Smoke from wildfires is not only an immediate threat to the respiratory and cardiovascular systems, but may also be linked to an increased risk of cancer, according to new research findings.
For years, attention focused mainly on the short-term effects of smoke exposure — breathing difficulties, eye irritation, coughing and heightened risks for vulnerable groups. However, recent findings suggest that long-term exposure to wildfire smoke could have far more serious health consequences.
The results were presented at the 2026 Annual Meeting of the American Association for Cancer Research (AACR). Researchers found that exposure to wildfire smoke is associated with a higher risk of lung, colorectal, breast and bladder cancer, as well as blood cancers. By contrast, no statistically significant link was found with ovarian cancer or melanoma.
Professor of Therapeutics, Epidemiology and Preventive Medicine Theodora Psaltopoulou, biologist Alexandra Stavropoulou, and Professor of Therapeutics, Oncology and Hematology Thanos Dimopoulos — all affiliated with the National and Kapodistrian University of Athens and Alexandra Hospital — explained that the study was based on data from the large-scale American PLCO Cancer Screening Trial.
The trial has monitored cancer incidence for years among adults from different regions of the United States. The current analysis focused on 91,460 participants who were evaluated for exposure to wildfire smoke.
Researchers combined air pollution data with satellite records tracking smoke presence from 2006 onward. To estimate exposure, they focused on three indicators: PM2.5 fine particulate matter from wildfire smoke, black carbon levels, and the number of days each area remained under smoke clouds. Exposure was recorded monthly until either a cancer diagnosis or the participant’s last follow-up in the study.
Particularly alarming is the fact that the associations were not limited to areas with extremely high pollution levels. Even low concentrations of PM2.5 appeared to increase cancer risk. Specifically, every increase of one microgram per cubic meter in average PM2.5 exposure over a 36-month period was associated with a 92% higher risk of lung cancer, 131% higher risk of colorectal cancer, 109% higher risk of breast cancer, 249% higher risk of bladder cancer and 63% higher risk of blood cancers.
Toxic Substances and Long-Term Effects
Wildfire smoke, experts note, contains a wide range of toxic substances, including known carcinogenic compounds such as polycyclic aromatic hydrocarbons. Although exposure initially occurs through the lungs, the effects are not confined there. These substances can enter the bloodstream, spreading carcinogenic agents throughout the body. In addition, smoke exposure triggers inflammation, a condition closely linked to cancer development.
Environmental Crisis and Public Health
The significance of the research grows as wildfires become increasingly frequent and intense, both in the United States and globally. Wildfire smoke has evolved into a major source of air pollution, undermining decades of progress in improving air quality. Scientists stress that this phenomenon is no longer solely an environmental or climate issue, but also a major public health challenge.
Limitations and Need for Further Research
Researchers point out that satellite smoke data are only available from 2006 onward, making it difficult to fully examine the role of smoke exposure in the initial development of cancer, since many years can pass before diagnosis. In addition, the analysis was based on participants’ place of residence and did not account for the amount of time they spent indoors or outdoors.
Overall, the findings suggest that wildfire smoke may have much deeper and longer-lasting effects than previously believed. Researchers say there is an urgent need for further studies, particularly regarding the chemical composition of smoke in different geographic regions and how it changes as it spreads through the atmosphere. At the same time, the data reinforce the need for greater public awareness and stronger policies to protect public health.
