Nano Dispersants and nano hysteria – time to think about the science folks!

by Andrew Maynard on May 28, 2010

Catching up with my email after a long day off the net, I see that a group of Non Government Organizations (NGOs) are urging EPA not to allow the use of an alleged nanotechnology-based dispersant in the Gulf of Mexico.  The letter from thirteen organizations was covered in a piece by Andrew Schneider on AOL Online earlier today – which had considerable pickup on the web from what I can tell.

Sadly, a combination of limited information from the company – Green Earth Technologies – and poor understanding by others – seems to have led to the situation being dominated by misunderstanding and misinformation.

Green Earth Technologies has been lobbying hard to get their product G-MARINE™ Fuel Spill Clean-UP! used in the Gulf of Mexico for some days now.  According to the company

G-MARINE Fuel Spill Clean-UP! is a unique blend of plant derived, water based and ultimate biodegradable ingredients specifically formulated to quickly emulsify and encapsulate fuel and oil spills. These plant derived ingredients are processed to form a colloidal micelle whose small particle size (1-4 nanometers) enables it to penetrate and breakdown long chain hydrocarbons bonds in oils and grease and holds them in a colloidal suspension when mixed with water. Once oil has been suspended in a nano-colloidal suspension, there is no reverse emulsion; the oil becomes water soluble allowing it to be consumed by resident bacteria in the water. This dispersant formula is protected by trade secrets pursuant to Occupational Safety and Health Agency (OSHA) Standard CFR-1910 1200. The ingredient list has been reviewed by the US EPA and contains no ingredients considered hazardous by OSHA.

Is seems to have been the “nano” in the above description – leading to the substance being dubbed a “nano-dispersant” – that has raised eyebrows.

The nano here is very small micelles – “particles” of molecules formed from molecules with one end that is attracted to water, and one which repels water.  I place particles in inverted commas as these really very small bubbles of one liquid in another – hardly like particles at all.  And like bubbles, they probably don’t last that long.

Reading the company’s Materials Safety Data Sheet (MSDS), it’s possible to get a good idea what is in the micelles – mainly natural oils, mild detergents and surfactants.  But the MSDS doesn’t go as far as being specific about the physical nature of the micelles.  This is not too surprising perhaps as micelles are commonly used in products, as well as occurring naturally.  They are also transient – they fall apart reasonably fast, just like bubbles.

Now to the letter from the NGOs.  It starts out

It has come to our attention that Green Earth Technologies (GET), Inc. is seeking approval from the EPA to disperse a large quantity of manufactured nanoparticles in the Gulf of Mexico, stating that the dispersal would remedy the oil spill recently suffered by the region. The for-profit company claiming to sell “totally green” products created from nanotechnology, wishes to scatter on land and in water its G- Marine Fuel Spill Clean-UP! (NANO Emulsion Technology) Oil Dispersant in areas affected by the BP rig collapse in the Gulf of Mexico.

The undersigned public-interest organizations respectfully urge the EPA to deny approval of this and similar projects that seek to release nanoscale chemicals or chemicals measuring less than 300 nanometers into the environment. In this case the company claims their product is composed of particles measuring 1-4nm. Manufactured nanoparticles have been shown to be toxic to humans, mammals, and aquatic life.

The argument made is that G-MARINE Fuel Spill Clean-UP! contains a nanoscale component, that nanoscale components have been shown to be toxic, therefore the dispersant should not be used.  The letter goes on to say:

We are not aware at this time of the exact nanoscale particles used in this ‘nano emulsion technology’ because this information is considered a trade secret by the company. Yet, we do know that most chemicals manufactured at the nanoscale hold unique and potentially toxic properties. While some new properties from the nanoscale may seem desirable, materials at this scale can also pose new toxicological risks. Nanoparticles have a very large surface area which typically results in greater chemical reactivity, biological activity and catalytic behavior compared to larger particles of the same chemical composition. Unfortunately, the greater chemical reactivity and bioavailability of nanomaterials may also result in greater toxicity of nanoparticles compared to the same unit of mass of larger particles. Other properties of manufactured nanomaterials that influence toxicity include: chemical composition, shape, surface structure, surface charge, catalytic behavior, extent of particle aggregation or disaggregation, and the presence or absence of other groups of chemicals attached to the nanomaterials.

