Dioctadecyl ether

Bioaccumulation: aquatic / sediment

Description of key information

Significant accumulation of the test item (dioctadecyl ether, CAS 6297-03-6) in organisms is not to be expected.

Additional information

A log Kow of 16.76 was estimated for the molecule, indicating potential for bioaccumulation. However, according to the REACH Guidance Document R11 (PBT Assessment), the BCF of substances with a log Kow of > 10 is probably lower than 2000 L/kg. Due to the lack of experimental data, the assessment of the bioaccumulation potential will be evaluated in a weight-of-evidence approach. Estimations of the BCF were performed with three different models.

- A BCF calculation using the CATALOGIC v.5.11.6 BCF base-line model v02.05 is available for dioctadecyl ether (CAS 6297-03-6). The BCF model calculates a BCF of 9.2 (log BCF = 0.96) using the estimated log Kow value of 16.76 and the estimated water solubility of 2.5E-012 mg/L. Furthermore, the influence of mitigating factors like ionization of the molecule, water solubility, size and metabolism are also considered by the model. Taking into account these mitigating factors the BCF is reduced to 7.4 (log BCF = 0.87), mainly due to the low water solubility.
Besides water solubility also metabolism and the molecular size reduce the log BCF as estimated by the model. Water solubility and molecular size is discussed within the literature whether certain threshold values are suitable as cut-off criteria for indication of limited bioaccumulation. Regarding molecular size, the PBT working group on hazardous substances discussed a maximum diameter of > 17.4 Å (Comber et al., 2006).The maximum diameter of the test item is determined to be 4.57 - 48.74 Å, depending on its conformation. Due to the high log Kow (out of the parametric domain), the test substance is not to 100% within the applicability domain of the model (BASF, 2012).

- EPISuite v4.1/BCFBAFv3.00: A BCF value of 3.2 (log BCF = 0.5) was estimated on the basis of the log Kow of 16.76. Using the Arnot-Gobas method including biotransformation rates the BCF for the upper trophic level was estimated at 0.9 (log BCF = -0.049) (BASF, 2012).

- T.E.S.T.v4.01 (US EPA model): Cluster models of the Hierarchical method, the Single Model method, Group Contribution method, the FDA method and the Nearest Neighbor method were applicable to the test item (input of log Kow and water solubility not necessary). The methods were validated by US EPA using statistical external validation using separate training and test data sets. The Consensus method averages the reasonable results from all applicable models. Following EPA, the Consensus method yields the best results in terms of prediction accuracy and coverage. Regarding the test item, the predicted BCF values of the applicable cluster models ranged from 4 to 14791. The BCF result of the Consensus method was 78.4 (log BCF = 1.89) (BASF, 2012).

 

CONCLUSIONS
The three separate estimation models (CATALOGIC v5.11.2, BCFBAF v3.01 and T.E.S.T v4.01) calculate maximum BCF values between 3.2 and 78.4. Considering mitigating factors like biotransformation, water solubility and molecular size, there is low potential for bioaccumulation. In addition, due to the very low water solubility exposure of aquatic organisms to significant amounts is unlikely. Therefore, unacceptable risks due to possible bioaccumulation are not expected.