Following use, nanomaterials may be released to the natural environment and distributed to various environmental components. They may affect a variety of organisms including aquatics, which illustrates the importance of aquatic nanotoxicology studies. Currently the most produced engineered nanomaterial is TiO2 with up to 10,000 ton of worldwide production. The aim of the present work was to study the toxicity of dispersed TiO2 nanoparticles (nTiO2) in an aquatic planktonic crustacean, Daphnia magna. Acute (48 hour) and chronic (21 day) toxicology tests were conducted in accordance to the OCED standard guidelines. According to the results of short term experiments, although the nTiO2 particles were highly ingested by the D. magna and accumulated under the carapace and on the external body surfaces, but these particles was non lethal to Daphnia, even up to a concentration of 200 mg/L. Thus it was not possible to estimate the 48h LC50 (median lethal concentration). However, according to the results of long term studies, nTiO2 (at tested concentrations of 25, 50, and 100 mg/L) have toxic effects to Daphnia such as increased mortality, growth retardation, and reduce the number of offspring. In general, the results show the importance of test duration in nano-ecotoxicology studies, especially in the case of nanomaterials such as nTiO2 which don’t show their toxicity in short term.
