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Endpoint:
activated sludge respiration inhibition testing
Type of information:
experimental study
Adequacy of study:
key study
Study period:
27 July 1992 to 11 December 1992
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Reason / purpose for cross-reference:
other: read-across target
Qualifier:
according to guideline
Guideline:
EU Method C.11 (Biodegradation: Activated Sludge Respiration Inhibition Test)
Deviations:
no
Qualifier:
according to guideline
Guideline:
other: 87/302/EEC page 118-122 Activated sludge respiration inhibition test
Deviations:
no
GLP compliance:
yes
Analytical monitoring:
no
Details on sampling:
No samples were taken for analysis of the test material concentration.
Vehicle:
no
Details on test solutions:
TEST CONCENTRATIONS
21.0, 9.1, 3.3, 1.4, 0.8 and 0.3 mg of the test material were weighed and added to the test medium. The volume was adjusted to 200 mL with water and aerated for 3 hours. This produced test solutions of nominal concentrations of 105.0, 45.5, 16.5, 7.0, 4.0 and 1.5 mg/L.

The sludge concentration in the test bottles was 1.60 g/L (dry weight) .

A reference compound (3,5-dichlorophenol) was also tested at 3 concentrations (32.0, 10.0, and 3.2 mg/L).
Test organisms (species):
activated sludge
Details on inoculum:
Activated sludge collected from the sewage treatment plant of CH-4153 Reinach on 28/09/92. The pH after collection was 7.0. The preparation was carried out according to the method described in the guideline. The sludge was separated from the aqueous layer by settling instead of centrifugation. The pH of the sludge before use was 7.8
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
3 h
Post exposure observation period:
none
Hardness:
Not stated
Test temperature:
Temperature was maintained at 20 ± 2 ºC.
pH:
pH was measured in blank (2 samples), reference standard (three samples) and test concentrations (six samples). The pH in blank number 1 was measured as 7.8 and in all other sameples was measured as 8.3.
Dissolved oxygen:
Oxygen consumption per hour in mg/litre was measured with an ORION - Electrode Type 97-08, ORION Microprocessor Ionaliser 901 and plotted on a recorder.
Salinity:
Not applicable
Nominal and measured concentrations:
Nominal concentrations of test material were 105.0, 45.5, 16.5, 7.0, 4.0 and 1.5 mg/L.
Actual concentrations were not measured.
Details on test conditions:
DESIGN AND PROCEDURE
Vessels: 250 mL BOD flasks with gas inlet
Water: Dechlorinated drinking water
Temperature: 20 ± 2 °C
Duration: 3 hours
Nutrient solution: 16 g Peptone, 11 g Meat extract, 3.0 g Urea, 0.7 g NaCl, 0.4 g CaCl2 • 2H2O, 0.2 g MgSO4 • 7 H2O, 2.8 g K2HPO4 are dissolved and made up to one litre with dechlorinated drinking water.

Deviations from guideline: Instead of a centrifuged sludge a settled sludge was used. Due to the poor solubility of the test material at test concentrations, no stock solution was prepared: The test material was given directly into the medium. Therefore, a constant factor between the test concentrations could not been achieved.
Reference substance (positive control):
yes
Remarks:
3,5-dichlorophenol
Key result
Duration:
3 h
Dose descriptor:
other: EC20
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Key result
Duration:
3 h
Dose descriptor:
EC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Key result
Duration:
3 h
Dose descriptor:
other: EC80
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Results with reference substance (positive control):
The calculated EC50 (3 h) for the reference substance, based on nominal concentrations, was 12.6 mg/L.
Reported statistics and error estimates:
The inhibitions were calculated on the basis of the measured time depend oxygen consumption of a Blank and Test solution. The Results ( ECxx Values ) were calculated with linear regression.

Table 5. Rates of inhibition (%) for control and test solutions.

Sample Conc (mg/l) Consumption rate (mg/l/h) Inhibition (%)
Blank 1 0.0 52.8 3
Blank 2 0.0 56.3 -3
Reference 1 32.0 11.0 80
Reference 2 10.0 31.8 42
Reference 3 3.2 50.4 8
Test conc. 1 105.0 50.8 7
Test conc. 2 45.5 53.9 1
Test conc. 3 16.5 55.7 -2
Test conc. 4 7.0 54.3 0
Test conc. 5 4.0 55.5 -2
Test conc. 6 1.5 61.1 -12
Validity criteria fulfilled:
yes
Conclusions:
Under the conditions of the study no significant inhibition of oxygen consumption was found over the test concentrations compared to the controls, therefore the resulting EC50 was >= 100 mg/L (the highest test concentration).
Executive summary:

The study was performed to investigate the inhibitory concentration of the test material on the respiration of aerobic waste water bacteria. The study was performed in accordance with the standardised guideline EU Method C.11, under GLP conditions.

The test was performed on activated sludge from a sewage treatment plant for a duration of 3 hours.

The study met the validity (quality) criteria of the guideline, though it deviated from the method in some minor ways (used settling instead of centrifugation for sludge, and test concentrations were not spaced by an equal factor). Due to the poor solubility of the test material at test concentrations, no stock solution was prepared. The test material was given directly into the medium. Therefore, a constant factor between the test concentrations could not been achieved.

Under the conditions of the study no significant inhibition of oxygen consumption was found over the test concentrations compared to the controls, therefore the resulting EC50 was >= 100 mg/L (the highest test concentration).

Endpoint:
activated sludge respiration inhibition testing
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
supporting study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Study conducted on read-across material
Justification for type of information:
Read Across to Octyltin tris(2-ethylhexylmercaptoacetate) (MOTE) (EC Number 248-227-6 and CAS No 27107-89-7) based on structural similarity and hydrolytical behaviour, see attached justification.
Reason / purpose for cross-reference:
read-across source
Key result
Duration:
3 h
Dose descriptor:
other: EC20
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Key result
Duration:
3 h
Dose descriptor:
EC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Key result
Duration:
3 h
Dose descriptor:
other: EC80
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate

Description of key information

Read-across to structurally similar substance: Octyltin tris(2-ethylhexylmercaptoacetate) (MOTE) (CAS No 27107 -89 -7)

Under the conditions of the study no significant inhibition of oxygen consumption was found over the test concentrations compared to the controls, therefore the resulting EC50 was >= 100 mg/L (the highest test concentration).

Key value for chemical safety assessment

EC50 for microorganisms:
100 mg/L

Additional information

Read-across to structurally similar substance: Octyltin tris(2-ethylhexylmercaptoacetate) (MOTE) (CAS No 27107-89-7).

The study was performed to investigate the inhibitory concentration of the test material on the respiration of aerobic waste water bacteria. The study was performed in accordance with the standardised guideline EU Method C.11, under GLP conditions. The study was awarded a reliability score of 1 in accordance with the criteria set forth by Klimisch et al. (1997).

The test was performed on activated sludge from a sewage treatment plant for a duration of 3 hours.

The study met the validity (quality) criteria of the guideline, though it deviated from the method in some minor ways (used settling instead of centrifugation for sludge, and test concentrations were not spaced by an equal factor). Due to the poor solubility of the test material at test concentrations, no stock solution was prepared. The test material was given directly into the medium. Therefore, a constant factor between the test concentrations could not been achieved.

Under the conditions of the study no significant inhibition of oxygen consumption was found over the test concentrations compared to the controls, therefore the resulting EC50 was >= 100 mg/L (the highest test concentration).