On October 12, 2017, the Organization for Economic Cooperation and Development (OECD) announced the release of 17 new, updated, corrected, or deleted Test Guidelines. The Test Guidelines include three specifically developed for nanomaterials. OECD states that Test Guideline 318: Dispersion Stability of Nanomaterials in Simulated Environmental Media provides a simple and effective tool that can analyze the dispersion stability of nanomaterials in aqueous media. It is one of the prerequisites for a subsequent robust and reliable safety testing of nanomaterials. The Test Guideline allows users to understand nanomaterials’ fate in natural waters and their potential behavior in test media. OECD updated Test Guideline 412: 28-Day (Subacute) Inhalation Toxicity Study and Test Guideline 413: 90-Day (Subchronic) Inhalation Toxicity Study to allow testing and hazard identification of inhaled nanomaterials. According to OECD, the updates concern bronchoalveolar lavage measurements; particle-size distribution for test atmospheres; post-administration duration; and lung burden measurements. OECD states that the information that will be gathered through these new endpoints make the Test Guidelines applicable for assessing potential inhalation hazards of nanomaterials, while also increasing the understanding on the mode of action by which nanomaterials may act.