Nanoparticles in my sunscreen ... should I be worried?

Sunscreens play an important role in protecting our skin from the harmful UVA and UVB rays emitted by the Sun. Their use has been proven to help prevent certain skin cancers, including melanomas and basal cell carcinomas.

In recent years there has been some concern about nanoparticles in sunscreens. This relates particularly to zinc oxide (ZnO) and titanium dioxide (TiO₂) nanoparticles and their ability to penetrate the skin to reach cells and the potential toxicity exerted by these chemicals.

Nanoparticles are particles between 1 and 100 nanometres (nm) in size. A nanometre (nm) is 10⁻⁹, which is one-thousandth of a micrometre, or one-billionth of a metre. This is the scale at which we measure atoms and the molecules they make.

To give you some idea of the nanoscale, a strand of DNA is 2.5 nm in diameter, while a red blood cell is about 7000 nm wide. Need a few more examples? A human hair is around 75,000 nanometres thick, while a pinhead is around a million nanometres wide. So, the particles we’re talking about in your sunscreen are very, very small.

The position of the Australian Therapeutic Goods Administration (TGA), based on several published papers (up to May 2013) as well as reviews of international authorities, is that nanoparticles are safe. ‘Several in vitro and in vivo studies using both animal and human skin have shown that these NPs do not penetrate the underlying layers of skin, with penetration limited to the stratum corneum. This suggests that systemic absorption is unlikely.’

A further study published in 2014 found that when exposed to zinc oxide nanoparticles, human immune cells (called macrophages) effectively absorbed the nanoparticles and broke them down.

Based on current evidence, neither zinc oxide nor titanium dioxide nanoparticles are likely to cause harm when used as ingredients in sunscreens. There are more risks associated with avoiding sunscreens (sunburn, skin cancers) than those posed by nanoparticles.

As summer approaches, you can feel confident that your sunscreen is safe when applied as directed (and preferably every day). To give yourself the best sun protection, don’t forget to Slip on a shirt, Slop on the 30+ sunscreen, Slap on a hat, Seek shade or shelter and Slide on some sunnies.