Unfortunately, the letter falls into the all too common trap of mistaking a relatively unstable cluster of small molecules as a “nanoparticle,” and prejudicially tagging it with properties associated with very specific nanoparticles – many of which are unlikely to have any relevance here.

This is a serious mistake to make, as it undermines any science-based discussion of safety and risk by claiming the ingredient in question is something it is not, then inferring properties on it which it is unlikely to have.  And the danger here is that as soon as the science is taken out of the equation, the real likelihood of harm being caused becomes extremely difficult to address.

Then there is the AOL piece.

In the main, the piece is straight reporting of the situation – albeit with an emphasis on the nano-safety issue.  But one section in particular jumps out:

The report of the possible use of nano-dispersants has outraged Harbut, who heads the Environmental Cancer Initiative at Michigan’s Karmanos Cancer Institute.

“A decision to use nanoparticle-based dispersants in the gulf is less an engineering or environmental decision, but more a public health and individual patient care issue. As does asbestos, nanoparticles have been shown to cause an aggressive cancer called mesothelioma,” he said.

And like asbestos in its early usage, human health effects of exposure, ingestion or breathing of nanoparticles have been rarely observed, let alone studied.

“To dump tons of nanoparticles into the food and respiratory cycle in this manner is irresponsible,” Harbut told AOL News

Here, the conflation between nanoscale micelles, nanoparticles and mesothelioma is wrong and it is irresponsible.  Nanoparticles in general have not been shown to cause mesothelioma, neither is there any theory to suggest that they might – this is pie in the sky speculation.  Carbon nanotubes – a specific form of nanomaterial – might possibly be associated with the disease under some conditions, but this is still uncertain.  But carbon nanotubes are not what may would recognize as nanoparticles, and are certainly not the same as micelles.

Then there is the conflation between micelles and nanoparticles again.  Okay so technically a micelle might be likened to a nanoparticle – but in the same way a soap bubble might be likened to a soccer ball!

So where does this leave us?

The root of the problem here seems to have been Green Earth Technologies’ use of the term “nano” – if they had just talked about micelles, no red flags would have been raised and it’s unlikely that the NGO letter would have found its way to EPA.  This term clearly term led to some confusion amongst organizations sensitized to the word.

Nevertheless, it would be irresponsible to throw the safety concerns out simply because of a definitional technicality.

Nanoscale materials do raise new safety questions – including nanoscale micelles.  But often, these questions can be addressed to a reasonable degree.  I’m not going to defend the safety evaluations that have been made by Green Earth Technologies as I don’t have the data.  In fact the company possibly shoots itself in the foot by being rather optimistic about the safety of their product.  This appeared today in an open letter from the company for instance:

Does G-MARINE OSC-1809 Oil & Fuel Spill Clean-UP! have any adverse affects on humans / animals or the environment?

None whatsoever. G-MARINE OSC-1809 Oil & Fuel Spill Clean-UP! has shown absolutely no adverse effect on humans or animals. All of our Marine products are manufactured from ingredient LISTED ON THE EPA CLEAN INGREDIENTS (1) List. It has a zero OHSA hazard rating and in Lab Tests (2) it has been shown to have no adverse affects whatsoever to nose (inhalation), mouth (ingestion), ears, skin, or eyes. Even if the person is subjected to a concentrated overdose, there has been no noticeable adverse affect. The Micelles BECAUSE of the EXTREMELY SMALL SIZE do NOT persist in the environment and Bio-degrade into harmless elements in 10 days as per EPA guideline in the CLEAN INGREDIENTS list.

“None whatsoever” is a dangerous assertion to make on adverse effects, as it implies every possible test has been done, and every conceivable eventuality accounted for.  And people tend to be suspicious of such absolute statements – better to be honest and admit the bounds of current knowledge.  Yet it is reasonable to assume that small micelles made up of well-evaluated ingredients are unlikely to have long-term environmental impacts that go beyond that of these ingredients – mainly because the micelles will break up and release their constituent components reasonably rapidly.

Could they get to places where they can cause harm in the short term because of their size?  It’s possible – and I would hope that toxicity tests would at least indicate whether this is an issue.  But there is a danger of making up potential yet implausible harm scenarios here because of a misunderstanding of the differences between micelles and other forms of nanomaterials.

