Pollutionwatch: How harmful ozone builds up near ground in heatwaves

New Delhi, India Jul 10, 2026 ALN: Widespread air pollution has become a significant concern during June’s record-breaking heat across western Europe, and it is likely to increase again as the UK braces for its third heatwave of the summer. The rising temperatures have led to heightened awareness about the detrimental effects of air quality, particularly the formation of ground-level ozone, which poses serious health risks to the population.

Weather warnings for extreme heat issued by the UK government from June 22 were accompanied by a rare high air pollution alert from the London mayor, highlighting the growing threat of ground-level ozone. This alert serves as a reminder of the critical need for public awareness and preventive measures to protect health during periods of extreme weather.

The Formation of Ground-Level Ozone

During heatwaves, ozone forms near the ground when other pollutants, such as volatile organic compounds (VOCs) and nitrogen oxides (NOx), react together under strong sunlight. This chemical reaction is exacerbated by high temperatures, leading to increased concentrations of ozone at lower altitudes. While the ozone layer in the upper atmosphere protects us from harmful UV radiation, ozone at lower altitudes can trigger a variety of health issues, including respiratory problems, cardiovascular diseases, and reduced lung function.

Historical Context and Health Impacts

The 2003 European heatwave serves as a stark historical context for understanding the potential impacts of extreme heat and air pollution. During that summer, approximately 2,000 additional deaths were reported in the UK, with around 800 attributed directly to ozone exposure. The Netherlands experienced between 400 to 600 extra deaths due to air pollution during the same period. Such statistics underscore the urgent need for effective air quality management, especially during heatwaves.

Laurence Rouil, director of the EU’s Copernicus Atmosphere Monitoring Service, stated: “Ozone remains one of the most challenging air pollution issues facing Europe and other parts of the world. Once an episode begins to develop, it becomes very difficult to halt or significantly reduce its intensity. This is why anticipation and prevention are key.”

Ozone Levels During the June Heatwave

Forecast maps from last month’s heatwave illustrate how ozone levels increased with the heat of each day, peaking in the late afternoons when sunlight was most intense. The worst conditions were initially observed over southern England, Belgium, northern France, and the Netherlands, before shifting eastward as the heat moved. This geographical pattern highlights how weather systems can influence air quality across borders, necessitating cross-national cooperation in monitoring and addressing air pollution.

Rouil noted that ozone concentrations were continuously elevated throughout Europe during the June heatwave, with the highest levels recorded in Germany, the Benelux countries, and Italy’s Po Valley, as well as locally in the Paris area, Spain, and the Czech Republic. In these regions, ozone concentrations were notably higher compared to previous years, indicating a worrying trend that could have long-term health implications.

Sources of Ground-Level Ozone

Historically, in 1943, residents of Los Angeles believed they were under a poison gas attack, which is now recognized as one of the first instances of ozone smog, primarily caused by traffic exhaust and petrochemical industry emissions. This early example of ozone pollution illustrates the long-standing challenge of managing air quality in urban s. Today, the main sources of ground-level ozone include emissions from vehicles, industrial processes, and various consumer products such as pesticides, coatings, printing inks, adhesives, cleaning agents, and personal care products. The cumulative effect of these sources can lead to significant increases in ground-level ozone, especially during hot weather.

Health and al Consequences

Short-term exposure to ozone can lead to respiratory diseases, throat irritations, and exacerbation of asthma. Vulnerable populations, including children, the elderly, and those with pre-existing health conditions, are particularly at risk. Additionally, ozone damages vegetation, causing browning and premature leaf drop, which can have significant implications for agriculture and biodiversity. In 2024, 21.5% of Europe’s agricultural land—nearly half a million square kilometers—was exposed to ozone levels exceeding EU targets, underscoring the need for urgent action to protect both public health and the .

During the June heatwave, maximum ozone concentrations were less than half of those recorded during the 1976 heatwave and also lower than those measured in 2003. However, despite the decline in peak concentrations, there is no clear trend for the average amount of ozone exposure, suggesting that while peak events may fluctuate, the underlying issue of ozone pollution remains a persistent challenge.

The Need for Coordinated Action

Ozone in the lower atmosphere is considered a super pollutant. Reducing its levels is crucial for addressing the climate crisis and improving public health. Rouil emphasized the need for coordinated mitigation strategies at international, national, and local levels, stating: “Ozone is also influenced by climate change—not only through heatwaves but also due to the increasing frequency and intensity of wildfires, which release significant amounts of ozone precursors.” This interconnectedness highlights the need for a holistic approach to air quality management that considers the broader implications of climate change.

International commitments, such as the global methane pledge and stricter regulations on methane emissions, can yield positive impacts, but experts caution that it will take time to see significant improvements. The complexity of air pollution dynamics means that immediate solutions may not be effective in the long term without sustained efforts and cooperation among various stakeholders.

In conclusion, as heatwaves become more frequent and intense due to climate change, the challenge of managing ground-level ozone pollution will require urgent and coordinated efforts across various sectors. Public health initiatives, regulatory measures, and community engagement will be essential components of a comprehensive strategy to mitigate the impacts of ground-level ozone and protect both human health and the . Only through collaborative action can societies hope to combat the dual threats of climate change and air pollution effectively.