Registration Dossier
Registration Dossier
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EC number: 406-530-2 | CAS number: - MDI
Toxicity to microorganisms
Administrative data
Link to relevant study record(s)
Description of key information
Based on the results of two valid activated sludge respiration inhibition studies, the substance is not toxic to STP microorganisms up to 1000 mg/L.
Key value for chemical safety assessment
Additional information
The toxicity to aquatic microorganisms was examined in a limit test according to OECD TG 209 and in compliance with GLP criteria. Microorganisms in activated sludge from a predominantly domestic sewage were exposed to nominal test concentrations of 0 (control) and 100 mg/L test item prepared by direct addition and 30 minutes of contact time or 24 hours of pre-incubation and 3 hours contact time. Significant inhibition of the respiration rate of the activated sludge was recorded only in one replicate tested in the 3 -hour experiment (14%). However, the duplicate measurement did not confirm this (-5%). Based on the findings in the test, the 30 -min and 3 -h EC50 values were determined to be >100 mg/L (expressed as nominal). It is considered that due to the very low water solubility of the test substance (<1 mg/L), concentration levels that might be toxic to aerobic bacteria could not be reached.
In a second study, also performed according to OECD TG 209 and in compliance with GLP criteria, microorganisms in activated sludge from a predominantly domestic sewage were exposed to nominal test concentrations of 0 (control), 32, 100, 320, and 1000 mg/L test item for 3 hours.
Up to and including the concentration of nominal 1000 mg/L the test item had no significant inhibitory effect (<15%) on the respiration rate of activated sludge after the incubation period of 3 hours. The highest test concentration of nominal 1000 mg/L showed a weak inhibitory effect of about 11%. The slightly increased inhibitory effect of about 11% at the highest test concentration was not determined as a significant toxic effect, since this value is within the range of normal variability of the results, and within the accepted variability of 15% for the controls. The determined concentration-effect relationship is probably due to the decrease in the activity of the activated sludge seen between the two controls at the start and the end of the test. Based on these findings, the 3 -h EC50 value was determined to be >1000 mg/L (expressed as nominal).
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