title: Impact of solar UV radiation on toxicity of ZnO nanoparticles through photocatalytic reactive oxygen species (ROS) generation and photo-induced dissolution.
abstract: The present study investigated the impact of solar UV radiation on ZnO nanoparticle toxicity through photocatalytic ROS generation and photo-induced dissolution. Toxicity of ZnO nanoparticles to Daphnia magna was examined under laboratory light versus simulated solar UV radiation (SSR). Photocatalytic ROS generation and particle dissolution were measured on a time-course basis. Two toxicity mitigation assays using CaCl2 and N-acetylcysteine were performed to differentiate the relative importance of these two modes of action. Enhanced ZnO nanoparticle toxicity under SSR was in parallel with photocatalytic ROS generation and enhanced particle dissolution. Toxicity mitigation by CaCl2 to a less extent under SSR than under lab light demonstrates the role of ROS generation in ZnO toxicity. Toxicity mitigation by N-acetylcysteine under both irradiation conditions confirms the role of particle dissolution and ROS generation. These findings demonstrate the importance of considering environmental solar UV radiation when assessing ZnO nanoparticle toxicity and risk in aquatic systems.
authors.affiliation: U.S. Environmental Protection Agency, Office of Research and Development, National Health and Environmental Effects Research Laboratory, Mid-Continent Ecology Division, Duluth, MN, USA. Electronic address: hongboma@uwm.edu.
authors.forename: Hongbo
authors.initials: H
authors.lastname: Ma
authors.affiliation: U.S. Environmental Protection Agency, Office of Research and Development, National Health and Environmental Effects Research Laboratory, Mid-Continent Ecology Division, Duluth, MN, USA.
authors.forename: Lindsay K
authors.initials: LK
authors.lastname: Wallis
authors.affiliation: Nanosafe Inc., Blacksburg, VA, USA.
authors.forename: Steve
authors.initials: S
authors.lastname: Diamond
authors.affiliation: U.S. Environmental Protection Agency, Office of Research and Development, National Health and Environmental Effects Research Laboratory, Mid-Continent Ecology Division, Duluth, MN, USA.
authors.forename: Shibin
authors.initials: S
authors.lastname: Li
authors.affiliation: Texas Tech University, Department of Environmental Toxicology, Lubbock, TX, USA.
authors.forename: Jaclyn
authors.initials: J
authors.lastname: Canas-Carrell
authors.affiliation: Texas Tech University, Department of Environmental Toxicology, Lubbock, TX, USA.
authors.forename: Amanda
authors.initials: A
authors.lastname: Parra
mesh_terms: D000818:Animals; D002384:Catalysis; D003621:Daphnia / Q000187:drug effects* / Q000502:physiology / Q000528:radiation effects*; D008027:Light; D053758:Nanoparticles / Q000737:chemistry / Q000633:toxicity*; D055668:Photochemical Processes; D017382:Reactive Oxygen Species / Q000378:metabolism*; D012995:Solubility; D014466:Ultraviolet Rays; D015034:Zinc Oxide / Q000737:chemistry / Q000633:toxicity*
chemical_list: D017382:Reactive Oxygen Species; D015034:Zinc Oxide
keywords: Photo-induced dissolution; Reactive oxygen species (ROS); Toxicity; UV radiation; ZnO nanoparticles