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Environmental fate & pathways

Biodegradation in water and sediment: simulation tests

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Description of key information

A formulated product containing the registered substance showed a low potential for biodegradation in seawater, with 28 day degradability rates of 29.6% at 2.5 mg/l and 22.1% at 3.5 mg/l. The test material was considered ultimately biodegradable but not readily biodegradable in seawater.

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Additional information

The biodegradability of the test material (a formulated product containing the registered substance) in seawater was determined in accordance with the OECD Guideline for Testing of Chemicals 306 using the Closed Bottle Procedure. The test material was used in concentrations of 2.5 mg/l and 3.5 mg/l, with 2.5 mg/l of sodium benzoate used as a reference material. The biodegradation of the test material at each concentration was calculated using the calculated Chemical Oxygen Demand (COD) values and dissolved oxygen data. Under these test conditions in the Closed Bottle Procedure the test substance showed limited potential for degradation at test concentrations of 2.5 mg/l and 3.5 mg/l, with 28 day degradability rates of 29.6% at 2.5 mg/l and 22.1% at 3.5 mg/l. In addition, an equivalent study was conducted on a formulated product containing a structurally similar substance to the registered substance (6 -[Methyl(phenylsulphonyl)amino]hexanoic acid, compound with 2,2',2''-nitrilotriethanol (1:1) (N-methyl salt). The test material achieved 21.5% biodegradation after 28 days. The test material can be considered inherently biodegradable but not ultimately biodegradable. The results also indicate that the test material is not classified as inhibitory at the test concentration. Read-across between the registered substance and the test substance (a formulated product containing N-methyl salt) is considered justified owing to the structural similarity of the two substances. Both are salts of a carboxylic acid and triethanolamine. The acid components are structural isomers and differ only in the position of a single methyl group in the N-methyl salt. This is not expected to change the behaviour or properties of the substances.