For at least the last several years, NGO’s like Friends of the Earth (FoE) have been leveraging preliminary studies that indicated that nanoparticles might pass right through our skin to call for a complete moratorium on the use of any nanomaterials in sunscreens and cosmetics.
Even if you’re a world-renowned expert on assessing the risk of nanomaterials, you had better not challenge the orthodoxy of that line of thinking. Or if you’re an NGO that investigated the issue of nanoparticles in sunscreens and found no risk, you should be prepared to be so marginalized by other NGOs that you will hardly warrant a mention.
On the contrary, the prevailing argument was that if you’re a company using nanoparticles in your sunscreen you had to prove your product was safe, even if there was no conclusive evidence that your product was risky and a fair amount of evidence that it was safe. So frightening and compelling was this scare screed that in a poll of Australians they said they would prefer to risk getting skin cancer rather than use a sunscreen that might contain nanoparticles. Fear almost always wins out over reason.
Unfortunately for the fear mongers, the evidence is mounting that nanoparticles cannot penetrate the skin. Researchers at the University of Bath in the UK found that even the smallest nanoparticles are not capable of passing through the skin barrier.
The research, which was published in the Journal of Controlled Release (“Objective assessment of nanoparticle disposition in mammalian skin after topical exposure”), employed laser scanning confocal microscopy to see whether fluorescently tagged polystyrene beads on the scale of 20 to 200 nanometers were absorbed into the skin.
“Previous studies have reached conflicting conclusions over whether nanoparticles can penetrate the skin or not,” says Professor Richard Guy from the University’s Department of Pharmacy & Pharmacology, in the press release. “Using confocal microscopy has allowed us to unambiguously visualize and objectively assess what happens to nanoparticles on an uneven skin surface. Whereas earlier work has suggested that nanoparticles appear to penetrate the skin, our results indicate that they may in fact have simply been deposited into a deep crease within the skin sample.”
This latest UK research certainly won’t put this issue to rest. These experiments will need to be repeated and the results duplicated. That’s how science works. We should not be jumping to any conclusions that this research proves nanoparticles are absolutely safe any more than we should be jumping to the conclusion that they are a risk. Science cuts both ways.
Dexter Johnson is a contributing editor at IEEE Spectrum, with a focus on nanotechnology.