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Ecotoxicological information

Toxicity to microorganisms

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Description of key information

The toxicity of the tosyl caboxylic acid component of the registered substance to microorganisms was determined in accordance with the OECD Guideline for Testing of Chemicals 209. The highest applied test substance concentration resulted in a total inhibition of ca. 48%. The 3 hour EC50 for respiration inhibition was determined to be >5000 mg/L. 

Key value for chemical safety assessment

EC50 for microorganisms:
5 000 mg/L

Additional information

The toxicity of the tosyl caboxylic acid component of the registered substance to microorganisms was determined in accordance with the OECD Guideline for Testing of Chemicals 209. The highest applied test substance concentration resulted in a total inhibition of ca. 48%. The 3 hour EC50 for respiration inhibition was determined to be >5000 mg/L. Read-across between the tosyl salt carboxylic acid (6-[(p-Tosyl)amino]hexanoic acid) and the registered substance is considered justified as the registered substance is manufactured directly from 6-[(p-Tosyl)amino]hexanoic acid by simple neutralisation with triethanolamine (TEA). Other than ionization of the carboxylic acid group, the 6-[(p-Tosyl)amino]hexanoic acid remains chemically unchanged upon salt formation. In water, the acid and amine components of 6-[(p-Tosyl)amino]hexanoic acid, compound with 2,2’,2’’-nitrilotriethanol (1:1) dissociate completely and behave essentially as independent substances. Since TEA can be considered non-hazardous, it is the acid component of the salt that will have a more significant impact on the outcome of any (eco)toxicological or environmental tests. The pKa of the carboxylic acid group in 6-[(p-Tosyl)amino]hexanoic acid (pKa = 4.90) is the same in the free acid as it is in the TEA salt. As a result, 6-[(p-Tosyl)amino]hexanoic acid will respond to changes of pH in the same way whether it is in the salt form or as the parent carboxylic acid and hence it’s bioavailability will be the same. In addition, the IC50 of triethanolamine to microorganisms was found to be >1000 mg/l. From the studies described above it can be seen that neither the carboxylic acid component or the triethanolamine component of the registered substance (tosyl salt) can be considered toxic to microorganisms. As the tosyl salt completely dissociates in water to leave the two components to behave essentially as independent substances it can be concluded that the registered substance is not considered toxic to microorganisms. The registered substance is supplied to users in diluted form in a formulated product and is therefore not expected to inhibit respiration of microorganisms as Sewage Treatment Plants (STP) at the concentrations used in the environment.