6-[methyl(phenylsulphonyl)amino]hexanoic acid, compound with 2,2',2''-nitrilotriethanol (1:1)

Biodegradation in water and sediment: simulation tests

Description of key information

A formulated product containing the registered substance showed a low potential for biodegradation in seawater, with 28 day degradability rate of 21.5% at 2.04 mg/l. The test material was considered ultimately biodegradable but not readily biodegradable in seawater.

 

According to column 2 of Annexes IX and X, further testing on biodegradation should be considered if the chemical safety assessment indicates the need to investigate further the degradation of the substance and its degradation products. Based on the screening study conducted with a structurally similar substance (tosyl salt) 6-[(p-Tosyl)amino]hexanoic acid, compound with 2,2',2"- nitrilotriethanol (1:1) it was concluded that the substance is not readily biodegradable but can be concluded to be inherently biodegradable. Furthermore the results from the CSA do not trigger a need for further investigation of biotic degradation as risk for the aquatic and sediment compartment are acceptable in every scenario (RCR < 1). With respect to PBT/vPvB properties the substance is not considered PBT/vPvB and therefore further testing on biodegradation is not triggered. In accordance with column 2 of Annexes IX and X, no further biodegradation testing in surface water and sediment are needed.

An assessment of likely degradation products has been performed by considering each of the constituent compounds in the title substance 6-[methyl(phenylsulphonyl)amino]hexanoic acid, compound with 2,2',2''-nitrilotriethanol (1:1) separately. Likely degradation products include  N-methyl-N-(phenylsulfonyl)glycine and N-methyl-4-aminobutyric acid as well as transient degradation products of diethanolamine and ethanolamine are expected with the release of acetaldehyde.

Additional information

The biodegradability of the test material (a formulated product containing the registered substance) in seawater was determined in accordance with OECD Testing Guideline 306. 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. In addition, an equivalent study was conducted on a formulated product containing a structurally similar substance to the registered substance (6 -[(p-Tosyl)amino]hexanoic acid, compound with 2,2',2''-nitrilotriethanol (1:1) (Tosyl salt) 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 material 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. Read-across between the registered substance and the test substance (a formulated product containing Tosyl 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 behavior or properties of the substances.