There is a lot of hype around sunscreen safety, and I think it is important for consumers to be informed from accurate sources regarding the issues at hand. See my original post here about sunscreen safety.
Today I wanted to specifically address the issue of nanoparticles. A lot of natural and organic sunscreens are marketing their sunscreens as “non-nano.” Why? The ingredients most likely to be nanosized are zinc oxide and titanium dioxide, which are top of the list for the “safe” sunscreen movement. So are the “safe” sunscreens not safe either???
Refresher
Nanoparticles refer to the size of the particles in the sunscreen. They are one billionth of a meter in length, aka a nanometer. Nanotechnology, the ability to create something that small, has revolutionized many industries, cosmetics included. And they’ve actually been used in sunscreens since the early 1980s!
Well let’s first look at the practical aspects of nano sunscreens. It has transformed the 1960’s white noses of lifeguards to inconspicuous, non-obnoxious sun shields. Since the particles are so small, they don’t have the light reflectivity and whiteness of old-school sunscreens. “Invisible zinc” is what some companies use to describe the technology.
But are they safe? If they are so small, can’t they penetrate through the skin and affect biological functions?
Luckily, nanoparticles are coated and only reach the very top level of the skin (the stratum corneum), where they reflect UV light. Additionally, our normal shedding of skin continuously removes them. Finally, in nature, the nanoparticles tend to clump, making them larger than true nanosize, but smaller than traditional zinc oxide particles (see figure). These real-life clumped nanoparticles definitely cannot penetrate the skin because they are too large, again easing fears of absorption. Don’t take my word for it, it’s been tested numerous times, and the sunscreens simply aren’t absorbed.
Nanoparticles clump on the skin. Photo credit: PMID: 22123418
Finally, a last concern was regarding the generation of pro-oxidant reactive oxidative species (ROS), as was found in some cell studies. Luckily, since sunscreen nanoparticles are coated in silica, an inert substance, they actually have no risk of generating ROS in the highly fine-tuned human body. Finally, in case you were worried (everything worries us now!), sunscreen nanoparticles were tested for both cancer-causing properties and phototoxicity and they were completely in the clear (Wang, 2011)!
Let’s also remember the long safety track record of both zinc oxide and titanium dioxide. Titanium dioxide is found in toothpaste, lotion, skimmed milk, cottage cheese, while zinc oxide is what we smear on our babies bottoms (diaper cream) and have used in our dandruff shampoo for decades.
For all the criticism of the FDA [i.e. not doing enough to regulate over the counter ingredients (true), not approving sunscreen ingredients fast enough (true)], at least they are on par with their more modern overseas counterparts. The European Union (EU) considers micro- and nanoparticles safe. The EU usually bans ingredients deemed unsafe/questionable before the US, so if they are OK with nanoparticles, you should be too.
An even stricter critic is the EWG (Environmental Working Group). While we often don’t agree, in this case, we do! The EWG tells consumers not to worry about nanoparticles! The EWG in general tends to favor zinc oxide and titanium dioxide sunscreens over chemical based sunscreens, and most of the commercially acceptable zinc and titanium-based products are nanosized. To date, no environmental repercussions have been discovered, and while continuing monitoring and research is needed, in general nano-sized zinc is A-OK by the EWG.
In conclusion, I don’t worry about the molecular size of my sunscreen ingredients. I’m just happy I don’t have to walk around with a white face to get good daily UV protection!
Photo credit: http://etsy.me/1D3PcYJ
References
Wang S, Lim H. Principles and practice of photoprotection. Springer, New York. 2016.
Wang S, Tooley IR. Photoprotection in the era of nanotechnology. Semin Cutan Med Surg. 2011 Dec;30(4):210-3.
Dr. Jacquelyn Dosal, Dermatologist 