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Ground level ozone

Being a trace gas, ozone is a natural component of the atmosphere. In the ground-level air layer, it is formed under sun radiation from the so-called ozone precursors.

As precursors, in particular nitrogen oxides and Volatile Organic Compounds (VOC) should be mentioned, besides also carbon monoxide and methane.  Due to the human-induced increase in emissions of these substances, the concentration of ground-level ozone has also increased to such an extent that it has become a considerable environmental problem. In an increased concentration, it impairs by its direct effect human health and results in damage of the vegetation.

The ground-level ozone has to be distinguished from the ozone occurring at a height of 15 kilometres – in the stratosphere. Ozone protects us by its existence at this great height from a too intensive short-wave UV radiation on the ground and thus, among other things, against health detriment such as skin cancer.

The ozone concentration in the ambient air depends very much on the meteorological conditions. High sun radiation and high temperatures over a longer period lead to a high exposure to ozone. Particularly high ozone concentrations occur thus predominantly in summer (“summer smog”). Ozone is transported in the atmosphere over long distances and is thus a common problem of Europe and even of the Northern hemisphere. The pollution in Austria is dominated by cross-border emissions. Due to the meteorological conditions, it is lower than in the Mediterranean region, but higher than in the Scandinavian states. 

In large parts of Austria, the level of ozone exposure is above the target values laid down in the Ozone Act:

  • In the past exceedances of the target value for the protection of human health were observed almost all over the Austrian territory, not including inner-Alpine valley or basin locations and measuring sites near transport routes. Particularly highly affected by exceedances were the high mountain ranges, the highlands, the Southeast of Austria and Southern and Eastern Lower Austria. Exceedances of the long-term goal for the protection of health are observed annually on almost all measuring sites.
  • The target value for the protection of vegetation is first and foremost complied with in Alpine valleys, whereas considerable exceedances occur in the high mountain areas, in the highlands and in the East-Austrian flat and hilly lands.

Exceedances of the information threshold, which means short-term load peaks, occur most frequently in the Northeast of Austria, in the case of high ozone contamination over large areas in Central Europe, but also in other regions of Austria. Exceedances of the alarm threshold have so far only been observed in the surroundings of Vienna.

As the exposure to ozone is sometimes fluctuating considerably from year to year due to the strong influence of the weather conditions, one can hardly identify a clear trend in the course of the past few decades. However, it has turned out that, according to the all-European trend, short-term high load peaks have decreased, whereas the long-term averages have shown an upward trend.

Which measures can be taken on the short run to reduce a high ozone Exposure?

In the case of high ozone pollution, for example in the case of exceedance of the information or the alert threshold, a short-term reduction of emissions can counteract a further increase in emissions.

Instead of driving by car, public means of transport should rather be used to the extent possible. One should not use appliances, which are driven by combustion engines exactly in times of high ozone exposure. Moreover, the use of solvent-containing lacquers should not take place during this period.

However, one should bear in mind that short-term regional measures do basically not reduce the ozone formation potential, as ozone is transported over large Areas.