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Toxicity to microorganisms

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Reference
Endpoint:
activated sludge respiration inhibition testing
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Remarks:
Study conducted to current OECD test guideline and in accordance with the German principles of GLP. A GLP certificate is present within the report
Qualifier:
according to
Guideline:
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test
Deviations:
no
GLP compliance:
yes (incl. certificate)
Analytical monitoring:
no
Details on sampling:
NA
Vehicle:
no
Details on test solutions:
Test solutions were prepared by direct addition of a weighed quantity of test substance to 200 ml of autoclaved tap water and stirred overnight.
Test organisms (species):
activated sludge of a predominantly domestic sewage
Details on inoculum:
The sludge was washed twice with autoclaved tap water and concentrated to a dry sludge concentration of 3.0 g/L +/_ 10% and used within 24 hours after sampling. The date of receipt was was 21 November 2011 and the dry sludge concentration was 2.93 g/L. The inoculum originated from a
municiple sewage treatment plant of D-31137 Hildesheim, Germany
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
3 h
Post exposure observation period:
NA
Hardness:
NA
Test temperature:
20.4 degrees C
pH:
Activated sludge: 7.84
Synthetic waste water: 7.74
Dissolved oxygen:
NA
Salinity:
NA
Nominal and measured concentrations:
Nominal concentrations: 10, 32, 100, 320 and 1000 mg/L
Details on test conditions:
The concentrations used for the definitive test were based on the results of a range finding test conducted at 10, 100 and 1000 mg/L.
The definitive test was conducted with triplicate control and test vessels. Test concentrations of 58, 100 and 180 mg/L were also included for the reference substance.

The test vessels were 1000 mL Erlenmeyer flasks containing a test medium volume of 500 mL that was composed of 250 mL inoculum, 16 mL synthetic waste water, 234 mL autoclaved tap water and a direct weighing of test substance.

Following the 3 hour incubation, the oxygen concentration of each control, reference item and test item replicate was determined using a oximeter immediatley after transferring the solution to the measuring cell. The oxygen depletion was recorded for at least 3 minutes on a flat bed recorder. During the measurement of oxygen depletion the temperature was determined once in the cell.
Reference substance (positive control):
yes
Remarks:
Copper (II) sulphate pentahydrate (CAS No. 7758-99-8)
Key result
Duration:
3 h
Dose descriptor:
NOEC
Effect conc.:
<= 10 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:
other: EC20
Effect conc.:
10.96 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Remarks on result:
other: <10 - 21.33
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
Key result
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
Details on results:
The EC20 was determined to be 10.96 mg/L and the EC50 was considered to be >1000 mg/L to the activated sludge of a municipal sewage treatment plant. The inhibition of respiration rate was 39% at 320 mg/L and 36% at 1000 mg/L
Results with reference substance (positive control):
The EC50 inhibition of respiration for the reference substance was in the expected range and calculated to be 105.4 mg/L (the recommended range of validity is 53 - 155 mg/L)
Validity criteria fulfilled:
yes
Conclusions:
The EC50 was > 1000 mg/L to activated sludge of a municipal sewage treatment plant.
Executive summary:

A 3-hour GLP compliant static respiration inhibition test with activated sludge was conducted according to OECD Guideline No. 209 was carried out with the test item 4,4-Biphenol, with the experimental phase on 22 November 2011. The activated sludge was obtained from the municipal treatment plant of D-31137 Hildesheim, Germany.

The EC50 was determined to be >1000 mg/L

Description of key information

EC20 determined to be 10.96 mg/L and EC50 was greater than the maximum tested concentration (>1000 mg/L)

Key value for chemical safety assessment

EC50 for microorganisms:
1 000 mg/L

Additional information

A 3-hour GLP compliant static respiration inhibition test with activated sludge was conducted according to OECD Guideline No. 209 was carried out with the test item 4,4-Biphenol (batch number: 071111370), with the experimental phase on 22 November 2011. The activated sludge was obtained from the municipal treatment plant of D-31137 Hildesheim, Germany.

 

The EC50 was determined to be >1000 mg/L

Suitable conclusions can be made based on the results of the study