2-tert-butylcyclohexyl ethyl carbonate

Endpoint summary

Description of key information

A fish study was performed as part of a preliminary test to determine the concentrations to use in a bioconcentration study. Chemical analysis was not performed and LC50 values were based on nominal concentrations as the test substance was prepared in a stock solution containing vehicle and then diluted. All concentrations used in the study were below the solubility limit of the test substance. As, in the BCF study, actual concentrations were found to be very close to the nominal values and as no significant loss of test substance over the 72 h study period occurred in the algae study, it is considered acceptable to base the LC50 on nominal concentrations for this substance. In conclusion, a 96h LC50 of 3.86 mg/L based on nominal concentrations was determined for Oryzias latipes.

The 48-hr acute toxicity of the test substance toDaphnia magnawas studied under static conditions. Daphnids were exposed totest chemical at nominal concentrations of 8, 11, 16, 22, 32, 45, 64, 90, 130 mg/L as well as to a controlfor 48 hr. Immobilization effects were observed. Certain but not all oncentrations were measured using DOC as a surrogate for specific analysis,

The authors took 100 mg/L of test substance and mixed it for 10 minutes with an ultrathurax then serial diluted. However, as the substance is only soluble at 11 mg/L it is therefore not possible to know how much was really in the test vessels. A DOC measurement found 6.9 mg/L at 48 h at a nominal of 32 mg/L. This would convert to 9.8 mg/L as TS (TS/C x concentration= 226/156 x 6.8). Earlier concentrations measured (T0 and T24 were higher) so this nominal of 32 mg/L is probably close to or above saturation in the study. 30 to 40% "mortality" was found at 48 h at this concentration so it can be assumed that the true toxicity approaches or exceeds the limit of solubility of 11 mg/L.

A value of 9.8 mg/L will be used as a conservative estimate of the 48 h EC50.

The influence of 2-tert-butylcyclohexyl ethyl carbonate on the growth of the freshwater green algae Pseudokirchneriella subcapitatawas assessed in a static dose response test in a GLP study following OECD 201. The 72-hour ErC50 value was calculated to be 10.7 mg test item/L.

The ErC10 value was calculated to be 3.76 mg test item/L, the 72-hour NOErC was determined to be 1.35 mg test item/L and the associated 72-hour LOErC was 3.35 mg test item/L. As the test item was found to be stable over the study period all results are based on initial measured concentrations (nominals were not used as the original stock solution was prepared at a concentration known to be above the solubility limit and all test solutions were either the stock solution itself or serial dilutions of it).