Repeated heatwaves in France are taking a toll on people's lungs, doctors say, with young patients with no prior respiratory issues increasingly being admitted to hospital, a leading pulmonologist has told RFI.
Issued on: 31/07/2026 - RFJ
According to an international consortium of researchers, global warming caused by human activity could reach 1.5C around 2030. REUTERS - Temilade Adelaja
"Extreme heat causes the bronchi to constrict. This bronchoconstriction leads to breathing difficulties," Professor Colas Tcherakian, a pulmonologist and consultant at Foch Hospital near Paris, told RFI. "You may feel unwell, even without having a respiratory condition."
"With the succession of heatwaves, we are learning that anyone can end up in hospital with a respiratory infection," Tcherakian added.
"It has now been clearly demonstrated that, when a heatwave lasts more than three days, the risk of developing this type of infection increases by 70 percent: that’s enormous."
Heat affects the range and circulation of bacteria, viruses, mould and other pathogens, while also reducing the body’s ability to fight infection.
"The first effect is that it inhibits our immune defences, which function less effectively above a certain temperature," Tcherakian said. "We become less able to defend ourselves against infection."
Heat also interferes with the development of a protein known as CFTR, which helps the body regulate fluid and electrolyte levels. In the lungs, it plays an important part in controlling the thickness of mucus.
That mucus normally traps infectious agents, dust and pollution before being moved out of the bronchial tubes by tiny hair-like structures. When it becomes too thick, it can no longer perform that function properly.
"All of this accumulates in the lungs, along with bacteria, viruses and an immune system that isn’t functioning properly," Tcherakian said. "Ultimately, this leads to more frequent lung infections."
Up to 10 million people in France have a respiratory condition such as chronic obstructive pulmonary disease, pulmonary fibrosis or lung cancer. Heat can quickly make breathing more difficult for them and increase the risk that their condition will worsen.
Children under 15, people over 75 and women are also more sensitive to heat, Tcherakian said.
"Extreme heat causes the bronchi to constrict. This bronchoconstriction leads to breathing difficulties," Professor Colas Tcherakian, a pulmonologist and consultant at Foch Hospital near Paris, told RFI. "You may feel unwell, even without having a respiratory condition."
"With the succession of heatwaves, we are learning that anyone can end up in hospital with a respiratory infection," Tcherakian added.
"It has now been clearly demonstrated that, when a heatwave lasts more than three days, the risk of developing this type of infection increases by 70 percent: that’s enormous."
Heat affects the range and circulation of bacteria, viruses, mould and other pathogens, while also reducing the body’s ability to fight infection.
"The first effect is that it inhibits our immune defences, which function less effectively above a certain temperature," Tcherakian said. "We become less able to defend ourselves against infection."
Heat also interferes with the development of a protein known as CFTR, which helps the body regulate fluid and electrolyte levels. In the lungs, it plays an important part in controlling the thickness of mucus.
That mucus normally traps infectious agents, dust and pollution before being moved out of the bronchial tubes by tiny hair-like structures. When it becomes too thick, it can no longer perform that function properly.
"All of this accumulates in the lungs, along with bacteria, viruses and an immune system that isn’t functioning properly," Tcherakian said. "Ultimately, this leads to more frequent lung infections."
Up to 10 million people in France have a respiratory condition such as chronic obstructive pulmonary disease, pulmonary fibrosis or lung cancer. Heat can quickly make breathing more difficult for them and increase the risk that their condition will worsen.
Children under 15, people over 75 and women are also more sensitive to heat, Tcherakian said.
Heat and pollution
High temperatures are not the only danger. Heatwaves generally occur during periods of strong sunshine and increased road traffic pollution, creating higher concentrations of ozone.
Sunshine, heat and exhaust fumes combine to produce the gas, which irritates the respiratory system. People are therefore exposed to both the direct effects of heat and increased air pollution.
France has experienced a sharp rise in emergency admissions during its recent heatwaves, particularly among older people. But the number of younger patients with respiratory infections has also surprised doctors.
"I was extremely surprised by the frequency of respiratory infections in people I wouldn’t have expected: young people with no risk factors being hospitalised for infections," Tcherakian said.
"I also saw a patient hospitalised with flu at this time of year, which points to quite significant changes in viral circulation and susceptibility to infections."
