In practical and economic terms, the corrosion due to SO2 is closely tied to
densely populated areas. Here, three conditions coincide: a high content of
atmospheric pollutants, a high population density and a large use of materials.
The corrosion rate decreases in general rapidly with increasing distance from the
source of emission. In many regions, atmospheric corrosion is therefore a local
effect. In certain densely populated regions such as Western or Central Europe,,
an important part of corrosion damage can also be caused by the transport of
pollutants over national borders