The toxicity of titanium dioxide nanopowder to early life stages of the Japanese medaka (Oryzias latipes) Gordon Paterson a,⇑ , Jamie M. Ataria b , M. Ehsanul Hoque a , Darcy C. Burns a,1 , Chris D. Metcalfe a a Worsfold Water Quality Centre, Trent University, Peterborough, Ontario, Canada K9J 7B8 b Landcare Research, Lincoln 7640, New Zealand article info Article history: Received 7 June 2010 Received in revised form 7 October 2010 Accepted 21 October 2010 Available online 11 November 2010 Keywords: Agglomeration Chronic toxicity Hatching Japanese medaka Titanium dioxide abstract In this study, fertilized Japanese medaka (Oryzias latipes) embryos were exposed from fertilization to 5 d post-hatch using static non-renewal assays to aqueous suspensions of titanium dioxide nanoparticles (nTiO 2 ) ranging in nominal concentrations between 0 and 14 lg mL 1 . The average size of the nTiO 2 in the stock solution before addition to the test treatments was 87 nm (±14 nm). TiO 2 materials accumu- lated in a concentration dependent manner on the chorionic filaments of developing medaka embryos with evidence of pericardial edema occurring during embryo development. However, no significant (p > 0.05) increases in mortality relative to control treatments were observed for the nTiO 2 exposed embryos. A concentration dependent increase in cumulative percent hatch was observed at 11 d, indicat- ing that exposure to increasing concentrations of nTiO 2 resulted in the premature hatch of medaka embryos. Post-hatch, a significant proportion of sac fry from the nTiO 2 exposure groups exhibited mor- ibund swimming behavior and these individuals also experienced greater mortality at 15 d post-hatch. Combined, these results demonstrate that exposure to nTiO 2 can impact the development of early life stages of fish. Ó 2010 Elsevier Ltd. All rights reserved. 1. Introduction Engineered nanoparticles (ENPs) are being used in a growing number of commercial materials, industrial pigments, antimicro- bial agents, and personal care products, and in biomedical applica- tions (Dunphy Guzman et al., 2006). Of these materials, metal oxide nanoparticles including nanoparticulate titanium dioxide (nTiO 2 ), zinc oxide (nZnO), and iron oxides (nFe 2 O 3 ), are among those produced in the highest volume, and thus have the greatest potential for release into the environment, including surface waters that receive industrial and municipal effluents (Pitkethly, 2004; Klaine et al., 2008). However, relatively little is known regarding the magnitude of ENP release and exposure to organisms living in impacted aquatic environments, as well as the potential for toxic effects to aquatic species. Due to its ultraviolet absorptive capacity, nTiO 2 has been widely used as a photocatalyst in solar cells and industrial coatings, and also in personal care products including sunscreens and cosmetics (Kaida et al., 2004). This photocatalytic capacity of nTiO 2 is also critical to its application as a bactericidal agent as the formation of reactive oxygen species during irradiation promotes the peroxi- dation of membrane lipid constituents, resulting in cell senescence (Maness et al., 1999). ENPs such as nTiO 2 have the ability to induce the formation of reactive oxygen species leading to the onset of oxidative stress in exposed animal tissues (Limbach et al., 2007; Yeo and Kang, 2009). Engineered nanoparticles have similar dimension to many biological molecules, including proteins, DNA, and membrane transport proteins, and thus possess the abil- ity to interfere at cellular and molecular scales (Metcalfe et al., 2009). Additional evidence has indicated that nTiO 2 preparations may induce physical damage to intestinal and respiratory epithelia in exposed fish species (Federici et al., 2007; Handy et al., 2008). These studies indicate that for ENPs such as nTiO 2 , there are multi- ple mechanisms for toxicity (Metcalfe et al., 2009). It has been demonstrated that nTiO 2 has the potential to induce chronic sub-lethal effects in early life stages of vertebrates (Federici et al., 2007; Warheit et al., 2007). To date, however, there has been little research on the toxicity of nTiO 2 to the early life stages of fish species. Due to the relatively high degree of cell dif- ferentiation and tissue organization occurring during embryonic development, the early life stages of fish are a sensitive risk group for the impacts of exposure to ENPs. Thus, it is of critical impor- tance to investigate the effects of ENP exposure during this life his- tory stage of a fish species. In this study, early life stages of the 0045-6535/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.chemosphere.2010.10.068 ⇑ Corresponding author. Present address: Great Lakes Institute for Environmental Research, University of Windsor, Windsor, Ontario, Canada N9B 3P4. E-mail address: gpaters@uwindsor.ca (G. Paterson). 1 Present address: Department of Chemistry, University of Toronto, Toronto, Ontario, Canada M5S 3H6. Chemosphere 82 (2011) 1002–1009 Contents lists available at ScienceDirect Chemosphere journal homepage: www.elsevier.com/locate/chemosphere