Human Safety of Sunscreens Containing ZnO and TiO2 UV Filters

The very properties of ZnO and TiO2, which render these metal oxides ideal for application as UV filters, have raised concerns regarding their safety when regularly applied to skin as actives in sunscreens. These concerns are related to the entry of UV filter particles, especially NPs, into the human body through dermal penetration, inhalation, ingestion, and other mechanisms, due to their diminutive sizes, and their potential effects in the body arising due to their high photoactivities, high surface areas, and other properties. This chapter discusses the findings of different studies reported in the literature on the safety of inorganic UV filters in sunscreens related to their propensity to move into the human body and potential to cause biological effects in cells.