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Just How Toxic Are Carbon Nanotubes?
11/29/2012

Researchers at Texas Tech University have come up with a new method for detecting CNTs in soils, which will help determine their toxicity. CNTs are so small that mean outer diameters of 13nm to 16nm are common in multi-walled tubes, shown here as grains partially smeared on paper (scale in centimeters).   (Source: Shaddack/Wikimedia Commons)
Researchers at Texas Tech University have come up with a new method for detecting CNTs in soils, which will help determine their toxicity. CNTs are so small that mean outer diameters of 13nm to 16nm are common in multi-walled tubes, shown here as grains partially smeared on paper (scale in centimeters).
(Source: Shaddack/Wikimedia Commons)

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naperlou
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life cycle concerns
naperlou   11/29/2012 10:50:27 AM
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Ann, this is indeed a concern.  Like many of the clever solutions to engineering problems, we have to think of the effect on living organisms, not just humans.  Semiconductor manufacturing also uses many toxic chemicals, for example, and these have to be controlled.  This is true at the point of manufacture and at the point of disposal.  I recall that even the ink used in thermal printers, such as those that are used to print receipts at stores, can be toxic.  We need to be careful in handling exotic, engineered materials.

One question I do have is about the detection method.  Since microwaves are used, I assume that the tests done on earhtworms are destructive.  Soil, even after being exposed to microwaves, is still just soil.  An earthworm on the other hand...

Tim
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Re: life cycle concerns
Tim   11/29/2012 12:44:52 PM
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Good article explaining the detection method for CNT's in soil. Are there toxicity concerns for CNT's in product? Also, are there concerns with the processing method used to add the CNT's to the base material?

Ann R. Thryft
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Re: life cycle concerns
Ann R. Thryft   12/3/2012 3:01:30 PM
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Tim and ervin0072002, based on the Japanese, US and European concerns about CNTs from all sources, which we covered here
http://www.designnews.com/document.asp?doc_id=237995
and especially during the manufacturing process, I think the answer to Tim's question is "yes."

Cabe Atwell
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Re: life cycle concerns
Cabe Atwell   12/3/2012 4:38:16 PM
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Great, one of the future super-materials is poised to kill us all. I suppose silicon has been killing life for decades directly and indirectly. What else is new. Perhaps the study should look at how the nano-tube compares to the material it is replacing. I'm sure as materials like this become commercialized, they will.

C

Dave Palmer
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Re: life cycle concerns
Dave Palmer   12/4/2012 10:43:19 AM
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@Cabe: Obviously everything has risks, but it's important to understand the risks, so that you can keep them under control.  There are three Superfund sites within walking distance of my house.  One is a former Johns Manville insulation plant that once employed 6500 people. It is still contaminated with more than 3 million cubic yards of asbestos.  Another is our harbor, which is contaminated with PCBs that were used in a former die casting facility that employed more than 4000 people.  Not only are the jobs gone, but we're left with the mess and its long-term effects.  This is why it's important to understand the health and environmental implications of a material before employing it on a mass scale.



Ann R. Thryft
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Re: life cycle concerns
Ann R. Thryft   12/4/2012 11:48:39 AM
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Dave, thanks for the info and links, and the perspective of one directly affected by environmental toxicity. Cabe, the toxicity potential is far, far worse with nanomaterials than with materials that have micro-sized particles, such as silicon. It's a matter of scale, for one thing: in this case, size matters enormously (pun intended). You might want to take a look at some of the background material, such as the links Dave provided or those in my previous nanomaterial legislation article, to understand how different events at the nanoscale can be from events at the microscale. It's an eye-opener.

Cabe Atwell
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Re: life cycle concerns
Cabe Atwell   12/4/2012 4:41:16 PM
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I see. "An ounce of prevention," and all that...

It is a shame what past generations left us, like these contaminated factories. Could they have known? Those 4000+ people probably all suffer from asbestos related problems. Could they have known in the past.

I agree with you all. There is no excuse for not testing for human safety in these new fabrication materials. Perhaps 4000+ people's lives will be saved with that work.



