The Organization for Economic Cooperation and Development (OECD) has published a May 22, 2018, report entitled Assessment of Biodurability of Nanomaterials and their Surface ligands.  The purpose of the report was to compile the relevant information on the biodurability of the pristine and functionalized nanomaterials in biological and environmental media in vitro and in vivo, as well as describing methods for measuring the stability and halftimes of nanomaterials.  The report presents the in vitro and in vivo systems that are used to measure biodurability in biological and environmental systems for the pristine nanomaterials of the OECD Sponsorship Program.  In addition, the report describes the effect of the physicochemical properties of these nanomaterials and the properties of the biological and environmental media, as well as surface coating and ligands on their dissolution and biodegradation.  Nanomaterials with low dissolution rates include titanium dioxide and cerium oxide, and because of their primary genotoxicity, it was proposed that their responses after long-term exposure be further evaluated due to their accumulation in systemic organs.  Nanomaterials with high dissolution rates include zinc oxide, copper oxide, and quantum dots that release zinc, copper, or cadmium ions, respectively, and induce severe toxicity.  Those that have not yet been investigated for their biodurability either through dissolution or biodegradation include dendrimers, nanoclays, and aluminum oxide nanoparticles.  Those nanomaterials with dissolution rates are not biodurable and hence may cause short-term toxicity and health effects, as opposed to those with slow dissolution rates that are biodurable and hence may cause both short- and long-term health effects and show high environmental persistency.  The report recommends that the existing identified in vitro and in vivo standard techniques be validated in relation to their ability to predict the pathogenic potential and environmental persistence of nanomaterials to increase the predictive potential of these tests.