Martin Pumera, Nanyang Technological University, Singapore, reports that much of the “older” (i.e. pre-2007) nanotoxicitiy-based research contains insufficient characterization of the nanomaterials under study and is of limited use. In a review of recent literature, he finds much of the observed toxicity of single- and multi-walled carbon nanotubes comes from metal impurities. These can remain in nanotubes even after treatment with HCl and produce •OH radicals which cause oxidative stress.

Defects and the size of nanotubes also play a role, with defect-free and smaller nanotubes causing less inflammation.

Two principal research directions are foreseen:

• Comparative testing and establishment of a broader base for cross comparison, and
• Studies to understand the molecular mechanisms of nanotoxicity.

• Nanotoxicology: The Molecular Science Point of View
  M. Pumera,
  Chem. Asian J. 2010, 5.
  DOI: 10.1002/asia.201000398