Species sensitivity and dependence on exposure conditions impacting the phototoxicity of TiO2 nanoparticles to benthic organisms

Authors

  • Shibin Li,

    Corresponding author
    1. National Health and Environmental Effects Research Laboratory, Office of Research and Development, Mid-Continent Ecology Division, US Environmental Protection Agency, Duluth, Minnesota, USA
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  • Lindsay K. Wallis,

    1. National Health and Environmental Effects Research Laboratory, Office of Research and Development, Mid-Continent Ecology Division, US Environmental Protection Agency, Duluth, Minnesota, USA
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  • Stephen A. Diamond,

    1. Nanosafe, Blacksburg, Virginia, USA
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  • Hongbo Ma,

    1. National Health and Environmental Effects Research Laboratory, Office of Research and Development, Mid-Continent Ecology Division, US Environmental Protection Agency, Duluth, Minnesota, USA
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  • Dale J. Hoff

    1. National Health and Environmental Effects Research Laboratory, Office of Research and Development, Mid-Continent Ecology Division, US Environmental Protection Agency, Duluth, Minnesota, USA
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Abstract

Toxicity of titanium dioxide nanoparticles (nano-TiO2) to aquatic organisms can be greatly increased after exposure to ultraviolet (UV) radiation. This phenomenon has received some attention for water column species; however, investigations of nano-TiO2 phototoxicity for benthic organisms are still limited. In the present study, bioassays of 3 representative benthic organisms (Hyalella azteca, Lumbriculus variegatus, and Chironomus dilutus) were conducted to evaluate nano-TiO2 phototoxicity. When exposed to 20 mg/L of nano-TiO2 and various light intensities (0–30 W/m2), H. azteca was the most sensitive, with a median lethal dose of 40.7 (95% confidence interval, 36.3–44.7) Wh/m2, and hence is a potential model organism in future toxicological guidelines for photoactive nanomaterials to freshwater benthos. Without the presence of nano-TiO2, no mortality was observed in L. variegatus and C. dilutus exposed to UV intensity ranging from 0 W/m2 to 41 W/m2. However, a sharp drop of H. azteca survival was observed when UV intensity was higher than 9.4 W/m2, demonstrating the importance of UV-only effects on the ultimate phototoxicity of nanomaterials. Furthermore, both bioavailability and surface attachment of nano-TiO2 onto organisms were affected by the exposure scenario, supported by the exposure scenario–dependent phototoxicity seen in H. azteca and C. dilutus. Overall, the present study demonstrates the importance of species sensitivity and exposure scenarios in future test guidelines of nano-phototoxicity. Environ Toxicol Chem 2014;33:1563–1569. © 2014 SETAC

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