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Phototoxicity of TiO2 Nanoparticles under Solar Radiation to Two Aquatic Species: Daphnia magna and Japanese Medaka
MA, H., A. BRENNAN, AND S. A. DIAMOND. Phototoxicity of TiO2 Nanoparticles under Solar Radiation to Two Aquatic Species: Daphnia magna and Japanese Medaka. ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY. Society of Environmental Toxicology and Chemistry, Pensacola, FL, 31(7):1621-1629, (2012).
One target of development and application of TiO2 nanoparticles (nano-TiO2) is photochemical degredation of contaminants and photo-killing of microbes and fouling organisms. However, few ecotoxicological studies have focused on this aspect of nano-TiO2, specifically whether this photoreactivity might significantly increase hazard and risk of the materials in the natural environment. In this study, we evaluated acute phototoxicity of nano-TiO2 under simulated solar radiation (SSR) to two aquatic species - Daphnia magna and Japanese Medaka, using 48-h and 96-h assays, respectively. A thorough characterization of the exposure system was performed by measuring particle agglomerationand TiO2 concentration in suspension in a time-course manner. Sedimentation and loss of bulk concentration of nano-TiO2 particles occurred at all concentrations above 2 mg/L and was more significant as concentration increased. Phototoxicity of nano-TiO2 under SSR was enhanced by two to four orders of magnitude as compared to toxicity under ambient laboratory light, with a 48-h LC50 of 29.8 µg/L in D. magna and a 96-h LC50 of 2.2 mg/L in Medaka. Our results also indicate that these effects are dependent on simultaneous exposure of the organisms to nanoparticles and SSR. This dramatic increase in toxicity of nano-TiO2 at environmentally-realistic levels of SSR indicates the need for incorporating this mode of action into risk assessment for nano-TiO2 and other photoreactive nanomaterials.
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Record Details:Record Type: DOCUMENT (JOURNAL/PEER REVIEWED JOURNAL)
Organization:U.S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF RESEARCH AND DEVELOPMENT
NATIONAL HEALTH AND ENVIRONMENTAL EFFECTS RESEARCH LAB
MID-CONTINENT ECOLOGY DIVISION
ECOLOGICAL TOXICOLOGY RESEARCH BRANCH