Are Sunscreens with Nanoparticles of Zinc Oxide Safe?
Products using nanotechology and materials has become more and more common. Zinc oxide (ZnO) and titanium dioxide (TiO2) are used in nanoparticle size in sunscreens. They provide physical blocks from the harmful UVA and UVB rays, protecting the skin from photo-damage which is known to cause skin cancers.
One nanometer (nm) is roughly 100,000 times smaller than a human hair. The physical and chemical properties of nanoscale materials, such as reactivity, persistence, or bioavailability, can differ significantly from their larger scale counterparts. This is the concern of the group Friends of the Earth who feel that sunscreens with nanoparticles are a risk to your health and urge you not to use them.
Zinc oxide and titanium dioxide nanoparticles used in sunscreens range in the 20 – 30 nm size. Their use in sunscreen has become popular as the nanoparticles appear transparent when applied to the skin rather than an opaque white cover. This transparency makes the sunscreen much more cosmetically acceptable than the larger-particle ZnO and TiO2 use.
While the FOTE quote a recent Australian study by Macquarie University's Professor Brian Gulson as evidence that sunscreens using nano-ZnO are potentially hazardous due to absorption into the blood stream through the skin, Gulson in an interview notes that his study doesn't shed any light on the question of whether the nano-particles themselves played a part in the zinc absorption. “That was the most critical thing. This isotope technique cannot tell whether or not it's a zinc oxide nano-particle that got through skin or whether it's just zinc that was dissolved up in contact with the skin and then forms zinc ions or so-called soluble ions. So that's one major deficiency of our study.”
Other studies not mentioned by FOTE suggest the case for safe, non-penetrating, transparent, topical ZnO sunscreen formulations appears to be strengthening as the one by Sheree Cross and colleagues.
Another concern in the use of nanoparticles in sunscreens is the exposure of the body due to oral and nasal uptake due to application to the lips and mouth area, around the nose, and via contact with sunscreened hands and food.