Sunny periods during summer without wind cause increasing ozone concentrations. This pollution has negative effects on human health, buildings, materials, and the climate. The policy of the Confederation aims at reducing precursor substances (nitrogen oxides and volatile organic compounds) on the basis of permanent measures.
Ozone is multifaceted. Up in the stratosphere it protects us against harmful ultraviolet radiation from the sun, but too much ozone at ground level - i.e. in the air that we breathe - is undesirable.
The ambient air quality standards stipulated in the Ordinance on Air Pollution Control (LRV) are still frequently exceeded in the summer months owing to the presence of nitrogen oxides (NOx) and volatile organic compounds (VOCs), the two precursors from which ozone is formed under the influence of sunlight.
The primary sources of these precursors are
- road transport
- and also industry.
The measures taken by the federal government to reduce summer smog are geared towards the long-term reduction of these precursors. Since summer smog is also caused by emission sources outside Switzerland, reduction measures need to be continued on the international level.
Ozone pollution: Current levels and trends
The ambient air quality standards stipulated in the Ordinance on Air Pollution Control (LRV) are still frequently exceeded in the summer months
Fact sheets on the formation of ozone, emissions of its precursor substances, air quality during summer, measures to improve air quality,
and effects on human health, ecosystems, physical goods, and the climate. (german, french and italian)
Sommersmog und Ozon: Grundlagen (PDF, 250 kB, 03.06.2019)(in German, French, Italian)
Entwicklung und aktuelle Belastung durch Ozon in der Schweiz (PDF, 555 kB, 03.06.2019)(in German, French, Italian)
Ozon: Reduktion der Vorläuferschadstoffe - was muss noch getan werden ? (PDF, 266 kB, 03.06.2019)(in German, French, Italian)
Auswirkungen der Ozonbelastung (PDF, 284 kB, 03.06.2019)(in German, French, Italian)
Last modification 03.05.2019