An ‘apocalyptic wall of flames’.
That’s how firefighters and local authorities have described the catastrophic wildfires sweeping across much of France and Spain, forcing more than 300,000 people to flee their homes or seek shelter.
But it’s not just the immediate threat to life from the flames or smoke that is putting the health of thousands in jeopardy.
Mounting evidence suggests there are serious – and potentially fatal – long-term consequences not just for those caught up in the fires but even for those hundreds of miles away.
For instance, one study found that people who inhaled higher average levels of wildfire smoke around their homes are more likely to suffer a stroke than those exposed to the lowest levels, the European Heart Journal reported earlier this year.
Based on analysis of the health records of almost 25million Americans aged 65 and over, the researchers found the risk was nearly twice that triggered by the same amount of pollution from traffic and industry – with wildfire smoke estimated to have caused around 17,000 additional strokes a year in the US. It’s a figure many fear will rise further due to global warming.
Crucially, even moderate levels of wildfire pollution appeared to increase the danger – not just when the air was visibly thick with it, the study found.
More immediately worrying for holidaymakers heading to wildfire-risk regions, other research suggests health can be damaged in just a matter of days.
And it’s not just mainland Europe where the danger lies. Last week, smoke from a wildfire in the Cairngorms in Scotland travelled 50 miles east to Aberdeen.
A blaze in Saint-Jean-d’Illac, near Bordeaux. Firefighters and local authorities have described the catastrophic wildfires sweeping across much of France and Spain as an ‘apocalyptic wall of flames’
‘Wildfire is often thought of as a problem for southern Europe, but that’s increasingly changing,’ says Dr Douglas Kelley, a global fire modelling expert at the UK Centre for Ecology and Hydrology.
‘In 2025, the UK experienced its most extensive recorded wildfire season, with record areas burned across the country.’
He says fires on heathland, moorland and peatland ‘can have significant impacts on air quality and public health, even when they occur far from major population centres’.
He adds: ‘The wildfire risk is expected to increase across much of the UK, with more frequent periods of longer fire seasons and larger fires.
‘That means smoke pollution is also likely to become a more important public health issue.’
The impact can be felt within just days. A study last year in The Lancet Planetary Health compared daily smoke levels from wildfires with death records covering 541 million people across 32 European countries.
It found the risk of dying from any cause rose during the seven days after wildfire pollution rose. And it seems wildfire smoke is more harmful than ‘standard’ air pollution, the researchers from the Barcelona Institute for Global Health noted.
The usual way of calculating the harm caused by air pollution assumes that tiny particles are equally dangerous whether they come from traffic, industry or a wildfire. Using this method, only 38 deaths a year would have been attributed to wildfire smoke.
Mounting evidence suggests there are serious – and potentially fatal – long-term consequences not just for those caught up in the fires but even for those hundreds of miles away
But when the researchers allowed for evidence that suggested particles released by fires are more harmful, the estimate rose to 535, almost 14 times higher.
Wildfire smoke is thought to damage the body so quickly because burning trees and vegetation release a mixture of toxic gases and fine particles known as PM2.5. These particles are less than one-thirtieth of the width of a human hair and can travel deep into the lungs.
They irritate the lung tissue, causing the immune system to release inflammatory chemicals. This can make the airways swell and tighten and increase mucus production, leading to coughing, wheezing, breathlessness and chest tightness.
The inflammation can also spread throughout the body, damaging the lining of blood vessels, making them stiffer and causing the blood to clot more readily – potentially increasing the risk of a heart attack.
It may also make fatty deposits inside if the arteries rupture. If a clot then blocks the blood supply to the brain, it causes a stroke.
Another major study, published in the Journal of the American College of Cardiology in February, which looked at 65.2million Americans aged 65 and over and their average three-year exposure to wildfire pollution, found that those who breathed in moderate amounts had a 4 per cent greater risk of being admitted to hospital with cardiovascular problems than those inhaling the least.
At higher exposure levels, the risk of heart failure was at least 20 per cent greater.
Associate Professor Kai Chen, an environmental-health epidemiologist at the Yale School of Public Health who led the study, told Good Health wildfire smoke ‘contains a greater share of much smaller, chemically reactive particles than typical urban pollution’.
The smallest particles may also pass from the lungs into the bloodstream where they can irritate and damage blood vessels and intensify inflammation, triggering chemical ‘stress signals’ which travel around the body.
These signals can disturb the nerves that keep the heart beating steadily, making its electrical rhythm unstable. The heart may then beat too quickly, too slowly or irregularly, known as an arrhythmia.
The signals also cause blood vessels to tighten, forcing the heart to work harder and raising the risk of a heart attack, particularly in someone whose arteries are already narrowed.
For people with asthma or chronic obstructive pulmonary disease, which affects around 1.2million people in the UK, the consequences can be more serious.
‘People with asthma or COPD already have sensitive or damaged airways,’ explains Dr Matt Swallow, clinical lead at the charity Asthma + Lung UK. ‘Smoke can trigger airway inflammation, making symptoms worse and increasing the risk of an asthma attack or COPD flare-up.’
Yet experts warn that people do not even have to be close to a wildfire to suffer the effects.
Powerful fires can propel smoke several miles into the sky, where faster winds may carry it across countries or even oceans. Changes in the weather can then bring the pollution back down into the air people breathe.
‘Distance alone is often a poor indicator of exposure,’ says Dr Mark Parrington, a senior scientist at the EU’s Copernicus Atmosphere Monitoring Service. ‘People do not need to be immediately downwind of a wildfire to experience wildfire smoke pollution.’
The extraordinary distance smoke can travel was demonstrated in 2023, when pollution from Canadian wildfires crossed the Atlantic and reached Europe.
A study published in Nature last year estimated that almost 48million Europeans experienced at least one day when particle pollution exceeded the World Health Organisation’s recommended daily limit of 15 micrograms per cubic metre of air, with Canadian wildfire smoke responsible for at least half of it.
The same fires sent smoke hundreds of miles across the US. The US Centers for Disease Control and Prevention found that A&E visits for asthma were 17 per cent higher than expected during 19 days when smoke pushed air pollution to unhealthy levels.
Dr Parrington says smoke from the current French and Spanish fires is being carried mainly eastwards and is not expected to reach Britain.
But he still fears Britain ‘may increasingly experience episodes of degraded air quality originating from fires hundreds or even thousands of kilometres away’.
‘These fires can have significant impacts on air quality and public health, even when they occur far from major population centres,’ he adds.
