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Toxicity to aquatic algae and cyanobacteria

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Description of key information

The toxicity to aquatic algae in a valid algae study resulted in a 72 hour EC10 and EC50 based on growth of resp. 323.8 and 476.7 µg a.i./L

Key value for chemical safety assessment

EC50 for freshwater algae:
476.7 µg/L
EC10 or NOEC for freshwater algae:
323.8 µg/L

Additional information

Two algae toxicity studies have been performed. One study performed to assess the algae toxicity of a range of comparable imidazoline products and one definitive study with 1H-Imidazole-1-ethanamine, 4,5-dihydro-, 2-nortall-oil alkyl derivs. (CAS no 68442-97-7). The 72 h EC10 based on growth is 343 µg/L based on the nomimal test substance concentration. Corrected for active ingredient which is 94.4% the EC10 is reduced to 323.8 µg/L.. The test was performed with river water as it is intended to be used in an evaluation of the environmental risks based on the Bulk approach where it is essential to show that the organisms were fully exposed to the nominal test concentration. During the test a decrease of the concentration is observed of about 70%. Imidazolines are susceptible to hydrolysis and the decrease observed could therefore be assigned to either hydrolysis or sorption or both processes. Imidazolines will however only hydrolyze to an amidoamine which is relatively resistant to hydrolysis under ambient conditions. As this hydrolysis will also occur under environmental conditions and amidoamines have a comparable ecotoxicity as the imidazolines the nominal concentration based on active ingredient is considered as the concentration to be used for the dose effect assesment. No significant adsorption to glassware was observed and the organisms were thus fully exposed the the nominal concentration based on active ingredient. Initially to the imidazoline which might have slowly changed into an amidoamine during the test. It is considered realistic to relate the observed effects to the nominal values based on active ingredient.

The effects observed in the definitive study are in good agreement with the results observed in the first study.