Environmental organization Global Witness has reported that around two-thirds of the population of the European Union suffered from high levels of ground-level ozone during the heatwave in June. It is estimated that about 300 million people, including almost 100 million children and the elderly, suffered from ozone levels above the WHO's maximum acceptable rate.

The data used for the research was collected from 162 air quality monitoring stations all across Europe from June 20 to June 26. The ozone levels measured at different locations were compared to the WHO's recommended eight-hour ozone exposure level, which is 100 micrograms per cubic meter. During the heatwave, air quality services in some parts of western and southern Europe recorded levels higher than recommended.

Ground-level ozone is different from ozone in the atmosphere because it is formed when a mix of pollutants, including nitrogen oxides and organic compounds, comes into contact in the sunlight.

The report indicates that during the period under review, countries like Germany, Belgium, the Netherlands, Northern Italy, and some areas in France and Spain experienced some of the most severe ozone pollution.

High levels of ozone can cause irritation to the lungs and difficulties in breathing in people, especially in asthma patients and those with lung diseases. Long-term exposure to ozone is also known to reduce lung functionality and increase the chances of hospitalization during very high temperature periods. 

This information comes against the backdrop of Europe suffering through an excessive heat wave. When the temperatures go up, ground-level ozone is formed more easily, and the air quality deteriorates further.

Global Witness said that reducing the emissions of nitrogen oxides and volatile organic compounds will reduce ozone pollution. Health authorities recommend limiting outdoor activity in areas during times of high ozone levels.