Long-term exposure to fine particulate air pollution may contribute to subtle heart tissue changes associated with the early signs of heart damage, according to research published in Radiology.
The study, which used cardiac MRI, found a connection between higher exposure to particulate matter and diffuse myocardial fibrosis – microscopic scarring in the heart muscle.
Although the relationship between air pollution and cardiovascular disease is well established, the specific tissue-level changes driving this risk remain unclear. This investigation aimed to clarify that link using imaging-based assessments of myocardial health.
MRI reveals early signs of fibrosis
The study examined 694 individuals in total, including 201 healthy participants and 493 people with dilated cardiomyopathy. Researchers measured each participant’s myocardial extracellular volume, a marker of fibrosis, using cardiac MRI. These values were then compared with estimates of long-term exposure to fine particulate matter, also known as PM2.5.
PM2.5 refers to airborne particles with a diameter of 2.5 micrometers or smaller. These particles are small enough to be inhaled deeply into the lungs and pass into the bloodstream. Common sources include traffic emissions, industrial activity and wildfires.
“We know that if you’re exposed to air pollution, you’re at higher risk of cardiac disease, including higher risk of having a heart attack,” said the study’s senior author Kate Hanneman, MD, MPH, from the Department of Medical Imaging at the Temerty Faculty of Medicine, University of Toronto and University Health Network in Toronto. “We wanted to understand what drives this increased risk at the tissue level.”
Participants with higher long-term exposure to PM2.5 exhibited greater levels of myocardial fibrosis. This association held true for both healthy individuals and those with existing heart disease. The most pronounced effects were observed in women, people who smoke and individuals with hypertension.
Reinforcing pollution as a risk factor
The findings contribute to a growing body of evidence suggesting that air pollution is an independent cardiovascular risk factor. This risk persists even when other major contributors, such as smoking and high blood pressure, are accounted for. The study also showed that health impacts may occur even when pollution levels fall below current global guidelines.
“Even modest increases in air pollution levels appear to have measurable effects on the heart,” Hanneman said. “Our study suggests that air quality may play a significant role in changes to heart structure, potentially setting the stage for future cardiovascular disease.”
“Public health measures are needed to further reduce long-term air pollution exposure,” continued Hanneman. “There have been improvements in air quality over the past decade, both in Canada and the United States, but we still have a long way to go.”
This research may support efforts to improve cardiovascular risk prediction. For example, air pollution exposure history could help clinicians refine risk assessments for patients in high-exposure settings, including outdoor workers or those living in highly polluted regions.
The results also underscore the role of radiologists and medical imaging in environmental health research.
“Medical imaging can be used as a tool to understand environmental effects on a patient’s health,” Hanneman said. “As radiologists, we have a tremendous opportunity to use imaging to identify and quantify some of the health effects of environmental exposures in various organ systems.”
Reference: Du Plessis J, DesRoche C, Delaney S, et al. Association between long-term exposure to ambient air pollution and myocardial fibrosis assessed with cardiac MRI. Radiology. 2025. doi: 10.1148/radiol.250331
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