And this is perhaps the most important message to come out of this situation.  In the case of the Gulf oil spill, inaction is not an option – but informed action must be based on the best possible information rather than questionable speculation.  This places the onus on companies to get the safety testing on their products right, even if it means going above and beyond what they consider necessary (especially if they decide to use a loaded term like “nano”).  It means that regulators need to ready to move fast when questions like this are asked – delayed action or misinformed action both have the potential to lead to adverse consequences.  And it also means that organizations and individuals influencing the debate and the decisions made must make sure they get the science right – speculative fear can only be divisive.

Making wise choices on the dispersants used in the Gulf of Mexico is vitally important, and bad choices could have lasting consequences.  And it is right and proper that questions should be asked over the use of one product over another.  But if the spill is to be dealt with effectively, these choices must be science-informed – otherwise no-ones interests are served in the long run.

1 David May 28, 2010 at 11:11 pm

In this kind of situation science does not lead. Rather hysteria based politically motivated agenda leads. The real environment continues on. The work and results proceed. The media environment then shapes the ongoing discussion among majorities which leads to further discussion.

2 Hilary Sutcliffe May 29, 2010 at 2:28 am

Thanks for this Andrew, this whole debacle is disappointing on so many levels as you say and no-one comes out of it well. I hope the government bodies are able to cut through the hype on both the company and ngo sides and obtain the appropriate information they need to make the right decision for the job at hand.

However, I do think it is avoidable, but of course now companies will now be sure to avoid using or mentioning nano at all in any of their communications materials, making it even more difficult to track usage.

But the lack of clear definition and clarity about the various nanotechnologies means we can’t make a real judgement on potential risk even if they did communicate better. But this crass promo strategy would probably be counterproductive whatever the technology, greentech companies need to be aware of over hyping their products just like anyone else.

But also this lack of understanding and at least expert consultation from the ngos may prevent us from using a viable clean up technology in a time of dire need, simply because of poor quality scientific knowledge and lack of real consultation. This is a key responsibility issue for them.

It is in companies own interests to share information about the testing and safety of their products and to undertake or commission appropriate safety testing. It is the responsibility of ngos to ensure the appropriate scientific basis for their opinions, particularly in such as situation as this. In addition, in the long term, they lose credibility and authority and will be increasingly exposed because of it I feel.

Lots of food for thought however for our business working group!

3 Michael R. Harbut, M.D. May 29, 2010 at 10:36 am

Dr. Maynard, aside from my deciding to exercise resraint in regard to your comments as they may relate to my own work, would you be kind enough to disclose the funding sources, now and previously, of your present employer.

Additionally, would you be kind enough to disclose any credential or license which allows you to dispense medical advice.

4 Andrew Maynard May 29, 2010 at 11:18 am

Dear Michael,

I would be happy to do this. My current funding comes entirely through the University of Michigan – some of it is associated with a gift given to the University of Michigan Risk Science Center by Charles Gelman. In my previous work at the Woodrow Wilson Center in Washington DC, I was funded through the Pew Charitable Trusts.

I do not believe I dispense any medical advice in the piece above, and I must apologise if it appears that I did. What I did do however is comment on the accuracy of statements made in the AOL Online piece, and voice my concerns over the dangers of making statements that do not appear to be supported by evidence.

I do believe my credentials to make such an assessment are reasonable. For many years, I have been an active researcher and advisor on the responsible development of nanotechnologies. I helped establish the research program into potential health impacts – and how to avoid them – at the National Institute of Occupational Safety and Health. I have published extensively in the area in the peer review literature – and was a co-author on the paper by Poland et al. indicating that some forms of carbon nanotubes have the potential to cause mesothelioma. And I have provided extensive expert advice in this field, from congressional testimony, to serving on National Academies panels, to advising the President’s Council of Advisors on Science and Technology. For five years I was the Chief Science Advisor to the Project on Emerging Technologies at the Woodrow Wilson Center. I currently direct the Risk Science Center at the University of Michigan School of Public Health.

From my research and my understanding, there is no evidence associating nanoparticles in general with mesothelioma. Morever, there is no evidence to my knowledge that soft nanoparticles – including nanoscale micelles – will show identical biological behavior to hard nanoparticles. In fact, the transient nature of micelles makes it extremely unlikely that they would be linked to a disease associated with biopersistent fibers.

In my comments, I was careful to comment on the AOL story, not your quote specifically – realizing that there was every chance that your comments had been taken out of context. It seems though that, from your comments above, you are comfortable with what was reported.

