A recently published paper in Nature Nanotechnology submitted by researchers at Edinburgh University led by Ken Donaldson has provided evidence that some carbon nanotubes''specifically multi-walled carbon nanotubes (MWNT) that are longer than 20 m''have the same pathogenic effects as asbestos.
Like asbestos, the MWNT''s toxicity is not due to their chemical composition but their physical characteristics, namely their length.
The pathogenic quality of both MWNTs of a certain length and asbestos occurs when the body''s phagocytes attempt to engulf the fiber, and when unable to get around the entire length of the fiber, the phagocytes try to kill the fiber with toxic products. The attempt fails to kill the fiber but succeeds in damaging the surrounding tissue.
If you don''t have a subscription to Nature, I suggest reading Richard Jones blog entry at Soft Machines, which gives a pretty thorough review of the findings and what it all means.
As Jones notes, ''not all carbon nanotubes are equal when it comes to their toxicity. Long nanotubes produce an asbestos-like response, while short nanotubes, and particulate graphene-like materials don''t produce this response.''
Jones further emphasizes, ''the experiments do not say anything about issues of dose and exposure.''
While Jones did not initially know what percentage of the carbon nanotubes on the market fit the description of those that were used in the tests, the International Council on Nanotechnology (ICON) provided a backgrounder that provides some information in this area.
The MWNTs that might fit this description, Jones notes, are integrated into a material matrix, which leaves the threats of exposure in two areas: workers who are working with the MWNTs before they are integrated into a material matrix and what happens in the life cycle of the products, especially after disposal.