Ozone Exposure Linked to Potential Heart Attacks
When many people think of the ozone, they imagine a layer of chemicals in the stratosphere, but there is also ground level ozone - created when pollutants from vehicles, power plants, industry, chemical solvents and consumer products react with sunlight - and breathing in too much of it, even for short periods, can set off heart-attack-like symptoms.
In a study by the U.S. Environmental Protection Agency's (EPA) National Health and Environmental Effects Research Laboratory, scientists exposed 23 young, healthy volunteers between the ages of 19 and 33 to 0.3 parts per million of ozone for two hours.
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The participants alternated between 15-minute periods of stationary cycling and rest during two controlled exposures, one to clean air and one to ozone-polluted air.
Though none of the participants reported any physical symptoms, tests showed that the ozone inhalation produced vascular inflammation, a potential reduced ability to dissolve artery-blocking blood clots, and changes in the nervous system that control the heart's rhythm. These symptoms were measurable immediately following and the morning after ozone exposure.
These physiological changes are associated with a higher risk of heart attacks, which could be related to the elevated risk of clotting seen in volunteers after they had breathed ozone-enriched air.
According to Science News, the pollutant altered levels of several clot-related proteins, including plasminogen, tissue plasminogen activator and plasminogen activator inhibitor. Concentrations of some went up, others down. Based on the pattern of changes, noted Cardiologist Wayne Cascio, of the EPA's National Health and Environmental Effects Laboratory, "one might predict that [high ozone] would slow the dissolving of clots." That suggests clots might propagate or enlarge, he says - "or potentially block up a vessel, causing a heart attack or stroke."
Many different conditions can cause blood clots, but once they form, this study's data shows that exposure to ozone might stop the body from dissolving them.
The World Health Organization estimates 2 million people worldwide, mostly elderly people with cardiovascular disease, die because of acute exposure to air pollution. The EPA puts the yearly U.S. toll at 40,000-50,000 deaths.
"This study provides a plausible explanation for the link between acute ozone exposure and death," said lead author Robert B. Devlin.
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