Wildfires — likely to have become more frequent due to climate change — made considerable contributions to air pollution last year, the United Nations weather agency said in a report on Friday.

Wildfires in the Amazon, Canada and Siberia have shown how air quality can be impacted on a vast scale, the World Meteorological Organization (WMO) said in the fifth edition of its annual Air Quality and Climate Bulletin.

How have wildfires impacted air pollution?

The report looked into the interplay between air quality and climate, highlighting the role of tiny particles called aerosols in wildfires, winter fog, shipping emissions and urban pollution.

"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.

Particles smaller than 2.5 micrometres (PM 2.5) are particularly harmful since they are small enough to penetrate deep into the lungs and enter the bloodstream.

In 2024, wildfires led to above-average PM 2.5 levels in Canada, Siberia and central Africa, the bulletin showed.

But the biggest surge in PM 2.5, the report said, was seen in the Amazon basin amid record wildfires in the western Amazon region and drought-fueled fires in northern South America.

Wildfires create 'witches' brew' of pollutants

The WMO also underscored the far-reaching consequences of last year's wildfire fury.

Its bulletin showed how PM2.5 emissions from wildfires in the Amazon basin resulted in a measurable degradation in air quality in faraway, densely populated urban areas in Brazil.

Wildfires in Canada also caused 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," WMO scientific officer Lorenzo Labrador said at a press conference.

Labrador said the wildfires were releasing a "witches' brew" of components that pollute the air.

While Friday's report focused on 2024, the WMO added that  record wildfires in southern Europe this year had contributed to pollution across the continent.

The bulletin also shed light on some positive signs, with particle pollution in Eastern China declining last year due to sustained reduction efforts.

Ambient air pollution results in 4.5 million premature deaths a year, according to the World Health Organization.

Edited by: Sean Sinico