Carbon nanotubes are a large family of carbon-based hollow cylindrical structures with unique physicochemical properties that have motivated research for diverse applications; some have reached commercialization. Recent actions in the European Union that propose to ban this entire class of materials highlight an unmet need to precisely define carbon nanotubes, to better understand their toxicological risks for human health and the environment throughout their life cycle, and to communicate science-based policy-driving information regarding their taxonomy, safe sourcing, processing, production, manufacturing, handling, use, transportation and disposal. In this Perspective, the authors discuss current information and knowledge gaps regarding these issues and make recommendations to provide research and development, and regulatory clarity, regarding the material properties of different carbon nanotube materials. A co-author of this article is Mijin Kim, assistant professor in the School of Chemistry and Biochemistry.