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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:
1990
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
comparable to guideline study with acceptable restrictions
Qualifier:
according to guideline
Guideline:
ISO 8192 (Water quality - Test for inhibition of oxygen consumption by activated sludge for carbonaceous and ammonium oxidation)
Deviations:
no
Principles of method if other than guideline:
method corresponds in most parts to OECD TG 209
GLP compliance:
yes
Analytical monitoring:
no
Vehicle:
no
Test organisms (species):
activated sludge
Details on inoculum:
- laboratory scale sewage treatment plant treating synthetic sewage (OECD 209)
- Initial biomass concentration: 6.0 g/L (dry weight)
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
3 h
Test temperature:
20.2 - 20.7 °C
pH:
7.5 - 7.6
Dissolved oxygen:
O2 - Start: 4.3 - 6.9
O2 - End: 2.1 - 6.1
Nominal and measured concentrations:
Nominal conc.: 100, 180, 320, 560 and 1000 mg/L
Reference substance (positive control):
yes
Remarks:
3.5-Dichlorophenol
Key result
Duration:
3 h
Dose descriptor:
EC50
Effect conc.:
784 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:
EC10
Effect conc.:
191 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Reported statistics and error estimates:
Statistical analysis is summarised in the attached document.

Result:

 Testing concentration (mg/L)

(nominal)

 Respiration rate [mg/L*h]

 Inhibition ( % )

 100  28.8  4.0
 180  28.0  6.7
 320  22.8  24.0
 560  19.5  35.0
 1000  12.0  60.0
Validity criteria fulfilled:
yes
Remarks:
on the basic of graphic evaluation
Conclusions:
Toxicity to microorganisms was assessed in a test with activated sludge and a duration of 3 hours was performed according to ISO 8192 (Test for Inhibition of Oxygen Consumption by Activated Sludge) using TCPP as test susbstance. An EC50 of 784 mg/L and an EC10 of 191 mg/L was determined.
Executive summary:

Toxicity to microorganisms was assessed in a test with activated sludge and a duration of 3 hours was performed according to ISO 8192 (Test for Inhibition of Oxygen Consumption by Activated Sludge) using TCPP as test susbstance. An EC50 of 784 mg/L was determined.TCPP was applied by direct weighing. 3,5 -Dichlorophenol is used as positive control.

Description of key information

ISO 8192 (Bayer AG, 1990): 3h EC50 = 784 mg/L; 3h EC10 = 191 mg/L

Key value for chemical safety assessment

EC50 for microorganisms:
784 mg/L
EC10 or NOEC for microorganisms:
191 mg/L

Additional information

Toxicity to microorganisms was assessed in a test with activated sludge and a duration of 3 hours was performed according to ISO 8192 (Test for Inhibition of Oxygen Consumption by Activated Sludge) using TCPP as test substance (Bayer AG, 1990). An EC50 of 784 mg/L and an EC10 of 191 mg/L was determined.TCPP was applied by direct weighing. 3,5 -Dichlorophenol is used as positive control. There is another test available presenting a lower effect value, but according to the Guidance on information requirements and chemical safety assessment (R.7b, ECHA, 2014) Vibrio fisheri is considered of low relevance for STP since they require a high salinity environment. Thus, the test system used is unsuitable to assess the risk towards microorganisms in a STP and was scored as not reliable.

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