In this H2020 SAbyNA deliverable, we discuss improvements required in existing release, fate and exposure models, with a particular focus on improvements that could be made to GUIDEnano. This deliverable dated October 2021 is an interim and acts as a progress report for Task 2.2. It is recommended to access the more complete report including results of improvements, available on Zenodo as Deliverable 2.4 (October 2022) under DOI 10.5281/zenodo.10822229. We report on our detailed assessment of environmental release, fate and exposure models, focussing on aspects such as processes and algorithms, input parameters, sensitivity/uncertainty analyses and scenarios/case studies. We identify a number of potential improvements to GUIDEnano, such as the inclusion of default parameter sets, updated processes algorithms, and the inclusion of results from sensitivity/uncertainty analyses performed on other exposure models. We discuss the progress to date for the improvements required in the human exposure models following on from M2.2. The improvements identified in MS2.2 included model assumptions, input parameters, algorithms and processes, uncertainty analysis and the inclusion of release rates. The main focus of our assessment to date has been in uncertainty analysis and we are currently developing methodology to improve the uncertainty analysis of the models. We also present the results to date and the work to be performed for the other improvements identified over the next year. The results of improvements required in both environmental and human models are presented in Deliverable 2.4 in October 2022 (DOI 10.5281/zenodo.10822229).