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Wildfire smoke may pose a greater health threat than comparable levels of air pollution from other sources, according to two large studies that found links to cardiovascular and respiratory hospitalizations and poorer survival among people with lung cancer.
Researchers at the Icahn School of Medicine at Mount Sinai found that fine particulate matter from wildfires, known as PM2.5, was associated with greater health risks per unit of exposure than PM2.5 from non-wildfire sources.
Published separately in The Lancet Oncology and Nature Communications, the findings add to evidence that the source of air pollution may matter along with how much pollution people breathe.
The research comes as wildfire smoke increasingly reaches communities far beyond traditional fire-prone regions, exposing tens of millions of people across the United States to elevated levels of air pollution.
“Wildfire smoke is no longer a regional environmental issue. It is becoming a nationwide public health challenge,” said Yaguang Wei, PhD, Assistant Professor of Environmental Medicine at the Icahn School of Medicine at Mount Sinai and senior author of both studies. “Our research shows that wildfire-related PM2.5 appears to be more harmful than equivalent levels of pollution from other sources. As wildfire activity increases, public health and environmental policies must account for both the quantity and the source of air pollution.”
Wildfire Smoke Linked to Poorer Lung Cancer Survival
In the first study, published in The Lancet Oncology, researchers examined the relationship between long-term wildfire smoke exposure and survival among 414,016 adults ages 65 and older with lung cancer in the SEER-Medicare database.
Researchers estimated wildfire-related and non-wildfire PM2.5 exposure based on where patients lived. Both types of particulate pollution were associated with increased mortality risk following a lung cancer diagnosis, but wildfire-related PM2.5 was associated with substantially greater toxicity when researchers compared equivalent increases in exposure.
Although wildfire-related PM2.5 accounted for only about 4% of total PM2.5 exposure, researchers found it was responsible for about 17% of mortality related to total PM2.5 exposure.
More smoky days and longer periods of smoke exposure were also associated with poorer survival. Researchers estimated that hundreds of deaths annually among the study population were attributable to wildfire-related PM2.5.
“Patients with lung cancer are already medically vulnerable, and our findings suggest that wildfire smoke may place them at even greater risk,” said Min Zhang, PhD, first author of both studies. “As wildfire-related air pollution becomes more common, reducing exposure could become an increasingly important component of cancer care and survivorship planning.”
The findings also point to the potential importance of considering environmental exposures in patient care.
“For people with lung cancer or chronic heart and lung diseases, monitoring air quality and limiting exposure during smoke events may be especially important,” Wei said. “Health care providers may increasingly need to consider environmental exposures as part of comprehensive patient care.”
Christine Ekenga, PhD, MPH, Rollins Assistant Professor at Emory University’s Rollins School of Public Health and a study co-author, said more research is needed to identify which patients may be most vulnerable.
“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.”
Heart and Lung Hospitalizations Also Increased
The second study, published in Nature Communications, analyzed hospitalization records from residents across 20 states between 2006 and 2019 and linked them to models estimating long-term exposure to wildfire-related and non-wildfire PM2.5.
The analysis 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 hospitalization risks for a range of cardiovascular and respiratory conditions, including 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,” said Zhang, a postdoctoral fellow in the Department of Environmental Medicine at the Icahn School of Medicine at Mount Sinai. “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.”
Researchers found particularly strong associations 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.
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 conducted the study, which the National Institute of Environmental Health Sciences supported.
What the Findings Mean for Nurses
For nurses, the studies broaden the clinical relevance of wildfire smoke beyond the immediate respiratory effects associated with smoky days.
The findings suggest long-term exposure may be particularly concerning for patients already at increased risk, including those with lung cancer and chronic cardiovascular or respiratory conditions.
They also highlight environmental exposure as a consideration in patient assessment and education. During wildfire smoke events, nurses caring for vulnerable patients may encounter questions about air quality, exposure, and ways to reduce risk.
Future research will focus on identifying which chemical components of wildfire smoke may contribute to its heightened toxicity and understanding the biological mechanisms through which wildfire-related PM2.5 affects cardiovascular health, respiratory disease and cancer outcomes.
“As wildfire activity continues to grow around the world, understanding the health consequences of wildfire smoke has become increasingly urgent,” Wei said. “These studies represent an important step toward identifying who is most vulnerable and what strategies may help protect public health in a changing climate.”
