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Environmental fate & pathways

Biodegradation in water and sediment: simulation tests

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Description of key information

No biodegradation is expected in water and sediment simulation testing

Key value for chemical safety assessment

Additional information

No simulation studies in water and sediment were performed on the substance under registration (CAS 67786-25-8). Some data are available on the analogous substances CAS 68971-49-3, the hydroxyethylamino derivative hexasulphonated sodium salt and CAS 16470-24-9, the dihydroxyethylamino derivative tetrasulphonated. The structural similarity between the substances is very high: Tanimoto similarity is > 95 % between the substance under registration and the analogous and all the three substances are characterized by a very high water solubility (1000 g/l CAS 67786-25-8, 650 g/l CAS 16470-24-9 and 278 g/l CAS 68971-49-3).

A simulation study was performed according to OECD 303A on the CAS 68971-49-3, for which a summary is available, indicating a percentage of TOC equal to 4 %, while the anaerobic degradation was evaluated on the analogous CAS 16470-24-9, according to procedures outlined into the ECETOC Technical Report No. 28. The resulting degradation rates are different and the reason of this difference is not evaluable.

A further field study at a full-scale STP on a similar substance in the category of the Stilbene Fluorescent Whitening Agents (CAS 16090-02-1) gave no evidence of biodegradation when the mass flow was monitored (Poiger, 1994 – Section 5.5.2: Field studies).

In virtue of a conservative approach, it is assumed that the test substance under registration (CAS 67786-25-8) would be non biodegradable in simulation tests.

Considering all biotic degradation studies for the members of the category (see Category Reporting Document attached to Section 13 of the dossier), structural similarities, estimated and calculated data, metabolic previsions, it can be assumed that all members have the same behaviour in the biotic compartment.

Further biotic degradation testing shall be proposed only if the Chemical Safety Assessment, according to Annex I, indicates the need to investigate further degradation of the substance and its degradation products. Based on the Chemical Safety Assessment the exposure of sediment and soil will be negligible, since the substance and its formulations are produced and used in plants with internal Sewage Treatment Plant, where the sludge is sent to incineration. The only potential dispersive use could be in the detergency field, with public consumer use. In this case there is a potential for exposure, but the quantities and secondary process of photooxidation lower the amount of the substance available in the environment.