Friends of Earth put out a report on nanotechnology and sunscreens recently. They bungled it. Big time.
A little background.
Zinc (Zn) and Titanium (Ti) Oxides are the best sun protectants known. They don’t break down in the sun and they have broad UVA UVB coverage. However, they are bright opaque white (you remember the thick white stuff lifeguards put on their noses and ears?). If you make it small enough, though, the solution will be clear, not white, and still do a good job. Most nanoparticles in sunscreen may be nano in terms of size, but nanotechnology (from a toxicology perspective) also means that the particle is built from the atom up which gives it a different structure and, therefore, different properties. Most ZnO or TiO2 sunscreens are just finely ‘micronized’ (i.e. ground up really good) to get down close to or in the nanoscale particle size range. The use of the word “nano” is nothing more than a marketing ploy in many cases, or misused for something finely micronized. However, true nanoparticles may be used in sunscreens as they are in other areas, so it’s worth looking into.
Risk to science that is…
That said, let’s dig into this report. I’ll start with the “risk to human health” section.
First, nanoparticles have unprecedented access to the human body… Crucially for the use of nanosunscreens, the jury is still out on how readily and how deeply nanoparticles penetrate skin. The ability of nanoparticles to be taken up through the skin and to access the blood stream remains poorly understood, although there is growing evidence that some nanoparticles may penetrate intact skin 9.
The jury is still out? The jury saw the evidence and came back in 5 minutes with “not-guilty”. Maybe some nanoparticles do get in but TiO2 and ZnO particles don’t. Study after study after study has shown no penetration past the dead layer of skin. I’m talking good studies. There is some question of what would happen under conditions of severely damaged skin. If you have damaged skin, you could stick to the Zn only sunscreens and since we already have Zn in our bodies, it won’t hurt at all to let a little more in. Also, the study that FOE references is about quantum dots. Any quantum dots in sunscreen? No. Any reasonable similarity between quantum dots and TiO2 or ZnO other than size? No. Do I care then? No.
When ingested, some nanomaterials may pass through the gut wall and circulate through our blood 8.
Okay, don’t eat your sunscreen. Good advice anytime. Also, the studies they cite aren’t about TiO2 or ZnO. One is about gold nanoparticles. An extra warning to my readers in Bel-Air: Warning, when applying your gold sunscreen, please don’t eat it.
Studies have also shown that particles 1,000 nm in size can cross human skin and gain access to the dermis (the lower or inner layer of the two main layers of tissue that make up the skin), up by cell mitochondria15 (the principal energy source for cells) and cell nuclei16, where they can induce major structural damage to mitochondria17, cause DNA mutation18 and even result in cell death19.
Let’s see about the references. One is about water-soluble biocompatible nanocontainers that were designed to penetrate the skin. Another is about air particulate matter (most likely from combustion engines). A third is about ultrafine TiO2 powder that is inhaled. The other reference numbers are actually repeats of the first two papers. So, the only extra thing we’ve learned about sunscreens is that you shouldn’t dry out TiO2 sunscreen, crush it, and snort it. Also good advice for any sunscreen.
That’s it. That’s the whole health risk section. So, ZnO and TiO2 don’t breakdown like other sunscreens, they do provide complete UVA UVB protection unlike other sunscreens, and don’t absorb into the skin like other sunscreens. So, actually, ZnO and TiO2 suncreens are safer than the conventional ones. Way to get it completely backwards FOE! I’m sure they mean well, but if you don’t have the expertise or the insight to even be able to interpert the papers you cite correctly, you shouldn’t even be thinking about doing a report. In fact, what were you thinking? Nanotech is hot and sounds scarry so we should do a report and cobble together any research on things that are small? Using research on any type of nanoproduct to talk about ZnO and TiO2 is like saying that “all chemicals are bad, look at these studies on pesticides!”
Here’s what I use (note to the manufacturer: Your name and packaging looks vaguely like Vagisil. I suggest a change). Here’s what I use on the kids (it’s a little thick to put on, but it doesn’t come off and that makes it worth it).
Caveat: Nanotechnology does present a lot of new risks that are poorly understood for most particles at this point. Many are really toxic, many are not. We clearly aren’t doing enough to study the real nanoparticles that are being currently used in commerce. Learn more about the risks of nanotechnology including sunscreens by reading this journal article.
Update (Aug 16th):
Texas Reader asked “Angry Toxicologist – would you please look into the criticism of a lot of the most popular suncreens [sic] by something called “The Environmental Working Group”?” I thought this was a question worthy of an update so here we go:
Short answer: I agree with most of their conclusions, but I don’t like how the message is put out there, and I think the ‘search for your cosmetics tool’ is near worthless with the exception of the very vaulable UVA/UVB part.
1) They are right on about the regulatory system for cosmetics;
2) I specifically looked for their stance on the nano and they have a pretty reasoned take on it, however,…
3) At the top of the search page you can click on “no nano-particles” for your cosmetics search. This seems really disingenuous. In the fine print they say that nano is fine but where most visitors look, they can click “no nano”. So really the implicit message that they are sending is that nano is a big problem (there aren’t boxes for any other special ‘no’ categories). It seems like Environmental Working Group is hedging their bets here, pandering to scientists/journalists and the general public in separate ways. If you don’t choose “no-nano”, the TiO2 and ZnO ones come out among the best.
4) Their “scoring system” for the cosmetic site as a whole is really arbitrary. I think the info they provide on full UVA/UVB protection is really useful, but I wouldn’t pay attention to a lot of the rest of the stuff. For instance, does everyone view cancer risk as worse than reproductive risk? Wouldn’t it depend on how potent that toxic chemical is? (EWG does some ranking on strength of evidence but that’s much different than potency) Wouldn’t every finding in there be contingent on the amount of each chemical in the product which isn’t known? (I doubt that manufactures told them the amounts) There is no sound reason behind how they added untested chemicals to the rating (how do you compare the risks of what you don’t know with what you do?). I haven’t looked through the whole thing, but I would guess that based on the scoring system well-tested chemicals fare much worse than those that we simply don’t know anything about. EWG has solid reports in many areas, but it seems like it should stay away from the cosmetics scoring business. I doubt they will quit, though, it gets a lot of press.
So this is somewhat insightful. As far as nanotech goes, where FOE just totally bungles it, EWG gets the science generally right but tries to be really slick about it. I don’t like it either way and I’m not sure which I like least, FOE’s boneheadedness or EWG’s sneakiness. Possibly, the slickness/hiding could be due to backlash among the other greenies. I got some evidence for that theory yesterday. From four e-mails, I got the distinct impression that I had stepped into a pissing match between FOE and EWG with my sunscreen/nanotech post. I didn’t actually know this until right now (it was on the EWG press page that I found for the link above), but there was a pretty good NYTimes blog post that describes this whole mess.
Texas, thanks for the follow up question.