Rising wildfires and heatwaves undermine air quality gains, UN warns

Wildfires and heatwaves are generating microscopic pollutants that threaten global progress on air quality, human health, and environmental protection, the World Meteorological Organization (WMO) said on Monday.

In its latest annual Air Quality and Climate Bulletin, the United Nations’ weather and climate agency highlighted the intensifying link between air pollution and climate change. Scientists say climate change is driving more frequent and severe heatwaves and wildfires, which in turn release harmful particles into the atmosphere.

“Extreme wildfires are increasing, leading to big health consequences because of the high toxicity of smoke,” the WMO said in a statement accompanying the report.

While stricter regulations in Europe and North America have reduced emissions of fine particulate matter (PM2.5) from industry and transport, the agency noted that exposure to fire-related PM2.5 has increased. PM2.5 refers to particles smaller than 2.5 micrometres in diameter, which can penetrate deep into the lungs and enter the bloodstream, posing serious health risks.

These particles come from fossil fuel combustion, agriculture, household heating, vehicles, and also from wildfires and dust storms.

The WMO bulletin stressed the need for better monitoring of air pollutants such as black carbon, microplastics, fine particles, and ground-level ozone. “These pollutants are not sufficiently monitored even though they are widespread and potentially harmful to ecosystems,” the report said. It called for coordinated policies on air quality and climate, warning that the two issues cannot be tackled in isolation.

Lorenzo Labrador, a scientist with the WMO’s Global Atmosphere Watch network, told AFP that air quality and climate change are deeply interconnected. “If one worsens, the other does too,” he said.

Labrador pointed out that regions with severe forest fires experience high levels of fine particle pollution. He noted that microparticles from burning vegetation are far more toxic than those from other sources, including vehicle exhaust. These particles can travel long distances on the wind, affecting people and wildlife far from the fire source, yet their harmful impact is often undercounted in air quality assessments.

The WMO said conventional risk models based on total PM2.5 concentrations may underestimate wildfire-related deaths by up to 93%. One study referenced in the bulletin found that extreme fire-smoke events have tripled globally since the 1990s, contributing to nearly 100,000 additional deaths per year between 2010 and 2018. The true number may be even higher.

The report also drew attention to ground-level ozone, another dangerous pollutant that accumulates during heatwaves when temperatures rise and atmospheric conditions stagnate. Recent heatwaves in China, Europe, and the southeastern United States have caused sharp increases in ozone exposure. The WMO warned that this could lead to tens of thousands of premature deaths, particularly from respiratory diseases.

Beyond human health, the bulletin examined the broader environmental impact of aerosol particles. These tiny particles can be carried across oceans and continents, affecting how sunlight is reflected in the atmosphere and altering the chemical properties of land and water. For instance, black carbon, or soot, deposited on snow and ice reduces their reflectivity, accelerating melting.

Microplastics, formed when plastic products break down under sunlight or other factors, are another emerging concern. They have been found in air, soil, and oceans worldwide. The WMO cited one simulation estimating 51 million tonnes of microplastics on land and 22 million tonnes in the ocean, without specifying whether these figures referred to total accumulated mass or annual flows.

The agency emphasised that better data and monitoring are essential to understand and address these risks. It said that protecting health and ecosystems from the growing impacts of wildfires, heatwaves, and related airborne pollutants requires urgent and sustained international cooperation.