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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:
1993
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Justification for type of information:
None
Qualifier:
according to
Guideline:
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test
Deviations:
yes
Remarks:
-Deionised water instead of dest. water for the stock solution. -Preparation of the inoculum : higher sludge weight after the washing procedure (Sludge concentrations in the test according to the guidelines). - 4 instead of 5 test concentrations
GLP compliance:
yes
Specific details on test material used for the study:
- Code number: FAT-31'016/P
- EN-Nr.: 414154.32
- Purity: 95 %
- Appearance: solid
- Solubility: 40 g/L (in water)
- Storage: room temperature
- Expiration date: 07/98
Analytical monitoring:
no
Vehicle:
no
Test organisms (species):
activated sludge of a predominantly domestic sewage
Details on inoculum:
- Organism : Activated sludge of a communal sewage treatment plant (ARA-Birsig Therwil)
- Sludge pretreatment : 3 times washing with tap water and addition of synthetic sewage (a day before the main test)
Test type:
static
Water media type:
other: deionised water
Limit test:
no
Total exposure duration:
3 h
Test temperature:
21.5 °C
pH:
7.8 - 8.0
Dissolved oxygen:
O2-consumption (in cm) 10 mg/l: 3.9, 32 mg/l: 2.4, 100 mg/l 0.7 and 320 mg/l: 0.4
Nominal and measured concentrations:
320, 100, 32 and 10 mg/l of the test substance
Details on test conditions:
- Temperature: 21.5 °C
- Sludge dry weight: 1.50 g/l
- Test volume: 100 ml
- Test duration: 3h
- Estimation technique: O2 - consumption, measured with an oxygen sensitive electrode system: OXI DIGI 530 (SAV : 00 109)
- Aeration: 0.1 - 0.2 l/min by pasteur-pipette
- pH of sludge: 7.9 before the test beginning
Reference substance (positive control):
yes
Remarks:
3,5-Dichlorophenol
Key result
Duration:
3 h
Dose descriptor:
IC50
Effect conc.:
21 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Results with reference substance (positive control):
The IC50 (3 h) of the reference substance 3,5-Dichlorophenol : 8.0 mg/l

Table: % inhibition observed for test concentrations

Test substance

(mg/l)

%

inhibition

320

93.02

100

84.88

32

61.63

10

29.07

Validity criteria fulfilled:
yes
Conclusions:
The IC50 (3 h) of the test substance FAT - 31 '016/P was determined to be 21 mg/l.
Executive summary:

The toxicity of FAT - 31'016/P to activated sludge was determined in a 3-hours respiration inhibition test according to the OECD Guideline No. 209, and to the EEC Method No. L 133/118.

The test was performed in compliance with the Good Laboratory Practice (GLP) Regulations of Switzerland. The test substance concentrations tested were 320, 100, 32 and 10 mg/l. The % inhibitions observed at test concentrations 320, 100, 32 and 10 mg/l were 93.02, 84.88, 61.63 and 29.07, respectively. Hence, the IC50 (3 h) of the test substance FAT - 31 '016/P was determined to be 21 mg/l.

Description of key information

The IC50 (3 h) of the test substance FAT - 31 '016/P was determined to be 21 mg/l.

Key value for chemical safety assessment

EC50 for microorganisms:
21 mg/L

Additional information

The toxicity of FAT - 31'016/P to activated sludge was determined in a 3-hours respiration inhibition test according to the OECD Guideline No. 209, and to the EEC Method No. L 133/118. The test substance concentrations tested were 320, 100, 32 and 10 mg/l. The % inhibitions observed at test concentrations 320, 100, 32 and 10 mg/l were 93.02, 84.88, 61.63 and 29.07, respectively. Hence, the IC50 (3 h) of the test substance FAT - 31 '016/P was determined to be 21 mg/l.