5-amino-6-methyl-1,3-dihydrobenzoimidazol-2-one

Endpoint summary

Additional information

Short term toxicity to fish

The acute toxicity to fish was assessed in a 96-h toxicity study according to OECD guideline 203 and EU method C.7 under GLP conditions. After a range-finding test, a limit test was performed with carp (Cyprinus carpio) exposed to 100 mg/L in a static system. Samples for analysis were taken at the start and the end of the test. Analysis of the samples taken during the final limit test showed that the measured concentration was in agreement with the nominal concentration. No visible effects occurred during the 96-hour test period. Hence, the 96h-LC50 for carp exposed to the test substance was > 100 mg/L, the maximum concentration to be tested. (NOTOX B.V., 1998)

Short term toxicity to aquatic invertebrates

The test substance was assessed in a short term toxicity study to Daphnia magna according to OECD 202 and EU method C.2. Results of a range-finding test showed that the 48h-EC50 was between 1.0 and 10 mg/L with 100% immobility at 10 mg/L. The project was continued with an EC50 test exposing daphnids to a range of 1.0 to 10 mg/L. In contrast to the range-finding test, the final percentage of immobility was 65% at 10 mg/L. Hence, a final test was performed with concentrations of 0 (control), 1.8, 3.2, 5.6, 10, 18 and 32 mg/L, increasing by a factor of 1.8. All EC50 tests were performed with 10 daphnids per vessel. Analysis of the samples taken during the final test showed that the measured concentrations were in agreement with nominal. the test substance did not induce acute immobilization of Daphnia magna at 1.8 mg/L after 48 hours of exposure (NOEC). The 48h-EC50 was 2.9 mg/L (95% confidence interval between 2.7 and 3.3 mg/L). (NOTOX B.V., 1998)

Toxicity to aquatic algae

The present study examined the influence of the test item on the growth of an unicellular green algae Selenastrum capricornutum according to OECD guideline 201 and EU method C.3. After a range-finding test, a final test was performed exposing exponentially growing algal cultures to concentrations ranging from 4.6 to 220 mg/L, increasing with a factor of 2.2. The initial cell density was 10^4 cells/mL. The total test period was 72 hours. The measured concentrations were comparable to the nominal concentrations and did not decrease during the 72 hours test period. Recoveries ranged from 101 to 116 % of nominal. The test substance inhibited cell growth and reduced growth rate of Selenastrum capricornutum significantly at 100 mg/L and higher. The EC50 for cell growth inhibition (EbC50:0-72 h) as well as the EC50 for growth rate reduction (ErC50:0-72 h) were > 100 mg/L. (NOTOX B.V., 1998)

Toxicity to microorganisms

The influence of the test substance on the respiration rate of activated sludge was investigated after a contact time of 30 minutes. The study procedure was based on OECD Guideline No 209. A stock solution of 0.5 g/L was prepared in Milli-Q water. 100 mg/L, corresponding to 100 mL of the prepared stock solution in 500 mL final volume, was tested in duplicate. No significant inhibition in respiration rate of the sludge was recorded at 100 mg/L. The duplicate measurement confirmed the result of the first measurement. Therefore no further testing was needed.

The respiration rates of the controls were within 15% of each other. The EC50 of the reference substance, 3,5-dichlorophenol, was 8 mg/L. Therefore, the test was considered to be valid.

In conclusion, under the conditions of this present test, the test substance was not toxic to waste-water bacteria at a concentration of 100 mg/L. (NOTOX B.V., 1998)