Abstract

Risks of both new and existing substances and of biocides in Europe are being evaluated using the Technical Guidance Document (TGD). The European Water Framework Directive refers to this document for establishing Environmental Quality Standards (EQSs) for water. Another guidance document for the derivation of EQSs was developed on the basis of the TGD by the Fraunhofer Institt (FHI) on request of the European Commission. Our study, as documented in this report, aimed to elucidate differences between the two guidance documents. Besides describing the main differences in background, aim and methodology, we also considered discrepancies at a more technical level. Risk assessment described in the TGD encompasses effect assessment, exposure assessment and risk characterisation. Determination of EQSs in the FHI document was found to overlap with the environmental effect assessment of the TGD. Differences were partly technical; however, for certain substances the Fraunhofer method could lead to lower values of EQS for water compared to the derivation of safe water concentrations (PNECs) according to the TGD. Only one PNEC for water is derived following the TGD, whereas according to the FHI document, several EQSs for water are calculated from toxicity data for predators and human consumption of aquatic products. Additionally, risk assessment described in the TGD takes into account multiple exposure routes, while the FHI document only encompasses exposure via water. Therefore, it is theoretically possibly that adopting PNECs as EQSs for the water compartment will not fully protect human health in the case of substantial exposure via air or food.