Nearly 300 million people across Europe were exposed to ozone levels above recommended limits during a record-breaking heatwave in June 2026, with roughly 100 million of those affected being children and the elderly. Two-thirds of European Union citizens breathed harmful ozone concentrations during the period, which saw the UK endure its third heatwave of the summer and a rare high air pollution alert issued by London's mayor.
The highest ozone readings were recorded in Germany, Benelux, Italy's Po valley, the Paris area, Spain, and the Czech Republic, with North Rhine-Westphalia registering 233.7 micrograms per cubic metre against an EU limit of 120. In Barcelona, the alert threshold was breached at the Badalona station on 8 July, prompting criticism from Ecologistas en Acción over inadequate public warnings.
Despite the scale of the episode, peak ozone concentrations during the June 2026 event remained below half those measured during the 1976 heatwave and lower than 2003 levels, when thousands of excess deaths were attributed to pollution across Europe. Agriculture accounts for more than half of EU methane emissions, a gas linked to a third of ozone formation.