Closing gaps for environmental risk screening of engineered nanomaterials

Engineered nanomaterials (ENM) have a widespread presence in human life and are components of many products and applications. This warrants an easy and fast evaluation of potential environmental risks. However, so far this is hampered by the multitude of different nanomaterials on the markets in addition to the many variations in form, size and surface modifications. Testing of each variation of ENM is not manageable, and hence the development and application of fast risk screening tools for ENMs is discussed. Here, we present the development of a scoring scheme with regard to ENM environmental risks under consideration of the two compartments water and soil. It allows for the ranking of ENM according to their environmental fate and hazard by taking into account criteria that are meaningful and relevant for ENM. The selection of the criteria is based on conceptual considerations, existing knowledge, and experimental work including transport and transformation studies as well as aquatic and terrestrial toxicity tests. The allocation of the ENM to the scores informs on the potential for transport and transformation and the hazard potential. Fate and hazard scores are subsequently combined into one risk score (1-10 for aquatic compartment, 1-7 for terrestrial compartment). The risk score has the intention to indicate which ENM may need prioritization for further action, i.e. with regard to the degree of detail for further testing or modelling. The applicability and consistency of the scoring schemes were assessed by taking different chemical species (e.g. of Ag, TiO2, SiO2, Cu, Fe) of ENM in various modifications (e.g. different shapes and coatings) into account. In conclusion, the established scoring schemes were found to be applicable to rank ENM according to their environmental fate and hazard potential, and thus to their environmental risk potential.