1-Heptanol, 2-propyl-, 1,1'-carbonate

Endpoint summary

Additional information

Short description of key information

Significant accumulation of the test item [carbonic acid, bis (2-propylheptyl) ester; CAS 1238449-42-7]) in organisms is not to be expected.

Discussion

Experimental studies indicate, that the logPow is > 6.5 (HPLC) resp. > 7.7 (computational method). Without a definitive experimental logPow, the log Kow was calculated for carbonic acid, bis (2 -propylheptyl) ester (CAS 1238449 -42 -7), using the BAC/BAF module of EpiSuite program. The resulting logPow of 8.93 is indicating the potential for bioaccumulation. Due to the lack of decisive experimental data, the assessment of the bioaccumulation potential will be evaluated in a weight-of-evidence approach. Estimations of the BCF were performed with four different models. - A BCF calculation using the CATALOGIC v.5.11.6 BCF base-line model v02.05 is available. The BCFmodel calculates a BCF of 1824 (log BCF = 3.26) using the estimated log Kow value of 8.93 and the estimated water solubility of 0.0002 mg/L. The influence of mitigating factors like water solubility, size and metabolism are also considered by the model. Taking into account these mitigating factors the BCF is reduced to 17 (log BCF = 1.24), mainly due to metabolism. Besides metabolism also molecular size and, to a minor degree, water solubility reduce the log BCF as estimated by the model. Water solubility and molecular size are 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 15.02 - 23.17 Å.The average maximum diameter is 17.5Å. Due to some unknown atom centered fragments (ACF), 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 383 (log BCF = 2.854) was estimated on the basis of the log Kow of 8.93. Using the Arnot-Gobas method including biotransformation rates the BCF for the upper trophic level was estimated at 828 (log BCF = 2.918) (BASF, 2012). - T.E.S.T.v4.01 (US EPA model): The cluster models of the Hierarchical method, the Single Model method, Group Contribution method and the FDA method were not applicable to the test item; only the Neighest Neigbor model could be applied. The methods were validated by US EPA using statistical external validation using separate training and test data sets. Regarding the test item, the predicted BCF values of the applicable cluster model is 19(log BCF = 1.28) (BASF, 2012). - OECD QSAR Toolbox v3.0.0.274 alpha: On the basis of trend analysis and using the estimated log Kow of 8.93, the OECD Toolbox model predicted a BCF value of 35.7 (log BCF = 1.55). Six structural analogues were identified to be within the defined category. The test item is within the applicability domain of the model.   CONCLUSIONS The four separate estimation models (CATALOGIC v5.11.6, BCFBAF v3.01, T.E.S.T v4.01 and OECD Toolbox v3.0) calculate maximum BCF values between 19 and 1824. Considering mitigating factors like biotransformation and molecular size, there is minor potential for bioaccumulation. In addition, due to the low water solubility exposure of aquatic organisms to significant amounts is unlikely.