Reaction Mass of 2,6-dimethyloct-7-en-2-ol and 2,6-dimethyloct-7-en-2-yl formate

Toxicity to aquatic algae and cyanobacteria

Description of key information

The 72h-EC50 and 72h-EC10/NOEC of Dimyrcetol are calculated to be 39.5 and 13.9 mg/L, respectively, based on the 72h-EC50 and 72h-NOEC of Dihydromyrcenol and the 72h-EC50 and 72h-EC10 of Dihydromyrcenyl formate. For the determination of the 72h-EC50 (10.2 mg/L) and 72h-EC10 (6.2 mg/L) of Dihydromyrcenyl formate, the values derived from Dihydromyrcenyl acetate (5.4 and 2.9 mg/L, respectively) were corrected for molecular weight and log Kow (Log EC50 target (mmol) = Log EC50 source (mmol) x log Kow source/Log Kow target). A weighted average (0.426*80 + 0.528*10.2) and (0.426*25 + 0.528*6.2) was used to determine the 72h-EC50 and 72h-EC10/NOEC of Dimyrcetol, respectively.

Key value for chemical safety assessment

EC50 for freshwater algae:

39.5 mg/L

EC10 or NOEC for freshwater algae:

13.9 mg/L

Additional information

No data on aquatic toxicity data is available for Dimyrcetol, however an algae study with Dihydromyrcenol and with the structural analogue of Dihydromyrcenyl formate: Dihydromyrcenyl acetate is available.

Dihydromyrcenol (Algae toxicity)

In a Freshwater Alga and Cyanobacteria, Growth Inhibition Test performed in accordance with OECD 201 and following GLP, Pseudokirchneriella subcapitata was exposed to the test substance in a 72-hour static test. The algae were exposed to nominal concentrations of 0, 6.25, 12.5, 25, 50 and 100 mg/L. The measured test concentration were 91% to 102% of nominal concentrations. The 72h-ErC50 and 72h-ErC10 were determined to be 80 and 25 mg/l, respectively.

Dihydromyrcenyl Acetate (Algae toxicity)

In a Freshwater Alga and Cyanobacteria, Growth Inhibition Test performed in accordance with OECD 201 and following GLP, Desmodesmus subspicatus was exposed to the test substance in a 72-hour static test. The test was performed using glass stoppered Erlenmeyer flasks (closed system) completely filled with test medium. The test item was added into test water in a requisite amount at a loading rate of 100 mg/L. Thereafter slow stirring was applied for 96 hours in a closed vessel to reach a maximum concentration of dissolved test item in the test water. After stirring, the lower equilibrated aqueous phase of the solution was carefully separated from the non-dissolved upper test item phase and was used as highest test concentration. This highest test concentration was further diluted with test water to obtain the following test item dilutions 1:320, 1:100, 1:32, 1:10 and 1:3.2. Additionally, a control (test water without test item) was tested in parallel. At the start of the test, the analytically measured concentrations of the test item in the dilutions 1:32, 1:10, 1:3.2 and undiluted test medium (loading rate of 100 mg/L) were 0.50, 1.6, 5.1 and 18 mg/L, respectively. At the end of the test, 79 to 91% of the initially measured values were found, in the samples with algae. This loss is likely due to adsorption of the test item to the growing algal biomass since measured concentrations at the end of the test in samples without algae were 94-100% initial. Nonetheless, the results were based on the mean measured concentrations (calculated as the geometric mean of the test item concentrations measured at the start and end of the test). The 72h-ErC50 and 72h-ErC10 were determined to be 5.4 mg/L (95% CI: 5.1-6.0) and 2.9 mg/L (95% CI: 2.2-3.4), respectively.