No safe level: Long-term air pollution linked to heart disease

Clinical takeaway: Long-term exposure to fine particulate matter and nitrogen dioxide was associated with more advanced coronary artery disease, particularly in women. This occurred even at pollution levels below current Canadian and US regulatory standards, suggesting clinicians may want to add environmental exposure history to cardiovascular risk assessment alongside smoking and family history.

Air pollution has long been linked to heart attacks and stroke, but a new study suggests the damage may begin far earlier and at exposure levels many assume are safe. Researchers used cardiac CT to show that a decade of exposure to common urban pollutants was independently associated with measurable coronary artery disease, even in a population breathing air that meets current regulatory standards.

Higher long-term exposure to both fine particulate matter (PM2.5) and nitrogen dioxide (NO2) was associated with worse outcomes across all three CT markers of coronary artery disease. For every small unit increase in decade-long PM2.5 exposure, participants had 11% more coronary calcium, 13% greater odds of higher plaque burden, and 23% greater odds of obstructive artery disease. Nitrogen dioxide showed similar but smaller associations. More than 9 in 10 participants had pollution exposures below Canada's regulatory threshold.

Researchers analyzed cardiac CT data from 11,128 adults seen at three Toronto hospitals between 2012 and 2023. Long-term pollution exposure was estimated using residential postal codes linked to provincial air quality monitoring data over the 10 years before each patient's scan. Models were adjusted for age, sex, socioeconomic status, and cardiovascular risk factors. Limitations include lack of data on diet, physical activity, and occupational exposures, and the fact that cardiac CT was clinically indicated, which may limit generalizability.

The findings suggest that air pollution's cardiovascular toll accumulates over years rather than short-term spikes. The association of small particulate matter with obstructive coronary disease was significant at 10-year exposures, but not at 1- or 5-year windows. The authors note that some cardiovascular risk factors may lie on the pathway between pollution and heart disease, meaning fully adjusting for them could underestimate the true association.

A notable sex difference also emerged: the link between pollution and obstructive coronary artery disease was significant in women but not in men in fully adjusted models, a pattern the authors attribute to biological differences including higher respiratory rates, estrogen-related inflammatory responses, and a greater proportion of noncalcified plaques in women.

"The fact that we can detect a measurable signal in coronary atherosclerosis at these levels suggests there may be no clear, safe threshold for cardiovascular harm from air pollution, and that even populations in countries with relatively clean air face meaningful cardiovascular risk from environmental exposure," said senior author Kate Hanneman, M.D., M.P.H., vice chair and associate professor at the University of Toronto, Department of Medical Imaging, and deputy lead of sustainability at the University Health Network's Joint Department of Medical Imaging at Toronto General Hospital.

Source: Castillo et al. Radiology. June 9, 2026. Sex-Specific Associations between Long-term Air Pollution Exposure and Coronary Atherosclerosis at Cardiac CT