health care providers ask survivors what they were doing in the hours and days before their attack.

"We ask them whether they left the house, where did they go to, and how did they get there," said Peters.

Studying 691 survivors between 1999 and 2001, researchers found that a disproportionate number had suffered their attacks within an hour of driving or riding public transportation in traffic.

The risk in the first hour was three times higher than at other times, an estimate that adjusted for other well-known risk factors such as heavy physical exertion. It also accounted for the well-established risk of having a heart attack shortly after getting up in the morning.

The study was not the first to explore the role of air pollution in heart attacks. A recent study in the Netherlands found that people living near major roads doubled their risk of dying from heart disease. In 2001, Peters and researchers at Harvard University found that the heart attack risk in several U.S. cities increased when the level of sooty particles in the air was higher.

In a commentary accompanying the German study, Dr. Peter H. Stone of Brigham and Women's Hospital in Boston wrote that "decades of epidemiological evidence" support a link between air pollution and sickness and death caused by heart disease.

"As both epidemiologic and now mechanistic evidence mounts, there is now greater urgency to accelerate our efforts to reduce particulate air pollution and to improve cardiovascular health," wrote Stone.

Peters conceded that it might be difficult for working people to reduce their exposure to air pollution, especially as taking public transportation doesn't appear to help. "Commuting is part of daily life," she said. "Exposure to traffic is necessary, and mobility is important to us."

"But if this is verified by other studies, then it might add to the case that it's important to control air pollution in urban areas and have cleaner vehicles and [better] city planning," Peters said.

Because researchers limited their study to Augsburg, it might be hard to compare it with Baltimore and other traffic-snarled cities in the United States. In any case, it is unlikely the news will be good. Ausburg has its share of heavy traffic but is neither as large or as congested as many East Coast cities, said Peters.

Although Baltimore's air quality is considerably better than Los Angeles', the metropolitan area fails to meet federal air quality standards and is among the worst 25 percent for soot particles, according to a recent report by the Environmental Protection Agency.

Another recent study by the Texas Transportation Institute found that Baltimore area motorists spend an average of 48 hours a year in traffic jams - five times as much as they spent 20 years ago. Still, Baltimore ranks 16th, far behind front-running Los Angeles, where motorists spend 93 hours a year stuck in traffic.

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