Zinc oxide (nano form)

6. Are sunscreens using zinc oxide nanoparticles safe?

The available evidence suggests that zinc oxide nanoparticles are safe to use as the UV filter in sunscreens applied to the skin. The committee judges that this is true for products containing up to 25 per cent of ZnO nanoparticles, and confirms that it still holds for products which contain larger particles of ZnO.

The nanoparticles themselves do not appear to penetrate the skin. They release a small amount of zinc into the sunscreen’s formulation, and a portion of this solubilized zinc might be absorbed through the skin. The amounts involved are small compared with the amount of zinc normally in the body. The test results, taken as a whole, suggest that if there is any skin penetration it is probably by zinc ions released from ZnO nanoparticles, rather than the particles themselves. This indicates that the solubility of ZnO is a key factor when it is prepared for use as an ingredient in sunscreens.

The conclusion of the safety assessment performed by the SCCS applies to ZnO nanoparticles (coated and uncoated) for which data was available in the dossier submitted to the committee. Any new coatings intended for use in cosmetics or sunscreens will need additional tests in case they promote skin penetration of nanoparticles.

There is evidence that ZnO nanoparticles can cause inflammation in the lungs if they are inhaled. This means that any products which spray such particles cannot be considered safe at present.

ZnO as a colorant in cosmetic products applied to the skin is also considered safe for use.

The assessment of ZnO does not imply that any other nanoparticles are necessarily safe, and other products containing different substances in nano form will still require separate case by case assessment. This will also depend on adding to currently available knowledge through development of more refined methods which are now evolving for assessing nanoparticles. These will go beyond those we now rely on which were originally developed for testing substances in non-nano form.