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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

The uvcb substance is not readily biodegradable.

Key value for chemical safety assessment

Additional information

No experimental data on biodegradability of the UVCB substance or its constituents are available.

Furthermore, the result of the biodegradation tests with an uvcb substance are difficult to interpret as mentioned in ECHA Guidance 7b (2017): “The OECD "Guidelines for the Testing of Chemicals, Revised Introduction To The OECD Guidelines For Testing Of Chemicals, Section 3 Part I: Principles And Strategies Related To The Testing Of Degradation Of Organic Chemicals" (OECD, 2006b) indicates that ready biodegradability tests are intended for pure substances and are generally not applicable for complex compositions containing different types of constituents, like UVCB. For an UVCB substance, observed biodegradation may indeed represent the biodegradation of only some constituents.” Therefore, experimental data on ready biodegradability are not performed.

The uvcb substance consists mainly of two branched isomer groups either monoalkylated or dialkylated and to a small amount of a branched isomer group trialkylated. Therefore, additional QSAR calculations with OASIS Catalogic v5.13.1.156, Catalogic 301C v11.15 were performed for 3 representative structures of the isomer groups. The model revealed a degradation of 9, 24 and 31% after 28d for the three investigated structures respectively. 109-134-135 metabolites were identified. All structures were in the applicability domain of the model.

It can be concluded that the uvcb substance and its constituents are not readily biodegradable.


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 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.

Therefore, further experimental studies on biodegradation are not provided.