Disodium wolframate

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2008-09-18 to: 2009-03-13

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

Well documented, scientifically sound study conducted in accordance to GLP and OECD Guideline 209 without deviation.

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

Deviations:

no

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:

- Concentrations: A stock solution of the test substance was prepared in reagent water at a concentration of 2.00 mg total product/mL. Stock solution volumes of 2.5, 8.0, 25, 80, and 250 mL were added to the 10, 32, 100, 320, and 1,000 mg total product/L test flasks, respectively, for the range finding test. Since there was no appreciable inhibition (e.g., >50%) up to a nominal of 1,000 mg/L, no further testing was required.

- A stock solution of the reference substance was prepared in reagent water at a concentration of 0.500 mg/mL and was used to add reference substance to the appropriate flasks. Stock solution volumes of 3.2, 10, and 32 mL were added to the 3.2, 10, and 32 mg/L test flasks, respectively.

Vehicle:

no

Details on test solutions:

no data

Test organisms (species):

activated sludge, domestic

Details on inoculum:

-Source of inoculum: Activated sludge, Columbia Wastewater Treatment Plant, Columbia, Missouri
- Preparation of inoculum for exposure: Repeated (11 times) centrifugation of 250 mL aliquots to concentrate the inoculum, followed by 3 rinses in ABC well water, and final suspension in a carboy with stirring and aeration with compressed air. The inoculum was sustained with a synthetic feed solution overnight. Suspended solids concentration was determined in triplicate, and the solution diluted with well water to a final suspended solids concentration between 3.6 and 4.4 g/L.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

30 min

Post exposure observation period:

None

Hardness:

N/A

Test temperature:

19.8-20.2 degrees C

pH:

8.03- microbial inoculum
8.23-8.35-test flasks, reference, and controls
8.23- abiotic control contact flask (containing no microbial inoculum)

Dissolved oxygen:

Tested parameter- see Results

Salinity:

N/A

Nominal and measured concentrations:

Nominal concentrations:
Test substance- 0 (control), 10, 32, 100, 320, and 1000 mg test substance/L
Reference substance- 3.2, 10 and 32 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel:
- Type: closed
- Material, size, headspace, fill volume: Glass 1 L, 200 mL inoculum added to flask for 30 min exposure, 500 mL final volume
- Aeration: 500-1000 mL/min
- No. of vessels per concentration (replicates): 1
- No. of vessels per control (replicates): 2 control, 1 abiotic control, 3 concentrations (1 each) reference substance

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: ABC Labs well water

OTHER TEST CONDITIONS
- Adjustment of pH: None
- Light intensity: Ambient

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : Oxygen consumption mg/L/hr, one reading per concentration.

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 3.2

Reference substance (positive control):

yes

Remarks:

3,5 Dichlorophenol

Duration:

30 min

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

Duration:

30 min

Dose descriptor:

EC50

Effect conc.:

14.4 mg/L

Nominal / measured:

nominal

Conc. based on:

other: 3, 5 dichlorophenol-reference substance

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Remarks on result:

other: acceptable value

Details on results:

Test Substance:
The test substance showed 12.4, 31.1, 11.3, 14.8, and 17.9% inhibition at concentrations of 10, 32, 100, 320, and 1,000 mg/L, respectively. Thus, the estimated 30-minute-EC50 value for sodium tungstate was estimated to be >1,000 mg (total product)/L. No further testing was required.

Controls:
- Respiration rates for the control flasks were 81.0 and 71.7 mg O2L-1hr-1 during the 30-minute exposure. These respiration rates were within 15% of each other. The respiration rate of the abiotic control was 0.0 mg O2L-1hr-1, indicating that rate of oxygen uptake by sodium tungstate dihydrate was effectively 0% of the mean respiration rate of the controls, 76.4 mg O2L-1hr-1.

Results with reference substance (positive control):

- Results with reference substance valid? Yes
- Relevant effect levels: The percent inhibitions for the three reference toxicant substance flasks were 22.6, 34.3, and 83.8% at 3,5 dichlorophenol nominal concentrations of 3.2, 10, and 32 mg/L, respectively
- Other: The 30 min EC50 for the reference substance of 14.4 mg/L well within the 5-30 mg/L acceptance range required by the method.

Reported statistics and error estimates:

no data

- The ASR system provided the oxygen consumption/depletion curve as a plot of the dissolved oxygen concentration (mg O2/L) versus time (seconds). The analyst selected the appropriate start and end times between which the oxygen depletion curve was linear, and the ASR system automatically calculated the oxygen consumption rate (respiration rate) and expressed these rates as mg O2L-1hr-1.

Conclusions:

The 30 minute EC50 value for sodium tungstate dihydrate to activated sludge is > 1000 mg/ L.

Description of key information

The 30 minute EC50 value for sodium tungstate dihydrate to activated sludge is > 1000 mg/ L.

Key value for chemical safety assessment

EC50 for microorganisms:

1 000 mg/L