Young, healthy adult volunteers exposed for two hours to ozone developed physiological changes associated with cardiovascular ailments, according to a study by researchers from the University of North Carolina School of Medicine and the U.S. EPA.
Signboard in Gulfton, Houston indicating an ozone watch
Study participants 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 young, healthy participants.
Ground level ozone is created when pollutants from vehicles, power plants, industry, chemical solvents and consumer products react in the presence of sunlight. Recent epidemiology studies have reported associations between acute exposure to ozone and death but little is known about the underlying pathophysiological pathways responsible.
“This study provides a plausible explanation for the link between acute ozone exposure and death,” said Dr Robert Devlin, senior scientist at the EPA’s National Health and Environmental Effects Research Laboratory and lead author of the study published in the journal Circulation.
Dr Devlin and his colleagues focused on a single, short-term exposure and not the effects of years of exposure to ozone.
Researchers exposed 23 volunteers, ages 19 to 33, 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,” Dr 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.
Epidemiology studies have also associated acute exposure to another ubiquitous air pollutant, particulate matter (PM), with death in elderly people with cardiovascular disease. Particulate matter is tiny airborne particles that can be inhaled into the lungs. “Controlled exposure studies of both humans and animals have described PM-induced changes that are very similar to those described in this ozone study, suggesting that both pollutants may be causing death by affecting similar pathways,” the researchers said.
“People can take steps to reduce their ozone exposure, but a lot of physicians don’t realize this,” Dr Devlin concluded.
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Bibliographic information: Devlin RB. et al. 2012. Controlled Exposure of Healthy Young Volunteers to Ozone Causes Cardiovascular Effects. Circulation. Published online before print June 25, 2012; doi: 10.1161/CIRCULATIONAHA.112.094359
