Researchers from the Institute of Environmental Assessment and Water Research (IDAEA-CSIC) are developing new methods to evaluate the doses of pollutants faced by wildland firefighters.
Firefighter facing a forest fire / Jordina Gili Ciurana (IDAEA-CSIC)
Large forest fires are blazes that spread uncontrollably, affecting both rural and urban areas. From ignition to extinction, they cause severe environmental and economic impacts, damaging flora, fauna, infrastructure, and even leading to loss of life. Moreover, due to the climate crisis, so-called “sixth-generation” fires — characterized by extreme intensity — are becoming increasingly frequent. A clear example is the “wave of fires” that swept across Spain last summer, burning nearly 400,000 hectares and making 2025 one of the worst years in recent history in terms of burned surface area.
For Joan Martí, geologist and researcher at the Institute of Environmental Assessment and Water Research (IDAEA-CSIC) in Barcelona, these large fires are not natural disasters but rather “human disasters, because nature does not create disasters. Nature simply maintains its balance.” Sometimes, he explains, such phenomena turn adverse for people. When that happens, the fire not only leaves behind material and human damage but also poses long-term health risks for those working to extinguish it, mainly due to smoke inhalation.
Addressing the issue of wildfires and their risks, the CSIC contributes scientific evidence to support public decision-making through research projects such as the European FIRE-RES project, which aims to increase resilience to wildfires in Europe by developing innovative technologies and economic, ecological, and social solutions.
Studying firefighters’ exposure
As part of this project, IDAEA-CSIC researchers are analysing firefighters’ exposure to the pollutants released by fire. Whether it is a wildfire or a prescribed burn — a controlled fire deliberately set by wildland firefighters to remove vegetation fuel and prevent or limit future fires — toxic substances are released when vegetation burns at relatively low temperatures.
These prescribed burns are carried out under specific weather conditions that allow scientists to predict the fire’s behaviour and its effects on the ecosystem in a delimited area. Their goals include reducing the probability or intensity of future fires by decreasing fuel loads, as well as regenerating pastures and restoring natural habitats for fauna and flora that depend on open spaces. This approach helps preserve mosaic landscapes, which reduce fuel continuity and fire hazard, and addresses the “fire suppression paradox”: by extinguishing all fires, fuel accumulation increases the likelihood of more severe fires in the future. Rural depopulation and the abandonment of traditional land uses are also contributing to the growing intensity of wildfires.
Through monitoring firefighters’ exposure during controlled burns in Catalonia between 2022 and 2024, the IDAEA team found that those responsible for igniting the fires — using torches filled with a mix of diesel and gasoline — experienced the highest exposure to soot (black carbon) and polycyclic aromatic hydrocarbons (PAHs), organic pollutants produced by incomplete combustion of biomass, according to a study recently published in the scientific journal Atmospheric Environment.
The total daily dose measured in the “torchbearers” was about five times higher than that of firefighters responsible for maintaining controlled firelines. During four-hour shifts, those handling the torches exceeded safety limits for exposure to carcinogenic smoke particles. The study notes that the concentration of other toxic compounds, such as dioxins and benzene, was not measured, suggesting that the risk could be even greater.
Silicone wristbands / Jordina Gili (IDAEA-CSIC)
To assess exposure, researchers used silicone wristbands that absorb organic contaminants carried by smoke. Firefighters wore them hanging from their suits rather than on their wrists to avoid contamination from sweat or substances unrelated to the air they breathe.
In 2019, IDAEA scientists had already used these wristbands to measure air pollution exposure among athletes during an international competition in Japan. This time, they went a step further, analysing which chemical substances firefighters breathe in while controlling and extinguishing wildfires.
Barend L. van Drooge, environmental scientist and researcher at IDAEA, explains that, along with the silicone wristbands, his team also measured exposure to soot and fine particles smaller than 2.5 micrometers (finer than dust, capable of reaching deep into the lungs) using geolocated sensors carried by firefighters during their operations. The filters capture and measure in real time the aerosols generated as the flames burn organic matter. Using this other methodology, results published this summer in the journal Chemosphere revealed that polycyclic aromatic hydrocarbons are present in high concentrations in the air firefighters breathe.
“This work is pioneering in quantifying their levels in the air. Until now, samples had been taken and measured, but without calculating the actual air concentration,” van Drooge adds.
The health effects of smoke
In 2023, the International Agency for Research on Cancer (IARC) classified firefighters’ occupational exposure as carcinogenic, causing bladder cancer and mesothelioma — the cancer affecting the membrane that lines the thorax, heart, and internal reproductive organs. IDAEA scientist Carmen Bedia studies how fire smoke affects human cells. In her laboratory, she used samples collected from filters placed on firefighters’ uniforms to expose substances released by fire to human brain organoids — complex cell cultures that reproduce brain tissue responses in the lab.
Firefighters of the Generalitat de Catalunya during extinction work / Jordina Gili (IDAEA-CSIC)
Her analysis showed that the filter extracts, particularly those with higher concentrations of compounds from biomass burning, caused significant changes in lipids — molecules involved in cell structure, energy storage, and essential cellular functions.
“Some of these altered lipids are vital for proper brain functioning and development. Such compositional changes could lead to brain ageing and neurodegenerative diseases,” explains Bedia.
The researchers recommend using FFP2 masks during higher-risk tasks. This protective measure, notes van Drooge, could also be applied to the general population exposed to smoke during wildfires. The Dutch researcher concludes that shorter shifts and rotating roles would help reduce individual exposure.
Fermín Grodira
Content produced under the 2024 CSIC–Fundación BBVA Scientific Communication Grant Programme
