Long-term exposure to wildfire smoke may significantly increase the risk of heart failure, particularly among older adults, women, and socioeconomically vulnerable populations, according to a major study published today in JACC, the flagship journal of the American College of Cardiology. This national, population-based investigation is the first of its kind to compare the health impacts of prolonged exposure to wildfire smoke with those of other familiar sources of air pollution. The findings reveal that as the concentration of wildfire-related air pollution increased over two years, the incidence of heart failure rose accordingly, marking an urgent public health concern amid escalating environmental changes.
At the heart of the study is PM2.5, a category of airborne particulate matter measuring 2.5 micrometres or smaller in diameter. These microscopic particles can bypass the body’s natural defences, travelling deep into the lungs and, in some cases, entering the bloodstream. Various sources, including motor vehicles, industrial processes, and the combustion of fossil fuels, emit PM2.5. However, wildfires are increasingly contributing to PM2.5 levels worldwide, a trend that is accelerating due to rising global temperatures and longer dry seasons. The uniquely hazardous composition of wildfire smoke, including organic chemicals and heavy metals, raises additional concern over its effects on human health.
The researchers, led by Dr Hua Hao of the Rollins School of Public Health at Emory University, analysed data from all Medicare Fee-For-Service beneficiaries in the United States between 2007 and 2018. They found that for each one microgram per cubic metre increase in wildfire-related PM2.5 over two years, the risk of heart failure rose by 1.4%. While this may appear minimal on an individual level, the implications are vast: the researchers estimate such exposure could contribute to over 20,000 additional heart failure cases annually among older adults alone. The study also assessed how frequently individuals were exposed to elevated smoke levels, measuring the number of days per year when PM2.5 from wildfires exceeded thresholds of 1 or 2.5 micrograms per cubic metre.
Notably, the increased risk was not uniformly distributed across the population. The data showed that women, Medicaid-eligible individuals, and those residing in lower-income areas were disproportionately affected. These findings underscore the compounded vulnerabilities faced by specific groups due to systemic inequities in healthcare access, environmental safety, and social determinants of health. Dr Hao noted that “even a small increase in smoke exposure can carry serious implications for heart health,” especially among those who are already at heightened risk. Such insights point to the need for targeted protective measures and public health strategies that prioritise at-risk communities.
A notable aspect of the study was its comparison of the health impact of wildfire PM2.5 with that of PM2.5 from other non-smoke sources. The researchers found that for the same increase in particulate concentration, non-smoke PM2.5 was associated with only a 0.5% rise in heart failure risk, compared to the 1.4% increase linked to wildfire smoke. This suggests that smoke from wildfires may be more toxic per unit of exposure than other forms of air pollution. The precise reasons for this disparity are still being investigated, but may include differences in chemical composition, particle size distribution, or the presence of volatile organic compounds in wildfire smoke.
In an accompanying editorial, Dr Joan A. Casey of the University of Washington highlighted the broader environmental context: “By century’s end, under a high-emission climate scenario, 74% of the globe is expected to experience significant increases in the duration and frequency of wildfire events.” Already in the United States, wildfire smoke days — once rare — now occur multiple times a year. This new everyday demands a re-evaluation of how environmental threats are managed, both in terms of mitigation and adaptation. As smoke exposure becomes more frequent, the cumulative cardiovascular burden may grow, particularly for those in smoke-prone regions.
Dr Harlan M. Krumholz, Editor-in-Chief of JACC and Professor at Yale School of Medicine, described the study as a crucial contribution to cardiovascular research. “This study highlights a growing and underappreciated threat to heart health,” he said. “As wildfire smoke becomes more common and more intense, even small long-term exposures are enough to elevate heart failure risk — especially among our most vulnerable populations.” He emphasised the importance of integrating these findings into public health policy, emergency preparedness, and clinical practice. While the study faced some limitations — including possible measurement errors in pollution estimates and unmeasured individual health variables — it offers a sobering look at how environmental stressors are shaping the future of cardiovascular health.
More information: Hua Hao et al, Long-Term Wildfire Smoke Exposure and Increased Risk of Heart Failure in Older Adults, Journal of the American College of Cardiology. DOI: 10.1016/j.jacc.2025.04.058
Journal information: Journal of the American College of Cardiology Provided by American College of Cardiology
