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Environmental fate & pathways

Biodegradation in water: screening tests

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biodegradation in water: ready biodegradability
Data waiving:
study scientifically not necessary / other information available
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data waiving: supporting information
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data waiving: supporting information
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data waiving: supporting information
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data waiving: supporting information

Description of key information

Not readily biodegradable (according to OECD criteria).

Key value for chemical safety assessment

Additional information

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 biodegradation. 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.

Data on the ready biodegradability of the described pigment are not available. However, model calculations using three different QSAR models have been conducted to assess the biodegradability. Since, the test substance is an UVCB substance consisting of three derivatives, all three structures have been used in the QSAR models.

The biodegradation was calculated by using CATALOGIC v5.13.1.156 (BOD 28 days MITI (OECD 301C) v11.15). It resulted in 5 - 14 % biodegradation after 28 d for the three derivatives. The structural domain was correct with at least 78.26 % (21.74 % unknown) for the bismethoxy-hexachloro derivative, up to 95.24 % correctness (4.76% unknown) for the octachloro derivative and, therefore, for the main derivative. The results of the calculation of the three derivatives show that the pigment is not readily biodegradable (according to OECD criteria).

This result ist supported by two other QSAR calculations using EPISuite v4.11 BIOWIN v4.10 and VEGA v.1.1.1 Ready Biodegradation model v.1.0.9. Both showing that the three derivatives of the test substance are not readily biodegradable. Even though, concerning VEGA all derivatives are out of the applicability domain, the results support the overall conclusion of the test substance. Regarding EPISuite the molecular weight of the test item was within the applicability domain of the model. However, the reliability is slightly reduced since the number of some fragment coefficients exceed the maximum number of fragment coefficients of the compounds within the training set. Nevertheless, the test substance is regarded as not readily biodegradable as a worst-case consideration.

Moreover, the pigment is practically insoluble and therefore considered to be essentially not bioavailable. Due to the large molecular size, cellular uptake of the pigment is unlikely. Hence intracellular biodegradation, which is the main degradation route of bacteria, is probably low. It can be concluded that the substance is likely to be persistent in the environment. For this reason no ready or inherent degradation studies are proposed.