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Environmental fate & pathways

Bioaccumulation: aquatic / sediment

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Description of key information

Prediction with BCFBAF v3.01 (EPIWIN software by US-EPA): 105.50 L/kg wet-wt, bioaccumulation is not very likely.
Prediction with CAESAR QSAR model v1.0.0.11: 142 L/kg, bioaccumulation cannot be excluded.
Prediction with VEGA BCF model v2.1.8: 142 L/kg, OUT of applicability domain

Key value for chemical safety assessment

BCF (aquatic species):
105.5 L/kg ww

Additional information

The bioconcentration factor (BCF) of the test substance was determined by three different QSAR model tools, which are scientifically accepted calculation methods and can therefore be assigned with reliability 2 (reliable with restrictions). No GLP criteria are applicable for the usage of these tools, but the predictions can be used for the chemical safety assessment.

The computer program BCFBAF v3.01 (EPIWIN software) was used as first approach to predict the BCF of the test substance. Furthermore, the whole body primary biotransformation rate estimation for fish was calculated by the same program with the notation that the bio half-life is normalized to 10 g fish at 15 °C. With this result it is possible to predict the apparent metabolism half-life in fish for three different trophic levels (lower, mid and upper). In general, the bioconcentration factor of a substance describes the accumulation potential of a substance dissolved in water by an aquatic organism. BCFBAF v3.01 calculates also the BAF (Bioaccumulation factor) of the chemical, which is defined as the steady-state (equilibrium) ratio of the substance concentration in an organism to the concentration in the surrounding medium. However, this value is not taken into account for the risk assessment and is not relevant for a registration under REACH Regulation (EC) 1907/2006. Using the regression-based estimate (traditional method) of the computer program BCFBAF from US-EPA a Bioconcentration Factor (BCF) of 105.5 L/kg wet-wt was calculated for the test substance.

The whole body primary biotransformation rate estimate for fish results in a half-life of 0.38 days, whereby the bio half-life is normalized to 10 g fish at 15 °C. The rate constant (kM) for 10 g fish is 0.46/day. This is taken into account to predict the apparent metabolism half-life in fish. With the Arnot-Gobas method it is possible to differentiate between three trophic levels. For the lower trophic level the BCF results in 850.60 L/kg wet-wt, for a mid trophic level the result is 776.50 L/kg wet-wt and for the higher trophic level 571.80 L/kg wet-wt. As conclusion it can be stated, that a bioaccumulation in aquatic organisms is unlikely, but cannot be completely excluded.

Another approach for the BCF prediction was performed with the CAESAR QSAR model version 1.0.0.11.This model is based on a dataset of 473 compounds with experimentally determined BCF values extracted from Dimitrov et al. (2005). This dataset was divided into a training set (378 compounds), used to develop the model and a test (95 compounds) used to assess the performance of the model in prediction. The final model is a Neural Network based on 8 molecular descriptors. This procedure is assessed according to the OECD principles (defined endpoint, unambiguous algorithm, defined domain of applicability, appropriate measures of goodness-of-fit, robustness and predictability and mechanistic interpretation). As result, a BCF of 142 L/kg body weight is given for the test substance.

The VEGA BCF model (CAESAR) version 2.1.8 was used as third weight of evidence approach. This model is based on the same data set as CAEASAR and the final model is a Neural Network based on 8 molecular descriptors. As result, a BCF of 143 L/kg body weight is given for the test substance.