Then I hear (repeatedly) accounts like yours where consumers are pretty smart when it comes to using the information provided.

Lesson – consumers are smarter than you might think!

I think the registry is a great idea but I’d like to see both labels and the registry on the principle that effective communication is that which helps people get information in the way they prefer to receive it, odd though their preferences may seem to be to those who don’t share them.

Reading back over my reply to Georgia, I realize I may have sounded harsher than intended on organizations taking decisions out of the hands of consumers. The reality of course is that it is exactly these organizations that are best positioned to help consumers make informed decisions, by providing relevant product information and the means to understand and interpret it.

Labeling is part of empowering consumers to make informed choices, but is complex. For instance, slapping a “nano inside” label on a bottle of sunscreen would tell you precisely nothing about the product – it could refer to a plethora of things, some of which are good for you, others of which you might be a little more leary of.

Adding the “nano” suffix to the list of active ingredients makes more sense – so it’s clear when the product contains nano-titanium dioxide or nano-zinc oxide. This is the route Europe will be taking later this year with cosmetics. The difficulty here is deciding what constitutes “nano.” Europe will be referring to particles with a size between roughly 1 – 100 nanometers, and agglomerates or aggregates of these particles (I don’t have the precise language to hand). This isn’t perfect, but it is a pragmatic solution which will be more informative than not.

What the EU definition doesn’t do though is deal with ingredients where the mean particle diameter is larger than 100 nm, but where there are a substantial number of nanometer-scale particles in the distribution. One way to handle this is to identify ingredients which are engineered to have particles in the nanometer size range, or where a substantial proportion of the particle size distribution lies below 100 nm.

Even with the nano prefix on ingredients labels there are problems. Manufacturers will claim it doesn’t mean anything to consumers. Otherws sill claim it doesn’t give enough information. One way around this that has been discussed is to have a public registry of products and ingredients – so you can go to the web and get detailed information on what is in your favorite sunscreen, and what the relative benefits and uncertainties surrounding each component (and their combination with other components) are. This would be a lot of work to establish, but it’s an intriguing way of informing consumers that want to make choices on the best possible information.

Of course, such a registry would have to be independent and trustworthy!

The bottom line though is that the more consumers can be helped to make informed choices for themselves, the better.

My informed choice, based on what I’ve learned to date from both scientists and dermatologists, and weighing the risks of not using sunscreen against the certainty that I will develop skin cancer if I live long enough (unless I’m prepared to stay indoors for the rest of my life) would be to use a non-photoactive nanotech zinc-oxide based sunscreen. What are the chances that I’ll be able to find one based on labeling alone? As an independent thinker (some might say born contrary), I like to make up my own mind on matters relating to both my health and my eco-footprint.

I would be the last to say that the safety of nanoparticles in sunscreens is a closed case – it clearly isn’t – but I do feel that pragmatic decisions need to be made, and that the balance of evidence so far is in favor of their use.

Working through your comments:

First, thanks for flagging up last year’s Safe Sunscreen Guide. It is important that consumers are aware that there are non-nano sunscreens available with mineral-based active ingredients. At the same time, I am a little wary that manufacturers are playing the definition game – finding ways of claiming that their products don’t contain nanoparticles, either because they have aggregated together, or they are a tad larger than the semi-formal 100 nm cut-off. This worries me because it moves the debate from what is safe, to a debate over definitions of size.

I would disagree that current skin penetration tests are being trivialized – there has been considerable investment in research in this area over the past few years, and despite trying hard, researchers are struggling to find any evidence for significant penetration. At the same time, there are gaps in our knowledge – which is why research continues. I would argue based on the current data that there are no compelling reasons not to use nanoparticles in sunscreens, but that to be complacent would be dangerous. Sally Tinkle’s study with the dextran beads (she didn’t use beryllium particles, although the study was designed to test a beryllium sensitization route hypothesis) is one of the very few studies that has shown the possibility of large particles penetrating through the skin, and should be interpreted very cautiously. At the time it was published, this was a very important piece of work – it demonstrated qualitatively that some particles could possibly pass through skin under some conditions. The setup she used was somewhat artificial and may have led to experiment-specific artifacts (which is why one experimental study alone is never enough to prove a point). But her work indicated that the question of skin penetration was an important one. Since then though, other researchers have failed to observe comparable skin penetration.

I must stress again that this doesn’t mean there is not an issue here – it just means that there is diminishing evidence for there being an issue. Maybe the right tests haven’t been done. Maybe we’re missing something. This is why the research needs to continue. But there comes a point where deciding against a product which could be potentially beneficial on the grounds of unsubstantiated speculation becomes counterproductive.

Next, the damaged skin issue you raise is an important one. There has been relatively little work on nanoparticle penetration through compromised or delicate skin – cuts, sunburn, baby skin, and this is an area that especially needs more work. It is beginning – see the citations in the EWG report – and the indications so far are that the issues related to using nanoparticle-based sunscreens on damaged skin are unlikely to be significantly worse than using non-nano sunscreens on such skin. Yet again, I don’t think we can afford to be complacent.

