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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:
10 February 2000 to 10 February 2000
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
Deviations:
yes
Remarks:
During the preparation of the inoculum the sludge weight after the washing procedure was higher as recommended. The sludge concentrations in the test were according to the guideline
Qualifier:
according to guideline
Guideline:
other: Commission Directive 87/302/EEC, Annex L 133, Part C, pp 118-122 (edition 1988)
Deviations:
no
GLP compliance:
no
Specific details on test material used for the study:
SOURCE OF TEST MATERIAL
- Source and lot/batch No.of test material: 99 Labormischung 1
- Expiration date of the lot/batch: January 2005

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: room temperature
- Stability under test conditions: insoluble
Analytical monitoring:
no
Details on sampling:
- Test concentrations: 1, 10 and 100 mg/L of the test substance.
The test substance was not soluble in the test medium. Therefore, it was given directly into the test system without preparation of a stock solution.
Vehicle:
no
Details on test solutions:
A synthetic sewage feed was made by dissolving the following amounts of substances in 1 litre of deionized water:
16.0 g peptone
11.0 g meat extract
3.0 g urea
0.7 g NaCl
0.4 g CaCl2*H2O
0.2 g MgSO4*7H2O
2.8 g K2HPO4
Test organisms (species):
other: Activated sludge of a communal sewage treatment plant.
Details on inoculum:
- Test system:
Activated sludge of a communal sewage treatment plant (ARA Therwil) collected on February 09, 2000.

- Sludge pre-treatment:
The inoculum was prepared 1 day prior to the experimental start. The freshly collected activated sludge was washed 3 times with tap water. Subsequently the sludge was aerated. A sample of the activated sludge was taken to determine the dry weight of the suspended solids. The final concentration of the inoculum was adjusted to about 5.0 g/L suspended solids. For the storage overnight synthetic sewage feed was added depending on the sludge concentration.
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
3 h
Test temperature:
21 °C
Nominal and measured concentrations:
Nominal concentrations: 1, 10 and 100 mg/L.
Details on test conditions:
Temperature: 21 °C
Sludge dry weight: 1.5 g/l suspended solids
Test volume: 100 ml
Aeration: 0.1 - 0.2 L/min by Pasteur pipette
Estimation technique: O2 consumption, measured with an oxygen sensitive electrode system: OXI DIGI 530 (SOP: 00 109)
pH value: The pH-values of the content of the test vessels were measured at the end of the test.
Reference substance (positive control):
no
Key result
Duration:
3 h
Dose descriptor:
IC50
Effect conc.:
> 100 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: IC20
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Details on results:
Calculation of inhibition:
- At 100 mg/L: 0 %
- At 10 mg/L: 4 %
- At 1 mg/L: 0 %
Validity criteria fulfilled:
yes
Conclusions:
The IC20 and IC50 for FAT 93503/A is greater than 100 mg/L.
Executive summary:

The bacteria toxicity test was done according to OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test). The aim of this study was to determine the IC50 of FAT 93503/A (Concentration of the test substance which inhibits the respiration activity of the activated sludge by 50 %). The activated sludge was obtained from a communal wastewater treatment plant. The duration of the test was 3 h. The test was conducted in static condition, at 21 °C, slowly aerated and the test volume was 100 ml. The control was done in duplicate using synthetic sewage feed, inoculum and water. The test was considered valid because the respiration rates of the two substances were within 15 % of each other. In conclusion, the IC20 and IC50 for FAT 93503/A is greater than 100 mg/L.

Description of key information

The bacteria toxicity test was done according to OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test). The aim of this study was to determine the IC50 of FAT 93503/A (Concentration of the test substance which inhibits the respiration activity of the activated sludge by 50 %). The activated sludge was obtained from a communal wastewater treatment plant. The duration of the test was 3 h. The test was conducted in static condition, at 21 °C, slowly aerated and the test volume was 100 ml. The control was done in duplicate using synthetic sewage feed, inoculum and water. The test was considered valid because the respiration rates of the two substances were within 15 % of each other. In conclusion, the IC20 and IC50 for FAT 93503/A is greater than 100 mg/L.

Key value for chemical safety assessment

EC50 for microorganisms:
100 mg/L

Additional information