Ozone exposure tied to cardiovascular risk
Now, a new study of adults in China reveals that it is also linked to cardiovascular changes that increase the risk of heart attack and stroke, and that these changes occur at levels below those of current environmental regulations.
But when ozone occurs at ground level, it is a harmful pollutant produced when oxides of nitrogen (NOx) react with volatile organic compounds (VOCs) in the presence of sunlight.
NOx and VOCs are emitted by motor vehicles and power plants that use fossil fuels, as well as some industrial processes.
Senior author Junfeng Zhang, a professor in global and environmental health at Duke University, says, “We know that ozone can damage the respiratory system, reduce lung function, and cause asthma attacks.”
However, he and his co-authors note that while exposure to ozone has been linked to deaths from cardiovascular disease, there is no clear biological understanding of how it affects the cardiovascular system.
They note that, because the participants “spent most of their time in controlled indoor environments,” this offered them an ideal setting “for better characterization of air pollutant exposure effects.”
Over the study period, the team measured indoor and outdoor ozone levels, as well as other pollutants.
Also, from “spirometry” breathing tests and blood and urine samples that the participants gave at four sessions spread across the study period, the team was able to measure a number of factors that can contribute to cardiovascular and respiratory disease.
The ozone exposure levels at which these links occurred were lower than levels that have been associated with impaired lung function, which is the main basis for the current air quality standard set by the Environmental Protection Agency (EPA) in the U.S.
“This study shows that standards for safe ozone exposure should take into account its effect on cardiovascular disease risk.”
Prof. Zhang adds that ozone pollution is difficult to control because the way it is produced in the atmosphere is complex. “For example,” he notes, “a reduction in nitrogen oxides does not necessarily mean a reduction in ozone levels.”
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