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Ecotoxicological information

Toxicity to microorganisms

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Reference
Endpoint:
toxicity to microorganisms
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Qualifier:
according to guideline
Guideline:
other: 87/302/EEC
Version / remarks:
1988
Deviations:
yes
Remarks:
the activated sludge was not only ventilated but also agitated
Qualifier:
equivalent or similar to guideline
Guideline:
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test
GLP compliance:
yes
Analytical monitoring:
no
Vehicle:
no
Test organisms (species):
activated sludge of a predominantly domestic sewage
Details on inoculum:
- Type: mixed population of aquatic microorganisms (activated sludge)
- Origin: aeration tank of a waste water treatment plant treating predominantly domestic sewage (Wupper area water authority)
- Pretreatment: aeration of the activated sludge; daily feed with synthetic medium
- pH of the suspension before application: 7.6
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
3 h
Test temperature:
18.9 - 19.3
pH:
7.3 - 7.9
Dissolved oxygen:
Start: 4.9 - 8.0 mg O2/L
End: 2.8 - 7.9 mg O2/L
Nominal and measured concentrations:
- Test substance: 1, 3.1, 10, 31, 100 mg/L
- Test substance concentration in physico-chemical oxygen consumption control: 100 mg/L
- Reference substance: 2.5, 5, 10, 20, 40 mg/L
Details on test conditions:
- Type of application: direct weighing
- Test concentration of the activated sludge: 400 mg/L suspended solids
- Test temperature: 20 ± 2° C
- Incubation time: 3 hours with permanent aeration
A physico-chemical oxygen consumption control is carried out, since some substances·can also consume oxygen by chemical reactivity. In order to be able to tell the difference between physico-chemical oxygen consumption and biological oxygen consumption (respiration), at least the maximum concentration of the test substance is tested without activated sludge.
Reference substance (positive control):
yes
Remarks:
3,5-Dichlorophenol (Aldrich, purity: 97 %, batch no. 02611ES-202)
Duration:
3 h
Dose descriptor:
EC50
Effect conc.:
6.3 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Results with reference substance (positive control):
Toxicity of the reference substance 3.5-Dichlorophenol to bacteria: 3h-EC50 = 8.3 mg/L
Reported statistics and error estimates:
The EC values are determined by statistical methods (probit analysis).

Test substance

 Test concentration [mg/L]  Respiratory rate test substance [mg/L*h]  Inhibition [%]
 1  30.0  18.5
 3.1  27.6  25.0
 10  13.5  63.3
 31  6.0  83.7
 100  2.0  94.6
Validity criteria fulfilled:
yes
Remarks:
respiratory rate of the 2 controls differs less than 15 %; respiratory rate of the controls < 60 mg O2/L·h; EC5o of the reference substance 3.5-dichlorophenol is in the range 5 - 30 mg/L
Conclusions:
For the test substance a 3h-EC50 of 6.3 mg/L towards bacteria was determined.
Executive summary:

This study was designed to assess the toxicity of the test substance to bacteria. The study was conducted according to the Commission Directive 88/302/EEC; Official Journal of the EC L 133 Part C (1988). This test method is in most parts identical with OECD Guideline 209.

The method assesses the effect of a test substance on microorganisms by measuring the respiration rate after 3 h under defined conditions in the presence of different concentrations of the test substance (1, 3.1, 10, 31, 100 mg/L). A physico-chemical oxygen consumption control is carried out, since some substances·can also consume oxygen by chemical reactivity. In order to be able to tell the difference between physico-chemical oxygen consumption and biological oxygen consumption (respiration), at least the maximum concentration of the test substance is tested without activated sludge.

For the test substance a 3h-EC50 of 6.3 mg/L towards bacteria was determined.

A toxicity of the reference substance 3,5 -Dichlorophenol of 3h-EC50: 8.3 mg/L was determined.

Description of key information

This study was designed to assess the toxicity of the test substance to bacteria. The study was conducted according to the Commission Directive 88/302/EEC; Official Journal of the EC L 133 Part C (1988). This test method is in most parts identical with OECD Guideline 209.

The method assesses the effect of a test substance on microorganisms by measuring the respiration rate after 3 h under defined conditions in the presence of different concentrations of the test substance (1, 3.1, 10, 31, 100 mg/L). A physico-chemical oxygen consumption control is carried out, since some substances·can also consume oxygen by chemical reactivity. In order to be able to tell the difference between physico-chemical oxygen consumption and biological oxygen consumption (respiration), at least the maximum concentration of the test substance is tested without activated sludge.

For the test substance a 3h-EC50 of 6.3 mg/L towards bacteria was determined.

A toxicity of the reference substance 3,5 -Dichlorophenol of 3h-EC50: 8.3 mg/L was determined.

Key value for chemical safety assessment

EC50 for microorganisms:
6.3 mg/L

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