BrooklynDodger(s) comment: Rarely do the Dodger(s) quote publications failing to find associations between exposures and health effects. Carbon nanotubes may not be the most potent material in the world. The Dodger(s) have opined this material is high tech carbon black. But carbon black is a 2B carcinogen. An inhalation bioassay of carbon nanotubes is needed to evaluate the toxic potential and provide some evidence regarding potency.
Absence of Carcinogenic Response to Multiwall Carbon Nanotubes in a 2-Year Bioassay in the Peritoneal Cavity of the Rat
Julie Muller*, Monique Delos
, Nadtha Panin*, Virginie Rabolli*, François Huaux* and Dominique Lison*,1 * Industrial Toxicology and Occupational Medicine Unit, Catholic University of Louvain, 1200 Brussels, Belgium Laboratory of Pathology, University Hospital of Mont-Godinne, Catholic University of Louvain, 5530 Yvoir, Belgium
1 To whom correspondence should be addressed at Industrial Toxicology and Occupational Medicine Unit, Catholic University of Louvain, Avenue E. Mounier, 53.02, 1200 Brussels, Belgium. Fax: +32 2 764 53 38. E-mail: dominique.lison@uclouvain.be.
Received April 8, 2009; accepted April 30, 2009
 | Abstract |
|---|
Toxicological investigations of carbon nanotubes have shown
that they can induce pulmonary toxicity, and similarities with
asbestos fibers have been suggested. We previously reported
that multiwall carbon nanotubes (MWCNT) induced lung inflammation,
granulomas and fibrotic reactions. The same MWCNT also caused
mutations in epithelial cells
in vitro and
in vivo. These inflammatory
and genotoxic activities were related to the presence of defects
in the structure of the nanotubes. In view of the strong links
between inflammation, mutations and cancer, these observations
prompted us to explore the carcinogenic potential of these MWCNT
in the peritoneal cavity of rats. The incidence of mesothelioma
and other tumors was recorded in three groups of 50 male Wistar
rats injected intraperitoneally with a single dose of MWCNT
with defects (2 or 20 mg/animal) and MWCNT without defects (20
mg/animal). Two additional groups of 26 rats were used as positive
(2 mg UICC crocidolite/animal) and vehicle controls. After 24
months, although crocidolite induced a clear carcinogenic response
(34.6% animals with mesothelioma vs. 3.8% in vehicle controls),
MWCNT with or without structural defects did not induce mesothelioma
in this bioassay (4, 0, or 6%, respectively). The incidence
of tumors other than mesothelioma was not significantly increased
across the groups. The initial hypothesis of a contrasting carcinogenic
activity between MWCNT with and without defects could not be
verified in this bioassay. We discuss the possible reasons for
this absence of carcinogenic response, including the length
of the MWCNT tested (<> of a sustained inflammatory reaction to MWCNT, and the capacity
of these MWCNT to quench free radicals.
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