June's unprecedented heatwave in Central Europe led to a spike in concentrations of pollutants in Central Europe. Requested by euronews, the Copernicus Atmosphere Monitoring Service has created a visualisation of how ozone levels evolved through the week.
For, comparison we also requested a visualization of the ozone levels from June 11 to June 16, which was a week with "normal" temperatures for the season.
The EU's Earth Observation programme animation shows how ozone levels bloom dramatically during the hottest hours of the day.
High atmospheric ozone depends on the intensity of sunshine, Vincent- Henri Peuch, head of Copernicus Atmosphere Service tells euronews. It is formed by nitrogen dioxide (emitted by fossil fuels) and volatile organic compounds, which are also released with more intensity during heatwaves.
The sunlight is only strong enough to spark episodes of ozone pollution from spring until the end of summer.
Normal ozone levels are around 100 - 120 micrograms per cubic meter (µg/m³). Last week Europe has seen levels above 180 µg/m³, the information threshold according to WHO, above which "national authorities should inform the public and give advice immediately after an exceedance".
According to European agencies, the threshold reflects a 'level beyond which there is a risk to human health from brief exposure for particularly sensitive sections of the population'. When the threshold is exceeded, national authorities are required to inform the public, states the European Environment Agency.
The alert threshold, which poses a direct risk for the population, is 240 µg/m3. In order to maintain good health, however, there should not be more than 25 days per year where ozone levels exceed 120 µg/m3 (on an 8-hour average).