Trend in annual mean of daily max 8 h-mean O3 concentrations (left) and trend in 93.2 percentile of daily 8 max h-mean O3 concentrations (right) (in μg/m3) for 2001–2010 per station type

All stations in EU Member States, with at least 75 % data coverage for at least eight years were included in the analysis. Concentrations per station type are given in μg/m3. In the diagrams a geographical bias exists towards central Europe where there is a higher density of stations.
The 93.2 percentile of daily max 8-h mean values is directly related to the target value for O3, as 25 days per year are allowed to have exceedances of the target value threshold of 120 μg/m3.