Synergistic toxic effect of nano-TiO 2 and As(V) on Ceriodaphnia dubia

Abstract

Due to the active development and application of nanotechnology, engineered nanomaterials (ENMs) are becoming a new class of environmental pollutants that may significantly impact the environment and human health. While many toxicity investigations have been conducted, there is little information about the synergistic effect of ENMs and other toxic compounds in the environment. In order to extend this knowledge, the combined effect of TiO 2 nanoparticles (n-TiO 2) and As(V) were investigated. High concentrations of As(V) can accumulate on the n-TiO 2 surface. Cultured Ceriodaphnia dubia (C. dubia) species were used to examine the synergistic toxic effect through exposure to 1) n-TiO 2 suspensions, 2) As(V) solutions, and 3) mixtures of n-TiO 2 and As(V) suspensions. Results showed that n-TiO 2 alone was not toxic when the concentration was less than 400 mg/L and that the 24-hour median lethal concentration (LC 50) of As(V) alone was 3.68 ± 0.22 mg/L. However, in the presence of low concentrations of n-TiO 2, the toxicity of As(V) increased significantly. At the same initial As(V) concentration, the toxicity of n-TiO 2 first increased, reached a maximum, and then decreased with an increase in n-TiO 2 concentration. Hydrodynamic size and sorption capacity were most important parameters for toxicity.