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Exposure to as Little as 2 Hours of Ozone May Prompt Heart Attack Among Vulnerable People

By Jennifer Warner
WebMD Health News

Reviewed by Brunilda Nazario, MD

June 26, 2012 -- A little ozone may go a long way in terms of hurting your heart.

A new study suggests exposure to as little as two hours of ozone may be enough to trigger inflammation and other changes in the body associated with heart attacks and sudden death.

"This study provides a plausible explanation for the link between acute ozone exposure and death," researcher Robert B. Devlin, PhD, a senior scientist at the U.S. Environmental Protection Agency's (EPA) National Health and Environmental Effects Research Laboratory in Research Triangle Park, N.C., says in a news release.

The World Health Organization estimates that about 2 million people worldwide, mostly older people with heart disease, die as a result of short-term exposure to ozone and air pollution.

Ozone is a common air pollutant. Ground level ozone is created when pollutants from vehicles, power plants, industry, and other sources react to sunlight.

New Link Between Ozone & Heart Attacks

Several recent studies have linked exposure to high levels of air pollution to an increased risk of heart attacks and death in people at risk. But researchers say most have looked only at the effects of air pollution on the lungs and respiratory system.

In the study, published in Circulation, researchers looked at changes in the hearts and cardiovascular systems of 23 healthy adults aged 19 to 33 in response to exposure to ozone-polluted or clean air.

Each of the participants was exposed to air containing 0.3 parts per million (ppm) of ozone or clean air for two hours. The exposures were at least two weeks apart, and during each session the participants alternated between 15-minute periods of cycling and rest.

The results showed changes in heart-related function immediately following and the morning after the ozone exposure compared with the clean air exposure.

These changes included:

• Increases in an indicator of inflammation known as interleukin-1-beta, which researchers say is a key player in heart disease.
• Decreases in components that play an important role in dissolving blood clots that may form along arterial walls (plasminogen activator inhibitor 1 and plasminogen).
• Changes in heart rhythm, an indication of an alternation in the nervous system's control of the heart rate.

Researchers say all of these changes were temporary and reversible in these young and healthy adults, but the changes could be more dangerous in those with existing heart disease or other risk factors.

Devlin says people can take steps to reduce their ozone exposure, such as limiting time outdoors on hot, sunny days when ozone levels are highest.

The EPA's web site, airnow.gov, also provides details on local air quality and ozone levels, along with tips on limiting ozone exposure.

SOURCES: Devlin, R. Circulation, June 25, 2012. News release, American Heart Association.

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