Dave Palmer
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Re: life cycle concerns
Dave Palmer   12/4/2012 8:48:12 PM
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@Cabe: It's definitely an exaggeration to say that everybody who worked at the Johns Manville plant in Waukegan died of asbestos related problems -- but many people did, and not just people who worked in the plant.  The company was careless about what it did with waste material (it was literally just strewn around the site), so there were significant amounts of airborne asbestos dust in the surrounding area.  This was well after asbestos was known to be harmful.

On the other hand, a company I worked for in Chicago went bankrupt in 2002 as a result of an asbestos class-action suit.  It was one of the small companies that lawyers went after once all of the big companies like Johns Manville went under.  As far as I know, the company's use of asbestos had always been relatively minor, and ended in 1972, when the dangers of asebstos began to be widely known.  But a few lawyers, including one who had a (now-defunct) website called MillionDollarLungs.com, saw dollar signs.

Asbestos continues to be widely used in the developing world, particularly in India, where the use of asbestos is actually expanding.

As George Santayana said, "Those who cannot remember the past are condemned to repeat it."

Ann R. Thryft
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Re: life cycle concerns
Ann R. Thryft   12/6/2012 4:42:15 PM
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It's also important to keep in mind that the problem of pollution and contamination, intended or not, is much greater today than in earlier times simply because it's expanded along with the world's expanding population. Even if the rates of careless materials production and handling had stayed the same, the geometric population expansion of the last century means that the problem has gotten a lot, lot worse.

Cabe Atwell
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Re: life cycle concerns
Cabe Atwell   12/7/2012 6:11:43 PM
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True, it is a bit of an exaggeration. I find the past ignorance to be troubling. I suppose they didn't know. Like smoking hazards became mainstream, only after centuries of oblivious use.

Exploitation of developing worlds has brought me to a similar frustration level. Labor practices in China being the most forefront.  What can be done to prevent such travesties? Not buying from those countries? Perhaps some products are more ethical... perhaps better research is the key to change?

C

Dave Palmer
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Re: life cycle concerns
Dave Palmer   12/7/2012 6:29:25 PM
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@Cabe: Smoking is a good analogy, since companies made an effort to conceal the risks.  Johns-Manville was aware of the dangers of asbestos as early as 1930.  By that time, there were already multiple reports in the medical literature, since doctors were starting to see patients dying of asbestos-related diseases.  But Johns-Manville made a conscious effort to cover this up, and pretty much succeeded in keeping the general public from finding out until the '70s.  They kept producing it until the end of the '80s.

Ann R. Thryft
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Re: life cycle concerns
Ann R. Thryft   12/12/2012 12:16:16 PM
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Unfortunately, Dave is right. A surprising number of polluting entities *did* know what they were doing and how dangerous it was, and spent a lot of time and energy and money covering it up. That's how the EPA came about in the first place.

ragtoplvr
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Re: life cycle concerns
ragtoplvr   12/13/2012 4:37:03 PM
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Remember Kent cigaretts witht eh Micronite fillters, the safest cigarette filter ever made.   Yep, asbestos.

 

Rod

GTOlover
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Re: life cycle concerns
GTOlover   11/30/2012 11:38:57 AM
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naperlou ...becomes lunch? Perhaps recylced for balogne:-)

 

Ann R. Thryft
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Re: life cycle concerns
Ann R. Thryft   12/3/2012 11:56:44 AM
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Lou, thanks for your comments. Researching and writing this article made me think how, for the nth time, we've gone off looking for new technologies without first considering whether the (new or old) materials involved are harmful to living beings when introduced into the ecosystem, or even how likely it is that the materials can easily get into the ecosystem. It's simply not one of the first questions we ask--and I think it should be.

Dave Palmer
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Re: life cycle concerns
Dave Palmer   12/3/2012 2:41:32 PM
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@Ann: You're definitely right that environmental and health impacts should be at the front of our minds when evaluating a new material.  That being said, there has been a lot of work done on the toxicity of nanomaterials, particularly over the past 5-7 years. A lot of people are working on this, to ensure that we aren't opening Pandora's box.

ervin0072002
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Its Carbon.
ervin0072002   11/29/2012 4:00:39 PM
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Its carbon, the thing that loves to react with oxygen... Light it up :) Let's find out how fast this material will decay or adhere to larger particles. How much of it is released in the industry, as well as from end use products and compare it with the amount of material required for it to be a threat prior to hitting the panic button.

