Australian Education Union advises against using nanoparticle-based sunscreens in schools

by Andrew Maynard on May 22, 2011

Last week, the Victoria branch of the Australian Education Union (AEU) passed a resolution recommending that “workplaces use only nanoparticle-free sunscreen” and that sunscreens used by members on children are selected from those “highlighted in the Safe Sunshine Guide produced by Friends of the Earth” as being nano-free.  The AEU also resolved to provide the Friends of the Earth Safe Sunscreen Guide and Recommendations to all workplaces their members are associated with.  Given what is currently known about sunscreens – nano and otherwise, I can’t help wonder whether this is an ill-advised move.

The debate over the safety or otherwise of nanoparticle-containing sunscreens has been going on for over a decade now.  Prompted by early concerns over possible penetration through the skin and into the body of the nanosized titanium dioxide and/or zinc oxide particles used in these products – and potential adverse impacts that might result – there has been a wealth of research into whether these small particles can actually get through the skin when applied in a sunscreen.  And the overall conclusion is that they cannot.  There have been a small number of studies that demonstrate that, under specific conditions, some types of nanoparticle might penetrate through the upper layers of the skin.  But the overwhelming majority of studies have failed to find either plausible evidence for significant penetration, or plausible evidence for adverse health impacts – a body of evidence that led the Environmental Working Group to make an about-face from questioning the use of nanoparticle-containing sunscreens to endorsing them in 2010.

So why is the AEU now advising against their use?  And why are they advocating selecting sunscreens based on a document that does not provide evidence-based advice on efficacy or safety – and may end up leading to decisions that increase the risk of sun-related skin damage in children (more on this below)? (Update 5/25/11 – see notes below)

In part, the answer lies in the uncertainty inherent in proving anything safe.  It’s not too difficult to show that something is unlikely to be harmful, or is probably safe.  But proving something is absolutely safe under all conditions of use is simply not possible – there is always some room for doubt.  This is why decisions on health risks are typically based on plausible risk and weight of evidence – evaluating the most reasonable and defensible interpretation of the data, and not basing decisions on speculation and fantasy.

With the use of nanoparticles in sunscreens, the weight of evidence is that they are safe and effective – and may be safer and more effective than a number of non-nanoparticle alternatives as they work by coating the skin rather than being absorbed into it.  That said, it’s always prudent to check whether anything has been missed with a relatively new technology like this, and so research is ongoing just to make doubly sure that the nanoparticles currently being used stay on top of the skin, and that manufacturers are using the safest possible types of nanoparticles.

But there is another reason I suspect why the ASU have released this advice, and that is due to a study using human volunteers that was published last year.

In this study by Brian Gulson and colleagues, sunscreens were formulated with zinc oxide particles made from a stable isotope of zinc that doesn’t occur in great abundance naturally: Zn-68. Using Zn-68 as a tracer, they were able to tell whether zinc from the applied sunscreen entered the bodies of the volunteers, and ended up in their blood and urine.

The detected presence of Zn-68 in the urine and blood of volunteers was used by Friends of the Earth Australia to renew their recommendations against using nanoparticle-containing sunscreens until more is known about their safety in.  And given the ASU’s reliance on the Friends of the Earth document, it seems to have influenced their decision to recommend not using nanoparticle-containing sunscreens.

But what does the Gulson study actually conclude?  In a nutshell, the researchers showed that:

  • Small amounts of zinc from sunscreens containing any form of zinc oxide particles tested found their way into the blood and urine of volunteers.
  • The amounts of zinc entering the body over the five day study were miniscule – around one thousandth of the concentration of zinc already in the volunteers’ bloodstream, and around one thousandth of the amount of zinc recommended in a person’s daily diet.
  • Women in the test generally showed higher uptakes of zinc than men.
  • Zinc levels in blood associated with the sunscreen peaked some days after applications ended, suggesting the zinc or zinc oxide was stored somewhere in or on the body and slowly released.
  • For men, zinc uptake from sunscreens was independent of particle size.  For women, zinc uptake was greater from the sunscreens containing smaller particles.

