Nearly 40% of the world’s population has been exposed to dangerous levels of ground-level ozone during the first eight months of 2026, as extreme heat and human-caused air pollution combine to create conditions that favour formation of the harmful pollutant.
The finding comes from a new global analysis by the Copernicus Atmosphere Monitoring Service (CAMS), which tracks the composition and movement of air pollution around the world.
Unlike the ozone layer high in the atmosphere, which protects people from ultraviolet radiation, ground-level ozone is a harmful air pollutant. It forms when precursor pollutants, including nitrogen oxides and volatile organic compounds, react in sunlight and high temperatures.
Transport, industry, solvents, vegetation and wildfires can all contribute to the pollutants involved in this chemical reaction.
The 2026 analysis, called Atmosphere Watch, found that only 5% of the world’s population was exposed to ozone concentrations classified as “Good” and within the World Health Organization’s recommended guideline levels.
Asia was the region most affected. About 60% of the continent’s population experienced “Extremely Poor” ozone levels during the first eight months of the year. When people exposed to “Poor” and “Very Poor” levels are included, the proportion rises to 90%.
Europe was also heavily affected, with half of its population exposed to “Poor”, “Very Poor” or “Extremely Poor” ozone levels.
Repeated heatwaves between June and August contributed to elevated ozone concentrations across parts of Europe, illustrating the link between extreme heat and air quality.
In North America, more than two-thirds of the population experienced “Poor”, “Very Poor” or “Extremely Poor” ozone exposure. Extreme wildfires in Canada and the western United States contributed to the high concentrations by releasing pollutants that can act as ozone precursors.
A pollutant that travels
The analysis also shows why air pollution cannot always be treated as a local problem.
During June and July, intense wildfires in Canada’s Northwest Territories and Ontario generated smoke that travelled thousands of kilometres across northern North America towards the Atlantic. The smoke contributed to air-quality problems in cities including New York and New Jersey.
Some smoke from North American fires travelled even farther, reaching the Arctic Ocean and Greenland and crossing the Atlantic into parts of Europe, where it contributed to increased concentrations of fine particulate matter known as PM2.5.
In Southeast Asia, seasonal fires produced widespread haze affecting countries including Thailand and Laos. Indonesia’s seasonal fires intensified from mid-July, with fires reported in Borneo and the provinces of West and Central Kalimantan. By mid-August, millions of people had been exposed to hazardous air pollution.
The analysis links the worsening fire conditions partly to the developing El Niño, which can create hotter and drier conditions that increase fire risk.
Dust was another major transboundary pollutant.
Saharan dust repeatedly moved beyond North Africa, with plumes travelling from West Africa across the North Atlantic towards Cape Verde and the Canary Islands. Some dust also crossed the Atlantic towards the Caribbean.
These episodes highlight how people can experience poor air quality from pollution generated thousands of kilometres away.
Africa faces a different ozone picture
Africa has so far experienced lower population exposure to extreme ozone levels than Asia, Europe and North America, according to the analysis.
Only 8% of Africa’s population experienced “Extremely Poor” ozone exposure during the first eight months of 2026, while 56% remained within “Good” or “Fair” ozone levels.
But lower ozone exposure does not mean that the continent is free from air-quality risks.
Seasonal biomass burning in both northern and southern tropical Africa continues to produce widespread smoke pollution, although emissions from these fires have declined over the past two decades. Saharan dust also remains an important influence on air quality.
The analysis points to the importance of looking beyond a single pollutant when assessing the health effects of air pollution in Africa.
Climate and air pollution reinforce each other
Ground-level ozone presents a particular challenge because climate and air pollution can reinforce one another.
Higher temperatures and strong sunlight can accelerate the chemical reactions that produce ozone. At the same time, ozone itself is a greenhouse gas, adding another connection between air pollution and climate change.
Wildfires add another layer because they release several pollutants and gases that can contribute to ozone formation while also producing smoke and fine particulate matter.
“Air pollution knows no border,” said Florian Pappenberger, Director-General of the European Centre for Medium-Range Weather Forecasts, which operates CAMS on behalf of the European Commission.
He said the findings show that climate change, air quality and public health are “deeply interconnected challenges” requiring coordinated action.
CAMS combines observations from satellites, ground-based monitoring networks, aircraft and other sources with atmospheric modelling. Its global system tracks more than 50 chemical species, allowing scientists to follow pollutants as they move between countries and continents.
The analysis comes as governments prepare for COP31, placing air quality alongside climate change as an issue with implications for health, ecosystems and food production.
For public health, the significance is not only where pollution is produced but where it eventually reaches.
As Laurence Rouil, Director of CAMS, put it, the movement of wildfire smoke, biomass-burning emissions and Saharan dust shows the need for global, evidence-based approaches to air quality that move alongside climate action.
The full Atmosphere Watch 2026 analysis covers the first eight months of the year and examines three major transboundary pollutants — ground-level ozone, biomass-burning smoke and dust.
source: https://atmosphere.copernicus.eu
