title: Modeling TiO₂ nanoparticle phototoxicity: The importance of chemical concentration, ultraviolet radiation intensity, and time.
abstract: As a semiconductor with wide band gap energy, TiO2 nanoparticles (nano-TiO2) are highly photoactive, and recent efforts have demonstrated phototoxicity of nano-TiO2 to aquatic organisms. However, a dosimetry model for the phototoxicity of nanomaterials that incorporates both direct UV and photo-activated chemical toxicity has not yet been developed. In this study, a set of Hyalella azteca acute toxicity bioassays at multiple light intensities and nano-TiO2 concentrations, and with multiple diel light cycles, was conducted to assess how existing phototoxicity models should be adapted to nano-TiO2. These efforts demonstrated (a) adherence to the Bunsen-Roscoe law for the reciprocity of light intensity and time, (b) no evidence of damage repair during dark periods, (c) a lack of proportionality of effects to environmental nano-TiO2 concentrations, and (d) a need to consider the joint effects of nano-TiO2 phototoxicity and direct UV toxicity.
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: li.shibin@epa.gov.
authors.forename: Shibin
authors.initials: S
authors.lastname: Li
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: Russell J
authors.initials: RJ
authors.lastname: Erickson
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: Stephen A
authors.initials: SA
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: Dale J
authors.initials: DJ
authors.lastname: Hoff
mesh_terms: D033304:Amphipoda / Q000187:drug effects*; D000818:Animals; D002940:Circadian Rhythm; D004305:Dose-Response Relationship, Drug; D004307:Dose-Response Relationship, Radiation; D008962:Models, Theoretical; D053758:Nanoparticles / Q000032:analysis / Q000633:toxicity*; D013997:Time Factors; D014025:Titanium / Q000032:analysis / Q000633:toxicity*; D023382:Toxicity Tests, Acute; D014466:Ultraviolet Rays; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000633:toxicity*
chemical_list: D014874:Water Pollutants, Chemical; C009495:titanium dioxide; D014025:Titanium
keywords: Bunsen-Roscoe photochemical law; Dosimetry model; Hyalella azteca; Nano-TiO(2); Phototoxicity