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Biodegradation in water and sediment: simulation tests

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According to EC 1907/2006, Annex IX, Column 2, testing for this endpoint is not required if the substance is highly insoluble in water.

Furthermore, Amides, C16-C18 (even), N,N'-ethylenebis is not readily biodegradable (5.5% after 28 days, OECD 301B) and has a high potential for adsorption to soil particles as indicated by log Koc values of 7.87 – 8.91 calculated for the main substance components (KOCWIN v2.00). The substance characteristics indicate that the substance will be removed from waste water in the primary settling tank of fat trap of STPs and only insignificant amount of substance will get in contact with the activated sludge organisms. The remaining substance will be absorbed by activated sludge. The available activated sludge respiration inhibition test determined no adverse effects of the substance on microbial activity. An inhibition of the degradation process by the substance is not expected. Therefore, the substance concentration in STP effluents is expected to be negligible.  Consequently, the exposure concentrations and the availability of the substance in the sediment compartment are low. Abiotic degradation by hydrolysis is not expected at environmentally relevant conditions but a photolytic half-life of 0.076 - 0.083 days was calculated for the main substance (AOPWIN v1.92, based on 24-h day). Additionally, a calculation using the Ready biodegradability model (version 1.0.9, Vega v1.1.4 software) was conducted for the main substance components. The prediction for the components was possibly ready biodegradable. The components of the target substance could be out of the applicability domain of the model. For all constituents only moderate similar substances with known experimental values in the training set have been found. The accuracy of prediction for similar substances found in the training set is not optimal for the components. However, the calculation indicates a possible biodegradability and thus a limited potential for persistence. Comparable results were found using the BIOWIN v4.10 model (EPI suite v 4.11). The single models do not predict a ready biodegradability of the substance but predict biodegradation over “days” or “weeks to months”. These predictions can be taken as an indication of a non-persistence. Based on the criteria set out in the “Guidance on information requirements and chemical safety assessment, Chapter R.11: PBT Assessment” (ECHA, 2017) the substance is not bioaccumulative. Because, based on the physico/chemical properties of Amides, C16-C18 (even), N,N'-ethylenebis such as low water solubility and high potential for adsorption a reduced availability in water is expected. An experimentally derived BCF of <6.2 for the substance indicates a low bioaccumulation potential of the substance. QSAR calculations performed for the main substance components with the VEGA software models CAESAR v2.1.14, Meylan v1.0.3 and: Read-Across v1.1.0 (Vega version 1.1.4) indicate a low bioaccumulation potential of the substance. All three models predict a low bioaccumulation potential for the main substance components. The CAESAR model v2.1.14, estimated BCF values of 2 - 3 L/kg for the main substance components. The predicted BCF values by Meylan v1.0.2 ranged from 5 - 46 L/kg and the calculation with the Read-Across v1.0.2 model resulted in BCF values of 11.75 - 53.33 L/kg. Though the components are outside the applicability domain of the model and the results may not be fully reliable, the results support the experimentally derived low BCF of the substance. Thus, if bioaccumulation is excluded, the evaluation of the persistence (P) is not relevant and the overall evaluation result is “not PBT” as well as “not vPvB”.

Summary: because: a) significant removal from the water column by adsorption to sewage sludge b) the absence of inhibitory effects on degradation process in commercial sewage treatment plants, and c) a possible degradation was predicted for the main components, and d) exposure of the sediment compartment is not expected, a study on biodegradation in sediment was not performed.