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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
Type of water:
freshwater

Additional information

No ready biodegradation was tested on the substance, but according to the estimation modelling BIOWIN v.4.10, the substance is predicted as non biodegradable; all substances of the Stilbene Fluorescent Whitening Agents category are predicted as non readily biodegradable and for many members of the category readily and inherently biodegradability tests have been performed confirming the previsions (see the Category Justification Report attached to the section 13).

A summary of a performed Zahn Wellens test indicates 18.7 % of adsorption after 3h.

The studies performed on 3a-DSA, the analogues subsatnces, are reported here as a Weight of Evidence. Both the substance under registration and the analogues are hexasulphonated sodium salts. The diethylamino substituent is less polar, less reactive and makes the molecule slightly less soluble compared to the dihydroxyethylamino derivative (201 vs. 278 g/l); the latter can therefore considered as a representative conservative analogous for the biodegradability endpoint.

No ready biodegradation was tested on the substance, but some existing information are summarized, reporting data about BOD5 and inherent biodegradation (Ciba-Geigy 1995 - Zahn Wellens OECD 302B). The Zahn Wellens study reports a variation in the DOC in the first 5 days of about 76 %, afterwards no or negligible degradation was observed. The existing BOD5 measurements (Whitehead M. 1990 and Ciba-Geigy 1995) indicate respectively no oxygen consumption and 10 % of oxygen consumption in the first 5 days, supporting the hypothesis that the DOC removal in the first 5 days is not related to biodegradation process, but to a slow adsorption process.

 

In conclusion, the substance can be considered as neither readily nor inherently biodegradable.