Air pollution is a constant source of concern. The different types of pollution are dangerous to human health and damaging to the environment as well as to buildings and monuments.
The pollutants include nitrogen dioxide (NO2) and volatile organic compounds and come from a range of different sources, mainly road transport (in particular diesel engines) and industry. Other pollutants are benzene, sulphur dioxide, carbon monoxide and ammonia.
Technical improvements have helped to reduce the emission of pollutants in the last two decades or so, but whereas industry is much less polluting than formerly, the increase in transport of all kinds has more or less cancelled out the gains made in this area by technical advances.
Transport accounted for nearly 31% of greenhouse gases in Switzerland in 2000.
Between 1990 and 2000 there was a particularly sharp rise in greenhouse gas emissions by planes, both national and international.