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Ecotoxicological information

Toxicity to microorganisms

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Link to relevant study record(s)

Reference
Endpoint:
activated sludge respiration inhibition testing
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2000-02-15 to 2000-02-15
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test
Version / remarks:
adopted 4 April 1984
Deviations:
no
GLP compliance:
yes
Analytical monitoring:
no
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: Each test solution was prepared by direct addition of the test substance in the test flask with an appropriate micropipette immediately before the start of the test.
- Controls: yes (two controls)
Test organisms (species):
activated sludge of a predominantly domestic sewage
Details on inoculum:
- Laboratory culture: no
- Source: the water treatment plant Emeraude (SIARR); 76141 Petit-Quevilly, France
- Preparation of inoculum for exposure: the inoculum was left to settle and the supernatant rejected. It was then filtered and washed with dechlorinated water. Four samples of 50 mL were taken to determine the content in suspended matter (dry weight). The concentration of sludge (8.80 g/L) was then adjusted to 4 g/L by addition of the appropriate volume of dechlorinated water.
- Initial biomass concentration: 1.6 g/L
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
3 h
Hardness:
280 +/- 20 mg/L as CaCO3
Test temperature:
22 °C
Nominal and measured concentrations:
- nominal concentration: 2, 10 and 20 mg/L
Details on test conditions:
TEST SYSTEM
- Test vessel: flasks which were made up to 300 mL with water
- Type: open
- Aeration: air was bubbled through each solutions at the rate of 0.5 to 1 L/min until the start of oxygen concentration measurements
- No. of organisms per vessel: 200 mL of inoculum
- No. of vessels per concentration: 2
- No. of vessels per control: 2
Reference substance (positive control):
yes
Remarks:
3,5- Dichlorophenol
Key result
Duration:
3 h
Dose descriptor:
EC50
Effect conc.:
> 20 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Key result
Duration:
3 h
Dose descriptor:
EC10
Effect conc.:
> 20 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Details on results:
The respiration rate of the test item solution at the highest concentration was equivalent to the respiration rate of the first control. Therefore, the oxygen consumption rate of the two other test solutions was not determined.
Based on the inhibition percentage of the respiration rate obtained in the test solution of highest concentration, the 3-hour EC10 of the test substance was also > 20 mg/L.
Results with reference substance (positive control):
The EC50 (3 h) of 3,5-Dichlorophenol was 14 mg/L (95 % confidence limits 12 - 17 mg/L).
Reported statistics and error estimates:
Determination of the EC50:
When for at least two concentrations, inhibition is > 0% and < 100 %, the EC50 is calculated according to Probit analysis. The confidence interval limits are calculated statistically according to Fieller`s method.
When at only one concentration, inhibition is > 0 % and < 100 %, the EC50 is also calculated by Probit analysis. In this case, the highest concentration causing no inhibition and lowest concentration producing 100 % inhibition are used as confidence limits.
If at all concentrations inhibition is 0 or 100 %, the EC50 corresponds to the geometric mean of the highest concentration causing no inhibition and the lowest concentration producing 100 % inhibition.
Validity criteria fulfilled:
yes
Conclusions:
The 3-hour EC50 of cyclohexylidenebis[tert-butyl]peroxide was determined to be > 20 mg/L for activated sludge. The 3-hour EC10 of the test substance was > 20 mg/L.
Executive summary:

The acute toxicity of cyclohexylidenebis[tert-butyl]peroxide on micro-organismus present in activated sludge was evaluated using a 3-hour static test according to OECD guideline no. 209. Three test solutions (2, 10 and 20 mg/L) were tested. The respiration rate of the test solution at the highest concentration (20 mg/L) was equivalent to the respiration rate of the first control. Therefore, the oxygen consumption rate of the two other test solutions was not determined. The 3-hour EC10 and the 3-hour EC50 of the test substance cyclohexylidenebis[tert-butyl]peroxide were determined to be > 20 mg/L.

Description of key information

The 3-hour EC50 of cyclohexylidenebis[tert-butyl]peroxide was determined to be > 20 mg/L for activated sludge. The 3-hour EC10 of the test substance was > 20 mg/L.

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:
20 mg/L

Additional information

The acute toxicity of cyclohexylidenebis[tert-butyl]peroxide on micro-organismus present in activated sludge was evaluated using a 3-hour static test according to OECD guideline no. 209. Three test solutions (2, 10 and 20 mg/L) were tested. The respiration rate of the test solution at the highest concentration (20 mg/L) was equivalent to the respiration rate of the first control. Therefore, the oxygen consumption rate of the two other test solutions was not determined. The 3-hour EC10 and the 3-hour EC50 of the test substance cyclohexylidenebis[tert-butyl]peroxide were determined to be > 20 mg/L.