Heart scans suggest ‘safe’ air can still harm

Even “safe” – A new study tracking more than 11,000 adults in and around Toronto finds that long-term exposure to fine particulate matter and nitrogen dioxide is linked to greater coronary artery disease on heart scans—effects that did not flatten at low pollution levels an

A person can check the daily air index, see numbers that look “good,” and still unknowingly carry damage deep in the arteries that feed the heart.

That’s the unsettling message emerging from a new analysis of heart scans—one that links long-term exposure to common traffic-related pollution to more advanced coronary artery disease, even when levels are near or below regulatory safety limits.

Researchers report the results in the June 2026 issue of Radiology. Their study ties exposure to fine particulate matter and nitrogen dioxide—pollutants emitted largely through vehicle traffic and fossil fuel combustion—to the buildup and progression of disease in coronary arteries. After adjusting for factors including high blood pressure and cholesterol. the association became weaker. suggesting that air pollution may partly increase risk by worsening established cardiovascular risk factors.

The study cannot prove that air pollution causes heart disease. but it adds weight to a growing body of evidence connecting the two. Cardiac surgeon Salil Deo. of Case Western Reserve University School of Medicine in Cleveland and not involved in the work. said there may be “no ‘floor’ at which air quality can be considered entirely safe for the human heart.”.

Coronary artery disease is driven by calcium deposits and plaque buildup that narrow the heart’s arteries. raising the risk of heart attack. Earlier research has linked air pollution with heart attacks and strokes. and experts estimate air pollution contributes to 4 million to 6 million of the 20 million cardiovascular deaths worldwide each year.

What sets this new work apart is where it looks. Instead of focusing on events like heart attacks. the study used heart scans to examine how long-term exposure is associated with arterial disease. Kate Hanneman. a cardiac radiologist at the University of Toronto. said the approach helps show how pollution tracks with the buildup and progression of coronary artery disease.

Hanneman and colleagues followed more than 11,000 adults in Toronto and surrounding areas who underwent heart scans from 2012 to 2023. To estimate long-term pollutant exposure, the team linked each participant’s residential history to air quality data from the previous decade.

The researchers focused on fine particulate matter and nitrogen dioxide, or NO2. Fine particulate matter consists of tiny airborne particles small enough to be inhaled deep into the lungs. NO2 is a gas produced mainly by vehicle traffic and fossil fuel combustion. Both, the study notes, can contribute to inflammation that affects the heart and blood vessels.

Most participants were exposed to levels below Canada’s annual air quality standards and within levels commonly seen across North American and European cities.

On scans, higher exposure to fine particulate air pollution corresponded to more visible signs of heart artery disease. As exposure increased, calcium buildup in the heart arteries was higher and plaque was more common. The study also found greater odds of serious artery narrowing—especially in women.

By comparison, the scans showed similar effects for NO2, but smaller ones.

“There was no level at which the risk clearly flattened or disappeared,” Hanneman says.

In men, the association between severe artery narrowing and higher pollutant exposure was not statistically significant. Still, both sexes showed more calcium and plaque as pollution increased.

Hanneman also pointed to the wider pattern seen in earlier work. “The pattern is consistent with earlier research,” she said. “It may reflect biological differences. such as breathing rates relative to body size. hormone-related inflammatory responses and higher levels of noncalcified. harder-to-detect plaque in women.”.

For everyday life, the researchers are careful not to suggest panic or constant rule changes. The findings don’t mean most people should overhaul their daily routines. But the study’s implications sharpen during episodes when pollution spikes—wildfire smoke being the obvious example.

During heavy pollution episodes, Deo said, people at higher risk of coronary artery disease—including those with heart disease, diabetes, or advanced age—may benefit from staying indoors, using air filtration, or wearing an N95 mask outdoors.

Hanneman framed the broader direction more boldly: “Reducing long-term exposure and moving toward stricter air quality standards could meaningfully protect cardiovascular health,” she said. “It’s an intervention that benefits both public health and the planet.”

The human takeaway is straightforward even if the science is nuanced: the arteries don’t wait for catastrophe. When pollution lingers day after day—even at levels meant to be safe—the heart can start accumulating damage that scans are now able to see.

air pollution coronary artery disease heart scans fine particulate matter nitrogen dioxide Radiology June 2026 cardiovascular deaths wildfire smoke N95 mask air filtration women