Heatwaves and wildfires, combined with human-caused emissions, exposed around one-third of the world’s population to extremely high levels of ozone pollution this year, according to a European Union report released on Wednesday.
In an analysis covering the first eight months of 2026, the European Union’s Copernicus Atmosphere Monitoring Service (CAMS) highlighted the close link between climate change and air pollution.
When heat and sunlight react with emissions from wildfires, vehicles and industrial activity, they produce ground-level ozone, which can damage lung tissue, cause breathing difficulties, trigger asthma attacks and contribute to other health problems.
Despite progress in reducing some of the most harmful air pollutants in recent decades, ozone has proved more difficult to control as climate change creates conditions that favour its formation.
This year’s ozone pollution was driven partly by record-breaking heatwaves and wildfires across Europe and North America, with smoke travelling far beyond the areas where the fires started.
Indonesia has also experienced major wildfires, while the warming El Niño weather pattern, which began in June and is expected to peak later this year, could fuel further fires in Southeast Asia, according to the analysis.
“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,” CAMS Director Laurence Rouil said in the Atmosphere Watch report.
CAMS uses satellite data and computer models to monitor air pollution and wildfires.
The report found that 34% of the global population was exposed to “extremely poor” air quality between January 1 and September 15, meaning ozone concentrations were well above the World Health Organization’s recommended exposure level.
The WHO guideline sets 100 micrograms of ozone per cubic metre as the maximum recommended exposure level, averaged over eight hours.
Another 17% of the global population was exposed to “very poor” air, while only 5% experienced “good” ozone levels.
Asia had the highest rate of exposure, with 53% of its population breathing “extremely poor” air and another 22% exposed to “very poor” ozone levels.
The continent’s high emissions are driven by industrialisation, economic development and transport, as well as wildfires and agricultural residue burning.
New Delhi, Dhaka, the Chinese megacity of Chongqing and Pakistan’s Lahore were among the cities where ozone levels were classified as “extremely poor”.
Two-thirds of the population in North America and 45% of the population in Europe were exposed to “poor” or “very poor” air quality.
EU regulations have helped reduce emissions of several air pollutants, but ozone remains an exception, the report said.
Ozone pollution is linked to around 60,000 premature deaths each year in Europe, Ian Marnane, an official at the European Environment Agency, told a media briefing.
Ozone levels in North America also remained “relatively unchanged” despite ambitious emissions-reduction policies, according to the report.
Smoke from forest fires, crop burning and cooking are significant contributors to air pollution in Africa, while Saharan dust can travel as far as Europe.
Eight percent of Africa’s population experienced “extremely poor” air quality this year, while conditions were “very poor” or “poor” for another 19%.
Ozone levels were very high in the Brazilian city of Sao Paulo and extremely elevated in Rio de Janeiro. However, 81% of South America’s population experienced “good” or “fair” air quality.
Oceania, including Australia and New Zealand, recorded the most favourable conditions, with 66% of the population experiencing “good” ozone levels and the remaining 34% living under “fair” conditions.