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

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 sub(2) nanoparticles (n-TiO sub(2)) and As(V) were investigated. High concentrations of As(V) can accumulate on the n-TiO sub(2) surface. Cultured Ceriodaphnia dubia (C. dubia) species were used to examine the synergistic toxic effect through exposure to 1) n-TiO sub(2) suspensions, 2) As(V) solutions, and 3) mixtures of n-TiO sub(2) and As(V) suspensions. Results showed that n-TiO sub(2) alone was not toxic when the concentration was less than 400mg/L and that the 24-hour median lethal concentration (LC50) of As(V) alone was 3.68 plus or minus 0.22mg/L. However, in the presence of low concentrations of n-TiO sub(2), the toxicity of As(V) increased significantly. At the same initial As(V) concentration, the toxicity of n-TiO sub(2) first increased, reached a maximum, and then decreased with an increase in n-TiO sub(2) concentration. Hydrodynamic size and sorption capacity were most important parameters for toxicity.