Sunscreens as a Source of Hydrogen Peroxide Production in Coastal Waters.

Sunscreens have been shown to give the most effective protection for human skin from ultraviolet (UV) radiation. Chemicals from sunscreens (Le., UV filters) accumulate in the sea and have toxic effects on marine organisms. In this report, we demonstrate that photoexcitation of inorganic UV filters (i.e., TiO2, and ZnO nanoparticles) under solar radiation produces significant amounts of hydrogen peroxide (H202), a strong oxidizing agent that generates high levels of stress on marine phytoplankton. Our results indicate that the inorganic oxide nanoparticle content in 1 g of commercial sunscreen produces rates of H202 in seawater of up to 463 nM/h, directly affecting the growth of phytoplankton. Conservative estimates for a Mediterranean beach reveal that tourism activities during a summer day may release on the order of 4 kg of T i0 2 nanoparticles to the water and produce an increment in the concentration of H202 of 270 nM/day. Our results, together with the data provided by tourism records in the Mediterranean, point to Ti02 nanoparticles as the major oxidizing agent entering coastal waters, with direct ecological consequences on the ecosystem. [ABSTRACT FROM AUTHOR]