Air Pollution in Canada Ups CAC, Total Plaque, and Obstructive CAD

MONTREAL, Canada—Long-term exposure to air pollution can lead to higher levels of coronary artery calcium (CAC), coronary plaque, and obstructive CAD, with differences seen between genders, according to Canadian registry data.

Prior studies, many from China, have already established a deleterious connection between air pollutants and cardiovascular health, but the new numbers highlight that this relationship can exist even in regions with relatively low levels of pollution.

Senior author Kate Hanneman, MD, MPH (University of Toronto, Canada), told TCTMD her team was not surprised by the findings. “This really was our hypothesis that long-term exposure would be associated with markers of atherosclerotic disease,” she said. “The strength of the association was really interesting, and the stratified analysis that showed that these associations with coronary calcium were significant in both men and women.”

These types of analyses are important, Hanneman continued, “particularly when we know that men and women have slight differences in their cardiovascular disease burden and outcomes. That was something we really wanted to focus on that was incremental to the existing literature.”

The study, which was presented as a poster by Felipe Castillo, MD (University of Toronto), last week at the 2025 Society of Cardiovascular Computed Tomography (SCCT) meeting, included retrospective data from 11,128 patients (mean age 59.1 years; 51.7% men) with suspected CAD who underwent outpatient CT in Canada between 2014 and 2023.

Researchers were interested in the effects of exposure to a 10-year mean level of small particulate matter < 2.5 µm (PM_2.5). Median annual PM_2.5exposure in the analysis was 7.5 µg/m^₃. Notably, the median CAC score was 3, with 45.6% of patients showing no plaque and 8.2% identified with obstructive CAD (≥ 70% diameter stenosis) on CT.

Every 1 µg/m^₃ increase in PM_2.5was associated with a 10.7% higher CAC score, 12.5% greater odds of higher total plaque burden, and 22.6% greater odds of obstructive CAD.

In a sex-stratified analysis, greater exposure to PM_2.5 was associated with increased risks of having higher CAC score and obstructive CAD but not total plaque in women. For men, higher CAC score and increased plaque burden were linked to greater PM_2.5 exposure, but not obstructive CAD.

Most of the patients in our study would’ve been below what the World Health Organization indicates as a safe exposure limit. Kate Hanneman

“Now we have data showing in this relatively large cohort that we see this association with coronary calcium scores in both men and women,” Hanneman said. “We also see the association at relatively low exposure levels. So this is really important [and] distinct from areas like China where patients typically have much higher exposure levels.”

Specifically, she added, “most of the patients in our study would’ve been below what the World Health Organization indicates as a safe exposure limit, for example, and we’re still seeing the association.”

Data like these provide insights into the underlying mechanisms of disease that tie air pollution to adverse cardiovascular outcomes, according to Hanneman. “Now we’re actually understanding that link—the intermediary—what’s happening at the tissue level,” she said. “This might allow us to think about having more careful monitoring of patients who have high exposure levels, maybe because they have high exposure [because] they work outside . . . or they, of course, live somewhere with fire pollution.”

These people might stand to benefit more than others by assessment with a CAC scan, Hanneman suggested. She also hopes the data will “empower” physicians and patients to consider air pollution exposure as a more serious cardiovascular risk factor.