Jack Rupert, PE
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Re: Its Carbon.
Jack Rupert, PE   11/29/2012 9:26:44 PM
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Based on that, are there alternatives for disposal?  Like a replacement for coal in the production of electricity?

TJ McDermott
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Re: Its Carbon.
TJ McDermott   11/29/2012 10:41:26 PM
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It's good to have that voice of reason to set some perspective.  Still, it's better to find it now and accomodate its problems than much, much later when it's everywhere.  Asbestos comes to mind in that regard.

3drob
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Re: Its Carbon.
3drob   11/30/2012 9:24:10 AM
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Asbestos is absolutely safe (inorganic and non-reactive).  It's the genetic material that rides along with it when asbestos (because it's ends are needle sharp) puncture a cell's wall that kills.  Which is why asbestos was used everywhere without any concern for human health (in schools, ships, tile floors).  Human history is full of examples of "safe" technology that that was over-exploited before realizing the dangers.

Carbon nanotubes probably have similar mechanical effects.  I was told by an ME friend that carbon fiber (yes, not nanotubes, but still relevant) is much more dangerous than fiberglass.  Where you get fiberglass on or in your skin, it works its way out.  Carbon fiber works their way in ...

I read in Science News a few years ago, nanotubes in the environment do NOT disperse like other polutants (perhaps this is a good thing?)

In any case, if they are so reactive to microwave's, perhaps this is the solution.  Just blast the contaminated soil with a high enough dose to destroy the bonds and turn them back into simple carbon.

ironhorse
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Re: Its Carbon.
ironhorse   1/9/2013 1:00:06 PM
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""Its carbon, the thing that loves to react with oxygen... Light it up :) Let's find out how fast this material will decay or adhere to larger particles.""

I suggest reading up on the subject of Polycyclic Aromatic Hydrocarbons.  "Lighting it up." is how this sort of stuff (including some actual fullerenes) is formed in nature.  The primary example of PAH is soot, from which the earliest known carcinogens were recognized.  The toxicities of PAHs in soot range from nontoxic to extremely toxic.

Carbon in this form is quite persistent in the environment.  For an easy example, consider how long charcoal lasts in soil.  Devoid of carbohydrate, it is not readily biodegradable (coal does not rot very fast ...)

Polycyclic aromatic hydrocarbons are naturally pervasive in the food supply.  The natural source is grass and forest fire.  The soot settles on leaves and soil and from there are absorbed into the plant oils. Environmentally released nanotubes and graphene would be able to participate in those same processes.

Now, given that PAH are both carcinogenic and pervasive, animals must have some means of tolerance of the toxicity. Healthy lungs should expel most air-borne PAH to the digestive track through mucus. Primary exposure to food-borne PAH is at the intestinal lining.  Healthy intestinal walls continuously shed their surface cells, so, if PAH happens to trigger a cancerous change in a cell, the cell is sloughed off with all the rest.  This suggests that anything that impairs intestinal lining health (e.g., gluten sensitivity, folate deficiency, folic acid supplements) should increase risks of intestinal cancers.

I am trying to imagine, though, an industrial life cycle "leak" of PAH or fullerenes comparable to a forest fire or a nation's population of scented candles.

 

Scott Orlosky
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CNT = Poison?
Scott Orlosky   11/30/2012 2:19:20 PM
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Interesting comments. This is the first I've heard about toxicity concerns in CNT's.  Guess it's time to dump my stock in graphene futures!  When I hear about toxicity concerns, the scientist voice inside my head always asks, "But what is the mechanism at work?".  As you point out, it may be an issue of mechanics rather than chemistry.  Once this is understood, then a potential solution is usually at hand.  In the meantime I'll start using a HEPA filter when I sharpen my #2 pencil.

William K.
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Toxic? carbon nanotubes
William K.   11/30/2012 3:22:07 PM
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It seems that the alleged toxicity of these nanotubes must be a mechanical thing, although none of the reports bothers to say anything about the mechanism of toxicity. The good news is that these nanotubes don't occur naturally, at least I have not heard of them being natural. So the proliferation should be quite a bit less. Also, they are kind of expensive, I think, so perhaps users may be motivated to avoid spilling them. 

It would be good if those who go around bleating out noninformational phrases could somehow be motivated to provide more actual information and less intention toward causing hysteria.

