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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

A Zahn Wellens study was performed on the substance under registration (CAS 16324-27-9) to measure the adsorption; the study was not terminated and the adsorption at 24 hours was reported as 37.1 %. Several screening available studies (BOD/COD; Various, 2014) confirm that the substance is not rapidly biodegradable and can be assumed as non readily biodegradable.

Furthermore, 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 readily and inherently biodegradability tests were performed, confirming the previsions (see the Category Justification Report attached to the section 13).

The studies performed on CAS 16470-24-9, the analogue dihydroxyethylamino derivative tetrasulphonated, are here reported. Both the CAS 16324-27-9 and the CAS 16470-24-9 are tetrasulphonated sodium salts, mono and dihydroxyethylamino derivatives, respectively. They share the same metabolic and degradation pathway.

In a ready biodegradability, test according to OECD guideline 301A, a DOC removal of 1.2 % was observed (Ciba-Geigy Ltd., 1992); hence, the substance CAS 16470-24-9 is considered not readily biodegradable. Additional information are given from two Zahn Wellens tests, performed according to the OECD 302B. One of them indicates a biodegradation of 24 % after 28 days (Ciba-Geigy Ltd., 1992c): this value is obtained at about the fifth day, afterwards the degradation process seems to stop. The slope of the 28 days curve and the second test of inherent biodegradation (Novartis Services AG., 1997) reported suggest that the 24 % of DOC removal recorded in the first test can still be related to a slow adsorption process more than a biological degradation.

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