Safety of nanoparticles in sunscreens

To the Editor: More than 1000 sunscreen products are marketed in Australia, and an increasing proportion (about one-third) incorporate engineered nanoparticles (ENPs). Defined as manufactured particles having one or more dimensions less than 100 nm (0.00001 cm), ENPs exploit the altered chemical reactivity and other changes that reduction to nanosize elicits. ENPs in sunscreen, such as titanium dioxide (TiO2) and zinc oxides, constitute effective broad-spectrum ultraviolet radiation (UVR) blocking agents with enhanced cosmetic transparency. The Australian Therapeutic Goods Administration (TGA), in approving such products, has stated that “there is no evidence that sunscreens containing these materials pose any risk to the people using them”.1 Similarly, authors of a recent article (written in collaboration with representatives of a cosmetic company) interpret the evidence as confirming that ENPs do not penetrate below the stratum corneum, or only in small amounts, producing limited cellular toxicity.2 Information on sunscreen packaging is not required to disclose the presence of ENPs.