In summer 2004, the levels of ground-level ozone were high in southern Europe with widespread exceedances of the information threshold value (180 µg/m3), as laid down in the ozone directive (2002/3/EC). The exceedances of the information threshold were similar to earlier years, except for summer 2003, when there was a record number of exceedances. Also the directive’s long-term objective to protect human health, 120 µg/m3 of ozone concentration over 8 hours, was extensively exceeded in the EU and other European countries. The target value to protect human health was also exceeded in southern and part of central Europe. The highest levels were reported from Italy and Spain, with a maximum ozone level of 417 µg/m3.
Observed ozone trends are in general not statistically significant over the period 1996–2002. More in-depth analysis, e.g. by correcting for meteorological variability is needed, but the data suggest that the decreasing trend in peak values that was observed earlier has levelled off during recent years. Median concentrations show an increasing trend for all station types, although the increase is more pronounced for street and urban stations.