Toxicity of TiO2 nanoparticles to cladocerans, algae, rotifers and plants - Effects of size and crystalline structure

With the rapid development of nanotechnology, there is an increasing risk of human and environmental exposure to nanotechnology-based materials. However, the data on the potential environmental effects of nanoparticles are scarce. The aim of this study is to assess the effect of particle size and crystal structure (anatase and rutile) of titanium dioxide on their toxicity. Thus, acute and chronic toxicity tests included a modified acute test (72 h) using daphnies and algae, rotifers and plants as model organisms. Gradient of toxicity varied with the tested biological organisms. Our results revealed that TiO2 nanopartides in anatase crystal structure are toxic in the entire set of tests conducted. However, at high concentration, through their antimicrobial properties, they significantly promoted growth of roots. Because of its lipophilicity, the rutile crystalline structure of TiO2 NPs form larger aggregates in aqueous medium; then they have less effect on biological organisms, and thus a lower toxicity than the anatase crystalline form of TiO2. We also demonstrated that exposure duration, aggregation and concentrations are contributing factors in nanoparticles-mediated toxicity. (C) 2012 Elsevier Ltd. All rights reserved.