The World Meteorological Organization said on Monday that pollution from increasingly intense wildfires and heatwaves could undermine efforts to improve air quality and protect public health. The warning accompanied the agency’s annual Air Quality and Climate Bulletin, released on the International Day of Clean Air for blue skies.
The report sets out a growing challenge for air-quality policy. Regulations in Europe and North America have reduced fine particulate matter, known as PM2.5, from industrial activity and transport. Exposure to PM2.5 produced by fires has risen, however, offsetting some of those improvements.
The WMO said air pollution and climate change are closely connected and should be addressed through coordinated policies rather than as separate problems. It warned that complying with the World Health Organization’s air-quality guidelines will become harder as the likelihood of extreme wildfires increases.
PM2.5 levels in 2025 exceeded long-term averages in northern Canada, parts of Russia and western-central Africa because of heightened fire activity, the WMO said. Northwestern Spain also became a PM2.5 hot spot after exceptional late-summer fires.
Fine particulate matter can travel deep into the lungs and into the bloodstream. The WMO report identifies PM2.5 and ground-level ozone as pollutants associated with respiratory and cardiovascular disease.
Lorenzo Labrador, a scientific officer at the WMO, said smoke can affect places that have otherwise reduced their pollution. “No matter how clean your city or your region is ... if you have a lot of pollution brought about by wildfires, that has the potential to negatively impact air quality in those regions as well.”
Labrador, of the WMO’s Global Atmosphere Watch network, said microparticles created by burning vegetation are ‘much more toxic’ than particles from other sources, including car exhaust. The brief does not specify the molecular mechanisms that account for the difference in toxicity.
A study cited in the bulletin found that extreme fire-smoke events have tripled globally since the 1990s. It estimated that such events may have contributed to nearly 100,000 additional deaths annually between 2010 and 2018.
The WMO also pointed to limits in the way health risks are measured. Conventional risk models that use total PM2.5 concentrations may underestimate mortality attributable to wildfire smoke by as much as 93 percent, the report said. It remains unclear whether that potential gap is consistent across different regions and populations.
The health effects associated with wildfire smoke include increased asthma attacks, hospitalizations for chronic obstructive pulmonary disease (COPD), increased use of respiratory medication, and effects on mental health and birth outcomes, according to the WMO.
Heatwaves add a separate pressure on air quality. The agency said extreme heat is becoming more frequent, more intense and longer-lasting as the planet warms. Higher temperatures, stagnant atmospheric conditions and intense solar radiation can all promote the formation of ground-level ozone.
Long-term exposure to ozone is associated with higher mortality, especially from respiratory diseases, the WMO said. Greater exposure could lead to tens of thousands of additional premature deaths. In heavily polluted regions, roughly one in five deaths from COPD is now attributed to long-term ozone exposure.
The report also flagged gaps in pollution monitoring. Black carbon and microplastics are widespread and could harm ecosystems, the WMO said, yet they are not sufficiently monitored.
The agency’s central conclusion is that progress on industrial and transport emissions alone may not secure cleaner air where climate extremes are intensifying. It said policy on air pollution and climate change will need to account for the health effects of both wildfire smoke and heat-driven ozone pollution.
Comments (0)