John Wiley & Sons, Ltd.

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

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Toxicity of TiO2 nanoparticles (nano‐TiO2) to aquatic organisms can be greatly increased upon exposure to ultraviolet radiation (UV). This phenomenon has received some attention for water column species; however, investigations of nano‐TiO2 phototoxicity for benthic organisms are still limited. In this 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 to 30 W/m2), H. azteca, with a median lethal dose of 40.7 (95% CI, 36.3–44.7) Wh/m2, was the most sensitive, and hence 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 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 phototoxcity seen in H. azteca and C. dilutus. Overall, this study demonstrated the importance of species sensitivity and exposure scenarios in future test guidelines of nano‐phototoxicity. Environ Toxicol Chem © 2014 SETAC

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