Are Multi-Walled Carbon Nanotubes More Like Asbestos Than We Thought? Part II

John Balbus, M.D., M.P.H., is Chief Health Scientist.

A new study published today in Nature Nanotechnology finds that multi-walled carbon nanotubes (MWCNTs) cause inflammatory changes in mice that closely resemble those caused by asbestos.  This is the second study in a few months to make this finding.  (I posted on the first, Takagi et al., a few weeks ago.)  So is the case closed on multi-walled carbon nanotubes?  Or is too early to draw conclusions?

These two studies used different approaches to compare the effects of MWCNTs and asbestos.  Although both directly injected the nanotubes into the peritoneal cavities of mice (the peritoneum is the lining of the abdominal organs and walls, and is the part of the body – along with the pleura lining the lungs – where asbestos causes mesotheliomas to arise), the new study used a 60-fold lower dose and measured only inflammatory changes, not the actual development of mesotheliomas.  Takagi et al., on the other hand, used special mice that were genetically highly susceptible to cancer formation, and observed the mice until they developed tumors.

Despite these differences, these studies together make a strong case that multi-walled carbon nanotubes cause inflammation and cancers in a similar fashion to asbestos, at least if they have been deposited directly within the peritoneum.

But the studies only tell a part of the story.  In order to have a better handle on the risks from inhaling MWCNTs, studies need to be done to determine whether there could be substantial concentrations in the air that workers (or other exposed persons) breathe.  Then we need to find out whether inhaled MWCNTs will make their way from the airspaces of the lungs, through the lung tissue, to the lung and abdominal cavity linings – something asbestos does with relative ease.

If these first two steps in causing disease are demonstrated, it is likely that MWCNTs will persist and continue to cause inflammation as long as asbestos does, but this needs further investigation as well.  So the case isn’t closed, but the evidence is stacking up.

Until these questions are answered, companies using MWCNTs should carefully characterize their materials and refrain from exposing workers to nanotubes longer than 5 microns with fibrous shapes.  And researchers developing applications for MWCNTs should look to develop forms that don’t have those size and shape characteristics.  These studies don’t show that other forms are harmless, but it can’t hurt to sidestep the trouble you can see.

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  1. Posted May 21, 2008 at 7:47 am | Permalink

    For anyone interesting in reading more on this, the International Council on Nanotechnology (ICON) at Rice University has put together a useful backgrounder with comments from a variety of nanotechnology voices. It can be found at:

  2. Maggiemae
    Posted May 28, 2008 at 7:34 pm | Permalink

    I truly believe there have been a LOT of studies done, but of the Tuskeegee variety. I am a suffering victim of “nanotech” disease called Morgellons. I suggest anyone that has expertise in the field take a good long look at the photos in this report. See Jan Smith’s Nanotech Nightmare – Morgellons Exposed site.

    It is across the board, we all have the same manifestations. How does one grow polymer fibers and pick nano devices out of their skin? How did they get there in the first place? BIG BIG money is keeping this one sequestered…you can be sure.
    Thanks for your efforts and as the previous poster acknowledged, “top notch” information.

  3. Aaron McDonald
    Posted January 25, 2009 at 8:58 am | Permalink

    I will tell you right now what the problem is: researchers and writers are confused and haven’t grasped even an idea of the factors that asbestos researchers always talk about.

    I have just spent 3 hours IN VAIN trying to figure out if I was exposed to danger when I spent 2 months working at a MWCNT factory where the MWCNTs were 20 microns in length but always SERPENTINE and never sharp and rod-like.

    Some writers (very few) refer to a hard-to-find Brown et al 2007 study that they say showed that long and straight was dangerous while short and curly was OK.

    BUT WHAT ABOUT LONG AND CURLY??? This shape is the predominant form in which MWCNTs come out of most ovens.

    It is upsetting to see scientists not logically crossing their Ts and dotting their i’s when making such discussions.

    Why can’t someone grasp this and deal with it? I want to know: does a long and curly nanotube, that has a tendency to aggregate into ropes, have any chance of even getting into the alveoli in the first place?

    I really don’t care to hear about 15 micron long straight nanotubes, which are obviously refined material, the powder of which would be too expensive to be allowed to float into the air and expose many workers.

  4. Posted May 21, 2009 at 3:08 am | Permalink


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