2-isopropyl-5-methyl-cyclohexanone

Endpoint summary

Additional information

Valid acute toxicity tests with the test substance or a structural similar read-across substance are available for three freshwater species from three trophic levels.

An acute aquatic toxicity test with fish was conducted with the reaction mass of isomenthone and trans-menthone as limit test (threshold approach). No mortality was observed over the study period of 96 hours and the LC50 value was greater than 28 mg/L.

No short-term toxicity test with aquatic invertebrates with the reaction mass of isomenthone and trans-menthone is available. A weight of evidence approach is being conducted, using two studies with read-across substances DL-Isomenthone (CAS 491-07-6) and L-menthan-3-one (CAS 14073 -97-3), respectively. The effects of the test item DL-Isomenthone (CAS 491-07-6) to daphnids (Daphnia magna) were investigated according to the EU Method C.2 (1992) under GLP conditions. The 64.5 % DL-Isomenthone is accompanied by 35.2 % of the diastereomeric DL-Menthone (CAS 89-80-5, as well considered isomolar) and is thus comparable with one of the qualities of submission item "reaction mass of isomenthone and trans-menthone 32/65" as given in chapter 1.2. The test organisms were exposed during 48 hours under static conditions in closed vessels to nominal concentrations of 0, 6.5, 13, 25, 50 and 100 mg/L. The dose was verified as Total Organic Carbon (TOC analysis) and found sufficiently constant under the test conditions. As the recovery was below 80 % the effects were assigned to measured concentrations. The 48 h EC50 for daphnids was calculated to be 25 mg/L. Additional evidence for the validity of this study result is being delivered by the study with L-menthan-3 -one (CAS 14073 -97 -3), where the test item consisted to 84% of L-menthan-3 -one and to 16% of D-Isomenthone. This study revealed an EC50 of 30.6 mg/L. As by the available two studies all four reaction mass components have been tested for acute Daphnia toxicity, the reaction mass therefore can be considered as adequately investigated for this endpoint. The two studies revealed very similar EC values, i.e. 25 mg/L and 30.6 mg/L, respectively. As outcome of the WoE approach, the EC50 value of 25 mg/L as derived by the study with test item consisting of 64.5 % isomenthone and 35.2 % menthone shall be considered as key value for chemical safety assessment.

A valid respiration inhibition test is not available. The toxicity control in the valid study on ready biodegradability showed no inhibition of microorganisms at a concentration of 2.4 mg/L, which can be seen as the NOEC for microbial inhibition.