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Reference
Endpoint:
activated sludge respiration inhibition testing
Type of information:
experimental study
Adequacy of study:
key study
Study period:
14 -15 April 2010
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test
Version / remarks:
(1984)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Analytical monitoring:
not required
Vehicle:
no
Details on test solutions:
The test substance was directly weighed out in each test vessel. After 24h of stirring the test substance was completely dispersed.
Test organisms (species):
activated sludge of a predominantly domestic sewage
Details on inoculum:
- Origin: Municipal sewage treatment plant of D-31157, Sarstedt Germany
- Preparation of inoculum for exposure:
- Pretreatment: The sludge was washed twice with autoclaved tap water and adjusted corresponding to a dry weight of 4.0 g/L ± 10%. The sludge was used within 24 h after sampling.
- Dry sludge concentration: 3.97 g/L
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
3 h
Hardness:
Not reported
Test temperature:
20.9 °C
pH:
6.89
Dissolved oxygen:
5.2 - 7.7 mg O2/L (determined at the start of the measurement)
Nominal and measured concentrations:
Nominal concentrations: 0 (control), 100, 180, 320, 580 and 1000 mg/L
Details on test conditions:
TEST SYSTEM
- Test vessel: 500 mL Erlenmeyer flasks
- Aeration: Permanent
- No. of vessels per concentration (replicates): 1
- No. of vessels per control (replicates): 2

TEST MEDIUM / WATER PARAMETERS
Composition of the test medium:
200 mL inoculum
16 mL synthetic waste water
284 mL autoclaved tap water
test item concentration (directly weighed out in each test vessel)


EFFECT PARAMETERS MEASURED:
The oxygen depletion of the control, reference and test item replicates was measured after 3 hours incubation by means of an oximeter and recorded for at least 3 minutes on a flat bed recorder.

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 1.8
- Range finding study: Yes
- Test concentrations: 0 (control), 10, 100 and 1000 mg/L
- Results used to determine the conditions for the definitive study: 0% inhibition at 10 mg/L, 4% inhibtion at 100 mg/L and 18% at 1000 mg/L
Reference substance (positive control):
yes
Remarks:
copper (II) sulphate pentahydrate
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
Details on results:
The EC10 is estimated by the reviewer to be 1000 g/L (11% inhibition at 1000 mg/L and 9% inhibition at 580 mg/L).
Results with reference substance (positive control):
The 3h-EC50 of the refence substance copper (II) sulphate pentahydrate was 103 mg/L which is within the recommended confidence range of 54 - 156 mg/L

Table: Respiration rates and inhibition of respiration of test and reference item concentrations.

Treatment

Concentration (mg/L)

Respiration rate (mg O2/L/h)

Inhibition (%)

Test item

1000

28.0

11

580

28.8

9

320

31.6

0

180

30.0

5

100

32.8

-4

Control

-

31.2

-

-

32.0

-

Reference item

180

9.2

71

100

14.8

53

58

23.6

25

 

Validity criteria fulfilled:
yes
Remarks:
The two control respiration rates differ not more than 15% in the study. The 3h-EC50 of copper (II) sulphate pentahydrate is within the accepted range of 54-156 mg/L.
Conclusions:
The 3h-EC50 of the test substance to activated sludge was > 1000 mg/L
The 3h-EC10 of the test substance to activated sludge, estimated by the reviewer was 1000 mg/L
Executive summary:

The toxicity of the test substance to activated sludge was investigated according to OECD guideline 209 and GLP.

The 3h-EC50 of the test substance to activated sludge was > 1000 mg/L

The 3h-EC10 of the test substance to activated sludge, estimated by the reviewer (based on 11% inhibition at 1000 mg/L and 9 % inhibition at 580 mg/L) was ca. 1000 mg/L.

Because the test was carried out according to OECD209 and GLP an no shortcomings were observed a reliability 1 was assigned.

Description of key information

The 3h-EC50 of the test substance to activated sludge was > 1000 mg/L.
The 3h-EC10 of the test substance to activated sludge, estimated by the reviewer was 1000 mg/L.

Key value for chemical safety assessment

EC50 for microorganisms:
1 000 mg/L

Additional information

The toxicity of the test substance to activated sludge was investigated according to OECD guideline 209 and GLP.

The 3h-EC50 of the test substance to activated sludge was > 1000 mg/L.

The 3h-EC10 of the test substance to activated sludge, estimated by the reviewer (based on 11% inhibition at 1000 mg/L and 9 % inhibition at 580 mg/L) was ca. 1000 mg/L. Based on the fact that this is an estimation, the worst-case EC50 value of 1000 mg/L is taken as key value for the CSA.

Since the test was carried out according to OECD209 and GLP, and because no shortcomings were observed a reliability 1 was assigned.