From 30th September – 7th October 2014, 21 experts from ten countries attended a meeting at the International Agency for Research on Cancer (IARC, Lyon, France) to assess the carcinogenicity of carbon nanotubes (CNTs), including single-walled (SWCNTs) and multi-walled (MWCNTs), as well as fluoro-edenite and silicon carbide (SiC) fibres and whiskers.
Results of these assessments have been described in an article in The Lancet Oncology, and will be officially published in Volume 111 of the IARC Monographs (in press).
For carbon nanotubes, no human cancer data was available to the IARC Working Group and therefore the evaluation focussed on the results of numerous in vivo studies assessing the carcinogenicity of SWCNTs and MWCNT in rodents including the specific MWCNT sample 'MWCNT-7' which has been the focus of several studies.
Based on a comprehensive assessment of the available evidence, a majority of the Working Group did not consider the mechanistic evidence for carcinogenicity to be strong for any particular type of CNT, in particular concerning chronic endpoints where data is severely limited. However given the evidence available, it was agreed to classify specifically the MWCNT-7 sample, as 'possibly carcinogenic to humans (Group 2B)'. Moreover, it was determined that, due to a lack of coherent evidence, it was not possible to generalise from one type of CNT to other types. Therefore, other forms of CNT, namely SWCNT and other types of MWCNT (excluding MWCNT-7), were categorised as 'not classifiable as to their carcinogenicity to humans (Group 3)'.
Further details of the Working Group considerations with respect to carbon nanotubes, and the other fibres assessed, are described in the Lancet article (free to access upon registration) and an updated list of agents classified by the IARC Monographs (Volumes 1 – 111) has also been made available.
Grosse Y., Loomis D., Guyton K.Z., Lauby-Secretan B., El Ghissassi F., Bouvard V., Benbrahim-Tallaa L., Guha N., Scoccianti C., Mattock H., Straif K. (2014). Carcinogenicity of fluoro-edenite, silicon carbide fibres and whiskers, and carbon nanotubes. The Lancet Oncology, dx.doi.org/10.1016/S1470-2045(14)71109-X