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

Toxicity to aquatic algae and cyanobacteria

Description of key information

The 72 hour EC50 of a formulated product containing the registered substance was 23 mg/l. The formulated product contains 44.7% of the registered substance. Assuming a linear dose-response relationship, 44.7% of 23 mg/l = 10.28 mg/l. Therefore the EC50 for the registered substance is proposed to be 10.28 mg/l. The substance is considered toxic to aquatic algae and is classified as Aquatic Chronic 3 according to EU CLP criteria.

Key value for chemical safety assessment

EC50 for marine water algae:

10.28 mg/L

EC10 or NOEC for marine water algae:

10.2 mg/L

Additional information

The toxicity of the test material (a formulated product containing the registered substance) to aquatic algae was determined in accordance with the EN ISO Guideline for Testing of Chemicals 10253:1998. The study was conducted using the marine algae Skeletonema costatum. Water Accommodated Fractions (WAF) of the test substance were prepared over a concentration range of 5.62 mg/l to 100 mg/l. The exposed algae was monitored over a period of 72 hours to determine the concentration of test substance which inhibited algal growth rate by 50% i.e. the EC₅₀. The 72 hour EC₅₀of a formulated product containing the registered substance was 23 mg/l. The formulated product contains 44.7% of the registered substance. Assuming a linear dose-response relationship, 44.7% of 23 mg/l = 10.28 mg/l. Therefore the EC₅₀for the registered substance is proposed to be 10.28 mg/l. The substance is considered toxic to aquatic algae and is classified as Aquatic Chronic 3 according to EU CLP criteria. An equivalent study was conducted on a formulated product containing a structurally similar substance (N-methyl salt) to the registered substance. The EC₅₀ of the formulated product was found to be 234.2 mg/l. The formulated product contains 44.7% of the N-methyl salt. Assuming a linear dose-response relationship, 44.7% of 234.2 mg/l = 104.6 mg/l. Therefore the EC₅₀ for the N-methyl salt is proposed to be 104.6 mg/l. The read-across substance (N-methyl salt) is not considered to be toxic to aquatic algae. Read-across between the registered substance and the test material (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 bioavailability of the substances, and both substances have shown similarity in the results of other physical endpoints such as water solubility. The EC₅₀ of triethanolamine was found to be >1000 mg/l. Triethanolamine was not considered to be toxic to aquatic algae.