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Getty ImagesWhen he was 10 years old, John OConnor was diagnosed with mitral valve prolapse, a condition that can affect blood flow to and from the left side of the heart. Today, the 23-year-old eats a meat-free diet, exercises regularly, and meditates to lower his stress and keep his heart healthy. But there's a hidden heart-health risk factor that he says he doesn't know much about: air pollution.

O'Connor lives in Philadelphia, which ranks No. 11 on the American Lung Associations list of most polluted U.S. cities in terms of unhealthy levels of ozone. Emerging research suggests that simply breathing the air in big cities like Philly increases O'Connors risk of having additional heart problems and potentially compromises his recovery if he had a heart attack.

A September study by Harvard University epidemiologists found that the microscopic particles in polluted air can decrease the hearts electrical functioning in people with serious coronary artery disease. Avoiding air pollution can reduce the risk of heart attack, heart failure, and other complications, especially in patients who are recovering after being hospitalized, according to Diane R. Gold, MD, the study's senior author and an associate professor of medicine and environmental health at Harvard.

In fact, air pollution plays a major role in the heart's health. Smoking is a well-documented culprit in heart disease, but a 2003 study by New York University researchers found that a nonsmoker living in a polluted city has about the same risk of dying of heart disease as a former smoker.

Next Page: Reasons to avoid traffic [ pagebreak ]

Reasons to avoid the stress (and mess) of traffic
The American Heart Association and the American College of Cardiology suggest that heart patients should avoid driving for two to three weeks after being treated in a hospital. But they want patients to stay clear of more than just the stress: “Our study provides additional rationale to avoid or reduce heavy traffic exposure after discharge since traffic exposure involves pollution exposure as well,” says Dr. Gold.

This study added to the growing body of research on air pollutions effect on the heart. A 2004 German study found that heart attack risk nearly tripled by exposure to heavy traffic, whether commuters are in a car, on a bike, or on public transportation. In 2007, another German study found that people living close to a major road are almost twice as likely to die from heart-related causes.

A 2003 Greek study associated a 10-unit increase in carbon monoxide, a poisonous gas found in car exhaust fumes, with a 46% hike in deaths from cardiovascular disease. And a 2002 study from Ireland found that cardiovascular deaths decreased by 10% when coal sales and coal burning were banned in Dublin.

  • Next Page: Five ways to protect your heart from pollution [ pagebreak ]
  • Five ways to protect your heart from pollution
  • Since it's unlikely that America will do away with cars and traffic jams anytime soon, patients with heart troubles need to take small steps to reduce their exposure to pollution. Russell V. Luepker, MD, a professor of public health at the University of Minnesota, offers these five suggestions.

1. Take a vacation
If you live in a polluted city, you may want to plan a vacation after a hospital procedure so that you can recover in a location with healthier air. “Historically, in Europe, when people had a procedure, theyd be sent to the country to recover for a few months,” Dr. Luepker says. “But when we have someone in the hospital, we keep them three or four days and they get back to work as soon as possible. Ill say to patients, ‘Take a month off and go down to Florida. Its just hard for people to do that in our society.”

2. Take a "staycation"
If you cant get away, try spending some extra downtime inside. “Being inside protects you to a certain degree,” Dr. Luepker says. “Most people live in houses that are sealed up in the winter or have air-conditioning in the summer, so some of the [pollution] is filtered out before it gets into your living room.”

3. Avoid heavily polluted areas
Even if you have places to go, try to stay away from areas that are likely to be badly polluted, like busy street corners or garages.

4. Consider where you live
Moving can be stressful, so doctors dont recommend moving right after a hospital stay. But certain cities and districts are better than others, Dr. Luepker says; it may be beneficial to consider the pollution level of where you live if youre worried about your heart health in the long-term.

5. Consider where you work
Like moving, getting a new job can be stressful too, so its not something to look for in the weeks after a heart procedure. But just like cities, different jobs are associated with different levels of exposure to pollution, says Dr. Luepker. For example, he did a study on truck drivers and found they have a much higher risk for heart attack, in part, because they are constantly around diesel fumes.