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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

Under test conditions no biodegradation observed.

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed

Additional information

Biodegradation was tested for the substance according to the Zahn Wellens method (Novartis Services AG., 1997), where the substance is demonstrated to adsorb to the sludge from 67 to 84 % in 24 h and no biodegradation is observed. As a consequence the substance can be considered ad non readily biodegradable. The result is confirmed by a number of studies with low reliability, summarised in a report (Various, 2014) and the provisional calculations based on the chemical structure.

Based on the structural similarity, the Ready biodegradation test according to OECD 301A conducted on an analogous substance of the Stilbene Fluorescent Whitening Agents category, group 3, CAS 16470-24-9, is reported. The analogous and the substance under registration (CAS 16470-24-9 and CAS 4193-55-9, respectively) are very similar and are constituted by the same functional groups, except for the fact that CAS 16470-24-9 is tetrasulphonated instead than disulphonated, sodium salt. The difference in sulphonation can have an influence on water solubility, but not on the biodegradation potential, since both substances have the same organic groups in the chemical structure. Quantity and chemical identity of the impurities has no influence on the possibility of Read Across for this end point. For further details refer to the Category Justification Report attached to the section 13.

In the ready biodegradability test (Ciba-Geigy Ltd., 1992) a DOC removal of 1.2 % was observed. Hence, the tested substance is not readily biodegradable.

In conclusion, the CAS 4193-55-9 is considered as neither readily nor inherently biodegradable.