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Toxicity to microorganisms

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Endpoint:
activated sludge respiration inhibition testing
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2008-01-28 to 2008-02-25
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Reason / purpose:
reference to other study
Reference:
Composition 0
Qualifier:
according to
Guideline:
EU Method C.11 (Biodegradation: Activated Sludge Respiration Inhibition Test)
Version / remarks:
88/302/EC
Deviations:
no
Qualifier:
according to
Guideline:
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test
Version / remarks:
1984-04-04
Deviations:
no
GLP compliance:
yes (incl. certificate)
Test material information:
Composition 1
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):
NA
Analytical monitoring:
no
Details on sampling:
NA
Vehicle:
no
Test organisms (species):
activated sludge, domestic
Details on inoculum:
Species / Origin:
Activated Sludge, micro organisms from a domestic waste water treatment plant was supplied by the municipal sewage treatment plant Darmstadt, Germany.

Conditioning:
The activated sludge was washed by centrifugation and the supernatant liquid phase was decanted. The solid material was re-suspended in tap water and again centrifuged. The latter procedure was repeated twice. The washed sludge was resuspended in tap water and sewage feed (50 mL per L) was added. The sludge was kept at room temperature under continuous aeration until use over night. Immediately before use, the dry weight of the activated sludge was determined and diluted to 3.8 mg/L with tap water. The pH of the activated sludge was 7.8 and therefore no adjustment necessary.
Test type:
static
Water media type:
not specified
Limit test:
no
Total exposure duration:
3 h
Hardness:
no data
Test temperature:
21°C during dissolution phase (24 hours)
19-21 °C during pre-incubation (3 hours)
18-20°C during evaluation period
pH:
At the start of the study the pH of the activated sludge was 7.8 and therefore no adjustment was necessary.
During the study pH values of 7.4 at the start and 8.6 at the end of study (after 3h) were determined.
Dissolved oxygen:
The concentration of dissolved oxygen did not drop below 2.5 mg O2/L during the incubation period and just before the measurements of the respiration rates the oxygen concentrations were at least 8.5 mg O2/L and thus >6.5 mg O2/L.
Salinity:
NA
Nominal and measured concentrations:
The test item is not soluble in water. Therefore, the test item was directly weighed into the test vessels and stirred for about 24 hours before using in the experiment. The respiration rates of the activated sludge treated with the test item at concentrations between 10 and 1000 mg/L differed by less than 10% from control.
The following test concentrations were checked:
1) Test substance: 10, 32, 100, 320 and 1000 mg/L
2) Reference substance 3,5 -Dichlorophenol: 3.2, 10 and 32 mg/L
Details on test conditions:
NA
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
Details on results:
Based on measured inhibition rates, the 3 -hour EC10, EC20 and EC50 could not be quantified because up to the highest nominal test concentration of 1000 mg/L less than 10% inhibition was noted after three hours incubation. No dose related response was found. The test according to OECD 209 guideline does not provide a threshold value for the determination of a NOEC. If a deviation of less ≤ 15% between test item treated activated sludge and control is considered not to be an effect, the NOEC of the test item will be established above 1000 mg/L.
Results with reference substance (positive control):
The 3 -hour EC50 of 3,5 -Dichlorophenol was calculated to be 10.4 mg/L with 95% confidence limits of 7.4 - 14.6 mg/L.

3 -hour EC10, EC20 and EC50 could not be quantified because up to 1000 mg/L less than 10% inhibition was noted. No dose related response was found. If a deviation of less ≤ 15% between test item treated activated sludge and control is considered to be without effect. The NOEC of the test item will be established above 1000 mg/L.

The 3 -hour EC50 of 3,5 -Dichlorophenol was calculated to be 10.4 mg/L with 95% confidence limits of 7.4 - 14.6 mg/L.

Validity criteria fulfilled:
yes
Conclusions:
Based on measured inhibition rates, the 3 -hour EC10, EC20 and EC50 could not be quantified because up to the highest nominal test concentration of 1000 mg/L less than 10% inhibition was noted after three hours incubation. No dose related response was found. The test according to OECD 209 guideline does not provide a threshold value for the determination of a NOEC. If a deviation of less ≤ 15% between test item treated activated sludge and control is considered not to be an effect, the NOEC of the test item will be established above 1000 mg/L.
The 3 -hour EC50 of 3,5 -Dichlorophenol was calculated to be 10.4 mg/L with 95% confidence limits of 7.4 - 14.6 mg/L (results see also attached).
Executive summary:

The test item is not soluble in water. Therefore, the test item was directly weighed into the test vessels and stirred for about 24 hours before using in the experiment. The respiration rates of the activated sludge treated with the test item at concentrations between 10 and 1000 mg/L differed by less than 10% from control.

Based on measured inhibition rates, the 3 -hour EC10, EC20 and EC50 could not be quantified because up to the highest nominal test concentration of 1000 mg/L less than 10% inhibition was noted after three hours incubation. No dose related response was found. The test according to OECD 209 guideline does not provide a threshold value for the determination of a NOEC. If a deviation of less ≤ 15% between test item treated activated sludge and control is considered not to be an effect, the NOEC of the test item will be established above 1000 mg/L.

The 3 -hour EC50 of 3,5 -Dichlorophenol was calculated to be 10.4 mg/L with 95% confidence limits of 7.4 - 14.6 mg/L.

Endpoint:
activated sludge respiration inhibition testing
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
comparable to guideline study
Justification for type of information:
For this endpoint a one-to-one read across was performed to a chemical similar compound of the same chemical class with a comparable phys. chem. profile and similar response in biological assays. The relevant study was performed according to GLP and the methods applied are fully compliant with OECD TG 209. A detailed read across justification is provided in chapter 13 of this dossier.
Reason / purpose:
read-across source
Related information:
Composition 1
Test material information:
Composition 1
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 heterotrophic respiration
Validity criteria fulfilled:
yes
Conclusions:
For this endpoint a one-to-one read across was performed to a chemical similar compound of the same chemical class with a comparable phys. chem. profile and similar response in biological assays. The relevant study was performed according to GLP and the methods applied are fully compliant with OECD TG 209. The EC50 of the structural analogue is above 1000 mg/L (nominal). A detailed read across justification is provided in chapter 13 of this dossier.

Description of key information

RA OECD 209: EC50 > 1000 mg/L (nominal)

Key value for chemical safety assessment

EC50 or LC50 for microorganisms:
1 000 mg/L

Additional information