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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:
2005-10-17 to 2006-02-21
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Test performed according to standard test guidelines (OECD, EC) and conform GLP requirements. The results of the test can be considered reliable without restrictions.
Qualifier:
according to
Guideline:
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test
Deviations:
no
Qualifier:
according to
Guideline:
EU Method C.11 (Biodegradation: Activated Sludge Respiration Inhibition Test)
Version / remarks:
Commission Directive 87/302/EEC, No. L 133
Deviations:
no
GLP compliance:
yes (incl. certificate)
Specific details on test material used for the study:
- Name of test material (as cited in study report): TIC2782 (T002907)
- Physical state: white solid
- Analytical purity: 99.9%
- Lot/batch No.: 00467090 (= charge 05C0836)
- Expiration date of the lot/batch: 2006-05-04
- Stability under test conditions: no data
- Storage condition of test material: at room temperature (~20°C) away from direct sunlight
- solubility in water: 32 g/L
- safety precautions: routine hygienic procedures
Analytical monitoring:
no
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: Due to the limited water solubility of T002907, no stock solution could be prepared. Test item amounts of 500.4 mg were directly weighed, then 284 ml of tap water was added. The test item was mixed into the tap water by ultrasonic treatment over 15 min. and intense stirring for 24 hours at room temperature in the dark to dissolve a maximum concentration of the test item in the test media.
- Controls: yes

Test organisms (species):
activated sludge of a predominantly domestic sewage
Details on inoculum:
- Source: predominantly domestic wastewater treatment plant, ARA Ergolz II, Füllinsdorf, Switzerland
- Washing procedure: washed twice with tap water by centrifugation, supernatant liquid phase decanted. The homogenized aliquot of final sludge suspension was weighed, dried, and ratio wet to dry weight calculated.
- Holding: an aliquot of washed sludge was suspended in tap water at 3 g dw/L, holding 3 days prior to testing, fed daily with 50 mL synthetic wastewater per L, kept at room temperature and continuous aeration.
- Initial biomass concentration: sludge concentration of 2.1 g/L dw
Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
3 h
Hardness:
not applicable
Test temperature:
20°C
pH:
control: 7.5-8.5
test item: 7.9-8.5
Dissolved oxygen:
8.0-8.8 mg O2/L
Salinity:
not applicable
Nominal and measured concentrations:
Nominal concentrations: 1000 mg/L.
Details on test conditions:
TEST SYSTEM
- Test vessel: 2000-mL glass beakers, 500-mL fill-volume
- Aeration: continuously aerated by intense stirring on magnetic stirrers.
- Number of replicates: 1
- Number of control replicates: 2
- Biomass loading rate: sludge concentration of 2.1 g/L (dw basis) (corresponding to ~0.8 dm / L test medium).

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: tap water + synthetic wastewater, as prescribed by guidelines

OTHER TEST CONDITIONS
- Adjustment of pH: The pH of the activated sludge inoculum was adjusted from 8.9 to 7.2 with a diluted sulfuric acid solution

EFFECT PARAMETERS MEASURED (with observation intervals if applicable): respiration rate measured after 3 h of exposure (well-mixed sample poured into a BOD flask and not further aerated, dissolved oxygen concentration measured with oxygen electrode (WTW TriOxmatic 300 and an oxygen meter WTW Oxi 539, Weilheim, Germany) and continuously recorded for at least 10 minutes)

TEST CONCENTRATIONS
- Spacing factor for test concentrations: none (limit test)
- Range finding study
- Test concentrations: no information
- Results used to determine the conditions for the definitive study: no information
Reference substance (positive control):
yes
Remarks:
3,5-dichlorophenol
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
Remarks on result:
other: could not be calculated
Duration:
3 h
Dose descriptor:
NOEC
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: no
- The 3-h EC20 > 1000 mg/L.
- The 3-h EC80 > 1000 mg/L.
Results with reference substance (positive control):
- Results with reference substance valid? yes
- Relevant effect levels: 3-h EC50 = 24 mg/L (95% CL = 14-44 mg/L). This is within the recommended range of 5-30 mg/L confirming suitability of the activated sludge used.
Reported statistics and error estimates:
The 3-h EC50 of the reference item was calculated by Probit analysis.
Validity criteria fulfilled:
yes
Conclusions:
An activated sludge respiration inhibition test (limit test) (according OECD guideline 209) with activated sludge from a predominantly domestic wastewater treatment plant resulted in a 3-h EC50 of > 1000 mg T002907/L. The NOEC was >= 1000 mg T002907/L. The results of the study can be considered reliable without restriction.

Description of key information

The study of Grützner (2006), investigating the toxicity of T002907 to microorganisms according to OECD guideline 209, was considered as the key study for endpoint coverage. The 3-h ELR50 was > 1000 mg/L. The 3-h NOELR was >= 1000 mg/L.

Key value for chemical safety assessment

Additional information