UN warns wildfires and heatwaves threaten global air quality gains
The World Meteorological Organisation reports that extreme wildfires and heatwaves generating toxic airborne pollutants risk reversing progress on air quality and endangering human health worldwide.
UN warns wildfires and heatwaves threaten global air quality gains
Extreme wildfires and heatwaves are generating dangerous microscopic airborne pollutants that threaten to undermine decades of progress in improving air quality and protecting public health, the World Meteorological Organisation warned on Monday.
The United Nations weather and climate agency released its annual Air Quality and Climate Bulletin on the International Day of Clean Air for Blue Skies, highlighting the growing connections between air pollution and climate change. Scientists say rising global temperatures are leading to more frequent and intense heatwaves and wildfires.
Extreme wildfires are increasing, leading to big health consequences because of the high toxicity of smoke. Whilst regulations in Europe and North America have reduced industrial and transport PM2.5 emissions, exposure to fire-related PM2.5 has increased.
Particulate matter PM2.5 consists of microscopic particles and droplets smaller than 2.5 micrometres in diameter. These particles pose serious health risks because they can penetrate deep into the lungs and enter the bloodstream. They are emitted by fossil fuel-driven industrial activities, farming, domestic heating and transport, as well as by wildfires and dust storms.
Geographic patterns of pollution
The bulletin, which examines air quality trends from 2025, revealed a complex global picture. While regulatory action has reduced aerosol concentrations in parts of North America, Europe, and East Asia, levels remain high or are increasing in South Asia, South America, and high latitudes, largely due to wildfires and industrial activity.
In 2025, PM2.5 concentrations exceeded long-term averages in northern Canada, parts of the Russian Federation, western-central Africa, and north-western Spain due to increased fire activity. Spain experienced exceptional fires in late summer 2025 that significantly impacted regional air quality.
Regional variations continue to emerge. India maintains above-average PM2.5 levels due to biomass burning and other pollution sources, while China's PM2.5 levels remained below the long-term average in 2025, reflecting declining emissions from human activities.
Deadly smoke from wildfires
Air quality and climate change can't be dealt with separately. If one worsens, the other does too.
Microparticles generated by burning vegetation are much more toxic than those from other sources, including vehicle exhaust, Labrador emphasised. These particles damage the health of people and wildlife far from the fire itself as they are carried by wind, yet their poisonous effects are not sufficiently accounted for in air quality assessments.
Conventional risk models based on total PM2.5 concentrations may underestimate wildfire-attributable mortality by up to 93 percent.
Research published in The Lancet Planetary Health found that wildfire PM2.5 poses significantly greater mortality risks than non-fire-related particles. Each one microgram per cubic metre increase in fire-related PM2.5 was associated with a 0.7 percent increase in all-cause mortality, 0.9 percent increase in cardiovascular mortality, and 1 percent increase in respiratory mortality.
One study cited in the bulletin indicates that extreme fire-smoke events have tripled globally since the 1990s, contributing to nearly 100,000 additional deaths per year between 2010 and 2018, though this may be an underestimate.
Heatwaves and ozone pollution
Ground-level ozone represents another major source of air pollution that intensifies during periods of high temperatures, stagnant atmospheric conditions and intense solar radiation, such as recent heatwaves in China, Europe and the southeastern United States.
This increased exposure to ozone pollution has the potential to lead to tens of thousands of additional premature deaths.
The report noted that the world needs better monitoring of air pollutants such as aerosols, including black carbon and microplastics, fine particles and ground-level ozone. These pollutants are not sufficiently monitored even though they are widespread and are potentially harmful to ecosystems.
Airborne microplastics
Aerosol particles can travel across oceans and continents far from their source, altering how the atmosphere reflects sunlight, changing the chemical properties of land and water, and polluting otherwise pristine environments.
Black carbon, or soot, deposited on snow and ice reduces the amount of sunlight these surfaces reflect, which can accelerate melting processes.
Microplastics, formed when plastics break down due to sunlight or other factors, are now found virtually everywhere in the air, soil and oceans. Recent research published in Nature found that land sources release approximately 600 quadrillion microplastic particles into the atmosphere annually, about 20 times more than the 26 quadrillion particles contributed by oceanic sources.
One simulation in the bulletin estimates there are 51 million tonnes of microplastics on land and 22 million tonnes in the ocean, which in turn serve as sources of atmospheric microplastics.
Global plastic production has surged from under 2 million tons per year in 1950 to 390 million tons per year in 2021, with more than 8,300 million tons manufactured since World War II.
As plastic production and, critically, mismanaged plastic waste, continues to increase, monitoring the airborne pathways that carry microplastics from their source and deposit them in remote environments will be crucial.
The WMO emphasised that complementary and coordinated policies on air quality and climate are essential because they cannot be dealt with in isolation.
