Environmental hazard of selected TiO 2 nanomaterials under consideration of relevant exposure scenarios

In the last decades the production and use of nanomaterials, such as titanium dioxide nanomaterials (nano-TiO2), increased extensively. To support a sustainable nanotechnology, it is essential to investigate the environmental risks of nanomaterials. However, it remains unclear whether in the context of the European Chemical Regulation Registration, Evaluation, Authorization and Restriction of Chemicals (REACH) the nano and bulk form of a substance have to be registered separately or not, and if parameters considered with approved and standardized test guidelines (OECD) are sufficient to describe the potential environmental implications of manufactured nanomaterials. These guidelines do not consider relevant exposure scenarios such as solar radiation and mixture toxicity which might be of special importance for manufactured nanomaterials, including nano-TiO2 which is known to be photoactive and to adsorb organic co-contaminants. Therefore, we conducted water flea tests with nano-TiO2 (Daphnia magna, OECD 202) under laboratory light (LL) and simulated solar radiation (SSR) and examined the potential mixture toxicity of nano-TiO2 materials and the organic antimicrobial substance triclocarban to earthworms (Eisenia fetida, OECD 207 and 222), daphnids, fish embryos (Danio rerio OECD 236) as well as to activated sludge (OECD 209). Different sized uncoated, anatase TiO2 materials were tested to account for particle size specific effects (nanomaterials: NM 101, 7-10 nm and NM 102, 15-25 nm; bulk: NM 100, 200-220 nm). Furthermore, we investigated: a) whether the ionic strength of the test medium has an influence on the outcome of Daphnia sp. acute immobilisation tests of nano-TiO2 materials; b) whether solar radiation influences the aquatic toxicity of TCC and the extent of potential mixture toxicity of nano-TiO2 and organic co-contaminants; c) whether TCC has an effect on the reproduction of earthworms; d) whether oxidative stress was induced in earthworms by nano-TiO2, TCC and mixtures of both. We showed that in ...