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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:
02 December 1992 to 01 January 1993
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
Version / remarks:
April 4, 1984 (Edition : Paris, 1993).
Deviations:
yes
Remarks:
1) Deionised water instead of distilled water; 2) Preparation of the inoculum: higher sludge weight after the washing procedure (Sludge concentrations in the test according to the guidelines); 3) 4 instead of 5 test concentrations.
GLP compliance:
yes
Specific details on test material used for the study:
Code number: FAT - 40138/D
Batch-Nr.: 275605.26
Purity: 79 %
Appearance: solid
Solubility: 100 g/l [in water]
Storage: room temperature
Expiration date: July, 1993
Analytical monitoring:
no
Vehicle:
no
Test organisms (species):
activated sludge of a predominantly domestic sewage
Details on inoculum:
- Name and location of sewage treatment plant where inoculum was collected: Communal sewage treatment plant (ARA-Pro Rheno Basel)
- Pretreatment: 3 times washing with tap water and addition of synthetic sewage (a day before the main test)
Test type:
static
Water media type:
not specified
Limit test:
no
Total exposure duration:
3 h
Test temperature:
21.9 °C
pH:
6.8 before the test beginning (Sludge)
7.2 - 7.8 (after 3 h)
Dissolved oxygen:
0.95 - 1.03 mg O2 pro min/l
Nominal and measured concentrations:
320, 100, 32 and 10 mg/l of the test substance.
32, 10 and 3.2 mg/l of the reference substance.
Details on test conditions:
TEST MEDIUM / WATER PARAMETERS
Sludge dry weight: 1.50 g/l
Test volume: 100 ml
Test duration: 3 h
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: 6.8 before the test beginning
Reference substance (positive control):
yes
Remarks:
3,5-Dichlorophenol
Key result
Duration:
3 h
Dose descriptor:
IC50
Effect conc.:
> 320 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Details on results:
The % inhibition observed was 0, 2, 4 and 5 % for 320, 100, 32 and 10 mg/L, respectively.
Results with reference substance (positive control):
The IC50 (3 h) of the reference substance 3,5-Dichlorophenol : 7.5 mg/l
Validity criteria fulfilled:
yes
Conclusions:
IC50 (3 h) of FAT 40138/D was determined to be >320 mg/l.
Executive summary:

The toxicity of FAT 40138/D to activated sludge was determined in a 3-h respiration inhibition test according to OECD Guideline 209, in compliance with GLP. The test substance concentrations tested were 320, 100, 32 and 10 mg/l. Exposure was carried out for 3 hours. The % inhibition observed was 0, 2, 4 and 5% for 320, 100, 32 and 10 mg/L respectively. Hence, IC50 (3 h) of FAT 40138/D was determined to be >320 mg/l.

Description of key information

IC50 (3 h) of test substance was determined to be >320 mg/l.

Key value for chemical safety assessment

EC50 for microorganisms:
320 mg/L

Additional information

The toxicity potential of FAT 40138 to microorganisms was assessed on the basis of three available studies. In a key study, the toxicity of FAT 40138/D to activated sludge was determined in a 3-h respiration inhibition test according to OECD Guideline 209, in compliance with GLP. The test substance concentrations tested were 320, 100, 32 and 10 mg/l. Exposure was carried out for 3 hours. The % inhibition observed was 0, 2, 4 and 5 % for 320, 100, 32 and 10 mg/L, respectively. Hence, IC50 (3 h) of FAT 40138/D was determined to be >320 mg/l. In two other supporting studies, 21-day IC50 for FAT 40138 was calculated to be >300 mg/L.