Recent heatwaves appear to be affecting a different range of patients from those seen during previous episodes.
"These heatwave episodes are really very different from what we’ve seen before," Tcherakian said. "This is probably due to better management of patients who are already vulnerable. But we’re still seeing a change in the profile of people affected during heatwaves."
People ride the ferry to Toronto Island, as wildfire smoke from northwestern Ontario, combined with an intense heat wave, fills the sky, prompting health warnings and calls for residents to limit outdoor activity in Toronto, Ontario, Canada, 15 July 2026.
© Carlos Osorio / Reuters
Wildfire smoke adds another respiratory threat. It can travel hundreds or even thousands of kilometres, meaning fires in southern France can affect people in Paris – smoke from Canadian wildfires has previously reached France.
The smoke contains gases and extremely fine particles known as PM2.5, which are also found in vehicle exhaust fumes. Measuring about 2.5 microns, they can penetrate deep into the lungs and enter the bloodstream.
"They are extremely toxic, capable of penetrating deep into the lungs, and can even enter the bloodstream, causing cardiovascular effects," Tcherakian said. "This increases the risk of heart attacks and can cause neurological disorders, such as the onset of dementia. And, of course, it triggers respiratory diseases."
Particles released by wildfires are more toxic to the bronchial tubes than particles from conventional pollution, he added. More frequent fires could therefore produce a lasting rise in pollution and respiratory illness.
Pollution is already linked to 300,000 new cases of asthma each year in Europe, Tcherakian said.
Wildfire smoke adds another respiratory threat. It can travel hundreds or even thousands of kilometres, meaning fires in southern France can affect people in Paris – smoke from Canadian wildfires has previously reached France.
The smoke contains gases and extremely fine particles known as PM2.5, which are also found in vehicle exhaust fumes. Measuring about 2.5 microns, they can penetrate deep into the lungs and enter the bloodstream.
"They are extremely toxic, capable of penetrating deep into the lungs, and can even enter the bloodstream, causing cardiovascular effects," Tcherakian said. "This increases the risk of heart attacks and can cause neurological disorders, such as the onset of dementia. And, of course, it triggers respiratory diseases."
Particles released by wildfires are more toxic to the bronchial tubes than particles from conventional pollution, he added. More frequent fires could therefore produce a lasting rise in pollution and respiratory illness.
Pollution is already linked to 300,000 new cases of asthma each year in Europe, Tcherakian said.
Environmental factors
A national study led by Tcherakian and published in the British Medical Journal in December 2025 examined the health records and living environments of 660,000 patients in France.
The researchers studied several social and environmental risks at the same time, including temperature, pollution, climate, pollen and viral outbreaks. They then compared people’s exposure with their risk of hospital admission for respiratory illness.
Previous studies had generally considered those risks separately or focused on particular diseases and population groups.
"No one had looked at all the risk factors at the same time, and no one had done so on a national scale," Tcherakian said.
The study found that densely built cities with large amounts of concrete were areas of particular vulnerability, especially for people with asthma. Green spaces and wetlands appeared to offer some protection against hospital admission.
But rural and mountain areas were not automatically healthier. People living near vineyards treated with pesticides, livestock farms or homes using wood-burning heating could also face increased respiratory risks.
Research by the French National Institute of Health and Medical Research, INSERM, in Bordeaux had previously found that children living near vineyards treated with pesticides were more likely to experience worsening asthma. The national study found a similar effect across the wider population, regardless of whether people already had a respiratory condition.
The healthiest model appeared to be a green city combining access to healthcare with a balance of built-up areas, vegetation and possibly water.
"Ultimately, our model suggests that a green city is best for health," Tcherakian said. "Because you’re likely to have access to healthcare, you’re not exposed to too many risk factors, you have a good balance of built-up areas and green spaces, and possibly a body of water."
Prevention could also reduce the growing cost of treating respiratory illness, particularly by lowering temperatures in the areas facing the greatest risks.
"If we were to invest in high-risk areas to bring temperatures down, we’d make significant savings because what’s very costly in the management of respiratory diseases is hospitalisation, not the treatments given to patients," Tcherakian said.
This article has been adapted from an interview in French by RFI's Géraud Bosman-Delzons.
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