Having provided you with the information you requested, I wonder if you could be so good as to do something for me. Could you provide me with refeernces to the work you refer to showing nanoparticles cause mesothelioma?

Thank you

5 HCSKnight June 2, 2010 at 6:12 pm

Let’s see…. since the good doctor asked for credentials, I though I’d do some checking on him. It seems he had to go to the Caribbean {American University of the Caribbean School of Medicine; http://www.vitals.com/doctors/Dr_Michael_Harbut.html#} for an education.

He also looks like a doctor who has a vested interest in creating fear about substances…. maybe because it’s good for business…

Sorry, in my book, every day in which the good doctor remains silent is another day demonstrating his bias and ignorance.

AMDG

6 Patric Hale May 29, 2010 at 2:41 pm

It has now been 3 hours and no word back from Dr. Harbut, even though Dr. Maynard responded within 45 minutes to Harbut’s innuendo on Maynard’s credentials. Could it be because Harbut’s linking ALL nano-particles to mesothelioma rather than just those from asbestos – is the biggest pseudo-science crock we’ve read in a long time?

“Nano” means “really, REALLY small” – 1/billionth. So let’s get over this fear mongering over the word “nano”. I’m not a scientist, but I know how GETG’s entire corporate focus really IS to make entirely bio-degradable, environmentally-safe alternatives to hydro-carbon based products. It’s motor oil is the ONLY green substitute for petroleum based oil that has been certified by the API and EPA as such. Its creation of this and other of its products ARE entirely green and the management is committed to truly green solutions – and having them verified so reassure the public.

What an irony that the ONLY company that has products that CAN clean up the oil slick in an environmentally friendly way is being held up by environmentalists themselves because of an irrational fear simple because of the word “nano”! In the meantime, BP is spraying the entire Gulf with dispersants that do NOTHING to break up oil cobblants and whose toxicity is KNOWN to be HIGHLY damaging!

So a much better solution to the toxic dispersant now being used is being held up because GETG’s product hasn’t been tested up the wazoo – and would take years to mitigate all of these irrational claims before being put to use. This is like Christian Scientists with appendecitis – wishing away the oil in the Gulf won’t work, anymore than the use of the toxic dispersant BP is now using is working. GETG’s product is composed of ingredients that ARE on EPA’s NON-toxic list, and has been so certified. Let them use it at least in a part of the Gulf and let’s see if it works. We know that oil eventually gets broken down into smaller and smaller micelles overtime and absorbed into the environment – this takes years to do naturally. GETG’s product accelerates this naturally process by using natural, biodegradable products. I thought THAT’s what we NEED!

Only people with nano-brains should worry about the word “nano”. In the meantime the Gulf is getting worse with both oil and toxic dispersant that DOESN’T work! Even if you think GETG’s product might not be “green enough”, the FACT remains it is a far better and greenER dispersant that what’s being used!

Patric Hale

7 Green Oil Man June 2, 2010 at 1:56 pm

Why is there not a group of scientists that are pro-GETG and writing a letter to the EPA disputing the previous letter by NANO bashers? Mr. Maynard, could you work to get a group of your colleagues to write a scientific letter which helps prove that not all small particles are harmful to both humans and the environment? This could help the entire situation and could help GETG get their product to use and help clean up the disaster.

For those who want to test out the oil spill clean up or use it, try the website above. I have ordered oil through them as well as other products and they have all worked great. No reason to think that the spill clean up wouldn’t…

8 Green Oil Man June 2, 2010 at 1:57 pm
9 Ruth Seeley June 5, 2010 at 4:07 pm

@GreenOilMan It’s up to the company to line up independent third-party experts to endorse the viability of their product, not up to the scientific community to spontaneously rally around a particular product or company.

10 Fred June 2, 2010 at 4:05 pm

I’m guessing by your excitement and use of capitalization that you Patrick work for GET?

11 Ruth Seeley June 5, 2010 at 4:13 pm

@Fred I think you might just want to Google Patric Hale (no k on Patric) to see who he is. He doesn’t appear to be affiliated with GET in any way, shape or form. Unless I’ve got the wrong one here: http://www.linkedin.com/in/patrichale

12 Dingsheng Li June 3, 2010 at 10:32 pm

It is quite a pity to see this nano=hazard situation emerging. Pretty much like a few years ago when nano=wonder. It is even more unfortunate that these NGOs are ignoring the fact that the product GET proposed to use is not even what they are attacking. I thought NGOs would have a better sense of what they were talking about.

