The use of pesticides can lead to a build-up of toxic and ecologically harmful residues in the soil. Until recently, it was not possible to ascertain in detail to which pesticides this applies and to what extent. Now, researchers from the Helmholtz Centre for Environmental Research (UFZ), working in partnership with colleagues from the Technical University of Denmark (DTU), have developed a model which allows the formation of potentially toxic residues to be more accurately predicted. The model could be used for future hazard assessment in the pesticide approval process of the European Chemicals Agency (ECHA). The study appears in the current edition of Environmental Science and Technology.