Ozone is one of the strongest oxidising agents and irritant gases in existence. It attacks human, animal and plant tissues and materials. In human beings it most noticeably affects the respiratory tract and lung tissue. In plants, high concentrations of ozone cause visible damage to leaves. If high concentrations of ozone persist for lengthy periods, this causes harvest losses in the agricultural sector. Acidic pollutants and photo-oxidants also attack buildings, monuments and other materials, resulting in bleaching and general deterioration. Ground-level ozone is a secondary pollutant which is formed from nitrogen oxides and volatile organic compounds under the influence of sunlight.
Ozone concentrations exceed the limit levels at all measuring stations and thus represent a widespread problem with correspondingly far-reaching consequences.
The immissions are connected to the high levels of nitrogen oxide and volatile organic compounds in the air. In Switzerland, as in the majority of central European countries, the immissions of these precursors have decreased significantly in the past few years. However, although the maximum levels of ozone pollution are also declining, the trend does not lead to the target value being reached in the near future. For this reason, the development is assessed as unsatisfactory.
Summer smog can only be combated by massively reducing the precursor pollutants nitrogen oxide and volatile organic compounds at the local, national and international levels, for example by applying the best available technologies to vehicles, industrial and agricultural equipment, and heat generators.
- Related indicators
- Volatile organic compounds emissions
The member states of the EU also measure ozone immissions and calculate similar indicators. The level of ozone pollution in Switzerland is similar to that in its neighbouring countries.
The current status and development of air pollution throughout Switzerland are measured and recorded by the National Air Pollution Monitoring Network (NABEL), which is jointly operated by the FOEN and EMPA (Swiss Federal Laboratories for Materials Science and Technology). It comprises 16 measurement stations distributed throughout the country, which provide data relating to all the most important pollution situations. For the assessment of ozone immissions, data are collected from NABEL stations with permanent measurement cycles.
|Targeted trend||Initial value||Final value||Variation in %||Observed trend||Assessment|
|Decrease||Average 1991-1993||Average 2018-2020||(1) -15.00%, (2) -2.94%||(1) Decrease, (2) Stabilisation||positive|
|(1) south of the Alps, (2) north of the Alps|