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Rising global temperatures and a punishing wildfire season have combined to push ozone air pollution to dangerous levels for roughly one in three people worldwide, according to a new assessment from the European Union's climate monitoring service. The findings underscore how climate change is complicating decades of progress on cleaner air.
The Copernicus Atmosphere Monitoring Service (CAMS), which tracks atmospheric conditions using satellite observations and computer modeling, reported that 34 percent of the global population breathed what it classifies as "extremely poor" ozone air during the first eight and a half months of 2026. The analysis covers the period from January 1 through September 15.
Ground-level ozone forms when heat and intense sunlight interact with emissions from vehicles, industrial facilities and wildfires. Unlike the protective ozone layer high in the stratosphere, this pollutant accumulates near the surface, where it can scar lung tissue, aggravate breathing difficulties, set off asthma episodes and contribute to a range of other health problems.
The report, released Wednesday as part of CAMS's Atmosphere Watch publication, highlights the tight coupling between a warming climate and deteriorating air quality. Record-shattering heatwaves and extensive fires across Europe and North America during the year created ideal conditions for ozone to build up, with smoke plumes drifting far past the regions where they originated.
Wildfires also ravaged Indonesia, and forecasters warn that the El Nino weather pattern, which emerged in June and is expected to intensify before the end of the year, may spark additional fires across southeast Asia. El Nino typically brings drier conditions to parts of the region, raising the risk of uncontrolled burning.
"Air pollution does not stop at borders. It can travel thousands of kilometres, crossing continents and oceans and affecting air quality far from its source," said Laurence Rouil, director of CAMS, in the report.
The scale of exposure is striking. Beyond the 34 percent of people living with extremely poor ozone levels, another 17 percent of the world's population experienced "very poor" air, while just five percent enjoyed what the monitor deemed "good" ozone conditions.
Asia recorded by far the highest burden. More than half of the continent's residents—53 percent—were exposed to extremely poor ozone air, with an additional 22 percent enduring very poor levels. The report attributes the region's pervasive pollution to a mix of rapid industrialization, economic expansion and heavy transport use, compounded by wildfires and the widespread burning of agricultural residue.
Among the cities singled out for extremely poor ozone readings were New Delhi, Dhaka, the Chinese megalopolis of Chongqing and Lahore in Pakistan.
The picture was somewhat less severe but still concerning in North America and Europe. Two-thirds of North American residents and 45 percent of Europeans breathed air classified as poor or very poor.
The report noted that while European Union regulations have successfully driven down emissions of most harmful air pollutants, ozone has proven stubbornly resistant. Ian Marnane, an official with the European Environment Agency, said at a media briefing that ozone pollution is associated with 60,000 premature deaths annually across Europe.
North American ozone levels have remained "relatively unchanged" despite aggressive emission-reduction policies, according to the assessment.
Africa's air quality challenges stem from a different mix of sources. Forest fires, crop burning and household cooking are major contributors, while Saharan dust frequently travels northward as far as Europe. Eight percent of Africa's population faced extremely poor air quality this year, and conditions were very poor or poor for another 19 percent.
In South America, ozone concentrations were notably high in Sao Paulo and extremely elevated in Rio de Janeiro, though overall the air was good or fair for 81 percent of the continent's population.
Oceania stood out as the year's brightest spot. In Australia, New Zealand and surrounding areas, 66 percent of residents experienced good ozone levels, and the remaining 34 percent lived under fair conditions.
The World Health Organization sets its exposure guideline at a maximum of 100 micrograms of ozone per cubic meter, averaged over an eight-hour period. Concentrations well above that threshold are what CAMS defines as extremely poor.
The report's authors stress that ozone has resisted the cleanup gains achieved for other pollutants. While emissions of sulfur dioxide and fine particulates have fallen in many regions thanks to stricter rules and cleaner technology, ozone remains difficult to control because its formation depends heavily on temperature and sunlight—factors that climate change keeps pushing in the wrong direction.
CAMS relies on a combination of satellite instruments and atmospheric models to produce its assessments, allowing researchers to track both pollution concentrations and the wildfires that contribute to them. The service is part of the EU's broader Earth observation program.
The findings add to a growing body of evidence that heatwaves and wildfires are becoming more frequent and intense, and that their effects on air quality reach well beyond the immediate burn zones. Smoke from fires in one country can degrade air quality in neighboring nations and even on other continents, complicating efforts by individual governments to protect public health.
The report also notes the potential for the strengthening El Nino to worsen conditions in southeast Asia in the months ahead, suggesting that the global ozone burden may not ease soon. As heat records continue to fall, the interplay between a hotter planet and the chemistry of the air people breathe is likely to remain a central public health challenge.
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