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Bioaccumulation: aquatic / sediment

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Weight of evidence comparison of predicted BCFs and BAFs to B Criterion: BCF>2000 L/kg and vB Criterion: BCF>5000 L/kg indicates that the vegetable oil derivative is "not B" and "not vB" according to REACH and applicable guidance. 

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Additional information

1. Evaluation of log Kow

Each of the QSAR-predicted log Kowvalues exceeded the screening criterion, indicating a potential for bioaccumulation. Based on this comparison, it was not possible to classify the molecule as “not B” according to the log Kowcriterion alone. As a screening criterion, the log Kowthreshold represents bioaccumulation potential based on partitioning and uptake behavior but does not account for mitigating factors such as molecular size and biotransformation and, therefore, the BCF and BAF predictions provide a better representation of overall bioaccumulation potential. Thus, the bioaccumulation assessment relied primarily on comparison of the QSAR estimates of BCF and BAF to the definitive criteria from Annex XIII.

 

2. Evaluation of BCF and BAF

Using the KOWWIN estimates for log Kow, the ranges of BAF and BCF predictions are as follows:

 

-Vegetable Oil Derivative: 0.3 to 79.4 L/kg.

 

All of these values were far below the BCF and BAF criterion of 2000 providing support for a “not B” conclusion for the substance group.

 

Using the ALOGPS estimates for log Kow, the ranges of BAF and BCF predictions are as follows:

 

Vegetable Oil Derivative: 0.50 to 2041 L/kg.

 

The large ranges in predictions are due to wide ranges in log Kow estimates using KOWWIN and the lowest value from ALOGPS.  

The high end of the BCF range for the vegetable oil derivative exceeds the BCF/BAF criterion of 2000; but, this is not deemed to be representative of the FLL Substances as a whole based on the following considerations:

 

- The prediction is based on an unrealistically low QSAR estimate for log Kow.

- Predicted BCFs near or at the criterion were obtained with only 1 of the 3 QSAR models (OASIS BCFmax model). The EPIWIN predictions using regression-based log BCF and Arnot-Gobas BCF/BAF were much lower, ranging up to a maximum of 79.4 L/kg.

- In the OASIS BCFmax model, adjustments for molecular size could not be applied because the molecular size of the sulfonated natural oil molecules is not known. However, given the molecular weight of the molecules, it is possible that they are near the threshold where molecular size begins to limit uptake. Thus, without accounting for this factor, the OASIS BCFmax model may have over-predicted the BCF to an unknown degree.

 

A final consideration is that given that the QSAR predictions are not precise estimates, it can be argued that the 2041 value is virtually at the B threshold and therefore does not provide conclusive evidence of a BCF exceeding the BCF/BAF criterion of 2000.

 

3. Weight of Evidence Conclusion

At the higher log Kow values predicted by KOWWIN that are considered more realistic because of the observed/predicted extreme low water solubility and expected lipophilicity of the substances, the BAF and BCF predictions are far below the 2000 criterion. In addition, using the worst-case estimates of log Kow from ALOGPS, all but one of the BAF and BCF predictions were below the 2000 BCF/BAF criterion; and, the one prediction that exceeded the criterion was not deemed to be representative of the substance of concern and of the substance group as a whole.

 

These findings provide a weight of evidence that the vegetable oil derivative does not have significant bioaccumulation potential. By read-across, none of the substances in the group of sulfonated oils are expected to be bioaccumulative.

 

Thus, classifications of “not B” and “not vB” are considered appropriate for the FLL Substances according to the REACH B Criteria and applicable guidance.