34ème Congrès Annuel de la SFT - Paris, 20-21 octobre 2008 Nanotechnology, Cosmetics And The Skin: Is There A Health Risk? Gerhard J. Nohynek 1a , Eric K. Dufour 1 and Michael S. Roberts 2 Although cosmetic formulations may contain nano-sized components including nanoemulsions and microscopic vesicles (nanosomes, niosomes or liposomes) consisting of traditional cosmetic materials.Given that such liquid/liquid-based formulations are intrinsically instable, it is uncertain whether they should be qualified as actual nanomaterials . 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 / penetration of ingredients in traditional formulations (solution, gels or creams), nano-sized formulations may enhance or reduce skin absorption of ingredients, albeit at a limited scale. Modern sunscreens contain titanium dioxide (TiO 2 ) or zinc oxide (ZnO) nanoparticles (NP), which filter UV more efficiently than larger particles. The results of a number of studies suggest that insoluble NP do not penetrate into or through human skin. The results of in vivo toxicity tests confirmed that TiO 2 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-genotoxicity, acute toxicity, sensitisation and ecotoxicology studies on TiO 2 NP found no difference in the safety profile of micro- or nano-sized materials, all of which were non-toxic. Although some in vitro investigations on TiO 2 or other insoluble particles reported uptake by cells, oxidative cell damage or genotoxicity, 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 and other insoluble particles support the traditional view of toxicology that toxicity of small particles is generally related to their chemistry, rather than their particle size. There is little evidence supporting a general rule that adverse effects of particles to the skin or other tissues increase with smaller particle size, or produce novel toxicities relative to those of larger particles. Overall, the weight of current scientific evidence suggests that nano-sized cosmetic or sunscreen ingredients pose no or negligible potential risk to human health, whereas their use in sunscreens has large benefits, such as the protection of human skin against skin cancer. |
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