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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:
1994
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Justification for type of information:
None
Qualifier:
according to guideline
Guideline:
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test
Deviations:
yes
Remarks:
- Deion. 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
Principles of method if other than guideline:
Guideline followed
GLP compliance:
yes
Specific details on test material used for the study:
- Code number: FAT 20042/D
- Batch no. : 276
- Purity: ca 50%
- Solubility: insoluble
- Storage: room temperature
- Expiration date: 10/98
Analytical monitoring:
no
Details on sampling:
None
Vehicle:
not specified
Details on test solutions:
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
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:
freshwater
Limit test:
no
Total exposure duration:
3 h
Remarks on exposure duration:
None
Post exposure observation period:
None
Hardness:
None
Test temperature:
21.0 °C
pH:
7.0 before the test beginning, after 3 h : 7.5 - 7.9
Dissolved oxygen:
None
Salinity:
None
Conductivity:
None
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:
Sludge dry weight: 1.44 g/L
Test volume: 100 mL
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: 7.0 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:
growth inhibition
Details on results:
The % inhibitions observed with 320, 100, 32 and 10 mg/L test concentrations were 3.27, 1.96, 4.58 and 12.42 % respectively.
Results with reference substance (positive control):
IC50 (3 h) of the reference substance 3,5-Dichlorophenol: 9.5 mg/l
Reported statistics and error estimates:
The respiration rate of each test concentration was calculated as a percentage of the mean of the two control respiration rates. The results were plotted on a logarithmic (concentration) / normal (% inhibition) graph, where the IC50 was evaluated.

None

Validity criteria fulfilled:
yes
Conclusions:
The IC50 (3 h) of the test substance FAT 20042/D was determined to be >320.0 mg/L
Executive summary:

The toxicity of FAT 20042/D to activated sludge was determined in a 3-hours respiration inhibition test according to the EEC Method No. L 133/118 -122 and to the OECD Guideline No. 209. The test substance 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. The % inhibitions observed with 320, 100, 32 and 10 mg/L test concentrations were 3.27, 1.96, 4.58 and 12.42 % respectively. Based on the findings, the IC50 (3 h) of the test substance FAT 20042/D was determined to be >320.0 mg/l and the IC50 (3 h) of the reference substance 3,5-Dichlorophenol was 9.5 mg/l.

Description of key information

The IC50 of Acid Red 195 is greater than 320 mg/L.

Key value for chemical safety assessment

EC50 for microorganisms:
320 mg/L

Additional information

The toxicity of FAT 20042/D to activated sludge was determined in a 3-hours respiration inhibition test according to the EEC Method No. L 133/118 -122 and to the OECD Guideline No. 209. The test substance 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. The % inhibitions observed with 320, 100, 32 and 10 mg/L test concentrations were 3.27, 1.96, 4.58 and 12.42 % respectively. Based on the findings, the IC50 (3 h) of the test substance FAT 20042/D was determined to be >320.0 mg/l and the IC50 (3 h) of the reference substance 3,5-Dichlorophenol was 9.5 mg/l.

In other supporting studies that evaluated toxicity to microorganisms, the IC50 for Acid Red 195 was found to be >300 mg/l.