Air pollution could be contributing to clogged arteries, a new study says.

People exposed long-term to common air pollutants have an increased risk of advanced heart disease caused by hardened arteries, researchers reported Thursday at the annual meeting of the Radiological Society of North America, in Chicago.

Even air pollution levels near or below government standards were associated with early signs of heart disease, researchers found.

“Even at low exposure levels, air pollution is associated with more plaque in the coronary arteries,” lead researcher Dr. Felipe Castillo Aravena, a cardiothoracic imaging fellow at the University of Toronto in Canada, said in a news release.

Further, the more air pollution a person had been exposed to during their lifetime, the greater the odds that their arteries were clogged, results show.

For the study, researchers tracked the heart health and air pollution exposure of more than 11,000 adults treated at three hospitals in Toronto.

The team used chest CT scans to look at patients’ heart arteries and estimated their air pollution exposure using environmental data and the patients’ home postal codes.

Results showed that for each 1 microgram per cubic meter increase in long-term exposure to particle air pollution, there was:

• An 11% increase in calcium build-up in the coronary arteries.

• A 13% greater odds of more arterial plaques.

• A 23% increased risk of heart disease caused by clogged arteries.

Exposure to another form of air pollution, nitrogen dioxide, showed similar trends but with smaller effects, researchers said.

There also were differences between men and women, researchers found.

“In women, long-term exposure to fine particulate matter was linked to higher calcium scores and more severe narrowing of the arteries,” Castillo said. “In men, higher long-term exposure to fine particulate matter was associated with higher calcium scores and higher plaque burden.”

This study couldn’t draw a direct cause and effect link, but only shows an association between air pollution and heart health, researchers noted.

More research is needed to understand why air pollution might harm the heart and blood vessels, and to firm up a causal link between the two, Castillo said. 

“This is one of the largest studies to link long-term gaseous and particulate air pollution at contemporary exposure levels with multiple markers of coronary artery disease assessed by cardiac CT,” senior researcher Dr. Kate Hanneman, a cardiac radiologist and vice chair of research at the University of Toronto, said in a news release.

“Heart disease is the number one cause of death globally,” Hanneman added. “The results of this study add to the growing body of evidence that air pollution is a modifiable cardiovascular risk factor and reinforce the need for further research to understand why these associations differ between men and women.”

Findings presented at medical meetings should be considered preliminary until they’re published in a peer-reviewed journal.