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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Description of key information

With high probability acutely not harmful to aquatic algae.

Key value for chemical safety assessment

EC50 for freshwater algae:
133 mg/L
EC10 or NOEC for freshwater algae:
25 mg/L

Additional information

In a non-GLP, 72-hour static test with the green alga Scenedesmus subspicatus according to a national standard method (DIN 38412 L9), the algae toxicity of Imidazole was studied (BASF 1989). Statistical evaluation of the endpoint growth rate revealed an EC50 (72h) of 133 mg/l and a NOEC (72h) of 25 mg/l, both related to the nominal concentrations.

In order to support the data on CAS 288-32-4, imidazole, acute data were also taken from CAS 693-98-1, 2-methylimidazole and CAS 916 -47 -7, 1 -methylimidazole. These substances reveal comparable structures as they consist of a imidazole-ring with an additional methyl group at the 2 -C or 1 -C atom, respectively. This additional methyl group is neither supposed to change the chemical properties signifacantly (as the comparison of the phys-chem properties indicates) nor should it lower the intrinsic toxicity. Instead, the additional methyl group leads to an increased logPow which indicates a higher toxicity if base-line toxicity is considered to be the relevant mode of action.Hence, the read-across is deemed valid.

These data support the assumption that imidazole is of low toxicity to aquatic organisms. Due to all the data present, it can be concluded that imidazole is of low toxicity to algae.

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