Toxicological studies in recent years have shown that the prediction of pathogenic properties of nanomaterials is not per se possible and that significant knowledge on the nanomaterial itself and its behaviour in the environment is necessary. Quite a few of these studies also strongly indicate that particle surface area and the potential to form reactive oxidants are highly promising metrics to predict the toxic potency of manufactured nanomaterials (MNM). In this project a grouping of MNMs is envisaged by using a combined strategy which, on the one hand, comprises an in-depth analysis of the physical characteristics of selected MNM suspensions and, on the other hand, the thorough evaluation of their toxic response in human cells. The study will focus on the most appropriate prediction metrics for nanomaterials, the surface area and the oxidant generation potency. It will be investigated which type of surface reactivity is most relevant and in how far the novel prediction metrics (oxidant generation capacity/reactivity and surface area, combined to reactivity per surface area) can be used, standardized and ultimately implemented to reduce toxicological screening of MNM and improve hazard and risk assessment. It is envisaged that this approach provides bridging of nanomaterial characterization and toxicity evaluation by simplifying a MNM classification e. g. for MNM producers.