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Air Pollution Increases Heart Attack, Stroke Risk

Physicians Suggest Limiting Exposure to Fine Particulate Matter

By Katrina Woznicki
WebMD Health News

Reviewed By Elizabeth Klodas, MD, FACC

May 10, 2010 -- More evidence reveals that short- and long-term exposure to air pollution directly increases the likelihood of heart attack, stroke, or other cardiovascular problems, leading physicians to issue new recommendations to help people reduce their risk.

The new recommendations were released Monday by the American Heart Association (AHA) and singled out fine particulate matter as a cardiovascular risk factor.

Fine particulate matter becomes suspended in the air as a result of various human activities, including burning fossil fuels, cooking, and other indoor activities. Forest fires and biomass burning can also result in increased concentrations of fine particulate matter in the air. Of the different sizes of particles that can become suspended in air, fine particulate matter appears to be most strongly associated with adverse effects.

Air Pollution and Heart Disease

The AHA expert panel reviewed epidemiological, molecular, and toxicological studies published during the past six years, updating the 2004 AHA statement about air pollution, and provided a more comprehensive look at the link between air pollution and cardiovascular disease, including the potential biological mechanisms. Among their findings:

  • A few hours or weeks of exposure to particulate matter can increase the risk of cardiovascular events, including heart attack, stroke, heart failure, irregular heartbeats, and death, particularly among vulnerable populations, such as those already at high risk for cardiovascular disease, the elderly, and possibly people with diabetes.
  • Long-term exposure to high concentrations of particulate matter further increases cardiovascular disease risk and can shorten life expectancy by several months to a few years.
  • There is a strong link between air pollution exposure and ischemic heart disease, which reduces the blood supply to the heart.
  • There is a "moderate, yet growing link" between air pollution and heart failure and ischemic stroke.
  • There is a "modest" association between air pollution and peripheral vascular disease, irregular heartbeats, and cardiac arrest.

"Particulate matter appears to directly increase risk by triggering events in susceptible individuals within hours to days of an increased level of exposure, even among those who otherwise may have been healthy for years," says author Robert D. Brook, MD, a cardiovascular medicine specialist at the University of Michigan in Ann Arbor. "People can limit their exposure as much as possible by decreasing their time outside when particle levels are high and reducing time spent in traffic -- a common source of exposure in today's world."

The biological associations between air pollution and cardiovascular disease are unclear, but physicians suspect particulate matter triggers inflammation in the blood vessels, which in turn, stymies a healthy blood supply, Brook and colleagues say.

"It's possible that certain very small particles, or chemicals that travel with them, may reach the circulation and cause direct harm," Brook says. "The lung nerve-fiber irritation can also disrupt the balance of the nervous system throughout the body. These responses can increase blood clotting and thrombosis, impair vascular function and blood flow, elevate blood pressure, and disrupt proper cardiac electrical activity, which may ultimately provoke heart attacks, strokes, or even death."

Group: Particle Air Pollution Unsafe

The research team says the current information suggests there is no safe level of particulate matter exposure and that particulate matter should be considered a modifiable risk factor for heart disease.

Based on their findings, the panel recommends:

  • Continued efforts to address other cardiovascular disease risk factors through smoking cessation, weight loss, exercise, and a healthy diet to mitigate susceptibility to air pollution.
  • Informing people with, or at high risk for, cardiovascular disease of the dangers associated with air pollution and the steps that can be taken minimize exposure.

The World Health Organization (WHO) estimates that fine particle air pollution contributes to about 800,000 premature deaths per year, making it the 13th leading cause of worldwide mortality. The WHO estimates that by cutting particulate matter pollution from 70 micrograms per cubic meter to 20, air quality-related deaths could be reduced by about 15%.

The American Heart Association and the Environmental Protection Agency are co-sponsoring a Congressional briefing on Capitol Hill to educate lawmakers about the link between air pollution and cardiovascular disease. The AHA statement and related study results will be published in the June 1 issue of Circulation, Journal of the American Heart Association.

SOURCES: News release, American Heart Association.

Brook, R. Circulation, June 1, 2010.

World Health Organization: "Air Quality and Health."

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