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Environmental fate & pathways

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The bioaccumulative potential of the substance Paliocolor LC 1057 was assessed in an Weight-of-Evidence approach with several QSAR estimations.

 

In Article 13 of Regulation (EC) No 1907/2006, it is laid down that information on intrinsic properties of substances may be generated by means other than tests, provided that the conditions set out in Annex XI (of the same Regulation) are met. Furthermore according to Article 25 of the same Regulation testing on vertebrate animals shall be undertaken only as a last resort.

 

 

According to Annex XI of Regulation (EC) No 1907/2006 (Q)SAR results can be used if (1) the scientific validity of the (Q)SAR model has been established, (2) the substance falls within the applicability domain of the (Q)SAR model, (3) the results are adequate for the purpose of classification and labeling and/or risk assessment and (4) adequate and reliable documentation of the applied method is provided.

 

 

For the assessment of the present compound (Q)SAR results were used. The criteria listed in Annex XI of Regulation (EC) No 1907/2006 are considered to be adequately fulfilled and therefore the endpoint(s) sufficiently covered and suitable for risk assessment.

 

 

The single QSAR-models and their results are summarized in the table below.

 

Model

 

BCF

Log BCF

Remarks

Catalogic v5.11.17

 

8.32

0.92

all mitigating factors applied

T.E.S.T. v4.1

 

2.38

0.37

Nearest neighbor method; in domain

EPISuite v4.11

Regression-based estimate

544

2.73

Does not take biotransformation into account

Arnot-Gobas upper trophic level

1.03

0.011

Including biotransformation rate estimates

 

All models show results with low BCF values. However, the results of some models are more reliable than others because the substance is outside of the applicability domain of the respective model or does not consider biotransformation.

 

The BCF basel-line model integrated in Catalogic is a sophisticated model which takes into account different mitigating factors, i.e. acids, metabolism, phenols, size and water solubility. The compound was inside the parametric and the mechanistic domains of the compound but only 30.77% of the fragments of the target chemical are present in correctly predicted training chemicals. Nevertheless, the result is regarded as reliable and suitable to be used in a weight of evidence approach. With all mitigating factors applied the BCF is determined as 8.32. The biggest influence on the bioaccumulative potential has the size of the molecule which limits the uptake. Metabolism has an influence on bioaccumulation, too.

 

The average diameter of the molecule calculated by Calalogic is about 27 Angström which is for above the diameter which allows uptake through biological membranes. Even the min. diameter with 19.3 Angström is still above. Therefore, bioaccumulation is unlikely to occur in large extent.

 

US EPA’s Toxicity Estimation Software Tool (T.E.S.T.) uses five submodels to estimate the BCF of the target chemical. These results are than averaged in the consensus approach to provide a higher reliability. The target compound is inside of the applicability domain of one of the single submodels (nearest neighbor). This model revealed a BCF values of 2.38. The confidence in the estimated BCF values of this single submodel is moderate according to the respective and the external training. Still, only one out of the five methods revealed a result.

 

US EPA’s EPISuite includes the regression-based estimation by Meylan et al. and the Arnot-Gobas model which takes biotransformation processes into account. The target chemical is within the applicability domain of the regression-based estimation tool and the BCF was predicted with 544. A correction for alkyl chains was applied in the equation used for the estimation. However, this result is not regarded as informative, as biotransformation is not explicitly taken into account. The Arnot-Gobas model predicted BCF values of 1.025 for the upper trophic level. The compound’s molecular weight exceeded the recommended range of the model for calculation of the biotransformation rate (848.82 instead of < 600 g/mol) but is still within the range of the training set. Nevertheless, the result by the Arnot-Gobas model is regarded as suitable as all other domain parameters are fulfilled.

 

In conclusion the reliable QSAR estimations clearly lead to the conclusion that the substance does not significantly accumulate in organisms.