The chemical pollution of European water bodies is greater than previously believed, according to a new study by the University of Koblenz-Landau and the Helmholtz Centre for Environmental Research (UFZ), Germany, published in the latest edition of the scientific journal Proceedings. Together with fellow scientists from Switzerland and France, the researchers analysed data on 223 chemicals taken from over 4000 monitoring sites and estimated the extent to which risk thresholds were exceeded for fish, invertebrates and algae. The study reveals that in 42% of European water bodies chemicals are likely to have negative long-term effects on aquatic organisms, such as impacts on breeding or higher vulnerability to disease. In 14% of the sites, the concentrations of chemicals could exert acute lethal effects on species. Up to now, most authorities and scientists have considered toxic chemicals to be rather a local problem while this study shows that chemical pollution is a large-scale problem in Europe. Pesticides used in conventional farming are the main source of pollution, with herbicides being most harmful to algae and invertebrates. Other substances found in large quantities include organotin compounds, brominated flame retardants and polyaromatic hydrocarbons from burning petroleum or organic matter. According to the scientists, the EU focuses mainly on the occurrence of around 40 chemicals considered particularly hazardous to aquatic life. “The real problem, however, is that a large number of chemicals which are currently in use are not taken into account at all in the context of water quality monitoring”, says Dr. Werner Brack from the Helmholtz Centre. The authors suggest preventative measures, including the reduction in the use of pesticides in agriculture and the introduction of buffer strips where farming fields are close to rivers.