Successive heatwaves and vast wildfires, combined with emissions from human activity, exposed more than a third (34%) of the global population to dangerously high levels of surface ozone pollution this year, according to a report published today by the European Copernicus service.

Asia was the worst-affected region, with 53% of its population exposed to “extremely high” pollution levels during the first eight months of 2026, according to an analysis carried out by the European Union’s Copernicus Atmosphere Monitoring Service (CAMS).

In North America, two thirds of the population experienced air quality rated “poor” to “very poor”, as did 45% in Europe, Copernicus said. Its findings draw on satellite and ground-based observations, combined with atmospheric models.

Globally, more than 34% of the population was exposed to “extremely poor” air quality, while 17% breathed air rated “very poor”. Only 5% of the world’s population lived in areas with “good” ozone levels, and a further 15% in areas rated “acceptable”, according to the report, which highlights the close relationship between climate change and air pollution.

Ozone is an atmospheric pollutant formed through a series of chemical reactions. It arises mainly from nitrogen oxides (NOx), released chiefly by road and maritime traffic, industrial activity and wildfires, along with volatile organic compounds (VOCs), which come mostly from industrial processes and the burning of fossil fuels. Under the influence of the sun’s ultraviolet (UV) rays, these gases react chemically to form ozone.

This year’s high ozone levels were fuelled by record-breaking heatwaves and wildfires that swept across Europe and North America, spreading far beyond the areas where they began and underlining how climate change can worsen air pollution.

Ozone can penetrate deep into the human respiratory system, causing coughing, a burning sensation in the eyes and even breathing difficulties, and aggravating asthma attacks and the symptoms of respiratory disease.

Air pollution is “one of the most significant environmental risks to human health”, Ian Marnane of the European Environment Agency (EEA) told a press conference, noting that it causes around 180,000 premature deaths a year, of which 60,000 are attributed to ozone pollution.

The problem is compounded by the fact that “air pollution does not stop at borders”. Instead, it travels “thousands of kilometres”, crosses “continents and oceans” and ultimately “worsens air quality far from its source”, said Laurence Rouil, director of CAMS.

Despite “significant improvements” in recent decades in tackling “some of the most harmful types of pollution”, particularly in Europe thanks to an air quality directive, ozone remains “a particularly complex global challenge” and a “major environmental risk” both “to human health” and “to ecosystems”, Copernicus stressed.