Extreme heat and pollution exposed 40% of world population to dangerous ground ozone in 2026, Copernicus finds

Global reach of ground-level ozone

Extreme heatwaves and anthropogenic emissions exposed roughly 40% of the world population to dangerous concentrations of ground-level ozone during the first eight months of 2026. Data published on 30 September by the Copernicus Atmosphere Monitoring Service (CAMS), operated by the European Centre for Medium-Range Weather Forecasts (ECMWF) on behalf of the European Commission, indicates that only 5% of people globally breathed air meeting World Health Organization guidelines for good ozone levels. An additional 15% lived in areas with acceptable air quality, while 17% faced conditions classified as very poor and around one third experienced extremely poor levels. Unlike stratospheric ozone that shields the planet from ultraviolet radiation, tropospheric ozone forms in the lowest 10 to 12 kilometres of the atmosphere through chemical reactions between nitrogen oxides (NOx) and volatile organic compounds (VOCs). These precursor pollutants originate from road traffic, maritime transport, industrial combustion, domestic solvents, and vegetation, transforming into ozone when heated under strong solar radiation.

Regional disparities and hemispheric impact

Asia recorded the most severe impact between January and August, with 60% of its population exposed to extremely high tropospheric ozone concentrations. In North America, two thirds of the population breathed air rated as poor or very poor. In Europe, half of the population encountered poor, very poor, or extremely poor ozone levels during the summer months, despite long-term declines in other atmospheric pollutants. In the Netherlands, for instance, public health records indicate fine particulate matter concentrations have fallen by half since the 1990s alongside reductions in nitrogen oxides, but high temperatures maintained elevated ozone readings. By contrast, South America experienced the most favorable regional conditions, with 81% of its population exposed to good or acceptable ozone levels, although large urban centers such as Rio de Janeiro still recorded extremely poor concentrations. In Africa, approximately one in four people lived in areas with poor air quality.

Wildfire smoke and desert dust transport

The annual Atmosphere Watch 2026 assessment established that ozone pollution operated alongside intense wildfire smoke and desert dust to degrade air quality over intercontinental distances. Large wildfires across Canada generated dense smoke plumes that traversed the Atlantic Ocean and reached parts of Europe, raising local fine particulate matter (PM2.5) concentrations. Regional blazes across France, Spain, Belgium, and the United Kingdom also dispersed smoke and degraded air quality across hundreds of kilometers from their sources. Repeated plumes of Saharan dust traveled from North Africa across both the Mediterranean into Europe and across the Atlantic toward the Caribbean. ECMWF Director-General Florian Pappenberger addressed the cross-border transport of these pollutants ahead of the upcoming COP31 United Nations climate conference.

Atmosphere Watch shows that air pollution does not know borders. Wildfire smoke, ozone, and dust can travel thousands of kilometres, affecting communities far from their origin.

Public health risks and environmental consequences

Elevated concentrations of ground-level ozone pose direct risks to human health, causing respiratory inflammation, eye irritation, headaches, dizziness, and reduced lung capacity. Vulnerable groups include children, the elderly, pregnant women, and individuals diagnosed with pre-existing conditions such as asthma, cardiovascular disease, or diabetes. Within the lower atmosphere, ozone acts as a greenhouse gas that contributes to regional warming while damaging surrounding ecosystems and reducing agricultural crop yields. Estimates from the European Environment Agency associate overall air pollution with approximately 180,000 annual premature deaths across Europe, with roughly 60,000 of those fatalities linked directly to ground-level ozone exposure. CAMS Director Laurence Rouïl noted that managing these exposures requires recognizing how atmospheric pollutants travel across continents and oceans.