Whilst the results of this lab study study are interesting, more studies are needed reflecting real life conditions before any conclusions about the safety of nano zinc oxide in sunscreen can be drawn. Importantly, the paper draws no conclusions about the safety of nano-ingredients in sunscreen and also doesn’t look at other nano sunscreen ingredients such as titanium dioxide and cerium oxide.
The study found that when white blood cells are exposed to zinc oxide nanoparticles in the lab they absorb some of them and some of the particles dissolve. Only one white blood cell was looked at for this analysis. It is completely inappropriate to make inferences about safety based on the results of one in vitro study.
What the study does acknowledge is that nano-ingredients can penetrate the skin and get into the bloodstream. This is something our sunscreen regulator the Therapeutic Goods Administration has so far denied.
The view that nano-ingredients in sunscreen are safe is not shared by the European Commission’s Scientific Committee on Consumer Safety. This body recently recommended that certain nano titanium dioxide (TiO2) ingredients not be used in sunscreen because they strongly react with sunlight to produce free radicals and that nano TiO2 and nano zinc oxide (ZnO) not be used in powder or sprayable products because of the toxicity risk associated with inhalation.
A recent Italian study using pig ear skin found that nano titanium dioxide damaged the outer layer of skin. The researchers warned that this could allow nanoparticles and other unwanted chemicals to penetrate the skin – posing a potential human health risk.
The European Chemical Agency (ECHA) is currently reviewing the safety of titanium dioxide (including the nano form) because of concerns in may be harmful to the environment and human health. Meanwhile our regulators here have taken no action to remove these ingredients from sunscreen.