NEW YORK — The first study appeared in The Lancet Oncology on September 15, 2026, followed by the second study in Nature Communications on September 17, 2026. Min Zhang, PhD, served as the first author of both studies, while Yaguang Wei, PhD, served as the senior author. The investigations examined the long-term health effects of fine particulate matter from wildfires, known as PM2.5.

"Our research shows that wildfire-related PM2.5 appears to be more harmful than equivalent levels of pollution from other sources," Wei said. At equivalent concentrations, wildfire-related PM2.5 was consistently associated with larger increases in hospitalization risk than PM2.5 from non-wildfire sources. "We found that wildfire smoke can affect both the lungs and the cardiovascular system, and that its effects may be stronger than those of similar amounts of pollution from traffic, industry, and other sources," Zhang reported.

The first study analyzed data from 414,016 adults aged 65 years and over with lung cancer in the SEER-Medicare database. Researchers estimated patients' wildfire-related and non-wildfire PM2.5 exposure using total ambient PM2.5 estimates and wildfire-specific PM2.5 estimates published by researchers at Stanford University. Both wildfire-related and non-wildfire PM2.5 were associated with increased mortality risk among patients following lung cancer diagnosis.

Wildfire-related PM2.5 accounts for approximately 4 percent of total PM2.5 but is responsible for about 17 percent of mortality related to total PM2.5 exposure. Researchers estimated that annual deaths among study participants were attributable to wildfire-related PM2.5 exposure. Higher numbers of smoky days and prolonged periods of smoke exposure were associated with poorer survival outcomes for lung cancer patients.

"Patients with lung cancer are already medically vulnerable, and our findings suggest that wildfire smoke may place them at even greater risk," Zhang said. She added that "as wildfire-related air pollution becomes more common, reducing exposure could become an increasingly important component of cancer care and survivorship planning."

Christine Ekenga, PhD, MPH, an Assistant Professor at Emory University’s Rollins School of Public Health and a co-author of the study, emphasized the clinical implications. "Lung cancer patients are already navigating substantial health challenges, and our findings suggest that long-term exposure to wildfire smoke may add another, potentially preventable risk," Ekenga said. "We need to better understand which patients are most vulnerable and develop practical strategies to reduce their exposure."

The second study analyzed hospitalization records from residents across 20 U.S. states between 2006 and 2019. This investigation included more than 57 million cardiovascular hospitalizations and nearly 33 million pulmonary disease hospitalizations. Long-term exposure to wildfire-related PM2.5 was associated with increased risks of hospitalization for heart failure, ischemic heart disease, hypertension, asthma, pneumonia, chronic obstructive pulmonary disease, and other respiratory illnesses.

At equivalent concentrations, wildfire-related PM2.5 was consistently associated with larger increases in hospitalization risk than PM2.5 from non-wildfire sources. "This study provided a unique opportunity to directly compare the health impacts of wildfire smoke with other sources of air pollution on a large scale," Zhang said. The analysis found particularly strong associations between wildfire smoke exposure and health risks among racial and ethnic minority populations, residents of metropolitan areas, and people living in communities with lower educational attainment and higher levels of socioeconomic deprivation.

Wei described the shifting nature of the threat. "Wildfire smoke is no longer a regional environmental issue. It is becoming a nationwide public health challenge," he said. He advised that "for people with lung cancer or chronic heart and lung diseases, monitoring air quality and limiting exposure during smoke events may be especially important." He also noted that health care providers may increasingly need to consider environmental exposures as part of comprehensive patient care.

The studies were conducted by investigators from the Icahn School of Medicine at Mount Sinai, Harvard T.H. Chan School of Public Health, Stony Brook University, and New York University. Funding for the research was provided by the National Institute of Environmental Health Sciences. Wei concluded that as wildfire activity continues to grow around the world, understanding the health consequences of wildfire smoke has become increasingly urgent. He added that "as wildfire activity increases, public health and environmental policies must account for both the quantity and the source of air pollution."

Why It Matters

The research establishes that wildfire-related PM2.5, while constituting a small fraction of total particulate matter, drives a disproportionate share of mortality. This disparity suggests that current air quality metrics, which often treat all PM2.5 equally, may underestimate the specific danger posed by wildfire smoke. The findings indicate that policy frameworks must evolve to distinguish between pollution sources to accurately assess public health risks.

The studies also show disparities in health impacts, with stronger associations found among racial and ethnic minority populations and those in communities with lower socioeconomic status. As wildfire activity expands globally, these vulnerabilities point to an urgent need for targeted protective strategies. Healthcare providers are increasingly positioned to integrate environmental exposure data into patient care plans, particularly for individuals with pre-existing lung or heart conditions.

Timeline

The first study was published in The Lancet Oncology on September 15, 2026. The second study was published in Nature Communications on September 17, 2026. Researchers at the Icahn School of Medicine at Mount Sinai published two studies indicating that wildfire smoke poses greater health risks than other sources of air pollution.

What's New

Later reporting identifies the Icahn School as a medical school. Additional context notes that Mount Sinai is a mountain in the Sinai Peninsula of Egypt.