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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:
2002-07-01 to: 2002-07-12
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
other: Commission Directive 88/302/EEC
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test
GLP compliance:
yes
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):
no data
Analytical monitoring:
no
Details on sampling:
no data
Vehicle:
no
Details on test solutions:
The test substance was added to about 130 mL of deionized water and stirred overnight before testing (equilibration phase)
Test organisms (species):
activated sludge of a predominantly domestic sewage
Details on inoculum:
no data
Test type:
not specified
Water media type:
not specified
Limit test:
no
Total exposure duration:
3 h
Remarks on exposure duration:
permanent aeration
Post exposure observation period:
no data
Hardness:
no data
Test temperature:
20+2 degree C
pH:
pH of the suspension before application : 6.1
pH of the various test substance concentratoins: 7.2 - 7.4
Dissolved oxygen:
no data
Salinity:
N/A
Nominal and measured concentrations:
Nominal test concentrations (mg/L): 1000, 1800, 3200, 5600, 10000
Details on test conditions:
TEST SYSTEM
- Test vessel: aeration tank of waste water treatment plant treating predominately domestic sewage (Wupper area water authority)
- Test concentration of the activated sludge : 480 mg/L suspended solids
Reference substance (positive control):
yes
Remarks:
3,5-Dichlorophenol (purity of 97%)
Duration:
3 h
Dose descriptor:
EC50
Effect conc.:
> 10 000 mg/L
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Details on results:
- Tungsten trioxide showed 3.1 % respiration inhibition of activated sludge at a test substance concentration of 10,000 mg/L.
Results with reference substance (positive control):
- Results with reference substance valid? Yes
- Relevant effect levels: EC50 = 6.1 mg/L
Reported statistics and error estimates:
- The EC values were determined by statistical methods (probit analysis)

Test concentration: 1000 mg/L - Inhibition: 0.0% Test Concentration: 1800 mg/L - Inhibition: 15.4% Test Concentration: 3200 mg/L - Inhibition: 7.7% Test Concentration: 5600 mg/L - Inhibition: 7.7% Test Concentration: 10000 mg/L - Inhibition: 3.1% Physical-Chemical oxygen consumption was 0 mg/L-h for all test concentrations. The Respiratory rate-phsical-chemical oxygen consumption ranged from 22.0 mg/L-h to 27.0 mg/L-h

Conclusions:
Tungsten trioxide showed 3.1% respiration inhibition of activated sludge at the test substance concentration of 10,000 mg/L. The EC50 > 10,000 mg/L

Description of key information

Tungsten trioxide was not tested for toxicity to soil macro-organisms, and read across to sodium tungstate was used for this endpoint. In an earthworm reproduction test using Eisenia fetidaand testing sodium tungstate, the NOEC was found to be greater than or equal to the highest concentration tested (≥1000 mg sodium tungstate/L, or approximately 586 mg W/L).

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:
1 000 mg/L

Additional information