Three of the major concerns for European waters are anthropogenic nutrient enrichment, chemical and biological contamination, and sufficient, safe and good chemical and microbiological quality drinking water for EU citizens. The overall goal of this action is to provide methodologies, assessment tools and assessments of the exposure of EU waters to contaminants through experimental measurements and models. This will contribute to the understanding and quantification of the fate and effects of contaminants (chemical, biological) in inland, coastal and drinking waters of the MS and CC, and to assess how nutrient enrichment interacts with chemical and biological stressors. Methodologies for the assessment of the microbiological quality of drinking water and ecotoxicological quality of surface water will be developed and implemented. Rationale Release of chemical substances significantly impacts European waters. Impacts are both direct and indirect, through degradation products, acute and/or chronic toxic toxicity, and/or long-term effects via bioaccumation in aquatic food chains.