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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

readily biodegradable

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

The biodegradation potential of the substance was evaluated by taking in consideration data on the analogues substances. Experimental data on the substance is not available. Justification for Read Across is given in Section 13 of IUCLID.

The biodegradation of Similar Substance 02 was evaluated according to the OECD Guideline 301 D. The substance was inoculated with the activated sludge for 28 days. The dissolved oxygen concentrations were determined electrochemically using an oxygen electrode at day 0, 7, 14, 21, and 28. The biodegradation of a reference substance was also assessed. Biodegradation (28 d) = 71 %; biodegradation (21 d) = 60 %; biodegradation (14 d) = 47 %; biodegradation (7 d) = 24 %.

The substance is considered as readily biodegradable, failing the 10 -d window.

In the supporting study conducted on Similar Substance 01, the biodegradability was assessed according to the OECD 301 C (MITI I) for 28 days. This test used a concentration of 100 mg/l test substance and resulted in 82 % degradation based on BOD and 97 % degradation based on HPLC analysis.

According to the CLP Regulation (EC) No. 1272/2008, Annex I:, if other convincing scientific evidence is available to demonstrate that the substance can be degraded (biotically and/or abiotically) in the aquatic environment to a level > 70 % within a 28-day period the substance is still considered as rapidly biodegradable in the environment. Similar substance 02, even if does not meet the 10 -day window, it is expected to degrade in water to its respective alcohol and thiodipriopionic acid which are considered as readily biodegradable. Therefore, Similar Substance 02 is expected to be readily biodegradable.

In conclusion, supported by the two analogue substances' biodegradation potential, the substance is regarded as readily biodegradable even if it failed the 10 day window. The substance is an UVCB, therefore, according to the CLP Regulation (EC) No 1272/2008 the pass level of the 10 -day window can be waived and the pass level is applied at 28 days.