Pollution from intensifying wildfires and heatwaves threatens to reverse progress on cleaner air and increase risks to people and ecosystems, the World Meteorological Organization said in a new global bulletin released in Geneva on September 7. The United Nations agency called for climate and air-quality policies to be designed together, warning that the two problems reinforce each other.
The annual Air Quality and Climate Bulletin uses observations and research from the WMO Global Atmosphere Watch network and reviews pollution patterns during 2025. It focuses on fine particulate matter known as PM2.5, ground-level ozone and aerosols including black carbon and microplastics, all of which remain insufficiently monitored in many places.
WMO reported above-average PM2.5 concentrations in northern Canada, parts of Russia and west-central Africa because of increased fire activity. Exceptional late-summer fires also made northwestern Spain a hotspot. Levels stayed below the long-term average in China as human-caused emissions declined, while India remained above average because of biomass burning and other pollution sources.
The bulletin cited research indicating that extreme fire-smoke events have tripled worldwide since the 1990s and contributed to nearly 100,000 additional deaths a year from 2010 through 2018, a figure researchers say may be conservative. Another epidemiological study found that conventional models based on total PM2.5 may underestimate deaths attributable to wildfire smoke by as much as 93 percent because the particles can be more toxic.
Heat adds another danger by accelerating formation of ozone near the ground. High temperatures, stagnant air and strong sunlight have increased ozone during heatwaves in the southeastern United States, Europe and China, WMO said. Long exposure is associated mainly with respiratory mortality, while ozone also damages crops and ecosystems; future increases could cause tens of thousands of additional premature deaths.
The agency urged stronger observation systems and coordinated measures that reduce both warming emissions and conventional pollutants. It also highlighted black carbon settling on snow and ice, where it speeds melting, and atmospheric microplastics that can travel into remote environments. Released for the International Day of Clean Air for blue skies, the bulletin says better monitoring is essential as extreme fire weather becomes more frequent and meeting World Health Organization air guidelines grows harder.
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