The graphs are based on the 8-hourly mean concentration values; they present the range of concentrations at all station types (in mg/m3) officially reported by the EU Member States and how the concentrations relate to the limit value set by EU legislation (marked by the red line).
The diagram indicates the lowest and highest observations, the means and the lower and upper quartiles. The lower quartile splits the lowest 25 % of the data and the upper quartile splits the highest 25 % of the data.
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On very hot days use public transport rather than your car.
Car exhaust emissions react with sunlight and heat to cause polluting gases such as tropospheric ozone. This is the main ingredient of poor air quality and photo-chemical smog, which can cause breathing difficulties. To find out the level of ozone pollution across Europe, go to EEA's Live Ozone Map.
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