Within DIAGONAL project, the environmental sustainability of the Safe-by-Design (SbD) strategies is intended to be evaluated via the standardized life cycle assessment (LCA) methodology (ISO, 2006). To perform an LCA study, a life cycle inventory (LCI) is made to quantify all the environmental exchanges (emissions to the environment and use of natural resources) along the life cycle of the studied product or process. The LCI flows are then translated into environmental impacts via the step of life cycle impact assessment (LCIA). The flows are categorized and characterized depending on their effects in function of the unit of reference for the impact category. The conversion between the physical amount and the impact unit is done by characterization factors (CFs).Among the potential environmental issues that the release of nanomaterials can have, the most mentioned issue in literature is toxicity (Buist et al., 2017). For toxicity assessment, USEtox is developed as the consensus approach, which is, however, contains no CFs to characterize the impacts of nanomaterial emissions (Owsianiak et al., 2023). Consequently, the related effects of released engineered nanoparticles (ENPs) are not included in LCA results. As there are fundamental differences between chemicals and nanomaterials, there is a need to develop CFs for nanomaterials (Romeo et al., 2022a). To tackle this issue, task 3.6 of DIAGONAL aims at developing CFs for multi-component nanomaterials (MCNMs) and high aspect-ratio nanomaterials (HARNs).This work will be done based on the scientific consensus for toxicity impacts in LCA, i.e., the USEtox framework. Both freshwater ecotoxicity and human toxicity will be investigated, covering the different steps of the cause-effect chain modelling: fate, exposure and effect. This work intends to use the outputs from other modelling tasks or experimental results to feed the CF modelling.This deliverable 3.7 details this work. After providing a summary of the state-of-the-art, the report describes the methodology and finally details and discusses the results. The developed CFs could be applied in Task 5.2 for the LCA of the selected case studies and SbD strategies.