again, you make some really good points!

Many governments of the world (including here in Australia) have indeed placed themselves in a very messy and murky situation relating to this conflict of interest you allude to. This conflicting desire for governments to generate returns on their investments and generally not “stifle progress” on one hand, whilst also having the responsibility for safe-guarding their citizens and (supposedly) the environment on the other – does not inspire any confidence or trust in nanotechnology safety to me at all.

You may also well be right is suggesting that in the long run, the nanoparticles in sunscreen will probably not end up significantly harming humans or our environment. I really, really hope you are.
And given that these particles are already being released into our environment and no government seems intent on banning or regulating further use until more comprehensive safety tests are complete, we’ll just have to wait and see what happens in coming years as to whether they were right to do so….

I’m with you all the way on providing consumers with clear information on what is in the products they buy – obscuring information can only backfire in the end.

In terms of testing, I would agree that more work is still needed to ensure that we are testing the right things – especially when it comes to factors like photoactivity. However, there are no bright lines here between what is sufficient and what is insufficient – meaning that the decision to use a material or hold off is going to be a (hopefully well-informed) judgment call. In the case of nanoscale TiO2 and ZnO, my position would be that the data we currently have puts us on the “proceed but with caution” side of the fuzzy line – others will disagree.

Social and political drivers – a kettle of fish indeed! The social drivers include balancing skin protection and avoiding skin cancer with cosmetic “assurance,” ease of application, effectiveness, and avoiding adverse skin reactions. The non-nano sunscreens currently available are adequate in many cases, but certainly not perfect. A lot of this comes down to the market – is there a market for sunscreens that use alternative active ingredients?

Then there are the political drivers. I may be getting into murky waters here, but given the high level of government investment in nanotechnology around the world, there is a strong incentive to highlight nanotech success stories, and to avoid appearing to signal that some uses of nanotech are dangerous or ill-regulated. These are subtle drivers – but when you think of the fuzzy line I mentioned above between promoting or holding back on the use of nanoparticles in sunscreens, which side of that line do you think that a government investing rather a lot in nanotechnology would prefer to fall?

There’s also another sociopolitical driver which is more obvious in Australia – the desire find effective ways to tackle skin cancer associated with sun exposure. Again, the decision to act decisively in the face of fuzzy information comes down to a political decision – which technologies do you back, and how do you promote their use?

It seems that where we disagree, is that while research groups around the world begin to look at the all-important questions of persistence, photoactivity and toxicity – I maintain that we should insist that industry waits until more rigorous and long-term testing is performed. I simply not believe that most new products containing nanoparticles have been tested “as safely as we can”, so how can this argument be used to maintain that these nanoparticles should be approved for release. At the very least, we should insist on labelling such products, so that concerned consumers at least have a choice.
I refuse to see this as halting “progress”, when effective sunscreens exist on our shelves without the need for nanoparticles.

Your allusion to “social, political and economic drivers” opens up another whole kettle of fish. While the economic drivers are clear (i.e. industries must develop new products to adapt, expand and increase profits), could you please speculate on the social and political drivers behind the need for nanoparticles in sunscreen?

First, your question on where the particles go is a crucial one – especially where the particles aren’t that biodegradeable, like the TiO2 nanoparticles, and so may persist for some time in the environment. There are an increasing number of research groups around the world that are beginning to look at this question – as well as asking what the possible environmental impact might be. At this stage, it isn’t clear whether there are legitimate concerns or not, but it seems the potential is there for averse impacts if we are not careful. (The same goes for the release of non-nano sunscreens into the environment of course, although here the concerns are more related to the direct impact of the the chemicals used in the sunscreens, rather than persistent and possibly photoactive nanoparticles).

I should also add that understanding potential exposure routes is important. I would imagine that sunscreens that are washed off the body will not present a significant inhalation exposure to mammals. But there will be other groups of organisms that come into contact with them through ingestion and other uptake routes.

Your second question is a little more difficult to answer, and really taps into the whole business of innovation, economics, profit and progress. In this short comment, I think the best I can say is that halting “progress” until we know all there is about the safety of a product is unlikely to work (because of social, economic and political drivers), but we do have the option of developing new products as safely as we can, and in finding innovative ways to bridge the uncertainty gap between new products/technologies and their potential impacts. And to be fair, in the case of sunscreens, there are some compelling arguments why you might want to use titanium dioxide and zinc oxide over other active ingredients, based on the current state of knowledge.

Firstly, you claim “studies showing nanoparticles traveling from the nose to the brain have used rodents not humans – and human noses are very different” to support your argument that in this context, these sunscreens are more likely to be safe to humans than rodents. As a human, I take some comfort in learning this.
Furthermore, the nanotech industry claim that these new nanotech compounds are more stable than previously….surely a good thing as well, given that my tube of sunscreen can sit on my shelf for months or even sometimes years.

My question then is – If we probably don’t absorb these nanoparticles of zinc and titanium dioxide etc., where do these compounds go after we have rubbed them onto our skin?
Surely the answer must be into our surrounding environment?
Into the water (if we’re swimming), onto the grass or sand if we’re sunbaking, and also onto our clothing, and therefore into the sewage and ultimately our creeks, rivers and oceans.
So, isn’t it also important if these nanoparticles CAN pass into rodent’s brains? Perhaps many people don’t love rodents (especially those that experiment on them), but what about their own pets? Or smaller aquatic invertebrates and microorganisms? Have these safety tests been performed satisfactorily?

That leads me to my second point.
You rightly make the point “If there are links between nanoparticle exposure and neurodegenerative diseases, we need to know.”
So, if we don’t know exactly what the long term/chronic effects of many nanoparticles, such as those in our sunscreens as you suggest – how is it okay that the nanotech industry has been allowed to release them onto our shelves and ultimately into our environment?
I have used sunscreen all my life under the harsh Australian sun, and it seems to have been pretty good at protecting me from burns – when used correctly. I would have been fine waiting another decade or more for real long term safety tests to be performed on the nanoparticles in sunscreens before their release.
What’s the huge rush….?

May I ask, what does “old nanoparticle mean”? Forget the sunscreens, many cosmetic companies boost that their fluids or eyeshadows contain particularly modern high-tech nanoparticles, what can be said about this? What can be said about titatium dioxide added as an “inactive ingridient” to common pills, is it safe, just because this titanium dioxide was not especialy engineered?..

My apologies – I was aiming to be superficially provocative with that sentence, but from your comments I may have misjudged it! This wasn’t meant to be a criticism or even a direct statement or conclusion: I wanted to reflect an intuitive lay response to apparent news that a reasonably common product could be linked in a hitherto unnoticed way to a serious condition – while including enough qualifiers to prevent the sentence from reading like a definite statement. Clearly trying to be too clever by half!

You do raise an important point, and one I don’t tackle in the piece – that it’s dangerous to be dismissive when dealing with a poorly understood degenerative disease. It is not beyond the realms of possibility that the particles used in sunscreens and elsewhere could be linked with neurological diseases, which is why the research is justified. However, my contention here is that given the current balance of information, it is dangerous to draw associations where no justification yet exists.