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The fate assessment of nanomaterials in municipal sewage treatment plants (STP) is a crucial step for their environmental risk assessment and may be assessed by monitoring full scale STP, dosage to medium scale pilot STP or by laboratory testing. For regulatory purposes preferably standardised test protocols such as the OECD guidelines for testing of chemicals should be used. However, these test protocols have not yet been specifically designed for nanoparticles. Therefore, the fate and behavior of a TiO2 nanomaterial (P25, average hydrodynamic diameter250 nm) was investigated in laboratory sewage treatment plants according to the OECD Guideline for the Testing of Chemicals 303 A. It is concluded that this guideline is applicable for the testing of nanomaterials if modifications regarding the dosage, nitrifying conditions, and a characterisation of the nanoparticles in the effluent are applied. A compilation of the cumulative mass balance by comparison of the total dosage added with the amount in the outflow and in the activated sludge is recommended. In this study, the majority of the TiO2 nanomaterial (95%) was retained in the sewage sludge and only 3-4% was found in the effluent. No effect of the TiO2 nanomaterials on the biodegradation or nitrification was observed.

'Personal Care Products' contain a multitude of substances which introduce certain functions to the product and show a great variability in physicochemical properties. 'Poorly soluble substances', characterised by a low water solubility (< 1 mg/l), may constitute a substantial proportion of these products. Their production volume causes the need for aquatic risk assessment, as requested e.g. by the European Regulation on Registration, Evaluation, Authorisation and Restriction of Chemicals. As it is difficult to conduct toxicity tests at the threshold of the substance's water solubility a high lipophilicity complicates the performance of standardised ecotoxicological tests. For these substances, standard tests mostly provide insufficient results and are often not suitable to assess the risk appropriately. One promising approach to address this problem is the 'poorly solubles approach'. It assumes that highly lipophilic and poorly soluble substances have a low water concentration and consequently might cause low exposure to aquatic organisms. However, as these substances may bioaccumulate high internal exposure might be reached leading to long-term effects. The poorly solubles approach defines an 'ecotoxicological threshold of no concern'. According to the theory, below this concentration, neither acute nor long-term adverse effects on aquatic organisms are expected to occur. This threshold is derived from a comprehensive compilation of experimental data for inert substances with a narcotic mode of action and therefore currently restricted to such substances. Hence, considering this threshold concentration combined with the water solubility of a substance, derived by, e.g. quantitative structure-activity relationships methods, may allow a risk assessment without the need of further experiments. The 'poorly solubles approach' may also become relevant regarding the verification of potential persistent + bioaccumulative + toxic properties. The aim of the project ECOtoxicity investigations of COSMetic ingredients is to develop the 'poorly solubles approach' into a pragmatic tool for risk assessment of the important and environmentally relevant group of highly lipophilic substances with a narcotic mode of action. This project will adapt existing aquatic ecotoxicological test methods using lipophilic compounds to check whether the 'poorly solubles approach' may be useful for risk assessment of such substances.