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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

As the parent compound rapidly hydrolyses in aqueous systems the assessment of the biodegradability is based on the hydrolysis product butyric acid, which is readily biodegradable (according to OECD criteria).

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

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.

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.

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.

 

Assessment

Parent compound butyryl chloride (CAS 141-75-3):

No experimental data are available for the parent compound. The biodegradation of butyryl chloride in water was therefore estimated using the QSAR method of CATALOGIC 301C v12.17 (OASIS Catalogic v5.15.2), which predicted an O2-consumption (BOD) of 100% after 28d (BASF, 2022). With regard to the parametric and mechanistic domain, the test substance is to 100% within the applicability domain of the model. The substance is to 67% within the structural fragments domain, 33% of fragments are not present in the set of training chemicals. However, the overall results can be regarded as reliable.

Based on this results, the test substance is considered readily biodegradable according to OECD criteria.

However, since the substance is known to hydrolyse quickly to butyric acid and HCl, the assessment of the biodegradability is additionally based on the hydrolysis product butyric acid (CAS 107-92-6) and the structurally similar substance isobutyric acid (CAS 79-31-2).

 

Hydrolysis product butyric acid (CAS 107-92-6):

The biodegradation of butyric acid in water was estimated using the QSAR method of CATALOGIC 301C v12.17 (OASIS Catalogic v5.15.2), which predicted an O2-consumption (BOD) of 100% after 28d (BASF, 2022). The substance is completely within the applicability domain of the model.

 

Isobutyric acid (CAS 79-31-2):

These results are supported by read across to isobutyric acid. The biodegradation of isobutyric acid in water was estimated using the QSAR method of CATALOGIC 301C v12.17 (OASIS Catalogic v5.15.2), which predicted an O2-consumption (BOD) of 100% after 28d (BASF, 2022). With regard to the parametric and mechanistic domain, the test substance is to 100% within the applicability domain of the model. The substance is to 83% within the structural fragments domain, 16.7% of fragments are not present in the set of training chemicals. However, the overall results can be regarded as reliable.

 

Based on the available data on butyryl chloride, the hydrolysis product butyric acid and the structurally similar substance isobutyric acid, the parent compound is considered readily biodegradable.