Burning Questions: Are Sunscreens Containing Nanomaterials Safe?

John BalbusCal Baier-Anderson, Ph.D., is a Health Scientist.

Ah, summer!  It’s a great time to be outdoors, enjoying the warm, sunny weather.  Before you go outside, be sure to grab your sunscreen, that essential product that protects against skin cancer and sun damage.  But which kind of sunscreen is best?  There is a mesmerizing array of sunscreen options, but for our purposes let’s limit the question to one:  Nano or not nano?

We all recall the white noses of the beach lifeguards.  The zinc oxide or titanium dioxide in these nose-protecting potions form a thick, white barrier that blocks damaging ultraviolet (UV) radiation by reflecting and scattering light.  These days, nanoscale titanium dioxide and zinc oxide are increasingly popular sunscreen ingredients, as they provide a UV barrier but are nearly transparent.

One of the concerns raised by using nanoscale titanium dioxide and zinc oxide in sunscreens is the dearth of safety data on potential health that could arise from applying nanoscale minerals to the skin on a daily basis – including to skin that may be damaged (e.g., already sunburned).  The sunscreens are then released into lakes or oceans, or washed down the drain with the bathwater with unknown environmental effects.

First, it must be pointed out that the same concern – lack of adequate safety data — applies to many of the traditional chemical sunscreen ingredients.  Nanoscale materials may require additional scrutiny, however, because their properties can differ from their bulk-scale counterparts.

Some environmental advocacy groups, such as Friends of the Earth, citing the lack of safety data and unclear product labeling, have called on the Food and Drug Administration to require more testing and exercise better regulatory oversight.  Meanwhile, because of these problems, Friends of the Earth ranks nanomaterial-containing sunscreens among the worst.

In contrast, Environmental Working Group, while recognizing the critical data gaps, generally ranks sunscreens with nanoscale zinc and titanium oxides as having a lower hazard than those containing the most common active ingredients, such as oxybenzone and octyl methoxycinnamate.  As summarized by EWG, these non-nano ingredients are linked to a number of health hazards, including cancer and developmental and reproductive toxicity.  EWG argues that, in addition to being more effective, sunscreens made with nanoscale zinc and titanium oxides generally contain fewer hazardous ingredients overall.

A range of opinions regarding nanoscale zinc and titanium oxides are available on popular websites, including Treehugger, Huffington Post, and the Green Guide.  The one thing everyone seems to agree on is that the lack of adequate safety data makes it hard to draw definitive conclusions regarding the safety of nanomaterials in sunscreens.

The US Food and Drug Administration will soon be updating its “Sunscreen Monograph” – the regulatory document that specifies what chemicals can be used in sunscreen formulations, and in what concentrations.  This is a clear opportunity for FDA to be more proactive, by requiring that more data be developed to demonstrate sunscreen ingredient safety, and that more data be made publicly available so that consumers can make better-informed choices.

In the meantime, if we are to avoid the real harm that over-exposure to the sun can cause, we have little choice but to select among sunscreen formulations — all of which contain insufficiently tested ingredients — hoping that whatever we do is better than the burn.

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  1. Kristan Markey
    Posted July 17, 2008 at 3:22 am | Permalink

    Thanks for the balanced post explaining some of the differences between FoE’s and EWG’s reports – a few points:

    – FoE has not ranked nano-scale ingredients among the worst in their reports because they have not assessed the range of ingredients used in sunscreens. Their reports raise legitimate concerns regarding the safety of nano-scale ingredients only.

    – EWG’s assessments are driven to a significant degree by extensive evidence showing that nano-scale ingredients don’t or barely penetrate healthy skin. This contrasts with the most widely used other ingredients that either absorb themselves or enhance absorption of other ingredients. Further, many sunscreen ingredients breakdown when exposed to the sun, leading to exposures of unknown and unstudied chemicals.

    – Ironically, nano-scale sunscreen ingredients are better studied than most sunscreen ingredients even when completely excluding non-nanoscale studies on zinc oxide and titanium dioxide.

    Disclosure: I am one of the authors on the EWG sunscreen reports, though I am no longer employed by EWG. The views expressed are my own.

  2. Cal Baier-Anderson
    Posted July 18, 2008 at 10:02 am | Permalink

    Kristan – Thank you for your thoughtful response. One point I would like to add is that although several studies show that certain nanoparticles (notably zinc oxide and titanium dioxide) do not penetrate healthy, intact skin, few nanomaterials have been tested to date. Moreover, much less testing has been done on actively flexed or damaged skin.

    Recent studies have found that quantum dots can penetrate abraded skin, and that fullerenes can penetrate flexed skin. And while this does not mean that nanoscale zinc or titanium oxides will also penetrate flexed or abraded skin – the bottom line is we just don’t know.

    An additional complicating factor is that different manufacturing processes, as well as different surface treatments can alter physical, chemical and toxicological properties. So not all nanoscale titanium dioxide will have the same profile. This will be the subject of my next blog…

  3. Posted July 20, 2008 at 5:23 am | Permalink


    Thanks for this. One of the more attractive features of nanoparticle-based sunscreens is that the nanoparticles can be finely tuned to suppress potentially harmful chemical activity – such as the generation of free radicals in sunlight. But evidence has recently come to light from a rather unusual source that not all manufacturers are taking the necessary steps to avoid the generation of hydroxyl radicals when nanoparticles in sunscreens are exposed to ultraviolet light (see http://community.safenano.org/blogs/andrew_maynard/archive/2008/06/21/nano-sunscreens-leave-their-mark.aspx ).

    (I suspect am preempting your next blog entry here…)

    It’s unclear how much of an issue this in terms of possible skin damage or environmental harm (as the sunscreens are washed off and dispersed), but if there is no regulatory distinction between chemically active and chemically benign nano-ingredients, responsible manufacturers end up being put at a disadvantage while less-responsible (or aware) ones continue to use materials with a poorly understood risk profile.

    Something FDA will hopefully be thinking about as the Sunscreen Monograph is updated

  4. Posted February 19, 2009 at 8:33 pm | Permalink

    Thanks for the interesting post on the use nanotechnology in sunscreens. I am a lifeguard and actually use zinc oxide on a daily basis. It actually works great for me and does a better job than just applying regular spf 30. I’ve never really thought about the chemical effects it could have on my health, until i read this article. I think the FDA needs to another study on its effects.

    As for the environmental issues, i definitely think something needs to be done to make all sunscreens less harmful to the environment especially for the oceans reefs. I can remember many times going to a crowded beach and seeing the sunscreen oil slick in the water. Hopefully someone can find a solution to this problem.