Like asbestos fibers, multi-walled carbon nanotubes (MWCNTs) are small
enough to be inhaled or accidentally ingested as dust. Unlike asbestos,
which occurs naturally and is mined for commercial use, MWCNTs are
synthetic. These carbon-based molecules are shaped into concentric tubes
which resist chemical corrosion and are valuable for use in
electronics, optics, textiles, and other areas of manufacturing.
A new study contains more disturbing news for people who work in certain
areas of materials science. Researchers have once again connected
inhalation of multi-walled carbon nanotubes with the risk of developing
malignant mesothelioma, a deadly cancer most often associated with
asbestos.
All of the treated rats developed malignant peritoneal mesothelioma,
which was confirmed by microscopic and immuno-histo-chemical evaluation.
Most of these MWCNT - induced mesothelioma tumors occurred not only on the
peritoneum lining the abdomen, but also spread into peritoneal organs, suggesting an aggressive malignancy.
The goal of the new German study was to identify possible carcinogenic
effects of MWCNTs and to determine how the cancer triggered by these
molecules compares to mesothelioma triggered by asbestos. The team
injected different shapes and sizes of MWCNTs into the abdomens of 500
lab rats. A control group of rats received injections of amosite
asbestos.
But, even though mesothelioma developed in all cases, there were
differences in the time it took for tumors to occur. The researchers
theorize that the differences may lie in the shapes and sizes of the
MWCNTs.
The researchers report that, regardless of the cause, all of the
mesotheliomas that developed in the rats were similar to each other and
to human mesothelioma. The team concludes that all types of MWCNTs have
the potential to cause mesothelioma, but that certain varieties are more
carcinogenic than others. Mesothelioma is a highly aggressive cancer
that is currently considered incurable. The new study appears in the
journal Particle and Fibre Toxicology.
