Arterial blockages can begin to develop even in people breathing what regulators call clean air
Even the relatively clean air typical of North American cities can damage heart arteries, especially in women.
Long-term exposure to common air pollutants from automobiles, industrial activity and fossil fuel combustion is linked to advanced coronary heart disease, even at levels near or below current regulatory safety limitsreport the researchers in the June 2026 report Radiology. Adjusting for factors such as high blood pressure and cholesterol weakened the association, suggesting that pollution may partly worsen these established risk factors.
The study cannot demonstrate that air pollution causes heart disease, but adds weight to growing evidence linking the two, says heart surgeon Salil Deo, who was not involved in the work. “There may be no ‘floor’ at which air quality can be considered completely safe for the human heart,” says Deo, of Case Western Reserve University School of Medicine in Cleveland.
Coronary heart disease develops when calcium deposits and plaque buildup narrow the arteries of the heart, increasing the risk of a heart attack. Previous studies have air pollution linked to heart attacks and strokesand experts believe that air pollution contributes to 4 million to 6 million of the 20 million cardiovascular deaths worldwide each year.
Instead of focusing on events like heart attacks, the new study uses heart scans to show how long-term exposure is linked to the accumulation and progression of coronary heart disease, says Kate Hanneman, a cardiac radiologist at the University of Toronto.
Hanneman and colleagues followed more than 11,000 adults in and around Toronto who had heart scans from 2012 to 2023. To estimate long-term exposure to pollutants, they linked each participant’s residential history to air quality data from the previous decade.
The team focused on fine particles and nitrogen dioxide, or NO2. Fine particulate matter refers to tiny airborne particles small enough to be inhaled deep into the lungs, while NO2 is a gas produced mainly by automobile traffic and the combustion of fossil fuels. Both can contribute to inflammation that affects the heart and blood vessels. Most participants were exposed to lower levels of air pollution Canada’s annual air quality standards and in the levels commonly seen in North American and European cities.
The higher the exposure to fine particle air pollution, the more signs researchers can see of heart arterial disease on scans. As exposure increased, calcium buildup in the heart arteries was higher and plaque was more common. Additionally, the risks of serious narrowing of the arteries were higher, especially in women. Analyzes showed similar, but weaker, effects for NO2.
“There was no level at which the risk clearly stabilized or disappeared,” says Hanneman.
In men, the association between severe narrowing of arteries and higher exposure to pollutants was not statistically significant, although both sexes had more calcium and plaque as pollution increased.
“This trend is consistent with previous research,” says Hanneman. “This may reflect biological differences, such as respiratory rate relative to body size, hormone-related inflammatory responses, and higher levels of noncalcified, harder-to-detect plaque in women.”
The results for most people do not mean changing their daily habits. But during episodes of heavy pollution, such as forest fire smokepeople at higher risk of coronary heart disease, including those with heart disease, diabetes, or older age, may benefit from staying indoors, using air filtration, or wearing an N95 mask outdoors, Deo says.
“Reducing long-term exposure and moving toward stricter air quality standards could significantly protect cardiovascular health,” says Hanneman. “It’s an intervention that benefits both public health and the planet.”