ABSTRACT
Despite the fact that, all over the world, many people already live in large metropolitan areas, there is a clear tendency for urbanization to continue for many more years in most geographical regions. It is estimated that within the next decade more than half of the world's population will be living in big cities. Europe is the most urbanized continent in the world, with some 80% of the population permanently residing in densely populated areas. This is associated with the increase in all kind of human activities, which in turn results in the degradation of the local natural atmospheric environment.
