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Ecotoxicological information

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:
10 Dec 2009
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Analytical monitoring:
no
Vehicle:
no
Test organisms (species):
activated sludge, domestic
Details on inoculum:
- Laboratory culture: A fresh sample of activated sludge trom the aeration basin of a municipal sewage treatment plant (Moers, Germany) was collected one day before test start
- Preparation of inoculum for exposure: The activated sludge was filtered by means of a water jet pump through a filter paper. The sludge was washed twice with mineral medium. Afterwards, 4 g/L activated sludge was suspended in mineral medium, 50 mL synthetic sewage was added and the whole mixture was stirred and aerated obernightat 20 °C.
- Initial biomass concentration: 3 g/L
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
3 h
Hardness:
not specified
Test temperature:
20 ± 2 °C
pH:
7.27 - 8.16
Nominal and measured concentrations:
Nominal: 10, 32, 100, 320 and 1000 mg/L
Details on test conditions:
TEST SYSTEM
- Test vessel: 1L beakers (incubation period) + 300 mL Karlsruher flasks for O2 measurement
- Aeration: The incubation vessels were aerated with compressed synthetic air (0.5 - 1.0 L/min) under permanent stirring with a magnetic stirrer.
- No. of vessels per concentration (replicates): 1
- No. of vessels per control (replicates): 2

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: according to guideline
- Intervals of water quality measurement: The pH was measured at test start and after 3h contact time.

OTHER TEST CONDITIONS
- Adjustment of pH: no

EFFECT PARAMETERS MEASURED: O2 consumption was measured after a contact time of 3 hours for 10 minutes using an oxygen electrode.
Reference substance (positive control):
yes
Remarks:
3,5-Dichlorophenol
Duration:
3 h
Dose descriptor:
EC10
Effect conc.:
260.1 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Duration:
3 h
Dose descriptor:
EC50
Effect conc.:
> 1 000 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Details on results:
- Effect concentrations exceeding solubility of substance in test medium: yes, since undissolved test substance was not removed from the test solution
Results with reference substance (positive control):
- Results with reference substance valid? Yes
Validity criteria fulfilled:
yes
Conclusions:
In a GLP study according to OECD guideline 209, a 3h-EC50 value of the test substance was > 1000 mg/L, while the respective 3h-EC10 value is determined to be 260.1 mg/L.
Executive summary:

The toxicity of the test substance to microorganisms was evaluated in a study according to OECD guideline 209 under GLP conditions.

In a static study domestic activated sludge was exposed for 3h. The test material was applied directly to the test vessels.

Analytical monitoring was not performed. All validity criteria were fulfilled. The 3h-EC50 is determined to be > 1000 mg/L, while the respective 3h-EC10 value is dtermined to be 260.1 mg/L based on the nominal concentration.

Description of key information

EC50 (3h) > 1000 mg/L, EC10 (3h) = 260.1 mg/L (nominal) for activated sludge (OECD 209)

Key value for chemical safety assessment

EC50 for microorganisms:
1 000 mg/L
EC10 or NOEC for microorganisms:
260.1 mg/L

Additional information

One study investigating the toxicity of the test substance to aquatic microorganisms is available. The study was performed according to GLP and OECD guideline 209 (Wehrhahn 2010). In a static study domestic activated sludge was exposed for 3h. The test material was applied directly to the test vessels. Analytical monitoring was not performed. All validity criteria were fulfilled. The 3h-EC50 is determined to be > 1000 mg/L, while the respective 3h-EC10 value is determined to be 260.1 mg/L based on the nominal concentration.