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Environmental fate & pathways

Bioaccumulation: aquatic / sediment

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Description of key information

The test item does not significantly accumulate in organisms.

Key value for chemical safety assessment

Additional information

The test item is a multiconstituent substance with dicyclohexylamine as counterion for the dye complex. To estimate the potential for bioaccumulation QSAR calculations have been conducted (BASF SE 2018). The dye complex of the main components consist of two different organic structures complexed by Cr(3+)-ions. Since metal complexes cannot be calculated using QSAR models, one of the two organic parts has been calculated using EPISuite BCFBAF program (v3.01) as a worst case consideration. The used organic part (second part) is the most bioavailable structure, since the molecule has less polar moieties and is, therefore, more bioavailable compared to the second part or even the whole test substance. Since, the complete test substance has a very high molecular weight of 848.84 - 962.94 and a large diameter, bioaccumulation for the complete test substance is not expected due to the low bioavailability of the complete molecule based on the large structure that hinders the uptake (as reported in R 11 - PBT Assessment).

Additionally, the counterion dicyclohexylamine has a logKow of -0.4 according to the disseminated dossier at the ECHA homepage. Therefore, dicyclohexylamine has no potential for bioaccumulation and further calculations are not necessary.

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

Model

 

BCF

Log BCF

Remarks

Catalogic v5.12.1

 

4.79

0.68

all mitigating factors applied; 77.78 % in domain

T.E.S.T. v4.2.1

 

11.81

1.07

EPISuite v4.10

Regression-based estimate

10

1

The substance is within the applicability domain of the BCFBAF submodel: Bioconcentration factor

Arnot-Gobas upper trophic level

223.8

2.35

Including biotransformation rate estimates; MW and logKow is within the range of training set.

Arnot-Gobas mid trophic level

306.9

2.487

Including biotransformation rate estimates;MW iand logKow is within the range of training set.

Arnot-Gobas lower trophic level

338

2.529

Including biotransformation rate estimates;MW and logKow is within the range of training set.

 VEGA CAESAR v2.1.14   20  1.31 The predicted compound could be out of the Applicability Domain of the model
 VEGA Meylan v1.0.3    432  2.64 The predicted compound is outside the Applicability Domain of the model
VEGA KNN/Read-Across v1.1.0    6.6  0.82 The predicted compound is into the Applicability Domain of the model

Regarding the results of the model calculation, the calculated BCF values range from 4.79 (Catalogic) to 432 (VEGA Meylan).

Of these models, Catalogic, VEGA CAESAR and the Arnot-Gobas model from EPISuite v4.10 take into account mitigating factors, e.g. metabolism, water solubility and/or size.

Catalogic revealed a corrected BCF of 4.79 and the compound is 77.78% within the model’s applicability domain.

The Arnot-Gobas model from the EPISuite takes into account the biotransformation rate of the compound and calculates BCF values for the upper, mid and lower trophic levels. The values for the present compound range from 223.8 (upper trophic level) to 338 (lower trophic level). The model assumes default lipid contents of 10.7%, 6.85% and 5.98% for the upper, middle and lower trophic levels, respectively. Usually, in the context of REACH a default lipid value of 5% is assumed which represents the average lipid content of the small fish used in OECD 305 studies. Thus, the higher lipid values of the Arnot-Gobas model can be regarded as reasonable worst-case scenarios as higher lipid contents are usually associated with a higher potential for bioaccumulation. The MW and logKow is within the range of training set.

The regression-based estimate from the EPISuite revealed a BCF value of 10 and the test substance is in the applicability domain of the model. However, for the regression based estimate mitigating factors are not taken into account.

The T.E.S.T. package from the US EPA estimates BCF values using several different advanced QSAR methodologies. The recommended model of the T.E.S.T. package is the consensus method since it provides the most accurate prediction. This model estimates the BCF by taking an average of the predicted BCF values from the other applicable QSAR methods of the package. For the present substance the consensus method averaged the results from (1) the hierarchical clustering method, (2) the single model method, (3) the group contribution method, (4) the FDA method and (5) the nearest neighbor method. The resulting BCF value is 11.81.

The VEGA CAESAR model was developed with several descriptors and is based on a dataset of 473 compounds. It offers detailed information on the applicability domain. In the present case, the calculation gave a BCF value of 20. Since the Global AD Index was calculated to be 0.85 the substance could be out of the Applicability Domain of the model.

However, even though the test substance could be out of the Applicability Domain of some programs, the QSAR results support the overall conclusion that the test substance is not bioaccumulative, since all QSAR models give a BCF value below 500 of and the results of the models were the applicability domain is met are consistent with the results of all models.

In overall conclusion, regarding all available information the test item does not significantly accumulate in organisms.

QSAR-disclaimer

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 test substance (Q)SAR results were used for aquatic bioaccumulation.The criteria listed in Annex XI of Regulation (EC) No 1907/2006 are not entirely fulfilled, but deemed sufficiently covered for a weight-of-evidence approach.Therefore, and for reasons of animal welfare, further experimental studies on aquatic bioaccumulation are not provided.