Monitoring data can rarely be generalized unless one knows the significant connections and interactions between the parts of an ecological system. Similarly it is usually not possible to assess the ecological effects from bioassays or toxicity tests with individual organisms. In view of the great number of existing chemicals and considering the large amount of environmental pollutants created every day by civilization we need to develop and apply general concepts (physical chemical substance specific data, unit processes) on the behaviour, distribution and fate of pollutants in order to assess their environmental behaviour and their potential effects on ecological systems and on human health.