Ground-level ozone exposed around half of Europe’s population to poor, very poor or extremely poor air quality during the summer of 2026, according to analysis from the Copernicus Atmosphere Monitoring Service. The pollution was intensified by heatwaves, sunlight and wildfires, with people living with asthma among those facing the greatest health risks.
Unlike the protective ozone layer high in the atmosphere, ground-level ozone is a harmful air pollutant. It can penetrate deep into the lungs and enter the bloodstream, making the issue an important part of Europe’s climate and public-health debate.
Why ground-level ozone increased during Europe’s hot summer
Ozone at the Earth’s surface is not emitted directly in large quantities. It forms through complex chemical reactions involving pollutants such as nitrogen oxides and other substances, particularly when strong sunlight and high temperatures are present.
Those conditions became more common during the heatwaves recorded across Europe between June and August 2026. Hotter and drier weather also contributed to severe wildfires, which released additional pollutants and created smoke that travelled across national borders.
According to the Copernicus Atmosphere Monitoring Service, half of Europe’s population experienced poor, very poor or extremely poor ozone conditions during that period. Southern parts of the continent were particularly affected because they experienced some of the most intense and persistent heat.
A pollutant linked to both climate and health
Ground-level ozone highlights the close relationship between climate change and air pollution. As human-caused warming increases the frequency and severity of heatwaves, the atmospheric conditions that help ozone form can become more favourable.
The pollutant also contributes to warming. The Clean Air Fund estimates that ozone accounts for approximately 0.23°C of present-day global warming, describing it as a “super pollutant”.
Health risks are highest for people with asthma and other respiratory conditions, but ozone exposure can affect the wider population. Air pollution overall is associated with millions of premature deaths worldwide, while ozone can cause harm far from the roads, factories or fires that produce its precursor pollutants.
EU air-quality improvements have not solved the ozone problem
Europe has made progress in reducing several regulated air pollutants. The European Commission’s 2024 Ambient Air Quality Directive requires EU countries to monitor pollution and take action when limits are exceeded.
Copernicus data indicate that emissions of sulphur oxides and nitrogen oxides have fallen by roughly 3% to 5% a year across the European Union over the past decade. Since 2015, industrial sulphur oxide emissions fell by 59%, while industrial nitrogen oxide emissions declined by 39%. Road transport emissions also recorded substantial reductions, including a 40% fall in nitrogen oxides and a 34% reduction in fine particulate matter.
However, ozone has not followed the same downward trend. The chemical processes that create it are affected not only by local emissions but also by weather patterns and pollution transported across borders.
What EU ozone limits mean
Under the EU Ambient Air Quality Directive, the maximum daily eight-hour average ozone concentration should not exceed 120 micrograms per cubic metre on more than 18 days in a year. The long-term objective is 100 micrograms per cubic metre, in line with World Health Organization guidance.
These thresholds are designed to help authorities assess exposure, but ozone can still travel over long distances. Smoke from a major wildfire in Belgium in August 2026, for example, moved through Germany and reached Poland, showing how air pollution can affect communities well beyond the original source.
Milan among cities facing particularly high ozone exposure
Milan was identified as one of the cities with some of the highest ozone exposure levels in the world during 2026, alongside Rio de Janeiro, Mexico City, Delhi and Cairo.
The wider European pattern reflects the interaction between urban emissions, geography, sunlight and prolonged heat. Cities and regions in southern Europe have often faced especially difficult ozone conditions, while wildfire smoke can worsen air quality across much larger areas.
Globally, almost 40% of people were exposed to extremely high ozone levels during the first eight months of 2026, according to the analysis cited by Copernicus. Around 60% of people in Asia were affected, while only a small share of the global population experienced good long-term ozone conditions.
How governments can reduce ozone pollution
Experts say that reducing ozone requires sustained action on the pollutants that help create it, as well as better monitoring and public warnings. Measures that can contribute include:
- Reducing fossil-fuel combustion in industry, transport and energy production.
- Expanding public transport, cycling infrastructure and low-emission zones.
- Improving forecasts so residents can limit exposure during high-ozone episodes.
- Reducing emissions from solvents, paints and cleaning products.
- Strengthening wildfire prevention and smoke-monitoring systems.
- Coordinating air-quality action across borders.
The European Environment Agency has highlighted the importance of understanding how ozone forms and identifying its main sources. Within the EU, Croatia, France and Spain are among the countries that have developed or implemented air-quality plans specifically focused on ozone.
What individuals can do
Personal choices cannot replace government action, but they can help reduce precursor emissions. Walking, cycling or using public transport instead of driving can lower pollution. When driving is necessary, smoother acceleration, less hard braking and avoiding unnecessary speed can reduce fuel use and emissions. Using environmentally safer paints and cleaning products can also limit the release of chemicals involved in ozone formation.
Why the findings matter for Europe
The 2026 ozone exposure figures show that cleaner air policies can deliver measurable benefits for pollutants such as sulphur dioxide, nitrogen oxides and fine particles, while climate change creates new challenges for ozone control.
For EU countries, the next step is not simply to meet existing monitoring obligations but to connect air-quality policy more closely with climate, transport, energy and wildfire planning. The cross-border nature of ozone means that national action alone may not be sufficient.
For residents, the main lesson is that blue skies do not always mean clean air. During heatwaves, people with asthma and other respiratory conditions should follow local air-quality alerts, reduce strenuous outdoor activity when ozone levels are high and seek medical advice for worsening symptoms.
Ground-level ozone is therefore both a climate warning and a public-health issue. The strongest response will combine lower emissions, more reliable monitoring and coordinated European action before hotter summers make exposure even more widespread.
