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The potential for titanium dioxide (TiO2) and zinc oxide (ZnO) nanoparticles in sunscreens

to cause adverse effects depend primarily upon the ability of the nanoparticles to reach viable

skin cells.

To date, the current weight of evidence suggests that TiO2 and ZnO nanoparticles do not

reach viable skin cells, rather, they remain on the surface of the skin and in the outer layer

(stratum corneum) of the skin that is composed of non-viable, keratinized cells.

seen in these studies (with ZnO) may be due to an UV-induced experimental

Zinc oxide and titanium dioxide have been used as sunscreens for many years. They are

particularly valuable because of their ability to filter UVA as well as UVB radiation, giving

broader protection than other sunscreening agents. One disadvantage of zinc oxide and

titanium dioxide is that they are visible, giving the skin a white colour. This effect can be

reduced by decreasing the particle size of the material. When used in ‘nanoparticle’ form (less

than 100 nanometers, with a nanometer being one millionth of a millimeter), they can’t be

seen on the skin but still retain the sunscreening properties of the coarser material. Nanosized

Titanium dioxide particles have been used in sunscreens since at least 1990 and nanosized

zinc oxide since 1999.

In January 2006 the TGA conducted a review of the scientific literature in relation to the use

of nanoparticulate zinc oxide and titanium dioxide in sunscreens. That review concluded

that:-

(photo-mutagenicity with zinc oxide). However, this would only be of concern in people using

sunscreens if the zinc oxide and titanium dioxide penetrated into viable skin cells. The weight

of current evidence is that they remain on the surface of the skin and in the outer dead layer

(stratum corneum) of the skin

Currently, there is no

in vivo evidence to indicate possible toxicity of nanoparticulate TiO2 or

the skin.