The World Meteorological Organization (WMO) has warned that rising pollution from wildfires and heatwaves threatens to undermine international efforts to improve air quality, with growing risks to human health, agriculture and ecosystems.
According to the World Meteorological Organization, the relationship between climate change and air pollution is becoming increasingly difficult to separate, as rising temperatures, extreme fire activity and changing atmospheric conditions contribute to higher concentrations of harmful pollutants.
Among the report’s key concerns are ground-level ozone and aerosols, including black carbon and microplastics, whose ability to travel long distances can expose environments far from their sources.
According to the WMO, the challenge is compounded by gaps in atmospheric monitoring, with some pollutants not being sufficiently observed despite their widespread presence and potentially harmful effects on human health and ecosystems.
The organisation therefore stressed the need for air-quality and climate policies to be developed and implemented in a coordinated manner, arguing that the two challenges cannot effectively be addressed in isolation.
WMO noted that PM2.5, referring to microscopic particles and droplets measuring less than 2.5 micrometres in diameter, remains a significant public-health concern because the particles can penetrate deep into the lungs and enter the bloodstream.
PM2.5 originates from a wide range of sources, including industrial activities, agriculture, residential heating and transportation.
Wildfires and dust storms are also major contributors, making the pollutant particularly sensitive to changes in climate and weather conditions.
In 2025, PM2.5 concentrations remained above their long-term averages in northern Canada, parts of the Russian Federation and western-central Africa, largely due to increased fire activity, according to the bulletin.
Northwestern Spain was also identified as a hotspot following exceptional fires.
The situation differed in South America, where burning in the Amazon region was relatively lower.
China, meanwhile, continued to record PM2.5 levels below its long-term average, reflecting declining emissions associated with human activities. India continued to experience above-average concentrations, driven by biomass burning and other pollution sources.
For the first time, WMO incorporated models from four different sources in assessing particulate matter concentrations. Despite differences in the models and their inputs, the organisation revealed that the results were broadly comparable and consistent, providing greater confidence in the understanding of atmospheric processes.
The findings are particularly significant for Africa, where western-central parts of the continent recorded elevated PM2.5 concentrations linked to increased fire activity.
Extreme Wildfires and Heatwaves Raise Health Risks
The WMO report identifies extreme wildfires as one of the most significant emerging threats to air quality, warning that smoke from major fires can produce serious consequences for human health because of its high toxicity.
A study cited in a WHO bulletin indicates that extreme fire-smoke events have tripled globally since the 1990s.
WMO cautioned, however, that the actual health burden could be considerably higher.
One of the key concerns is that conventional air-quality assessments may not fully capture the health risks associated with wildfire smoke. The report points to epidemiological research suggesting that conventional risk models based on total PM2.5 concentrations could underestimate mortality attributable to wildfires by as much as 93%.
This is because particles generated by fires can have greater toxicity than particulate matter originating from some other sources, meaning that simply measuring the overall concentration of PM2.5 may not provide a complete picture of the health threat.
The WMO therefore argues that air-quality risk assessments need to account for the distinct characteristics and toxicity of fire-derived particles.
The organisation also warned that the challenge could become more difficult as climate change creates conditions that favour extreme fires.
Heatwaves present another major air-quality challenge, particularly through their relationship with ground-level ozone.
Unlike ozone high in the atmosphere, which protects the Earth from harmful ultraviolet radiation, ground-level ozone is a pollutant that can damage human health, agriculture and ecosystems.
The WMO noted that long-term exposure to ground-level ozone is associated with increased mortality, particularly through respiratory diseases.
Heatwaves can intensify the problem because higher temperatures, stagnant atmospheric conditions and strong solar radiation create conditions that favour ozone formation.
The WMO also drew attention to the wider environmental effects of aerosols, which can travel across national borders, oceans and continents.
Black carbon, commonly known as soot, is one example. When deposited on snow and ice, it reduces the amount of sunlight reflected by these surfaces, potentially accelerating melting.
Microplastics represent another emerging concern. Produced as plastic waste breaks down through exposure to sunlight and other environmental processes, microplastics have been detected in the atmosphere, on land and in the oceans.
The bulletin cited one Earth System Model simulation estimating that 51 million tonnes of microplastics are present on land and 22 million tonnes in the ocean, with these environments also serving as sources of microplastics entering the atmosphere.
However, WMO stressed that estimates vary substantially because sustained monitoring remains inadequate.
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