Firefighters and Smoke: Health Research and What It Means

Wildland firefighting exposes crew members to heterogeneous smoke plumes that contain fine and ultrafine particulate matter, volatile organics, and combustion byproducts from both vegetation and man-made materials; these mixtures vary by fire type and burned material. Because ultrafine particles can cross the alveolar barrier and enter the bloodstream, repeated seasonal exposures may have systemic effects that go beyond immediate respiratory irritation. Consequently, researchers have examined long-term outcomes, including cardiovascular disease and cancer, in personnel who have spent many seasons on the fireline.

The International Agency for Research on Cancer (IARC) has classified occupational exposure as a firefighter as carcinogenic to humans (Group 1). One modeled assessment estimated that lung cancer mortality could increase by 8 percent to 43 percent across different career scenarios, depending on days worked per year and career length. Moreover, a recent study of wildland-urban interface fires observed that 50 microRNAs changed in blood after exposure, suggesting molecular pathways that might explain elevated disease risk.

To address these uncertainties, NIOSH and partners have started field studies and a national registry; the NIOSH National Firefighter Registry for Cancer collects exposure and health data, and 24,000 firefighters had enrolled by March 31. NIOSH field teams have measured lung function, inflammatory and cardiovascular markers, and other indicators before and after fire seasons so that short-term shifts can be tracked and correlated with exposure history. At the same time, attention to contaminated gear and PFAS-treated equipment has increased, since chemical treatments themselves represent another potential carcinogenic pathway.

If protective practices are strengthened and monitoring is expanded, future crews may face lower cumulative risk; however, without sustained research and better controls, firefighters who work many seasons could remain at higher risk of chronic disease. These findings underline the importance of follow-up medical screening and improved respiratory protection during prolonged wildfire events.