This raises an important issue of what happens if nanoparticles do penetrate through the skin and enter the body? There is remarkably little information available here, so we are once again in the realms of science-informed speculation. We know that particles are most likely picked up by the lymphatic system where they accumulate in the lymph nodes. We know that particles like titanium dioxide are relatively insoluble, and so will hang around for some time unless the body has adequate ways of clearing them as nanoparticles. We know that zinc oxide nanoparticles are more soluble, and will probably dissolve over time. We know that titanium dioxide has a very low toxicity, although this does increase according to some measures as particle size decreases. And we know that what is important in causing harm is the amount of stuff that enters the body – not just whether it will enter or not.

Pulling all this together, it is hard to make the case for nanoparticles on the skin presenting a clear risk. Certainly on the basis of this I would not hesitate to use nanoparticle-based sunscreens. But I would expect government and industry to continue filling in the knowledge gaps – just in case there is a problem.

Finally, the issue of photo-active nanoparticles. This does concern me I must confess, and I wrote about the BlueScope study last year. There is no reason why nanoparticles in sunscreens should be photoactive – there are ways of suppressing this that most manufacturers use. Yet without clear regulatory guidance, it seems there is very little to stop manufacturers using photoactive nanoparticles – either inadvertently or intentionally (although the latter makes bad business sense, as the photoactivity also degrades the long-term effectiveness of the product).

Two questions seem important here: Are photoactive particles on the skin a serious concern, and how many (and which) products are likely to contain them? On the first point, photoactive particles produce free radicals in the presence of UV radiation – highly active chemicals that can cause a lot of damage. But to cause damage they need to have access to living cells – and ideally the genetic material inside the cells. Free radicals are a fact of life and our bodies have evolved to deal with them, so we do have some protection. Free radicals also have a reasonably short lifetime because of their reactivity, and so if they are generated at the surface of the skin they are not likely to get to places where they can cause harm. If photoactive nanoparticles could penetrate inside living cells that were also exposed to UV radiation, we might have more of a problem. But there is scant evidence for either this degree of cell penetration, or there being sufficient penetration of UV to living cells that would lead to the generation of significant quantities of free radicals.

That said – more research is needed still to make sure current choices of using nanoparticles in sunscreens are as reasonable as they seem.

At the end of the day, consumers do have a right to choose what they think is best for them. Where there is uncertainty – even if it is somewhat speculative – that can lead to hard choices. Which is why I would argue strongly for as much independent and unbiased information being as freely available as possible – and in a form that is understandable to anyone who needs it. If a sunscreen contains nanoparticles (either as primary particles or as aggregates), it should be clear. The benefits of this ingredient should also be clear when compared to alternatives. Likewise, the possible downsides – together with the weight of evidence supporting this information – should be clear, again compared to the alternatives.

What I don’t think is helpful is groups – industry, academics or others – deciding what is right for consumers without enabling them to make their own informed decisions. This is particularly important where deciding not to use a product could be as harmful potentially as deciding to use it – as I think is the case with sunscreens.

I am also concerned that the significant limitations to existing nanoparticle skin penetration studies are being trivialised. There is a reason that costly, long-term studies are still underway in the US, Australia and elsewhere, and that is because existing studies have failed to address a lot of important ‘real life’ variables. After all, researchers showed five years ago that skin flexing was sufficient to enable skin penetration of 1,000nm beryllium particles. It seems reasonable to suggest that skin penetration by nanoparticles 20-40nm in size used in sunscreens could occur when people are exercising. There is similarly no recognition of the fact that many sunscreens are used in moisturisers and face creams which may also contain substances that act as skin penetration enhancers.

Furthermore, I note that whereas everyone is talking about healthy adult skin, there is little recognition that pimples, shaving rash, sunburn, eczema or other skin conditions could leave sunscreen wearers more vulnerable to nanoparticle uptake. I have also yet to see any data that looks at nanoparticle penetration through baby skin.

Finally, I think there is more than “some evidence” that sunscreen products which contain photo-active nanoparticles are still entering the market. A study published last year by Australian researchers at BlueScope Steel found that the photo-catalytic properties of nanoparticle-containing sunscreens were dramatic. Where installation workers wearing nano-sunscreens had touched roofs they were installing, subsequent localised roof ageing was accelerated 100 times. These results were replicated in controlled laboratory conditions.

There are still some very good reasons that people may wish to make a precaution-based decision to avoid using nano-sunscreens. We should avoid giving the false impression that the choice available to consumers is ‘poorly understood nanoparticles’ vs ‘dangerous chemicals’.

It’s still a trade-off – do you go for the more effective and possibly safer product, even though it uses a new technology that hasn’t been tested to destruction, or do you stick with the product you know – even though it might be more harmful and not work as well?

Ultimately, this comes down to consumer choice – which means that the better the information we have available to us, the better off we are (in principle)!