Recently a non-profit organisation ChemSoc released the SIN (substitute it now) list of materials which should be banned, which included carbon nanotubes as an entire material class. In response, Prof Daniel Heller (Memorial Sloan Kettering Cancer Centre) wrote a response in Nature Nanotechnology, in conjunction with a number of other leading nanotechnology labs around the world, including NEL. Investigating the safety of our nanomaterials is absolutely critical for any material destined to be used in vivo, however we need to recognise that even nanomaterials in a particular class can demonstrate dramatically different physico-chemical properties. For this reason, there is no short-cut method - we need to evaluate each specific material on its merits.
As a relevant example to NEL - crystalline silica inhaled into the lungs can cause significant medical problems (e.g. silicosis), however amorphous silica injected into the bloodstream is proving to be a safe and highly efficacious approach to perform molecular imaging of tumors.