Safety of Nanotechnology in Sunscreens and Personal Care Products

Abstract

Persona] care product or sunscreen formulations may contain nano-sized components including nanoemulsions and microscopie vesicles consisting of traditional cosmetic materials. Numerous studies suggest that vesicle materials do not penetrate human skin beyond the superficial layers of the stratum corneum. When compared with the skin absorption I penetration of ingredients of traditional formulations (solution , gels, creams), nano-sized formulations may enhance or reduce skin absorption of ingredients, albeit at a limited scale. Modem sunscreens contain sol id titanium dioxide (Ti02) or zinc ox ide (ZnO) nanoparticles (NP) that filter UV more efficiently than larger particles. A series of studies suggest that insoluble NP do not penetrate into or through normai or compromised human skin. In vivo toxicity tests confirmed that Ti02 and ZnO NP are non-toxic, biologically inert and have a good skin tolerance. A series of in vitro and in vivo cytotoxicity, genotoxicity, photo-genetic, pulmonary or acute toxicity, sensitisation and ecotoxicity studies on Ti02 NP found no difference in the safety profile of micronor nano-sized materials, ali of which were non-toxic.
Some in vitro investigations on Ti02 or other insoluble particles reported cell uptake, oxidative cell damage or genotoxicity; however, such data should be interpreted with caution since they may be secondary to phagocytosis of cells exposed to excessive concentrations of insoluble particles. Data from studies on surgical implant-derived wear debris nano- and micro-particles or other insoluble particles support the traditional view of toxicology that their toxicity is generally related to their chemistry, rather than their particle size. At present, there is no evidence for a rule that adverse effects of particles to the skin or other tissues increase with smaller particle size or produce nove! toxicities. Overall, the weight of current scientific evidence suggests that nano-sized persona! care or sunscreen ingredients pose no or negligible potential risk to human health, whereas their use in sunscreens has significant benefits including protection of human skin against skin cancer.