Air pollution may quietly scar your heart

Hidden inside the chests of nearly 700 Toronto residents, doctors have spotted the faint fingerprints of air pollution.

Using one of medicine’s most sensitive tools – cardiac magnetic resonance imaging – researchers have shown that long-term exposure to fine particulate matter, or PM2.5, is linked to subtle scarring of the heart muscle, known as diffuse myocardial fibrosis.

The finding helps explain why people who live with polluted air face a greater risk of heart failure, heart attacks, and other cardiovascular problems.

Tiny pollutant, big damage

PM2.5 refers to particles less than 2.5 micrometers in diameter, small enough to bypass the lungs’ natural filtering defenses and pass directly into the bloodstream.

Traffic exhaust, coal-fired power plants, industrial smokestacks, and even wildfire smoke all contribute to PM2.5 pollution.

While previous studies have repeatedly shown correlations between high PM2.5 levels and cardiovascular disease, the biological chain of events connecting the two remained hazy.

Kate Hanneman, a cardiothoracic radiologist at the University of Toronto and the University Health Network, is the senior author of the study.

“If you’re exposed to air pollution, you’re at higher risk of cardiac disease, including having a heart attack,” she said. “We wanted to understand what drives this increased risk at the tissue level.”

Heart scans uncover pollution’s toll

Hanneman’s team recruited 201 healthy volunteers and 493 patients diagnosed with dilated cardiomyopathy, a condition that weakens the heart’s pumping ability.

Each participant underwent a sophisticated MRI scan that measures how strongly the heart muscle holds onto a contrast dye. From that signal, physicians can calculate the degree of microscopic scarring that standard tests would otherwise miss.

The researchers then used satellite data, government air-quality monitors, and residential histories to estimate a decade’s worth of PM2.5 exposure for every participant.

Even within the relatively modest pollution levels found in Canadian cities, a clear pattern emerged. Higher long-term exposure to PM2.5 was linked with higher levels of myocardial fibrosis.

Particulate pollution may harm hearts even without pre-existing disease, affecting both cardiomyopathy patients and healthy individuals.

Pollution hits harder for some

A deeper dive into the numbers revealed that some groups bear a disproportionate burden. Women showed a stronger pollution-fibrosis relationship than men. Smokers and people with hypertension also displayed heightened sensitivity.

Those findings suggest that physiological or lifestyle factors can amplify the heart’s vulnerability to polluted air.

“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.”

Below the regulatory radar

One of the study’s most striking conclusions is that harmful changes occur well below many national and international air-quality standards.

Most of the Toronto cohort lived in neighborhoods that meet Canadian and World Health Organization guidelines. Yet the researchers still saw progressive scarring as pollution levels rose incrementally.

Public health policy often hinges on the idea of a safe threshold, but these results challenge that assumption.

“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,” Hanneman said.

She argues for more stringent regulations, better monitoring, and meaningful reductions in emissions from transportation, industry, and wildfire-prone landscapes.

Pollution seen through MRI

The work also expands the role of medical imaging beyond traditional diagnostics. “Medical imaging can be used as a tool to understand environmental effects on a patient’s health,” Hanneman explained.

By identifying and quantifying early tissue changes caused by pollution, imaging specialists can collaborate with cardiologists, epidemiologists, and public health officials to refine risk prediction and guide interventions.

For clinicians, the practical takeaway is that environmental history belongs in the exam room.

If a patient commutes along congested highways, works at an industrial facility, or lives downwind of frequent wildfires, physicians may want to factor that exposure into cardiovascular risk assessments.

These environmental risks could be considered alongside established factors like smoking or hypertension.

Tracking long-term heart damage

The Toronto team plans to follow its volunteers over time to see whether diffuse fibrosis translates into overt heart disease and whether reducing pollution exposure can halt or reverse the damage.

The experts also hope to replicate the study in regions with higher PM2.5 levels to test whether the relationship strengthens under harsher conditions.

Meanwhile, policymakers can draw a clear lesson: cutting particulate pollution yields not only cleaner skies but healthier hearts. Every gram of soot kept out of the atmosphere is a gram of microscopic scarring averted in the population’s cardiac muscle.

The study is published in the journal Radiology.

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