Nanoparticles and sunscreen

Skin cancer, including melanoma and non-melanoma, is Australia's most common cancer. Regular sunscreen use has been proven to prevent basal cell carcinomas and melanomas.

Nanotechnology has been used in sunscreens for many years. To date, our assessment, drawing on the best available evidence, is that nanoparticles used in sunscreens do not pose a risk. However, we continue to monitor research and welcome any new research that sheds more light on this topic.

Sunscreen formulas and their components are regulated through the Therapeutic Goods Administration (TGA). The TGA has conducted a review of the scientific literature in relation to the use of nanoparticle zinc oxide and titanium dioxide in sunscreens.

The TGA's report concerning the safety of sunscreens can be found here.

The TGA review concluded that:

• The potential for titanium dioxide and zinc oxide nanoparticles in sunscreens to cause adverse effects depends primarily upon the ability of the nanoparticles to reach viable skin cells.
• To date, the current weight of evidence suggests that titanium dioxide and zinc oxide nanoparticles (commonly used sunscreen active ingredients) do not reach viable skin cells; rather, they remain on the surface of the skin and in the outer layer of the skin that is composed of non-viable cells.

Since the TGA's review, more recent research into nanoparticles has been undertaken in Australia. A study published in early 2014 exposed human immune cells (called macrophages) to zinc oxide nanoparticles to see how they would respond. The study showed that the human immune system effectively absorbed the nanoparticles and broke them down.

The study did not look at whether the particles are absorbed through the skin and into the bloodstream. The current available evidence indicates that this does not happen and the particles remain on the surface of the skin.

Cancer Council looks closely at TGA's advice, as well as our own evidence-based reviews.

Sunscreens also use "microfine" or "micronised" particles, which are larger than nanoparticles:

• Nanoparticles are smaller than 100 nanometres and invisible to the human eye - a nanometre is 0.000001 millimetre.
• Microfine particles are smaller than those used in conventional white zinc sunscreens, however, are larger than nanoparticles - usually in the range of 100 to 2500 nanometres.

In the manufacturing process used to produce microfine particles, some particles can inadvertently be ground smaller, ending up being classified as nano-sized. Manufacturers advise this is a small percent and does not classify the sunscreen as nano-based.