Exposure to ozone, a powerful greenhouse gas and a widespread air pollutant in many major cities, may cause cardiovascular diseases, such as heart attack, high blood pressure and stroke, according to a new study of Chinese adults.
Ozone is a pollutant formed through a chemical reaction that occurs when sunlight interacts with nitrogen oxides and other organic compounds that are generated by coal-burning, vehicle exhaust and some natural sources. It has long been associated with adverse health effects in children and adults.
"We know that ozone can damage the respiratory system, reduce lung function and cause asthma attacks," said study author Junfeng Zhang, from Duke Kunshan University. "Here, we wanted to learn whether ozone affects other aspects of human health, specifically the cardiovascular system."
Zhang and his colleagues studied 89 healthy adults living in Changsha City, the provincial seat of Hunan in China for one year. They monitored indoor and outdoor ozone levels, along with other pollutants.
At four intervals, the study team took participant blood and urine samples and used a breathing test called spirometry to examine a set of factors that could cause cardiovascular and respiratory diseases.
The team examined inflammation and oxidative stress, arterial stiffness, blood pressure, clotting factors and lung function in participants.
They noted blood platelet activation, which is a risk factor for clotting, and an increase in blood pressure, suggesting a possible mechanism by which ozone may affect cardiovascular health.
These effects were found with ozone exposure lower than that which affects respiratory health, and lower than current US Environmental Protection Agency (EPA) air quality standards.
"This study shows that standards for safe ozone exposure should take into account its effect on cardiovascular disease risk," said Zhang.
These findings, by a team from Duke University, Tsinghua University, Duke Kunshan University and Peking University, were published Monday in the US journal JAMA Internal Medicine.
"This study provides mechanistic support to previously observed associations between low-level ozone exposure and cardiovascular disease outcomes," the study concluded. "Given that global tropospheric ozone concentration is rising, it is imperative to determine how to minimize its harms on health."