Of course, if the nanotubes are locked into a composite material they may be a lot less free to cause any type of problems, although it would seem that machining the composite could be a bit hazardous.

sbkenn
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Re: Toxic? carbon nanotubes
sbkenn   12/1/2012 1:29:19 PM
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I believe that CNN's do occur naturally, as in Damascus Steel of the Medieval to mid 1800's, when the iron ore mines(thought to have been in Kerala in India) were cleaned out.

etmax
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Re: Toxic? carbon nanotubes
etmax   12/2/2012 10:36:25 PM
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Are you sure it was carbon in Damascus steel?? I thought it was cobalt or something like that?

Dave Palmer
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Re: Toxic? carbon nanotubes
Dave Palmer   12/3/2012 2:35:47 PM
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A German research group published an article in Nature in 2006 showing that a Damascus blade produced in the 17th century contained multi-walled carbon nanotubes, as well as cementite nanowires.  It's believed that the nanotubes formed in-situ during the forging process.  You can read the article here.

The article mentions that cobalt, along with other alloying elements present in small amounts, played an important role in providing the steel with its distinctive microstructure.

feierbach
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CNT Environmental Hazard
feierbach   11/30/2012 3:53:44 PM
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If microaves can heat up the CNT then they can destroy them. Collect the waste and bath it with microwaves, waste disposal problem solved. Light them up! A plasma furnace would also work and other metals can be recovered. iRobot can probably build a Roomba robot that will do manufacturing cleanup and CNT destruction at the same time.

William K.
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Carbon nanotubes
William K.   12/1/2012 3:56:12 PM
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Damascus steel is certainly some impressive stuff, but my understanding is that it is created through a great deal of work, bonding and folding and rebonding to get steel with alternating layers of hard and tough steel. Definitely not a naturally occurring material. Free lead, nickle, cadmium, and copper all occur in their free state and can be found naturally. Likewise asbestos, although it is usually in with mica, I think.

Of course heating to ignition with microwaves would be an effective means of disposal for CNT waste, but first it would need to be located. That is probably going to be the challenge if quantities of CNT material are spilled.

CLMcDade
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"Hysteria"???
CLMcDade   1/7/2013 3:08:08 PM
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Ann,  I don't know how I missed this article when it was first published, but I'm glad you wrote it.  I have long said that the two things that scare me the most when it comes to the future of the human race are GMOs and notechnology/nanomaterials.

Though commenting on old articles rarely re-starts a discussion, I'd question why some of the commentors chose to use words like "hysteria" and "hysterical" when describing the voices that are preaching concern and safety.  The "alarmist" accusation has become the standard strategy of AM talk radio hosts and neo-cons who feel that any limitations/regulations/restrictions on industry are automatically bad.

Such knee-jerk responses are not conducive to constructive conversation like those which take place after a good article like this one; rather they are designed to shut down the exchange of thoughts.

 

Ann R. Thryft
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Re: "Hysteria"???
Ann R. Thryft   1/7/2013 6:03:27 PM
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Clint, I don 't know if those 2 are the scariest for me, also, but GMOs are certainly at the top of my list. I was really, really disappointed to find out how toxic CNTs appear to be. Thanks for the feedback on the "alarmist attitude" and AM radio--I'm not a listener so I didn't realize that might be the source of this puzzling attitude. That attitude also seems to apply to comments on some of the stories we've posted about alternative energy, implying that climate change either isn't occurring, or is nothing to worry about.

CLMcDade
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response
CLMcDade   1/9/2013 2:44:15 PM
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Ironhorse,

Great parallel.  Burning "stuff" is a quick solution used too many places in the world.  When the fire is out, the stuff is gone and out of mind.  But what is out of mind oftimes becomes the stuff in the lungs, the bloodstream, the organs and cells.

As for the scented candles, hopefully the proliferation of LED "fake" candles on the store shelves this year lead to fewer scented candles that must be endured.  A Christmas wish for 2013 and beyond?

ironhorse
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Iron
Re: response
ironhorse   1/9/2013 5:34:58 PM
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My point is 3 fold:

"Burning stuff" is how nature does it.  [I've been presented lake sediment data showing prehistoric fire events were quite periodic (every 25-27 years)]

It doesn't go away.

We evolved eating and breathing it.  (we didn't evolve eating grains)

 

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