Les transports et la pollution par l'ozone en Suisse

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Economic growth, consumption habits and an exponential growth of mobility have led to a tremendous increase in motor vehicle traffic and road transportation over these past years. Subsequently, this traffic increase yielded an increase in related nuisances, in particular air pollution. In addition to classical pollutants (CO, SO2, NOx, soot, etc.), derived product should also be studied. Indeed, photochemical reaction of precursors such as nitrogen oxides in the presence of volatile organic compounds generates ozone and other photochemical products, as secondary pernicious pollutants. Ozone is an extremely noxious gas owing to its high oxidizing property. Amongst its noxious effects for human health, we can mention: irritation of mucous membranes of throat and eyes, reduced immune defence mechanisms, intensification of chronic lung respiratory diseases and increased risks of chronic lung diseases. As regards vegetation, ozone can lead to acute or chronic diseases even in the case of short exposures. Very high ozone concentrations contribute to the forest decline and lead to reduced agricultural productivity. The productivity decrease observed ranges from 5% to 15% according to the crop, the region and the year studied. The Air Quality Standards in the Swiss Ordinance on Air Pollution Control and the similar guidelines for air quality established by international specialized organizations such as the WHO, the Association of German Engineers and the UN/ECE-expert groups. ‘Effects of Pollutants’ have often been exceeded, sometimes considerably, in Switzerland during the summer period. At concentrations higher than these standards living beings are directly affected, the more the higher the concentration. Air pollution must therefore be reduced. Considerable reductions of emissions of the precursor pollutants NOx and VOC in the range of 70–80%, with reference to the amount of emissions in the first half of the eighties, are particularly required in order to reduce the ozone concentration on a large scale down to a concentration which is tolerable for human beings and the environment. The Federal Government has established its goals in air hygiene in the Strategy on air pollution control of September 10, 1986. According to this Strategy, the emissions of nitrogen oxides and volatile organic compounds should be reduced at least to the level of 1960. This means a reduction of nitrogen oxides of 66% compared to 1984 and a reduction of VOC of 56%. These goals can only be achieved in the medium-rather than in the short-term period. Special emphasis must be put on measures referring to urban areas, to industrial and commercial VOC sources as well as to motor vehicle emissions. As mentioned in the report Control Strategies for Photochemical Oxidants Across Europe (OECD, 1990, p. 65): ‘mobile sources are the largest source of man-made VOC (44%), NOx (54%), (and CO) in OECD Europe. Controls which reduce both VOC and NOx emissions from this source to the maximum extent technologically feasible are therefore most effective at reducing widespread high levels of ozone’. In Switzerland, 70% of the man-made emissions of NOx and 25% of VOC come from mobile sources. It becomes obvious that technical measures are not sufficient to solve the problem. Therefore measures that tend to change the behaviour (in energy, mobility and consumption fields) of all the citizens must be adopted.