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Long-term toxicity to aquatic invertebrates

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Description of key information

The following results were obtained with the test substance in a 21-day semi-static chronic toxicity test to Daphnia magna: NOEC value of 0.22 mg/L based on reproduction; LOEC value of 0.44 mg/L based on reproduction and EC50 and EC10 values 0.58 and 0.33 respectively based on reproduction as well. The results were based on measured concentrations.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates
Effect concentration:
0.22 mg/L

Additional information

The study evaluated the effects of the test substance on the reproductive output of Daphnia magna. Young female Daphnia were exposed to aqueous test media containing the test item for 21 days at a range of concentrations.

The nominal test item concentrations were 0.19, 0.38, 0.75, 1.50 and 3.00 mg/L. The measured test item concentrations deviated more than 20 % from the nominal during the experiment therefore the time-weighted mean of the measured start and end concentrations at each water renewal period were calculated in order to determine exposure concentrations. The calculated time-weighted mean concentrations were the followings: 0.12, 0.22, 0.44, 0.89 and 1.65 mg/L. All biological results are based on these measured test item concentrations.

The test was run in a semi-static water renewal system, with daily renewal periods. The test solutions were prepared using water-miscible solvent (acetone). An untreated control (only Elendt M4 Medium) and an additional solvent control group were investigated concurrently. Ten Daphnia were investigated in each group (per concentration and controls). Samples were taken from each testing concentration at the start and at the end of each water renewal period. Controls were analysed at the start of each water renewal period. The validity criteria of the test were fulfilled.

The offspring produced by each parent animal were removed and counted daily from the appearance of the first brood. The statistical evaluation of the mean number of living juveniles showed that the offspring production for concentrations 0.44, 0.89 and 1.65 mg/L (measured) was statistically significantly different from that of the solvent control. No significant reduction of the offspring production was observed in the two lowest test concentration (0.12 and 0.22 mg/L; measured) and in the untreated control when compared to the solvent control group.

Accordingly, the 21-day NOEC related to reproduction was determined to be 0.22 mg/L (measured). The 21-day LOEC was 0.44 mg/L (measured). The 21-day EC50 was determined to be 0.58 mg/L (95 % confidence limits: 0.53 – 0.62 mg/L). The 21-day EC10 was determined to be 0.33 mg/L (95 % confidence limits: 0.28 – 0.36 mg/L).

Aborted broods were observed in some cases at the two highest concentration (0.89 and 1.65 mg/L; measured). Stumpy limbs of parent animals were noticed in the highest test concentration (1.65 mg/L; measured) at the end of the study (on 21st day). The mortality among the parent animals was recorded daily. Significant mortality was observed in the two highest concentration (0.89 and 1.65 mg/L; measured) when compared to the solvent control, therefore mortality in these concentrations were considered as a test item effect and the produced number of juveniles in replicates where parental mortality occurred were also included in the data analysis related to reproduction. In the lower concentrations (as well as in the controls) no significant parent mortality was observed (based on the statistical evaluation) and therefore the replicates of dead parents were excluded from reproductive performance analysis. At the end of the test body length measurements of the parent animals were performed and the obtained data was statistically evaluated. Statistically significant differences were observed for concentrations 0.89 and 1.65 mg/L (measured), when compared to the solvent control group.