Forest fire: what impact on respiratory health?
Southern France, California, Canada… Every year, as soon as the summer season begins, many regions are hit hard by flames. Unfortunately, the summer of 2025 was no exception. Starting in May, Canada catches fire. With 470 fires classified as uncontrollable and nearly 7.3 million hectares burned, particularly in the provinces of Manitoba and Alberta, this fire season ranks as the second most devastating after 2023. Then it was Southern France’s turn on July 8, with a fire breaking out near L’Estaque in Marseille. About 750 hectares went up in smoke between Les Pennes-Mirabeau and L’Estaque. In early August, another fire started near Ribaute, in Aude. It would devastate 16,000 hectares, tragically becoming one of the strongest French fires in recent years. In August, other European countries also had to face significant forest fire episodes, such as Spain, Portugal, Turkey, and Greece.
These forest fires, which can be accidental or criminal in origin, are fueled by climate change and drought, which increase their frequency.
Beyond the threat to the safety of property and people that these fires represent, they also have a significant negative impact on the air quality we breathe.
Globally, more than 1 billion individuals1 are exposed at least one day per year to air pollution caused by forest fires. This is a particularly alarming figure considering that the particles emitted by these fires (PM2.5) are among the most dangerous to human health.
So where do these fires come from? Why are they becoming more frequent? What are their impacts on our respiratory health? Our TEQOYA team has decided, by relying on the recording of environmental data in numerous regions, to show the impact of forest fires on air quality on a large scale. At the same time, a scientific study, published in May 2025 in the American journal Science Advances, has just validated the use of air purifiers as an effective solution to protect against their particles indoors. Analysis.
Forest Fire: an Increasingly Frequent Phenomenon
Forest Fires: Causes and Definition
Not all fire outbreaks are forest fires. The “Notre Environnement” website of the Government reminds us that at least 0.5 hectares of forest must have burned for a fire to be classified as a forest fire. The upper parts of the trees must also have been scorched. A forest fire results from three simultaneous elements: an ignition source (any element that can cause a spark or even a flame), a fuel (that burns), and weather conditions that favor the spread of flames.
Weather conditions conducive to fires are those with warm temperatures, which promote plant transpiration, combined with relatively low humidity and insufficient water reserves in the soil. The vegetation, thus dried out or even dead, is then more likely to catch fire. Wind can also be an aggravating factor and favor the spread of flames (ONF).
In 90% of cases, human activity is the cause of the fire. Human activity is also often the cause of fire outbreaks. In the case of the Canadian fires in the summer of 2025, the government agency Alberta Wildfire, responsible for managing forest fires in the region, considers that more than half of the fire outbreaks were due to human activity. Fires can occur during professional activities (construction sites or agricultural work) or daily activities (improperly extinguished cigarette butts, barbecues, etc.)2.
Why Are Forest Fires Becoming More Frequent?
While hot and dry weather conditions are often conducive to the ignition and spread of a forest fire, climate change is also a particularly aggravating factor.
In Canada, for example, the area of burned hectares has increased exponentially from 1.5 million hectares in 2012 to 5.5 million in 2025. Mike Flannigan, a Canadian professor specializing in forest fires at Thompson Rivers University, attributes this deterioration to climate disruption, which causes a general drying of ecosystems, leaving forests more susceptible to catching fire quickly. Europe unfortunately faces the same fate. EUSTAFOR (The European State Forest Association) identifies climate change as an aggravating factor for forest fires, especially in the Mediterranean region, the hottest area of the continent, including Spain, Portugal, and Greece.
In France, according to the Reference Trajectory for Adaptation to Climate Change (TRACC) promoted by the authorities and Météo France, the risk of forest fires will increase in the coming years. By 2050, nearly the entire French territory should be exposed to fire risk. Thus, 50% of metropolitan forests will be at risk of fire, compared to one-third currently.
Practically, with rising temperatures, regions already affected, such as Southern Europe or Canada, should experience a longer fire season (1 to 2 additional months3), while other regions currently spared could become subject to these phenomena. Forest fires have already been increasing sharply in recent years. For example, the government recorded 7,084 forest fires between January 1 and August 15, 2022, compared to an average of 4,000 over the decade 2007–20184. INRAE estimates that large fires will increase from 7 to 10 per year by 2050. They could rise to 20 by 2090 if greenhouse gas emissions and temperatures continue to grow5.
Source: Climate disruption increases forest fire risks, INRAE [Online], 2025
The Impacts of Forest Fires on Health
A Considerable Degradation of Air Quality
With the increase in forest fires, it is essential to consider the effects of these fires on our respiratory health. Indeed, forest fires have a highly degrading effect on air quality.
Using professional tools to measure outdoor air quality, our TEQOYA teams were able to analyze extensive data on the fires of summer 2025 and identify a significant increase in fine particles in the air coinciding with the start of the forest fires.
The following graphs show the evolution of air quality over two months, July and August 2025, in European areas affected by large-scale fires. They allow for a comparison of usual fine particle levels with those recorded during these events.
In August 2025, numerous simultaneous fires broke out on the Iberian Peninsula, notably in Riaño, Plasencia, and Ourense in Spain, and in Arganil in Portugal.
As shown in the graphs below, these locations then experienced an exponential increase in fine particles in the air, either on the same day or in the days following the start of the fires. The measured values approached those of pollution peaks in major Chinese or Indian cities.
In France, for example, during the fire that broke out at Les Pennes-Mirabeau in Marseille on July 8, 2025, the Regional Air Quality Agency (ATMO-SUD) reported that air quality had never been worse in the region than during this major event. Peaks in fine particles were observed in the days following the fire, as shown in the graph below.
