The European Medicines Agency (EMA) regards the potential risks of human medicinal products to the environment and their impacts are assessed, as well as management to limit this impact. Hazard assessment of novel materials, which differ from conventional chemicals, e.g. nanobiomaterials, poses testing challenges and represents a work-in-progress with much focus on the optimization of required methodologies. For this work-in-progress, we here highlight where changes/updates are required in relation to the main elements for international testing based on OECD guidelines, supported by knowledge from the nanotoxicity area. The outline describes two major sections, nanobiomaterials and environmental hazards, including its challenges and learned lessons, with recommendations for implementation in OECD guidelines. Finally, the way forward via a testing strategy is described.[Figure not available: see fulltext.].