How Air Pollution Causes Heart Disease

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It's well known that measures such as exercise, a healthy diet and not smoking can help reduce high blood pressure, but researchers at the University of Michigan Health System have determined the very air we breathe can be an invisible catalyst to heart disease.

Inhaling air pollution over just two hours caused a significant increase in diastolic blood pressure, the lower number on blood pressure readings, according to new U-M research.

The study findings appear in the current issue of Hypertension, a publication of the American Heart Association.

Nearly one in three Americans suffer from hypertension, a significant health problem that can lead to heart attack, heart failure, stroke, and other life-threatening problems.

"Although this increase in diastolic blood pressure may pose little health risk to healthy people, in people with underlying coronary artery disease, this small increase may actually be able to a trigger heart attack or stroke," says Robert D. Brook, M.D., lead author and assistant professor of medicine in the Division of Cardiovascular Medicine at the University of Michigan Health System.

In the study, researchers hoped to identify which air pollutants are harmful and how the pollutants work to damage the cardiovascular system.

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Eighty-three people in Ann Arbor and Toronto were involved in testing and breathed air pollution, concentrated by a mobile air quality research facility, that was similar to what would be found in an urban environment near a roadway.

"We looked at their blood vessels and then their responses before and after breathing high levels of air pollution," explains Robert Bard, M.S., co-author and clinical research manager at U-M.

Ozone gases, a well-known component of air pollution, were not the biggest culprit. Rather, small microscopic particles about a 10th of the diameter of a human hair caused the rise in blood pressure and impaired blood vessel function, tests showed. The blood pressure increase was rapid and occurred within 2 hours, while the impairment in blood vessel function occurred later but lasted as long as 24 hours.

It's believed these fine particles deposit deep into the lungs and certain components may gain entrance to the blood stream, or cause an inflammatory response throughout the body. There is also evidence that functions in the body's nervous system are also disrupted.

The research is the latest in the relatively new field of environmental cardiology which looks at the association between air pollution and heart disease. Brook says the findings support efforts to maintain current ambient air quality standards set by the Environmental Protection Agency.

"It really bolsters and strengthens the importance of maintaining air quality for human health," says Brook.

There are practical ways to avoid exposure to high levels of air pollution, such as avoiding unnecessary travel or commutes and not exercising during rush hour, or near busy roadways, Brook says. In modern society, the burning of fossil fuels is the primary source for air pollution.

"If air pollution levels are forecasted to be high, those with heart disease, diabetes or lung disease should avoid unnecessary outdoor activity," he says.

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