Welcome to a special, one-off Chemical Watch podcast on substance identity issues that have been raised as part of the ongoing REACH revision. In particular, we will be looking at a range of changes proposed by Germany’s Federal Institute for Occupational Safety and Health (Baua). These would tackle potential registration problems of substances with hazardous impurities and nanomaterials. They include amending the definition of a substance as given in the legal texts of legislation, including REACH. Chemical Watch’s science editor Andrew Turley is joined by Kristof Seubert and Angelina Gadermann both from Baua and Bernaette Quinn from REACHLaw. The consultancy has concerns over the ongoing use of the 'one substance' phrase commonly used in chemicals legislation. REACH takes a ‘one substance, one registration’ approach to data submission. An analogous phrase – one substance, one assessment – is used in the chemicals strategy for sustainability.