Effect of titanium dioxide nanomaterials and ultraviolet light coexposure on African clawed frogs (Xenopus laevis)

Titanium dioxide nanomaterials (nano-TiO2) exhibit stronger photochemical oxidation/reduction capacity compared with their bulk counterparts, but the effectiveness of nano-TiO2 interaction with ultraviolet (UV) light strongly depends on particle size. In this study, the dependence of nano-TiO2 toxicity on particle size and interaction with UV light were investigated. Toxicity tests with Xenopus laevis included eight concentrations of nano-TiO2 in the presence of either white light or UVA (315400nm). We quantified viability and growth of Xenopus laevis. Results showed that, regardless of UV light exposure, increasing TiO2 concentration decreased X. laevis survival (p<0.05). Coexposure to 5-nm TiO2 and UVA caused near-significant decreases in X. laevis survival (p=0.08). Coexposure to 10-nm TiO2 and UVA significantly decreased X. laevis survival (p=0.005). However, coexposure to 32-nm TiO2 and UVA had no statistical effect on X. laevis survival (p=0.8). For all three particle sizes, whether alone or with UV light, the nano-TiO2 concentrations significantly affected growth of tadpoles as determined by total body length, snoutvent length, and developmental stage. High-concentration TiO2 solutions suppressed tadpole body length and delayed developmental stages. Further research to explore reasons for the growth and mortality in tadpoles is still underway in our laboratory. Given the widespread application of nano-TiO2, our results may be useful in the management of nano-TiO2 released from industrial, municipal, and nonpoint sources. Environ. Toxicol. Chem. 2012;31:176183. (C) 2011 SETAC