How safe are carbon nanotubes?

Royal Society of Chemistry ^ | 09 September 2009 | David Barden

[neverdem]

Carbon nanotubes are increasingly being used in everyday products such as sporting equipment, biomedical devices and aeroplanes. But questions remain as to how safe these nanotubes really are. 

A main factor in nanotube toxicity are the metal contaminants that remain from manufacture, which are typically one to ten per cent by weight, say Martin Pumera and Yuji Miyahara at the National Institute for Materials Science, Ibaraki, Japan. 'Carbon nanotubes are often viewed as homogenous materials, which is of course incorrect - they often contain impurities which are not even listed by the manufacturers,'  says Pumera.  The pair have used an electrochemical method to assess the effect metals have on nanotube toxicity. They say that their method is quicker and cheaper than laborious and expensive biomedical tests and could be more useful for initial assessments of carbon nanotube toxicity.  

Impurities in carbon nanotubes

Pumera and Miyahara measured how well five nanotube samples reduced or oxidised two simple biomarkers - hydrogen peroxide and hydrazine. They found that just 100 ppm of iron was needed to dominate the reduction ability, and therefore the toxicity. Pumera says this is very disturbing, as this value is significantly lower than the detection limits of the methods routinely used to assess nanotube purity. 'It is very likely that metallic impurities are responsible for large scatter in results of toxicological studies,' he adds. 

"Carbon nanotubes are often viewed as homogenous materials, which is of course incorrect - they often contain impurities which are not even listed by the manufacturers"
- Martin Pumera, National Institute for Materials Science, Ibaraki, Japan

Kostas Kostarelos, who works at the Centre for Drug Delivery Research, The School of Pharmacy, London, UK, says 'this work is yet another testament of the imperative need for well-characterised and reproducible standardised carbon nanotube properties. Until this is achieved, comparative studies will continue to be difficult to interpret and predictive assays of complex interactions impacting the toxicological profile of the material will be difficult to establish.'

References

M Pumera and Y Miyahara, Nanoscale, 2009 (DOI: 10.1039/b9nr00071b)

Link to journal article

What amount of metallic impurities in carbon nanotubes is small enough not to dominate their redox properties?
Martin Pumera and Yuji Miyahara, Nanoscale, 2009
DOI: 10.1039/b9nr00071b

Also of interest

Instant insight: A calculated risk

How safe are nanoparticles? Amanda Barnard reveals how computation can help to identify and prevent nanohazards

Nanotubes with added nitrogen are less toxic

Mice survive injections of nitrogenous tubes

Nanotechnology safety up for grabs in US

Nanotechnology safety up for grabs in US

Nanotechnology risk research demanded

US government urged to invest more and act fast

[Nick Danger]

[Bean Counter]

Interesting article. As always, in order to solve a problem, one must thoroughly understand exactly what the problem really is...

[dr_who]

The most disturbing thing about this report is that it doesn’t explain what these impurities are, how much exposure a person will get to these impurities, how inherently dangerous these impurities are....

[dr_who]

You ever wonder whether toxicity research is just ready employment for mediocre chemists?

[GRRRRR]

Well I’ve never had a problem with them.

[bvw]

I’d think that nanotubes could act like long term irritants that get trapped in various parts of the body, like asbestos fibers. Anyone know about that kind of problem or theory?

[Voter62vb]

http://www.organicconsumers.org/articles/article_18928.cfm

http://www.newkerala.com/nkfullnews-1-99068.html

quickly grabbed examples...I have not vetted ithem.

I have read other articles on the subject.

[Abathar]

Interesting, I heard that carbon fiber dust has very sharp features that look much like asbestos fibers under a microscope.

I wonder if it can pierce cell walls and cause abnormal cell growth (i.e. cancer) like asbestos does, being sharp and jagged the body can’t eliminate it like most particles.

I guess when we start seeing massive amounts of ambulance chasers on tv we will have our answer.

[Abathar]

I think we have heard the same rumors. See post 9

[dr_who]

The tubes with added nitrogen may be less toxic because they have a segmented, bamboo-like structure that makes them less prone to sticking together into thick wads, suggests Laclette. He now hopes that further research may help to understand what causes some nanotubes to be more toxic than others.

I can see how that would explain how sticking nanotubes up mouse noses results in them dying.

[bobsatwork]

...100 ppm of iron was needed to dominate the reduction ability...Pumera says this is very disturbing, as this value is significantly lower than the detection limits of the methods routinely used to assess nanotube purity - 100ppM of iron is significantly lower than the detection limits of WHAT methods? I'm measuring ppb of iron all the time (soil and groundwater).

[Defiant]

Are there any planets out there composed entirely of carbon nanotubes? If so, we know that it can go awry.

[dr_who]

When hysteria matters more than facts do, the number of ambulance chasers has nothing to do with how toxic a given material is. Thanks for the Memories: How lawyers get the testimony they want.

[bvw]

? 9 is my own post.

[Abathar]

7 is yours.

[tiki]

This article is their cue to enter, stage right.

[Abathar]

Last Friday I totaled out my Suburban in a head on crash with an elderly man who was “confused” and made a left hand turn directly into me.

I now have a stack, and I mean a STACK of mailings from local lawyers advertising their prowess of milking insurance companies, many of them are about 20 pages thick.

Both vehicles destroyed but neither one of us was hurt, yet they send this crap to me anyway. One even mentioned that I was not found to be in any fault so they do read the police reports before they mail them.

Makes me sick.

[Mogollon]

You ever wonder whether toxicity research is just ready employment for mediocre chemists?

Try doing a little toxicokinetics and drug/toxin metabolism studies with radiolabeled drugs/or toxins.

[bvw]

Hey, right — thought I was reading what I had written.