Registration Dossier
Registration Dossier
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EC number: - | CAS number: -
Toxicity to microorganisms
Administrative data
Link to relevant study record(s)
Description of key information
An inhibitory dose response effect was not observed for the treatment groups. The EC50 value calculation is not possible for the test item as a stimulatory dose response was observed. The abiotic treatment mixture dosed with 1000 mg/L of test item had a respiration rate of 0.3 mg O2/L/hr showing there was no significant uptake or release of oxygen resulting from abiotic reactions of the test substance (OECD 209).
Key value for chemical safety assessment
Additional information
GUIDELINE
The potential effect of the test item on activated sludge microorganisms maintained in an aerobic environment was assessed by the Activated Sludge Respiration Inhibition Test Method (OECD Guideline 209).
METHODS
The test contained control, reference and treatment groups. The control replicates were used to determine the background respiration rate of the sludge and were not dosed with the test or reference substance. The reference group was dosed with 3, 5-dichlorophenol, a known inhibitor of respiration, at concentrations of 3, 15 and 50 mg/L. The treatment group was dosed with test item at concentrations of 10, 100, and 1000 mg/L. The 1000 mg/L treatment was tested in triplicate. An abiotic control was dosed with the test substance at a concentration of 1000 mg/L to discriminate between abiotic uptake by the test substance and microbial respiration. After an exposure period of three hours, the respiration rates of the test solutions were measured using an YSI Model 5000 Dissolved Oxygen Meter.
RESULTS
The respiration rates in the two controls were 27.04 and 29.08 mg O2/L/hr. Both controls had respiration rates above or equal to 26.53 mg O2/L/hr, which is the low limit based on the validity criteria for mixtures with 1.33 g dry weight of suspended solids per litre. The coefficient of variation of the two control respiration rates was 5.14%, and was within the 30 % limit established for the test. The validity of the test was further supported by the results from the 3, 5-dichlorophenol reference group, which resulted in an EC50 value of 15.00 mg/L, with 95 percent confidence limits of 3 mg/L and 50 mg/L. The EC50 for the reference substance was within the 2 to 25 mg/L range considered acceptable for the test.
CONCLUSION
An inhibitory dose response effect was not observed for the treatment groups. The EC50 value calculation is not possible for the test item as a stimulatory dose response was observed. The abiotic treatment mixture dosed with 1000 mg/L of test item had a respiration rate of 0.3 mg O2/L/hr showing there was no significant uptake or release of oxygen resulting from abiotic reactions of the test substance.
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