World Meteorological Organization: Heatwaves and Wildfires Worsen Air Pollution

Heatwaves and wildfires are worsening air quality across Europe, while climate change threatens to undermine efforts to improve it, the World Meteorological Organization said in its annual report on climate and air quality.

The report, released for the International Day of Clean Air on September 7, links rising temperatures to two major sources of pollution. Extreme heat encourages severe fires, whose toxic smoke contains large amounts of fine particulate matter. Heatwaves also bring the high temperatures, stable weather and intense sunlight that promote the formation of ground-level ozone.

Both pollutants pose serious health risks. The WMO said long-term exposure to ozone is associated with higher mortality, particularly from respiratory disease. Fine particles can travel deep into the lungs and enter the bloodstream, increasing the risk of heart attacks, irregular heart rhythms, strokes and pulmonary embolisms. Particles from wildfires are especially harmful because they contain many toxic chemicals.

Fine-particle pollution comes from industry, agriculture, household heating, traffic and wildfires. Emissions from industry and transport have fallen in Europe and North America in recent years because of tighter regulations. But the number of extreme fire events worldwide has tripled since the 1990s, according to a study cited by the WMO, increasing pollution from smoke.

In 2025, fire-related fine-particle concentrations were above long-term averages in northern Canada, parts of Russia and west-central Africa because of elevated fire activity. Northwestern Spain also became a hotspot after exceptional fires in late summer. The report's central warning is that air pollution and climate change are closely connected, making progress on one increasingly dependent on addressing the other.