Nitrogen dioxide immissions
The term "nitrogen oxides" (NOx) embraces nitrogen dioxide (NO2) and nitrogen monoxide (NO). Nitrogen oxides form in the combustion of motor and heating fuels, especially when combustion is at high temperatures. Road transport is the main source. They are an important precursor in the formation of acid rain, secondary particulate matter and - in combination with volatile organic compounds - photo-oxidants (ozone/summer smog). Along with ammonia they form particulate matter and contribute to the over-fertilisation of ecosystems. Nitrogen dioxide and other irritant gases are also a causal factor in diseases of the respiratory tract. Children are particularly susceptible.
Ambient limit levels in urban areas are consistently exceeded, whereas in rural areas concentrations are usually below the specified limits. Concentrations in suburban areas are around the limit level. Since the mid-1980s, NO2 levels have fallen by 30 to 50% thanks to the adopted air pollution control measures (e.g. the tightening of exhaust limit levels and the introduction of catalytic converters for cars). However, nitrogen oxide pollution is still a serious problem that affects large areas of Switzerland. People are still being exposed to excessive nitrogen oxide concentrations and as before, ntrogen compound loads in sensitive ecosystems are still well above the tolerance levels. Further measures are necessary, including for example applying the "best available technologies to vehicles, industrial and agricultural equipment, and heat generators.
EU member states also measure nitrogen dioxide immissions and produce corresponding indicators. The levels of NO2 pollution are lower in Switzerland than in its neighbouring countries (fewer diesel vehicles and no thermal power plants).
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 nitrogen dioxide immissions, the measurement data from stations for the various site types were averaged, taking into account only rural stations on the north side of the Alps. The data of the station Sommer had to be homogenized due to a station shift, the method is described in the annual report.
|Targeted trend||Initial value||Final value||Variation in %||Observed trend||Assessment|
|Decrease||Average 1991-1993||Average 2018-2020||(1) -42.91%, (2) -51.72%, (3) -46.11%, (4) -42.47%, (5) -44.44%||(1) Decrease, (2) Decrease, (3) Decrease, (4) Decrease, (5) Decrease||positive|
|(1) urban, heavy traffic, (2) urban, (3) suburban, (4) rural, (5) pre-alpine/Jura range|