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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
Study period:
2008-07-08 - 2008-11-06
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: The study was conducted according to an internationally accepted guideline. All study parameters are based on the specific guideline.
Qualifier:
according to
Guideline:
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test
Deviations:
no
GLP compliance:
yes (incl. certificate)
Analytical monitoring:
not specified
Vehicle:
yes
Details on test solutions:
Preparation and incubation of the test solutions:
Solutions of the test item were freshly prepared at the start of the test using a stock solution. Preparation of the test item solutions:
The weighed amount of the test item was mixed with tap water to prepare seven test item solutions immediately before application.
Preparation of the control solution:
24 ml. of synthetic sewage feed (prepared in accordance with OECD guideline 209), 426 mL tap water and 300 mL sludge suspension were pipetted into an incubation vessel (1 L glass flask).
Preparation of the test solutions:
100 mL of the respective test item solution, 24 mL of synthetic sewage feed (prepared in accordance with OECD guideline 209), 326 mL tap water and 300 mL sludge suspension were pipetted into an incubation vessel (1 L glass flask).
Afterwards, the total mixture (750 mL) per vessel was aerated with oil-free air with an air flow of 0.5 to 1 L per minute. The incubation of the test solution was performed at a temperature of 20 ± 2 °C over a time span of three hours (contact time).
Test organisms (species):
activated sludge
Details on inoculum:
As microbial source (inoculum) for the test, activated sludge from the municipal sewage treatment plant 04451 Borsdorf, Germany was used (date of collection: 16.07.2008).
Before test start, the collected sludge was washed with tap water to remove possible disturbing substances (e.g. respiration inhibitors).
For this purpose the sludge was centrifuged and the developed supernatant was decanted. Afterwards, tap water was added and mixed with the sludge. This suspension was centrifuged again and the supernatant was decanted. The washing procedure was repeated three times.
After the washing procedure was finished, a small amount of the washed sludge (approx. 10 g) was weighed and dried for the determination of the sludge dry weight (sludge d.w.). From this result an activated sludge suspension was prepared with a concentration of about 4 g sludge dry weight per litre tap water.
Since the activated sludge could not be used for the test on the day of collection (16.07.2008), 50 ml_ synthetic sewage feed (prepared in accordance with OECD guideline 209) were added to each litre of the sludge suspension and then aerated at 20 ± 2 °C until the test was started (17.07.2008).
Before use, the pH-value of the activated sludge suspension was measured as 6.5 (required pH 6.0 - 8.0).
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
3 h
Test temperature:
20 ± 2 °C
pH:
6.5
Dissolved oxygen:
Aeration of the test vessels: continuously during the contact time
Nominal and measured concentrations:
Nominal: 100, 375, 750, 1500, 3000, 6000 and 12000 mg test item/L
Reference substance (positive control):
yes
Remarks:
3,5-Dichlorophenol
Duration:
3 h
Dose descriptor:
EC50
Effect conc.:
2 120 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth inhibition
Results with reference substance (positive control):
To verify the sensitivity of the test system the reference item 3,5-dichlorophenol was tested in a separate study (BioChem project No,: R 08 10 48 001 D) on the same batch of activated sludge like the test item at concentrations of 2.5, 5.0, 10.0, 20.0 and 40.0 mg/L. The EC50 was calculated to be 6.4 mg/L (required 5 - 30 mg/L).

Effects on activated sludge after treatment with P70/05/S-4

Treatment group

O2 consumption [mg/L/10 min]

O2 consumption [mg/L 60 min]

per replicate

mean

Inhibition [%]

Control

4.09

4.25

24.54

25.50

25.02

 

100 mg P70/05/S-4/L

2.91

17.46

-

30.2

375 mg P70/05/S-4/L

2.74

16.44

-

34.3

750 mg P70/05/S-4/L

2.66

15.96

-

36.3

1500 mg P70/05/S-4/L

2.20

13.20

-

47.2

3000 mg P70/05/S-4/L

1.97

11.82

-

52.8

6000 mg P70/05/S-4/L

1.67

10.02

-

60.0

12000 mg P70/05/S-4/L

1.42

8.52

-

65.9

Validity criteria fulfilled:
yes
Conclusions:
The toxicity of N-[3(5)-Methyl-1 H-pyrazol-1 -yl-methyl]acetamide to microorganism was determined according to OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test). The EC50of the test item after 3 hours of exposure to the micro-organisms of activated sludge was calculated to be 2120 mg/L.

Executive summary:

The toxicity of N-[3(5)-Methyl-1 H-pyrazol-1 -yl-methyl]acetamide to microorganism was determined according to OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test). The EC50of the test item after 3 hours of exposure to the micro-organisms of activated sludge was calculated to be 2120 mg/L.

Description of key information

The toxicity of N-[3(5)-Methyl-1 H-pyrazol-1 -yl-methyl]acetamide to microorganism was determined according to OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test). The EC50 of the test item after 3 hours of exposure to the micro-organisms of activated sludge was calculated to be 2120 mg/L.

Key value for chemical safety assessment

EC50 for microorganisms:
2 120 mg/L

Additional information

The EC50 of the test item after 3 hours of exposure to the micro-organisms of activated sludge was calculated to be 2120 mg/L.