So did the particles go through the skin?  The study only showed that the zinc passed through the skin, and did not provide any evidence of particle penetration.  Two possible explanations for this are that the particles penetrated and entered the bloodstream, or that the applied particles dissolved, and that it was dissolved zinc that was penetrating into the body.

Out of the two possibilities, there is minimal evidence for particle penetration being a plausible mechanism. On the other hand, zinc oxide is sparingly soluble, and under the acid-conditions of the outer layers of the skin the particles would have readily released zinc ions.  The weight of evidence to date therefore strongly supports dissolution of the particles and subsequent dermal penetration of dissolved zinc.  This is supported by the similarity in uptake seen in men of zinc for two different sizes of zinc oxide particles.

In other words, this study provides neither compelling evidence that nanoparticles in sunscreens can pass through the skin, or that they can lead to worrying internal exposure to harmful materials.  It did indicate on the other hand that any sunscreen containing zinc oxide will lead to zinc entering the body via the skin – including sunscreens that rely on large zinc oxide particles.

And this is where it is worth returning to the Friends of the Earth recommendations.

The Friends of the Earth Safe Sunscreen Guide recommends:

Use a nano-free zinc-based SPF 30+ broad spectrum sunscreen in conjunction with protective clothing, a broad-brimmed hat, sunglasses and shade to stay sun safe.

It goes on to list sunscreens that are “nano and chemical free”, “may use nano” and “use nano” (based on information from manufacturers and assumptions from Friends of the Earth).

Passing over the fact that Friends of the Earth are advocating the use of sunscreens that demonstrate the same behavior – zinc penetration through the skin into the body – as the sunscreens they recommend people don’t use, it’s hard to understand how this document provides an authoritative and evidence-based guide for the use of sunscreens on school children – as suggested by AEU.

For a start, this is a document that is specifically concerned with nanoparticle-containing sunscreens, and is not aimed at providing advice on selecting sunscreens as a whole based on their safety and efficacy.  It is advocating a specific course of action, and is not a tool for taking informed action. And in this respect alone it is a questionable document to be distributing to school workers. But it gets worse.

The sunscreens listed in the document are listed solely with respect to their nanoparticle content.  There is no – let me repeat that no – information on how effective these sunscreens are at protecting against UVA and UVB, and what the specific safety issues associated with their use are (update 5/25/11 – see notes below).  What is more, the top tier products – those that appear to be most strongly endendorsed by Friends of the Earth – also claim to be “free of UV-absorbing chemicals”.  In other words, this is a document that appears to be endorsing the use of products that do not necessarily protect against ultraviolet light. (Update 5/25/11 – see notes below).

To be fair to Friends of the Earth – and this is not a critique of their document so much as a questioning of its use as authoritative guidance – they do recommend the use of sunscreens providing substantial UV protection that are (presumably) based on large zinc oxide particles.  But if school workers were to base their choice of what to slather onto kids on the list of products, rather than the one sentence top level recommendation, they could well be applying sunscreens that do not protect against skin damage.

And this is my greatest concern here – by advocating the use of the Friends of the Earth document, AEU could actually be endangering the health of children in the care of their members. (Update 5/25/11 – see notes below)

Of course, there are important issues to grapple with here – including how appropriate sunscreens should be selected for use on children, irrespective of the technology being used.  But surely these selections should be based on the best possible evidence that is focused on what is most appropriate for the children, and not on an action campaign by an advocacy group, no matter how well intentioned.

Update, 5/25/11:  As clarified by Georgia Miller of Friends of the Earth Australia in the comments below, the sunscreens listed in the top tier of the Friends of the Earth document are all – as far as I can tell – marketed as offering SPF 30 + protection.  This is something that I do not think is explicitly clear in the document, and the heading of “nano and chemical-free”, clarified with “products also free of UV-absorbing chemicals” raises an obvious question to the naive reader over whether these products do indeed offer significant protection.  I also continue to have serious reservations over the use of a document designed to steer people away from nanoparticle-containing sunscreens as authoritative advice on sunscreen protection for children, given it’s lack of independent testing and evaluation of all significant factors that might affect choice in a given situation.  Nevertheless, given the protection ratings of the recommended sunscreens, I have on reflection retracted the statements made in regard to the protection offered above.

