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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:
2012
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:
no
GLP compliance:
yes (incl. QA statement)
Remarks:
EL
Analytical monitoring:
no
Vehicle:
no
Test organisms (species):
activated sludge of a predominantly domestic sewage
Details on inoculum:
- Preparation of inoculum for exposure: Sludge collected on the day of analysis. Coarse particles were removed by settling for ca. 15 min, the upper layer was decanted and aerated at test temperature until it was used in the test.
- Initial biomass concentration: 1.5 g/L
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
3 h
Test temperature:
20.2 - 20.9 °C
pH:
7.91 - 8.02
Nominal and measured concentrations:
nominal: 10, 100, 1000 mg/L (preliminary test)
nominal: 1200 mg/L (definitive test)
Details on test conditions:
TEST SYSTEM
- Test vessel: 1000 mL
- Aeration: yes

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: synthetic sewage feed according to OECD 209
Reference substance (positive control):
yes
Remarks:
3,5-dichlorphenol
Duration:
3 h
Dose descriptor:
other: EC20
Effect conc.:
60.9 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Remarks on result:
other: result calculated from preliminary and definitive test
Duration:
3 h
Dose descriptor:
other: EC30
Effect conc.:
502.22 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Remarks on result:
other: result calculated from preliminary and definitive test
Duration:
3 h
Dose descriptor:
EC50
Effect conc.:
> 1 200 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Remarks on result:
other: result of definitive test
Results with reference substance (positive control):
EC50 = 15.80 mg/L (total)
EC50 = 20.51 mg/L (heterotrophic)
EC50 = 9.37 mg/L (nitrification)

Results with test substance concentration 1200 mg/L:

Total inhibition: 36.36%

Heterotrophic inhibition: 36.59%

Nitrification inhibition: 36.49%

Validity criteria fulfilled:
yes
Executive summary:

The toxicity of TC to microorganisms was tested in a respiration inhibition test according to OECD 209. The highest applied test substance concentration resulted in an inhibition of ca. 36% related to both total, heterotrophic and nitrification inhibition. The EC50 (3 h) was determined to be >1200 mg/L.

Description of key information

The toxicity of TC to microorganisms was tested in a respiration inhibition test according to OECD 209.

Key value for chemical safety assessment

Additional information

The highest applied test substance concentration resulted in an inhibition of ca. 36% related to both total, heterotrophic and nitrification inhibition. The EC50 was determined to be >1200 mg/L.