Reaction mass of 3a,4,5,6,7,7a-hexahydro-4,7-methano-1H-inden-5-yl isobutyrate and 3a,4,5,6,7,7a-hexahydro-4,7-methano-1H-inden-6-yl isobutyrate

Long-term toxicity to aquatic invertebrates

Description of key information

The effects of Cyclabute on mortality and reproduction of Daphnia magna were determined in a semi-static test with an exposure period of 21 days. The 21 day NOEC and EC10 were determined to be 0.462 and 0.126 mg test item/L for reproduction. Usually, the EC10 represents the key value for reproduction studies. In contradiction to the usual evaluation in this study the NOEC is presented as the key value. With regard that in this study no clear dose response was found at the lower test item concentrations, the statistical output showed the EC10–value to be lower than the NOEC; At the lowest test item concentration of 0.0089 mg/L an inhibition of 11.9 % was observed, compared to an inhibition of -1.3 % at the next higher test item level of 0.0307 mg/L. At the test item concentration of 0.164 mg/L the inhibition increased to 9.7 %. Even at the test item concentration of 0.462 mg/L the inhibition of 13 % in reproduction is only slightly above the inhibition observed at the lowest test item concentration. In sum this affects the statistical evaluation of the EC10. In addition, the two lowest test item concentrations had to be averaged with the LoD according to the test guideline, which also affects the calculation of the EC10 towards a less realistic value compared to the reported NOEC. In contrast to the EC10 the NOEC is based on realistic averaged measured concentrations between two water renewals (without being averaged with the LoD). Therefore, we conclude for this study based on the summarized results that the NOEC is a better key value than the EC10.
The 21 day EC10 and NOEC were determined to be 0.126 and 0.462 mg test item/L for reproduction. For mortality of the adult test animals the EC10 and NOEC were determined to be 1.599 and ≥ 1.83 mg test item/L. The EC50 for reproduction was 3.30 mg test item/L (extrapolated value) and >1.830 mg test item/L for mortality.
The initial concentrations and the maintenance of the exposure concentrations during the test were verified in the analytical part. All reported results refer to time weighted average concentrations, since the test item concentrations were not within ± 20% of the nominal or measured initial concentrations during the test.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Dose descriptor:

NOEC

Effect concentration:

0.46 mg/L