Wildfires release a “witches’ brew” of pollutants that can wreck air quality even a continent away, posing risks for infrastructure, ecosystems and human health.
Published On 5 Sep 2025
Wildfires made significant contributions to air pollution last year, according to the United Nations’ weather and climate agency.
In a report released on Friday, the World Meteorological Organization (WMO) said wildfires, likely to have been made more frequent by climate change, are releasing a “witches’ brew” of pollutants that can end up wrecking air quality a continent away.
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Such blazes in the Amazon, Canada and Siberia have brought home how air quality can be affected on a vast scale, the WMO said in its fifth annual Air Quality and Climate Bulletin.
“Wildfires are a big contributor to particle pollution and the problem is expected to increase as the climate warms, posing growing risks for infrastructure and ecosystems and human health,” the WMO said in a statement.
“Climate change and air quality cannot be addressed in isolation. They must be tackled together in order to protect our planet, our communities, and our economies,” added Deputy Secretary-General Ko Barrett.
Highlighting the role of tiny particles called aerosols in wildfires, winter fog, shipping emissions and urban pollution, the WMO said particles with a diameter of less than 2.5 micrometres (PM 2.5) are considered particularly harmful since they can penetrate deep into the lungs or cardiovascular system.
Wildfires in 2024 led to above-average PM 2.5 levels in Canada, Siberia and central Africa, the WMO noted. The biggest PM 2.5 surge, however, was in the Amazon basin.
WMO Scientific Officer Lorenzo Labrador, who coordinated the bulletin, said wildfires in Canada also ended up causing air pollution in Europe.
“We had that last year and this year as well. So you have a degradation in air quality across continents when the meteorological conditions are right,” Labrador told a news conference.
“What we have from these fires is essentially a witches’ brew of components that pollute the air.”
The World Health Organization estimates that air pollution causes more than 4.5 million premature deaths each year.
The WMO has called for improved monitoring and better policies to safeguard human and environmental health, and reduce agricultural and economic losses.
When countries take measures to combat poor air quality, the improvement can be clearly seen in meteorological data, said Paolo Laj, the WMO’s global atmosphere chief.
“Look at Europe, Shanghai, Beijing, cities in the United States: Many cities have taken measures and you see in the long term, a strong decrease” in recorded air pollution, he told the AFP news agency.
“Over a 10-year period, Chinese cities have improved their air quality in a dramatic way. It’s really impressive what they have done.”
In eastern China, PM 2.5 levels continued to decline last year, which the WMO has put down to sustained mitigation measures.
Laj said that while there was no all-purpose measure that could bring about drastic change in tackling air pollution, “when measures are taken, it works.”
