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Reference
Endpoint:
activated sludge respiration inhibition testing
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2002
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP / guideline study without deviations
Qualifier:
according to guideline
Guideline:
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Analytical monitoring:
no
Vehicle:
no
Details on test solutions:
0, 10, 32, 100, 320 and 1000 mg/L
0, 5, 16 and 50 mg/L of reference item (positive control)
Test organisms (species):
activated sludge of a predominantly domestic sewage
Details on inoculum:
The sludge was washed twice with tap water by centrifugation and the supernatant liquid phase was decanted. A homogenized aliquot of the final sludge suspension was weighed, thereafter dried and the ratio of wet to dry weight was calculated.
Immediately before use, the dry weight of the activated sludge was measured again in the inoculum used in the test. The pH was adjusted from 8.4 to 6.9.
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
3 h
Post exposure observation period:
no
Hardness:
not measured
Test temperature:
Measured in one control:
20 °C at the start of incubation period
19 °C at the end of incubation period.
Monitored in all test media and controls during measurement of respiration rate.
pH:
Measured in all test media and controls.
Start of test: 7.8 - 8.4 (controls)
8.0 – 8.3 (positive control)
7.9 – 8.1 (treated)
End of test: 9.0 (controls)
8.3 – 9.0 (positive control)
9.0 – 9.1 (treated)
Dissolved oxygen:
Oxygen
concentration
(mg O2/L)
Start End
7.7 8.3
8.2 8.0

7.9 7.1
8.3 8.2
8.1 8.0
8.3 8.3
8.3 7.7
Salinity:
not measured
Nominal and measured concentrations:
Nominal: 0, 10, 32, 100, 320 and 1000 mg/L
Reference substance (positive control):
yes
Remarks:
3,5-dichlorophenol
Duration:
3 h
Dose descriptor:
NOEC
Effect conc.:
>= 1 000 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Duration:
3 h
Dose descriptor:
other: EC20
Effect conc.:
>= 1 000 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:
EC50
Effect conc.:
>= 1 000 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Duration:
3 h
Dose descriptor:
other: EC80
Effect conc.:
>= 1 000 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Results with reference substance (positive control):
The results of inoculum controls and positive controls confirmed the suitability of the activated sludge and the method used.

The inhibitory effect of test item or of the reference item on the respiratory rate (oxygen consumption pr minute) is expressed as a percentage of the mean respiratory rate of the two inoculum controls.

The 3-hour EC50, EC20 and EC80 values for test item and their 95% confidence limits could not be calculated due to the absence of a toxic effect.

The 3-hour EC50 value of reference item 3,5-dichlorophenol was calculated by Probit Analysis.

All test results were based on nominal test item concentrations.

Validity criteria fulfilled:
yes
Conclusions:
Up to and including the concentration of 1000 mg/L, the test item d-Phenothrin had no significant inhibitory effect (<15 %) on the respiratory rate of activated sludge after the incubation period of three hours. Thus, the 3-hour NOEC (EC15) of d-Phenothrin to activated sludge microorganisms was at least 1000 mg/L or higher, since concentrations in excess were not tested.
The oxygen consumption rates of the two inoculum controls differed by 9.5%, which is within guideline-recommended maximum variation of 15%, and the 3-hour EC50 of reference item 3,5-dichlorophenol (positive control) was calculated to be 23 mg/L, which is within the guideline-recommended range.
Executive summary:

NOEC  1000 mg/L.

Description of key information

Up to and including the concentration of 1000 mg/L, the test item d-Phenothrin had no significant inhibitory effect (<15 %) on the respiratory rate of activated sludge after the incubation period of three hours. Thus, the 3-hour NOEC (EC15) of d-Phenothrin to activated sludge microorganisms was at least 1000 mg/L or higher, since concentrations in excess were not tested.

Key value for chemical safety assessment

EC50 for microorganisms:
1 000 mg/L
EC10 or NOEC for microorganisms:
1 000 mg/L

Additional information