Fifty per cent of Europe’s population was exposed to ground-level ozone at levels rated poor, very poor or extremely poor during record heatwaves and wildfires from June to August, the European Commission’s Copernicus Atmosphere Monitoring Service said.

The figures come from Atmosphere Watch, the first edition of a new CAMS report on air quality. Ground-level ozone forms through thousands of chemical reactions triggered by sunlight and high temperatures, and can “penetrate deep into the respiratory system and enter the bloodstream,” reaching almost all organs, with asthma sufferers most at risk, the report said.

“Ozone pollution is a stark reminder of how interconnected our atmosphere, climate, health, and livelihoods really are, with pollution and our changing climate impacting the chemistry of the air we breathe, determining the health of our ecosystems, and even governing our ability to grow food,” Laurence Rouil, the director of CAMS, told Euronews.

The nitrogen oxides involved in the reactions that produce ozone are mainly generated by the combustion of fossil fuels, the report said, naming industry, solvents and road transport as sources, along with biomass burning from wildfires.

As a greenhouse gas, ozone accounts for approximately 0.23°C of present-day warming, according to the Clean Air Fund, a UK charity that calls it a “super pollutant.” Ground-level ozone is distinct from the upper-atmosphere ozone layer that shields the planet from ultraviolet light.

“Air pollution knows no border. Wildfire smoke, ozone and dust can travel thousands of kilometres,” said Florian Pappenberger, director-general of the European Centre for Medium-Range Weather Forecasts. In August, Belgium suffered its worst wildfire in 100 years, and smoke columns travelled through Germany to Poland.

Air pollution causes more than four million premature deaths worldwide each year, according to the World Health Organization. In 2025, 56 deaths per 100,000 people in Europe and Central Asia were attributable to it.

The report said air quality in Europe had improved significantly for all pollutants regulated by the European Union’s 2024 Air Quality Directive. Since 2015, industrial emissions of sulphur oxides have fallen by 59 per cent and nitrogen oxide emissions from industry by 39 per cent, according to a 2025 Copernicus report, while road transport emissions of nitrogen oxides fell 40 per cent and of fine particulate matter by 34 per cent.

Ozone, however, “shows no clear downward trend and remains an issue,” the report said. Under the EU directive, the maximum eight-hour daily ozone average should not exceed 120 micrograms per cubic metre on more than 18 days a year.

Worst levels were recorded in southern Europe, where heatwaves were hottest and most prolonged, the report found. Globally, almost 40 per cent of the world’s population has been exposed to extremely high ozone levels so far in 2026, including 60 per cent of Asia’s citizens, according to the analysis. Milan, Rio de Janeiro, Mexico City, Delhi and Cairo recorded some of the highest exposures.

Only Croatia, France and Spain have developed or implemented air quality plans explicitly focused on ozone, the report said. It recommended improved monitoring, forecasting and public awareness, noting that as heatwaves become more frequent, ozone concentrations will rise in affected areas and partly offset gains from cutting precursor emissions.