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Toxicity to aquatic algae and cyanobacteria

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Description of key information

The toxicity of5-Aminobenzimidazolon trocken to the unicellular freshwater green alga Desmodesmus subspicatus was determined according to the principles of OECD 201. The EC50-value with 95 % confidence intervals for inhibition of specific growth rate (ErC50)  after 72 h was 56.1 (46.4 – 70.6) mg/L.

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Additional information

The toxicity of 5-Aminobenzimidazolon trocken to the unicellular freshwater green alga Desmodesmus subspicatus was determined according to the principles of OECD 201 in two tests.

In study I, 5-Aminobenzimidazolon trocken was found to inhibit the growth of the freshwater green alga Desmodesmus subspicatus after 72 h with the following effect values (nominal test item concentrations): The EC50-values with 95 % confidence intervals for inhibition of specific growth rate (ErC50) and yield (EyC50) after 72 h were 56.1 (46.4 – 70.6) and 16.2 (13.8 – 19.1) mg/L, respectively. All effect levels are given based on geometric mean measured concentrations of 5-Aminobenzimidazolon trocken.

In study II, 5-Aminobenzimidazolon TF ZW was found to inhibit the growth of the freshwater green alga Desmodesmus subspicatus after 48 h with the following effect values (geometric mean measured test item concentrations): The EC50-values with 95 % confidence intervals for inhibition of specific growth rate (ErC50) and yield (EyC50) after 48 h were 68.7 (64.5 – 74.1) and 48.2 (42.9 – 53.1) mg/L, respectively. All effect levels are given based on geometric mean measured concentrations of 5-Aminobenzimidazolon.

Since in study II the exposure time was only 48 hours, it was decided that the result of study II (exposure time 72 hours) is the more relevant one.