Long-term exposure to ambient ozone appears to accelerate arterial conditions that progress into cardiovascular disease and stroke, according to a new University at Buffalo study.

The research is the first epidemiological study to provide evidence that ozone might advance subclinical arterial disease—injuries that occur to the artery walls prior to a heart attack or stroke—and provides insight into the relationship between ozone exposure and cardiovascular disease risk. The open-access paper was published in the journal Environmental Health Perspectives.

This may indicate that the association between long-term exposure to ozone and cardiovascular mortality that has been observed in some studies is due to arterial injury and acceleration of atherosclerosis.

—lead author Meng Wang, assistant professor of epidemiology and environmental health in the UB School of Public Health and Health Professions

The longitudinal study followed nearly 7,000 people aged 45 to 84 from six US regions: Winston-Salem, North Carolina; New York City; Baltimore; St. Paul, Minnesota; Chicago; and Los Angeles. Participants were enrolled in the Multi-Ethnic Study of Atherosclerosis (MESA) and have been followed for more than a decade.

Atherosclerosis refers to the build-up of plaque, or fatty deposits, in the artery walls, which, over time, restricts blood flow through the arteries. This can cause blood clots, resulting in a heart attack or stroke, depending on which artery—coronary or carotid, respectively—in which the plaque accumulates.

The study found that chronic exposure to ozone was associated with a progression of thickening of the main artery that supplies blood to the head and neck. It also revealed a higher risk of carotid plaque, a later stage of arterial injury that occurs when there’s widespread plaque buildup in the intima and media, the innermost two layers of an artery wall.

We used statistical models to capture whether there are significant associations between ozone exposure and these outcomes. Based on this model, it suggests that there is an association between long-term exposure to ozone and progression of atherosclerosis.

—Meng Wang

While the study finds an association between air pollution and atherosclerosis, researchers aren’t clear on why.

We can show that there is an association between ozone exposure and this outcome, but the biological mechanism for this association is not well understood.

—Meng Wang

The study is unique in its focus on ozone exposure rather than particulate matter.

Wang’s study—which includes researchers from the University of Washington and the University of Wisconsin-Madison— has policy implications for the US, where the Environmental Protection Agency in 2015 lowered the federal health standards for ozone.

The EPA reports that particulate matter concentrations have decreased across the nation as efforts are made to reduce vehicle emissions and use clean energy. Ozone, however, is much trickier, Wang notes.

For policy in the US, the focus should be on how to effectively control ozone concentration, which may be harder because it’s a secondary pollutant.

—Meng Wang

Resources

• Meng Wang, Paul D. Sampson, Lianne E. Sheppard, James H. Stein, Sverre Vedal, and Joel D. Kaufman (2019) “Long-Term Exposure to Ambient Ozone and Progression of Subclinical Arterial Disease: The Multi-Ethnic Study of Atherosclerosis and Air Pollution” Environmental Health Perspectives doi: 10.1289/EHP3325