Ozone exposure could trigger heart attacks

Young, healthy adult volunteers exposed for two hours to ozone developed physiological changes tied to cardiovascular damage. They showed evidence of vascular inflammation, a potential reduced ability to dissolve artery-blocking blood clots, and changes in the autonomic nervous system that controls the heart's rhythm. The changes were temporary and reversible in these participants. Pollutants from vehicles, power plants, industry, chemical solvents and consumer products create ground level ozone by reacting in the presence of sunlight. Recent studies have linked acute exposure to ozone and death but little is known about the underlying pathways responsible, the journal Circulation reports. "This study provides a plausible explanation for the link between acute ozone exposure and death," said Robert B. Devlin, senior scientist at the US Environmental Protection Agency's (EPA) National Health and Environmental Effects Research Lab, who led the study, according to an EPA statement. Devlin and colleagues focused on a single, short-term exposure and not the effects of years of exposure to ozone. They exposed a group of volunteers, aged between 19 and 33 years, to 0.3 parts per million (ppm) of ozone. The dose was higher than the EPA's eight hour ozone standard of 0.076 ppm. However, a person breathing 0.3 ppm for two hours receives roughly the same amount of ozone as does a person breathing the lower 0.076 ppm for eight hours, Devlin noted. Study participants underwent two controlled exposures - one to clean air and one to ozone-polluted air - at least two weeks apart. During each exposure, participants alternated 15-minute periods of stationary cycling and rest. None of the participants reported complaints or physical symptoms after inhaling clean air or ozone. However, immediately following and the morning after ozone inhalation, tests showed significant ozone-induced vascular changes compared to clear-air exposure. The World Health Organization estimates two 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. "People can take steps to reduce their ozone exposure, but a lot of physicians don't realize this," Devlin said.