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

Abstract

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 (315–400 nm). 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, snout–vent 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;31:176–183. © 2011 SETAC