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Short-term toxicity to aquatic invertebrates

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Description of key information

The acute toxicity of hydroquinone to Daphnia magna was investigated in a study conducted equivalent or similar to OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test) under semi-static conditions and under GLP. A 48 h EC50=0.134 mg/L based on measured initial concentration was determined.

Key value for chemical safety assessment

EC50/LC50 for freshwater invertebrates:
0.134 mg/L

Additional information

Four studies dealing with the acute toxicity of hydroquinone to Daphnia are available; three studies with an exposure period of 48 hours and one study with 24 hours. The EC50 nvalues of the 48 hour tests ranged from 0.13 to 0.29 mg/L based on nominal or measured initial concentrations.

Only in one study the acute toxicity of hydroquinone to Daphnia magna was investigated equivalent to OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test) under semi-static conditions and under GLP. The daphnids (20 animals/concentration) were exposed to measured concentration of 0 (control), 0.029, 0.043, 0.074, 0.11, and 0.18 mg/L for 48 h. The test substance concentrations were measured by HPLC/UV. The endpoint examined was immobilization. The 48 h NOEC, EC50, and EC100 were determined to be 0.029, 0.061, and 0.11 mg/L based on mean measured concentrations. As it has not been possible to discriminate between the effect of hydroquinone and its oxidation products the initial concentration is regarded as relevant concentration.

Therefore, the daphnia test is re-evaluated based on the measured initial concentration. Thus, a 48 h EC50=0.134 mg/L (recalculated measured initial concentration) has to be taken into account for assessment. The testing/validity criteria laid down in the OECD guideline 202 are fulfilled. These findings are supported by a study conducted according to ISO 6341 15 (Water quality - Determination of the Inhibition of the Mobility of Daphnia magna Straus (Cladocera, Crustacea)) and in a study conducted according to DIN 38412, Part II 'Daphnia short-time test' (comparable to OECD Guideline 202 'Daphnia sp. Acute Immobilisation Test'). The 48 h EC50 values were found to be 0.13 mg/L nominal (ISO 6341 15; mean of two tests) and 0.29 mg/L nominal (DIN 38412, Part II). The very high acute toxicity of hydroquinone to Daphnia magna (24 h LC50=0.09 mg/L nominal) found in a study conducted comparable to the German DIN 38412, Part II in 1977 could not be confirmed in the aforementioned guideline studies.