Increasing pollution from increasingly severe wildfires and heatwaves is undermining global efforts to improve air quality and protect human health, the World Meteorological Organisation (WMO) warned on Monday.
In its annual report on air quality, the WMO highlighted the rise in “extreme wildfires”, warning that the toxic smoke they produce can have serious health consequences.
Climate change is fuelling extreme weather events, with heatwaves becoming more intense and wildfires increasing in frequency.
“Air quality and climate change should not be treated as separate issues. If one gets worse, the other also worsens,” said Lorenzo Labrador, a WMO scientist.
The report focuses mainly on two major air pollutants: fine particulate matter and ground-level ozone, both of which are linked to respiratory and cardiovascular diseases. It also examines aerosols, particularly black carbon and microplastics.
Wildfire smoke linked to rising mortality
According to the UN agency, concentrations of PM2.5 were significantly above average in 2025 in northern Canada, parts of Russia and central-western Africa because of wildfires. A significant increase was also recorded in north-western Spain following major wildfires during the summer.
The report cites research showing that extreme smoke-emission events have tripled globally since the 1990s and may have contributed to nearly 100,000 excess deaths annually between 2010 and 2018.
Although regulations introduced in Europe and North America have helped reduce PM2.5 from industry and transport, exposure to wildfire-related PM2.5 is increasing, the WMO said.
Fine particles released by burning vegetation in wildfires are also “much more toxic” than those produced by sources such as cars, Labrador explained.
These particles can affect people living far from active wildfires because they are transported by winds. Labrador also warned that current estimates of the health risks associated with air pollution often fail to adequately account for the increased toxicity of wildfire smoke.
An epidemiological study concluded that conventional models based on PM2.5 concentrations could underestimate wildfire-related mortality by as much as 93%.
Heatwaves fuel ground-level ozone
Ground-level ozone is another major source of air pollution with significant health consequences. Its formation is encouraged by heatwaves, such as those experienced across Europe in recent months, the WMO noted.
“Heatwaves create the right conditions for the formation of this ozone,” Labrador said.
Rising temperatures, stagnant air and strong solar radiation contribute to the formation of ground-level ozone during heatwaves, according to recent studies conducted in the southeastern United States, Europe and China.
Prolonged exposure to ground-level ozone is associated with increased mortality, particularly from respiratory diseases. The rising presence of this pollutant could therefore lead to tens of thousands of additional deaths, the WMO warned.
The report also raises concerns about atmospheric microplastics, whose concentrations and health effects remain difficult to assess accurately.
Black carbon, or soot, emitted mainly by wildfires, is another concern. When deposited on snow and ice, it reduces their ability to reflect sunlight, contributing to global warming.
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