1 Gaythia May 23, 2011 at 1:01 pm

My first negative reaction to the Friends of the Earth report above is in describing anything as “chemical free”. So then I started looking up the products . One of the products on the FOE Australia Nano and CHEMICAL-Free list linked to above, Grahams Sunclear Sunscreen, gives its ingredients (on the company website) as: “Ingredients: Capric/caprylic triglyceride (plant oil derived), Rose hip oil, Grapeseed oil, Sesame seed oil, Shea butter, Hydrogenated Vegetable oil, Vitamin E, Vitamin A, Phenoxyethanol. Active Ingredient: 260mg/g Zinc oxide.” All chemicals, of course. Then I started puzzling over their non-nano credentials. Grahams claim that their product “Uses the patented ZinClear technology”. Zinc oxide is normally opaque, which is the whole point in using it to block sun. So what did they do to make zinc oxide clear, other than making the particle size very small? How much not nano are they?

Another product on this list, with similar sounding issues, Invisible Zinc, describes it’s product this way: “Invisible Zinc® uses micro-fine Zinc Oxide which although invisible to the naked eye still provides outstanding broad spectrum protection against UVA and UVB rays.

It seems to me that any analysis of zinc oxide absorption by the skin would need to sort sunblock products accurately by particle size. Perhaps a division between macro and micro is more significant than whatever the line is between mirco-fine and nano. Or maybe they aren’t controlling for particle size that well, and actually have size mixtures.

But at any rate, the term “chemical free” should be banished.

2 Andrew Maynard May 23, 2011 at 1:11 pm

Thanks Gaythia.

I hadn’t got as far as checking these products, but terms like “invisible zinc” did ring alarm bells. “Micro-fine” usually refers to the use of sub-micrometer, and usually nano-sized, particles. The technology associated with ZinClear is a little less clear (if you’ll forgive the pun”. Now sold by Dow Chemicals, ZinClear is supposedly a transparent form of zinc oxide with a median particle size significantly larger than one micrometer. If anyone can tell me how they achieve this , I would be very interested in knowing!

3 Gaythia May 23, 2011 at 5:19 pm

But the two companies I picked to look up were on the nano (and chemical) free list!

If these companies are actively avoiding nano-particles, don’t we need to know the particle size distribution (and not just the median)? Do we need to count the number of nano sized particles present? Is there a threshold value?

I did look up ZinClear here: http://www.dow.com/personalcare/technologies/uvtechnologies/zinclear.htm. This part of the company is called Dow Personal Care, not Dow Chemical, although clearly chemicals are involved, even if some of them are “natural”. Much of what Dow makes involves applications of organic chemistry, as in derivatives of petrochemicals, but that is a topic for a different thread.

I love trying to wrap my chemist brain around the idea that a decidedly inorganic zinc oxide formulation could qualify for EXOCERT certification, which is (I think) a French organization for organic foods and cosmetics.

4 Georgia Miller May 25, 2011 at 10:41 am

Hi Andrew and all

There is as always a divergence in views in how we should respond to the uncertain risks inherent in nano-sunscreens. However I think there are some factual issues here that are important to clarify.

Andrew, you suggest that the sunscreens we list in the top-tier of the guide of sunscreens as those that do not contain “UV-absorbing chemicals” means that these sunscreens may not provide effective UV protection. This is not the case. The sunscreens in our top tier are based on non-nano physical UV blockers, rather than chemical absorbers, which I think is clear from the consumer guide. Every one of the top tier of our listed nano-free sunscreens offers SPF 30+, broad spectrum protection (ie both UVA and UVB protection).

It is therefore highly inaccurate to suggest that the sunscreens we list as nano-free may offer an inferior level of sun protection to those which may be nano-containing. Unlike the nano sunscreens on the market, nano-free sunscreens have gone through relevant safety and efficacy testing prior to market sale. This means that consumers can have confidence that these sunscreens will offer an effective level of sun protection.