13 Loren Amelang June 4, 2010 at 3:51 pm

I think GET has brought some of this hysteria upon themselves. Their web site seems less than straightforward about their use of nanotechnology.

(getg.com – GET Answers – What is the Technology Behind GET?)
—–
What is nano technology?

Simple, doing more with less: Our patent pending manufacturing process and materials, generally 5 nanometers in diameter, are compared to competitor’s micron size (see below) and generates 1,000 times increase in surface area and millions of time increase in the number of particles. The reason Green Earth Technologies’ products perform so well and are able to be sold at a competitive price is due in part to the precious chemicals added into the product that are performance packed. If you are interested in learning more about nanotechnology, check out our HOW WE DO IT!
—–

—–
Nano Technology – Doing More with Less

Our patent pending manufacturing process and materials, generally 5 nanometers in diameter, are compared to competitor’s one micron size and generates 1,000 times increase in surface area and millions of times increase in the number of particles.

The reason G.E.T. products perform so well and are able to be sold at a competitive price is due in part to the precious chemicals added into the product that are performance Packed.
—–

There doesn’t seem to be any “more” to be learned about their “precious chemicals”, and what they do say strikes me as somewhere between marketing hype and an effort to hide the reality behind their products. If they really are afraid to give a more satisfying explanation of their trade secrets, they should avoid mentioning both “nano” and “chemicals”.

From other sources I’ve read about the micelles, which sound relatively natural and short-lived. Yet GET implies that, like nano-scale ball bearings, they provide superior lubrication under the harsh conditions inside an automobile or even two-stroke snowmobile engine.

—–
G1 Racing Oil’s unique proprietary ingredient called NANO GEODESIC BEARINGS are tiny spherical shaped particles that are postulated to spin at unimaginable high speeds to support adjacent oil molecules to squeeze more precious horsepower out of the engine.
—–

Well, maybe the motor oils contain “hard” nano particles in addition to the micelles, but how are we to know? And that is exactly the point of groups like Friends of the Earth – the nanotechnology industry is conducting an experiment on the general public without their informed consent.

After hours of web searching, I still have no idea if I should actually use the bottle of G.E.T. Bar and Chain oil I bought at the local hardware store. Do I want nano micelles or maybe “hard” nano particles slung all over my body, lungs, and firewood?

Loren

14 Andrew Maynard June 5, 2010 at 1:40 am

Thanks Loren – I think that’s an important point that, when the line between science and marketing is blurred, it gets extremely difficult to know what is going on. In the case of the dispersant, it is possible to piece together some picture of the likely technology being used from the company’s descriptions and the Materials Safety Data Sheet – but only if you know enough to cut through the marketing smokescreens! In this sense, you are absolutely right – the company hasn’t done itself any favors at all!

In cases like this, far more transparency and far less hubris on the part of industry would be helpful in getting products out that work without causing unnecessary harm.

15 Andrew Maynard June 5, 2010 at 1:45 am

It’s been a week since I asked Dr. Harbut for more information on the link between mesothelioma and nanopatricles (see above). Despite also emailing him (mainly to see if we could tie up his dangling comments amicably), I have had no reply.

This is disappointing, to say the least.

Does his silence mean that, despite his comments, he has no information linking nanoparticles in general to mesothelioma?

16 David Bartley June 5, 2010 at 6:03 am

I’ve heard that both water and oxygen molecules measure less than 300 nm. The surface area per gram of these chemicals must be enormous, and we should probably all consider our fate.

17 Kevin Eddy June 5, 2010 at 8:58 am

Andrew,

Dr. Harbut may or may not have information with such a link as he describes, I’m not in a position to decide.

What I can do is notice that he has chosen the equivalent of cheap political methods to defend his scientific position. Why provide data when he can attack your credentials? Of course, if he’d bothered to type your name into a search engine he could have found quite a bit of information about you.

One hopes his research into medical issues is more thorough.

