title: Phototoxicity of TiO₂ nanoparticles to a freshwater benthic amphipod: are benthic systems at risk?
abstract: This study investigated phototoxicity of TiO₂ nanoparticles (nano-TiO₂) to a freshwater benthic amphipod (Hyalella azteca) using 48-h and 96-h bioassays. Thorough monitoring of particle interactions with exposure media (Lake Superior water, LSW) and the surface of organisms was performed using dynamic light scattering, UV/Vis spectroscopy, and Scanning Electron Microscopy. Large agglomeration and sedimentation (>77%) in LSW was observed after 0.5h. A simulated solar radiation (SSR)-favored surface attachment of nanoparticles was observed, indicating enhanced phototoxicity with the increased attachment. A 96-h median lethal concentration (LC50) of 29.9 mg/L in H. azteca was calculated, with a daily 4-h UV exposure of 2.2 W/m(2). Phototoxicity of nano-TiO₂ under SSR had a 21-fold increase as compared to that under ambient laboratory light. This phototoxicity was also dependent on UV dose, with calculated LC50s around 22.9 (95% CI, 20.5-23.3)Wh/m(2) when exposed to 20 mg/L nano-TiO₂. Also, H. azteca exhibited negative phototaxis in the presence of shelters, indicating that other factors might play a role in environmental systems. Finally, the environmental implications of nano-TiO₂ to benthic organisms were illustrated, emphasizing the importance of various environmental factors in the ultimate phototoxicity. This increased phototoxicity and its complex interactions with various environmental factors suggest further investigations are needed for future risk assessment of photoactive nanomaterials to benthic organisms.
authors: 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: li.shibin@epa.gov.
authors: Shibin
authors: S
authors: Li
authors: Lindsay K
authors: LK
authors: Wallis
authors: Hongbo
authors: H
authors: Ma
authors: Stephen A
authors: SA
authors: Diamond
mesh_terms: D033304:Amphipoda / Q000187:drug effects*; D000818:Animals; D004784:Environmental Monitoring; D005618:Fresh Water / Q000032:analysis; D007928:Lethal Dose 50; D008855:Microscopy, Electron, Scanning; D053758:Nanoparticles / Q000633:toxicity*; D013056:Spectrophotometry, Ultraviolet; D013997:Time Factors; D014025:Titanium / Q000633:toxicity*; D014466:Ultraviolet Rays; D014874:Water Pollutants, Chemical / Q000633:toxicity
chemical_list: D014874:Water Pollutants, Chemical; C009495:titanium dioxide; D014025:Titanium
keywords: Benthic organisms; Environmental factors; Hyalella azteca; Nano-TiO(2); Negative phototaxis; Phototoxicity