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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:
January 5, 1995 to February 10, 1995
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test
Deviations:
yes
Remarks:
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
Qualifier:
according to
Guideline:
other: EEC Directive 87/302, L 133/118 -122 "Activated Sludge, Respiration Inhibition Test"
Version / remarks:
Edition: 30.05.1988
GLP compliance:
yes
Specific details on test material used for the study:
SOURCE OF TEST MATERIAL
- Source and lot/batch No.of test material: P4
- Expiration date of the lot/batch: Feb 1999

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: room temperature
- Solubility of the test substance in the solvent/vehicle: 30 g/l [in water]
Analytical monitoring:
no
Vehicle:
no
Details on test solutions:
Stock solutions : 500 mg/l test substance / reference substance in deionized water.

Test concentrations: 320, 100, 32 and 10 mg/l of the test substance.
32, 10 and 3.2 mg/l of the reference substance.
Test organisms (species):
activated sludge of a predominantly domestic sewage
Details on inoculum:
Organism: Activated sludge of a communal sewage treatment plant (ARA-Pro Rheno Basel)
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:
freshwater
Limit test:
no
Total exposure duration:
3 h
Post exposure observation period:
Test terminates after 3 hrs.
Hardness:
No data
Test temperature:
20 ± 2 °C
pH:
7.4 before the test beginning
Dissolved oxygen:
No data
Salinity:
No data
Nominal and measured concentrations:
320, 100, 32 and 10 mg/l of the test substance
Details on test conditions:
TEST SYSTEM
- Test volume: 100 ml
- Aeration: 0.1 - 0.2 l/min by Pasteur-pipette
- No. of vessels per concentration (replicates): 1
- No. of vessels per control (replicates): 2
- Biomass loading rate: 1.44 g/l

TEST CONCENTRATIONS
- Results used to determine the conditions for the definitive study: O2- consumption
Reference substance (positive control):
yes
Remarks:
3,5-Dichlorophenol for synthesis (Merck 821768)
Duration:
3 h
Dose descriptor:
IC50
Effect conc.:
32 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Details on results:
The % inhibitions observed were 0, 50, 56.25 and 62.50 % at 10, 32, 100 and 320 mg/L, respectively.
Results with reference substance (positive control):
IC50 (3 h) of the reference substance 3,5-Dichlorophenol: 12 mg/l
Reported statistics and error estimates:
None
Validity criteria fulfilled:
yes
Conclusions:
IC50 (3 h) of the test substance FAT 20200/B is 32 mg/l.
Executive summary:

The toxicity of FAT 20200/B to activated sludge was determined in a 3-hours respiration inhibition test according to the OECD Guideline No. 209. This study has been performed in compliance with the Procedures and Principles of Good Laboratory Practice (March 1986) issued by the Swiss Federal Department of the Interior recognizing the "OECD Principles of Good Laboratory Practice" Paris, 1981. This study was carried out for determination of the test substance concentration, which reduces the respiration of activated sludge by 50 % (IC50 value). Activated sludge from communal sewage treatment plant (ARA-Pro Rheno Basel) was collected and used to carry out this study. The sludge was pretreated by washing with tap water thrice and addition of synthetic sewage feed a day before the main test. The test substance concentrations tested were 320, 100, 32 and 10 mg/l. The % inhibitions observed were 0, 50, 56.25 and 62.50 % at 10, 32, 100 and 320 mg/L, respectively. The reference substance, 3,5-Dichlorophenol when tested at concentrations of 32, 10 and 3.2 mg/l, showed 76.25, 43.75 and 15 % inhibition, respectively.

In conclusion, IC50 (3 h) of the test substance FAT 20200/B is 32 mg/l while IC50 (3 h) of the reference substance 3,5-Dichlorophenol is 12 mg/l.

Description of key information

IC50 (3 h) of the test substance FAT 20200/B was determined to be 32 mg/l.

Key value for chemical safety assessment

EC50 for microorganisms:
32 mg/L

Additional information

The toxicity of FAT 20200/B and FAT 21016/C to activated sludge was determined in two 3-hours respiration inhibition tests according to the OECD Guideline No. 209. These studies were carried out for determination of the test substances concentration, which reduces the respiration of activated sludge by 50 % (IC50 value).

For both test substances concentrations tested were 320, 100, 32 and 10 mg/l. The reference substance, 3,5-Dichlorophenol was tested in concentrations of 32, 10 and 3.2 mg/l.

IC50 (3 h) of the test substance FAT 20200/B is 32 mg/l.

IC50 (3 h) of the test substance FAT 21016/C is >320 mg/l.

IC50 (3 h) of the reference substance 3,5-Dichlorophenol is 12 mg/l.