2-ethylimidazole

Endpoint summary

Additional information

Short-term toxicity to fish:

The test on acute toxicity to fish was conducted according to OECD guideline 203 (BASF AG, 1995). 10 zebra fish (Brachyodanio rerio) per concentration were exposed to test substance concentrations of 0 (control), 21.5, 46.4, 100, 215 and 464 mg/L under static conditions. Mortality and sublethal effects were observed after 1, 4, 24, 48, 72 and 96 hours. 100% mortality was observed at 464 mg/L. All animals were found dead after 24 hours. Tumbling was observed in the two highest testing groups. At 215 mg/L fish showed tumbling between 24 and 72 hours of exposure. In the highest testing group tumbling was observed after 4 hours. Results were based on nominal and analytically determined values:  Results (nominal): LC50(96 hours) = 250 mg/L, NOEC(96 hours) = 100 mg/L.  Results (analytical): LC50(96 hours) = 232 mg/L, NOEC(96 hours) = 89mg/L.
Short-term toxicity to aquatic invertebrates:
The 48-hour acute toxicity of the test substance to Daphnia magna STRAUS was studied under static conditions (BASF AG, 1993). Daphnids were exposed to control and test substance at nominal concentrations of 0, 12.5, 25, 50 and 100 mg/L for 48 hours. Immobilisation and sublethal effects were observed at 0, 3, 6, 24 and 48 hours. None of the animals showed any adverse effects or immobilisation at any of the concentrations tested. The 48-hour EC50 was above 100 mg/L.

Toxicity to aquatic algae and cyanobacteria:
In a 72 hour acute toxicity study, cultures of green algae (Scenedesmus subspicatus, CHODAT SAG 86.81) were exposed to the test substance at nominal concentrations of 0 (control), 0.78, 1.56, 3.13, 6.25, 12.5, 25, 50 and 100 mg/L under static conditions in accordance with EU method C.3. NOEC, EC10 and EC50 values based on growth rate were 25 mg/L, 58.1 mg/L and above 100 mg/L. No compound related phytotoxic effects were observed during the study (BASF AG, 1994).

Toxicity to microorganisms:
The inhibitory effect of the test substance on the growth rate of Pseudomonas putida were examined in a static test according to DIN 38412, part 8. Bacteria were cultivated under specific conditions and growth rate was determined under the influence of the test substance compared to blank controls. Therefore the optical density of the bacteria suspension was measured at 436 nm after incubation with a photometer. The grade of toxicity was determined in comparing the extinction values of the controls with the test samples.
Bacteria were exposed to the test substance at concentrations of 0 (control), 39.06, 78.13, 156.3, 312.5, 625, 1250, 2500, 5000 and 10000 mg/L for 16 hours. 4 replicates were performed for each concentration. At the four highest test concentrations a raise of pH was observed. Neutralization resulted in a reduction of harmful effects, i.e. a reduction of growth inhibition. No bacteriotoxic effects were observed at concentrations below 1250 mg/L. An EC50 of 865 mg/L and an EC10 of 499 mg/L were determined (BASF AG, 1993).

The inhibitory effects of the test substance on the respiration rate of aerobic waste water bacteria was examined in a static test according to OECD guideline 209 (BASF AG, 1998). Bacteria were cultivated under specific conditions and respiration rate was determined under the influence of test substance compared to blank and positive controls. As positive control substance 3,5-Dichlorophenol was used in concentrations of 0.5, 5 and 50 mg/L. An EC50 of 10 mg/L was determined for the positive control. The bacteria were incubated with the test substance at concentrations of 250, 500 and 1000 mg/L for 30 min and 3 hours. An EC50 of above 1000 mg/L was determined.

The results with Pseudomonas putida were chosen as key values due to the lower sensitivity and the shorter duration of the sludge respiration test.