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Short-term toxicity to aquatic invertebrates

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Description of key information

With high probability acute not harmful to aquatic invertebrates

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates
Effect concentration:
207 mg/L

Additional information

Two publications by Bringmann and Kuehn (1982, 1977) indicate that cyclohexanone is acutely not harmful to Daphnia. The 24h-EC50 values are 800 mg/L and 820 mg/L, respectively. Both studies were performed similar to German industrial standard, with a test period of 24 h and without analytical controls. Nevertheless these limitations were considered in a validity score of 2 (valid with restrictions), which is in the line with the validation in the ICCA SIDS program. The validity without analytical monitoring is reasonable, since cyclohexanone can be supposed as stable under the test conditions and the volatilization of cyclohexanone is negligible. Cyclohexanone has a Henry’s Law constant of 1.3 Pa/m³ mol and has therefore a low tendency to escape from the water phase.

The very low acute toxicity of cyclohexanone to aquatic invertebrates is confirmed by the results of an estmation conducted with the QSAR Toolbox (v4.3.1) using trend analysis within category members. The estimated EC50 of 207 mg/L is considered reliable and is taken, as a worst case, as key value for the chemical safety assessment.

A further indication of the low acute toxicity of cyclohexanone is supplied by the result of an investigation conducted with the very similar substance cyclopentanone (CAS No. 120 -92 -3). Both substances are saturated alicyclic ketones, whose only difference consists in a methylene group. The relevant physico-chemical properties are similar as well. The acute toxicity study on cyclopentanone to Daphnia magna was carried out in accordance with the OECD Guideline 202 (Rhodia, 2003). The principles of Good Laboratory Practices were fulfilled. For cyclopentanone no immobilisation was observed at the tested concentrations up to 100 mg/l at time 0; 24 and 48 hours. At the end of the test duration the recovery rate of the test item was > 80 % so that volatilisation can be excluded under the test conditions.