'The river Rhine, it is well known, Doth wash your city of Cologne; Butteil me, Nymphs, what power divine Shall henceforth wash the river Rhine?' The above strophe, composed by Samuel Taylor Coleridge early last century, shows that interest in environmental problems (in this case, the self-cleansing property of water) is not just something new, but was also present in the past. The reader may wonder, after this poetic contribution which is still very relevant, if there is any need to compile a book which handles environmental problems in a much less prosaic, i. e. scientific, way. It is my firm beliefthat present environmental problems, because of both s i z e and in t e n s y, i t deserve our profound attention. This concern will have to be shown not only by those directly involved, viz. the 'man in the street', but also by the authorities as well as by scientists. In view also of the social relevance of the environmental question, science may not be impartial but must make a (modest) attempt to analyse, explain and solve the present environmental question systematically.