18 ImperfectlyInformed June 7, 2010 at 12:43 am

Eh, this may sound nitpicky but I feel like Maynard is being (very slightly) disingenuous here. Clearly Harbut is referencing the “Poland” study connection between mesothelioma and carbon nanotubes. Maynard says nanotubes are not nanoparticles, but it’s not clear why – perhaps to a physicist who’s deeply involved in the field it might seem obvious, but taking other people to task on this mistake seems a little heavy-handed. See http://74.125.155.132/scholar?q=cache:UZZCXJTIyNEJ:scholar.google.com/&hl=en&as_sdt=400 for a 2010 review of carbon nanotubes and mesothelioma. I suppose Harbut can be accused of exaggeration, but in the context doesn’t seem like a big exaggeration to say that nanoparticles have caused mesothelioma. It’s not a journal article. As far as other nanoparticles, Hoet et al 2004 (http://www.jnanobiotechnology.com/content/2/1/12) discuss lung tumors in mice exposed to nanoparticles and says “it is remarkable that the low exposure (10 mg/m3) study [29] resulted in a greater lung tumour incidence than the high exposure (250 mg/m3) study [30] … primary particle size of the low dose study was 20 nm, while it was approximately 300 nm in the latter study”. Even if the lung tumors aren’t mesothelioma, it’s still rather concerning.

The lack of regulation for nanotechnology increases the chance of hysteria, I think, and in my mind the hysteria is a good thing if it can motivate some action. My concern with nanotechnology arose in 2006 when I noticed the the study which found that when mice inhaled silver nanoparticles, the particles went to the brain (http://www.urmc.rochester.edu/news/story/index.cfm?id=1191). The persistency of nanoparticles is another concern – out of curiosity,Dr. Maynard, do you have a general impression on when these nanoparticles tend to become regular particles?

Ignoring the semantic argument over whether a nanomicelle is a nanoparticle or not, I would agree that nanomicelles by themselves would not be much of a concern as they would not be persistent. I wouldn’t expect this product to have more than micelles but I don’t know much about dispersants and I guess it is trade secret.

19 Andrew Maynard June 7, 2010 at 8:09 am

Thanks for these carefully considered thoughts. It does make me wonder whether we – as the scientific community working in this area – need to think more carefully about the words we use, and how we use them.

Even though these may seem like semantic arguments, they are not – and I do worry that the confusion that is propagated as a result could harm attempts to prevent mesothelioma by making it seem that too many people are too ready to “cry wolf.”

Regarding mesothelioma, the key guiding principle here is what is known as the fiber paradigm – which is explained well in Ken Donaldson’s paper cited above. In a nutshell, this states that, for an inhaled material to be capable of causing mesothelioma, it must be long, thin, and biopersistent. Effectively, this describes fibers that are thin enough to penetrate to the deep lung and to the edge of the lungs if inhaled, that are too long for the scavenger cells – the macrophages – in the lungs to get rid of them, and that can persist in the lungs once there for years, without dissolving or otherwise being cleared.

If you apply this to long thin carbon nanotubes – as we did in the Poland et al. paper you cite – there is evidence that these follow the fiber paradigm. In the same paper, we showed that short fibers, and compact carbon-based particles, did not seem to follow this paradigm.

In fact, non-fibrous nanoparticles are cleared from the lungs by a range of mechanisms. They may still cause harm, depending on what they are made of – but there is no indication that they have what it takes to cause mesothelioma. This is an extremely important distinction.

Then you have micelles. If these are inhaled – and I’m not sure how easily a suspension of micelles could find their way into someone’s lungs – they enter an environment that is swarming with molecules similar to those making up the micelles. And as micelles are relatively weakly bound collections of molecules, it is likely that they will disperse reasonably fast. Then, their potential to cause harm (once they are in the body) is most likely going to be associated with the chemicals that they are made of – not their size.

And when it comes to comparing micelles with the fiber paradigm, they fail at every hurdle – they are not thin, they are not long, they are not biopersistent.

Although the differences between soft nanoparticles, hard nanoparticles and nano-fibers can appear trivial, this may be because they are not visible to the naked eye and so not easy to visualize – and of course, the rather loose language of nanoparticles that people are apt to use doesn’t help. Perhaps a helpful analogy is the similarities between a grape, a baseball and a spear. Each can cause harm – you can choke on a grape, a baseball can concuss if it hits you on the head, and you can be impaled by a spear. But to ban grapes because people get killed by spears might seem a little odd.

Of course, it’s hard to imagine anyone following such a suspect line of reasoning with objects that we can see and touch. But just because we cannot see and touch nanomaterials without the aid of sophisticated instruments, doesn’t mean that we are free to abandon reason.

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