Chemicals are an essential part of our daily lives and are used to produce consumer goods, to protect or restore our health and to boost food production, to name but a few examples. Some chemicals, however, are hazardous, raising concerns for the environment and human health. Hazardous substances are emitted to fresh and marine waters via a number of pathways and can have detrimental effects on aquatic biota. Humans can be exposed to hazardous substances in water through the ingestion of contaminated drinking water and the consumption of contaminated freshwater fish and seafood. A wide range of legislation now exists in Europe to address the release of hazardous substances to the environment, including water. New challenges exist, however, including the issues of chemical mixtures and emerging pollutants.