Fine PM2.5 Particles: Highly Volatile and Dangerous
Beyond the danger they pose to property and people near the flames, exposure to forest fire smoke extends far beyond the immediate vicinity. Smoke can affect populations hundreds or even thousands of kilometers away7 because particles from these fires can travel very long distances.
The fires in Canada in 2025 provide a striking example. The map below shows a marked increase in particle concentrations near the fire sources, particularly around Calgary, Candle Lake, and Winnipeg. Additionally, a significant deterioration in air quality is observed in cities located thousands of kilometers away, such as Montreal or Chicago. In August 2025, Chicago experienced a severe air pollution episode caused by persistent smoke from the Canadian fires, even after they were controlled. Montreal, on its part, recorded a global record by becoming the city with the worst air quality during summer 2025, with peaks comparable to those of the most polluted metropolises in the world.
The situation in Ribaute, France, also illustrates the volatility of particles. While the fire started on August 5 in the town, the wind initially spared the city by blowing the fine particles out to sea from the east. However, a peak in fine particles occurred on August 8 when the wind calmed. The measured levels then far exceeded the usual regional thresholds.
The effects of fine particles concern all of us, especially since they are particularly harmful to health. On one hand, they are among the smallest particles (PM2.5) and can penetrate deep into our respiratory and arterial pathways. On the other hand, they are extremely toxic in composition because they are heavily laden with pollutants8. To protect against the negative health effects of fine particles, the WHO recommends an average PM2.5 level below 5 µg/m³. In Ourense, Spain, this threshold was exceeded almost throughout August 2025. Additionally, the smoke contained high concentrations of carbon dioxide and nitrogen, both highly toxic to health.
The Effects of Forest Fires on Our Health
Exposure to forest fire smoke can therefore cause numerous health problems, such as eye and skin irritation, or lead to the onset of acute or chronic diseases.
The European Climate and Health Observatory estimates that forest fires caused over 1,400 premature deaths in Europe in 2005. They also observed a twentyfold increase in respiratory disease cases after a series of forest fires around Vilnius, Lithuania, in 2022. The observatory further highlighted strong correlations between the frequency of forest fires and the rise in pneumonia cases in Portugal.
While everyone is affected by these risks, vulnerable populations are on the front line regarding their consequences: children, the elderly, pregnant women, and people with preexisting cardiovascular and/or respiratory conditions.9
Air purifiers as a solution to protect your respiratory health indoors
The benefits of using an air purifier indoors during a wildfire event
To protect themselves during a wildfire event, authorities generally advise people in nearby safe zones to stay indoors to avoid exposure to outdoor smoke.
Unfortunately, it is nearly impossible to fully shield oneself from wildfire fine particles, as they are among the smallest (PM2.5). Scientists estimate that on wildfire days, indoor pollution levels can be nearly three times higher than on normal days, even with windows closed10.
In this context, the study published in May in *Science Advances* demonstrated that using an air purifier indoors can have particularly beneficial effects on health11. An experiment conducted in California showed that using portable air purifiers helped reduce indoor PM2.5 particle concentrations. This had a positive effect by reducing the number of hospital admissions, which was lower than usual during a wildfire episode12.
The study also confirmed the relevance of using indoor air purifiers during wildfires to prevent health complications related to asthma. While installing an air purifier is not an absolute solution against wildfire smoke, it can still help mitigate harmful effects by removing toxic particles from the indoor air.
TEQOYA air purifiers: the natural and effective solution to protect yourself
To protect yourself, you can choose TEQOYA air purifiers, which use ozone-free ionization technology. This highly effective technology eliminates up to 99% of polluting particles — especially the finest ones like PM2.5, which are most present in wildfire smoke. Their efficiency is proven by tests carried out in independent laboratories. With no planned obsolescence, they come with a 10-year warranty.
Unlike some filtration technologies, such as HEPA filters that require regular replacement, our air purifiers only need occasional cleaning to maintain their effectiveness and performance. Energy-efficient, our TEQOYA T200 (for small rooms) and TEQOYA T450 (for large rooms) purifiers are completely silent.
Conclusion:
As wildfires become increasingly frequent due to climate change, the harmful effects of their smoke on health are now well established. Whether we live close to the fire line or farther away, we will all eventually face the negative health impacts of wildfire smoke. To protect ourselves, the use of indoor air purifiers has been scientifically validated as an effective solution to preserve our health. In any case, if you are near a wildfire, always follow the safety instructions issued by the authorities.
Sources:
- 1 7 8 9 10 11 12 The cost of clean air: Global disparities in reducing indoor wildfire-related PM2.5 exposure, Jing Li and Yifang Zhu (2025)
- 6Fire in Aude: the blaze that destroyed 16,000 hectares "is contained," announces the prefect, Ici, [Online], 2025
- France still battling largest wildfire in 75 years, BBC.com, [Online], 2025
- Wildfire threatens Marseille, shuts down airport in southern France, CNN.com, [Online], 2025
- Fire prevention in the face of climate change, ONF [Online], 2025
- 4Forest Fires: What to Expect and How to Adapt?, Resource Center for Climate Change Adaptation, [Online], 2025
- 23INRAE warns about the consequences of climate disruption on forest fires, notre-environnement.gouv.fr, [Online], 2024
- Toxic wildfire pollution infiltrates homes of 1bn people a year, study finds, The Guardian [Online], 2025
- 5Climate disruption increases the risk of forest fires, INRAE [Online], 2025
- Forest Fires, European Climate and Health Observatory [Online], 2025
- Intense forest fire season in Alberta in 2025, Radio-Canada [Online], 2025
- Canada wildfire season already second worst on record as experts warn of “new reality,” The Guardian [Online], 2025
- Forest Fires in Europe: A Growing Challenge, EUSTAFOR [Online], 2025
- Canada experiences one of its worst fire seasons in history: the new norm?, Radio-Canada [Online], 2025
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