I understand Gaythia’s comments above on the confusion possible from describing sunscreens as “chemical-free”, however it is common to use the language of “mineral/ physical UV blocker” compared to “chemical UV absorber” to distinguish between these different types of active ingredients in sunscreens. Our guide specifically lists the active chemical ingredients (and fragrances) that we asked companies about in relation to the “chemical-free” claims.

I am also concerned that Andrew states that the zinc in the sunscreens we recommend, or similar sized particles, have been shown by the Gulson et al. (2010) study to penetrate skin. As readers may know, from the comments I posted in Andrew’s 2020 sunscreen blog earlier in detailed response to comments and criticisms re this, the Gulson et al study used a “non-nano” control that had particles 110nm in size. That is, although FoE regards this as a valuable and an important study, we recognise that it did not use an effective non-nano control. Further, as I also explained in detail in an earlier post, we are most concerned about the ROS production of nanoparticles.

FYI, many of the zinc sunscreens listed in our guide as ‘non-nano’ are based on particles 1000nm in size. The companies are still able to get an acceptable level of transparency.

Recognising that nanoparticles behave as new chemicals, the UK Royal Society back in 2004 recommended that they should be assessed as new chemicals by regulators before being permitted for use in commercial products. As many of you would be aware, although new European laws regarding nano-sunscreens and cosmetics will apply from 2013, in Australia, where we rely on routine sunscreen use as an important public health measure, our regulator has failed to close the legal loopholes that leave nano-sunscreens effectively unregulated.

Although researchers from BlueScope Steel have identified on sale in Australia nano-sunscreens that act as extreme photocatalysts, the Therapeutic Goods Administration has taken no action to require these products to be removed from the market, or even for the manufacturers to submit safety information that is relevant to these nano-forms. Given the situation, many Australians want to avoid the use of nano-sunscreens, hence the production of our guide.

Friends of the Earth recognise that using a high SPF sunscreen is part of an effective sun protection strategy. Our guide specifically recommends: “Use a nano-free zinc-based SPF 30+ broad spectrum sunscreen in conjunction with protective clothing, a broad-brimmed hat, sunglasses and shade to stay sun safe.”

Georgia Miller
Friends of the Earth Australia

5 Andrew Maynard May 25, 2011 at 12:46 pm

Thanks for this Georgia, and for keeping me on my toes!

I must confess that, reading through the FoE guidance, I did not find the link between efficacy and recommendations that clear – there is an implicit link, but not an explicit one. However, having checked out the details of your top-tier recommended products, they all appear to offer SPF 30+ protection. My apologies for missing this – I will update the blog to reflect this.

That said, I do feel using the wording “free of UV-absorbing chemicals” is confusing at best if the document is to be used as general guidance for sunscreen selection – rather than guidance on not purchasing nanoparticle-containing sunscreens.

Regarding the Gulson study, thanks for the reminder that the larger particles were still relatively small (110 nm +/- 46 nm, as opposed to 19 nm +/- 8 nm for the smaller ones). However, this is still sufficient difference to call into question size-specific effects in the study.

If, on the other hand, dissolution is an important mechanism by which zinc is transported from a zinc oxide containing sunscreen through the skin and into the body, the questions being raised about risk are surely just as pertinent to sunscreens using larger particles.

The ZinClear material which some of your recommended sunscreens use btw is an interesting material, and one that probably deserves greater attention. I must confess to being unsure what the mechanism is by which micrometer-sized zinc oxide particles are rendered transparent, but this does seem to be an interesting alternative inorganic active material. The reported size distribution of the material is given here: http://dowhpc.custhelp.com/app/answers/detail/a_id/9227/~/zinclear—particle-size-distribution – I would also be interested in micrographs of it, if anyone has any!

Photoactivation is an issue with TiO2 in sunscreens, as we have discussed before. However, while action definitely should be taken to ensure photoactive materials are not used in sunscreens, there are technologies and products that use non-photoactive TiO2 nanoparticles.

6 Gaythia May 26, 2011 at 6:41 pm

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