According to the analysis carried out by the Copernicus Atmosphere Monitoring Service (CAMS) within the European Union Center for Medium-Range Weather Forecasts (ECMWF), ground level ozone, a less prominent but harmful secondary pollutant, is formed when certain pollutants enter into chemical reactions under the influence of sunlight and high temperatures.
The CAMS analysis reveals the global landscape of transboundary air pollution, including ozone, smoke from biomass fires and desert dust, over the eight months to 2026, the events shaping air quality on every continent and their impacts on people, livelihoods and the environment.
Accordingly, ground-level ozone harms human health, ecosystems and agricultural crop yields. This year, different factors combined to cause ground-level ozone concentrations to rise to high levels in many regions, affecting billions of people around the world.
While 40 percent of the world's population is affected by dangerous ozone pollution, only 5 percent of the population was found to be exposed to "good" ozone levels within the World Health Organization guidelines.
The region most affected by ozone pollution was Asia, followed by Europe and North America.
In Asia, pollution from industry and transportation, as well as multiple natural sources of precursor emissions, have led to high ozone levels during the part of the year so far. This year, 60 percent of the continent's population was exposed to extremely high ozone levels.
50 percent of the European population experienced "bad" and "very bad" ozone levels this year. Successive heat waves in Europe caused significant ozone exposure during the summer months. This highlights the increasingly strong link between climate-driven extreme events and air quality.
In North America, population-weighted ozone concentrations based on global data from CAMS remained at high levels, due in part to ozone precursor emissions from extreme wildfires in 2026. More than two-thirds of the continent's population was exposed to "bad" or "extremely bad" ozone levels.
In his assessment of the issue, ECMWF Director General Florian Pappenberger stated that the analysis shows that air pollution knows no boundaries.
"As the international community prepares for the United Nations climate summit COP31, these findings are a timely reminder that climate change, air quality and public health are deeply interconnected issues and require coordinated action on a global scale," he said, noting that wildfire smoke, ozone and dust can travel thousands of kilometers and affect communities far from their source. he said.
CAMS Director Laurence Rouil underlined that ozone pollution clearly reveals how interconnected the atmosphere, climate, health and livelihoods really are, and said:
"Pollution and our changing climate affect the chemistry of the air we breathe, determine the health of our ecosystems and even affect our capacity to grow food. At the same time, air pollution does not recognize national borders. Wildfire smoke, emissions from biomass burning and clouds of Saharan dust can travel thousands of kilometers and affect communities far from their source. This underlines the urgent need for evidence-based action on air quality on a global scale, simultaneously with climate action."
