tungsten zirconium oxide

Short-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2017-10-30 to 2018-02-20

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.2 (Acute Toxicity for Daphnia)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

- Sampling method: Samples were taken from the control and each test group from the freshly prepared bulk test preparation at 0 and 24 hours and from the old or expired pooled replicates at 24 and 48 hours for quantitative analysis of dissolved zirconium and tungsten.
- Sample storage conditions before analysis: Triplicate samples were taken at each sampling occasion, two of which were stored frozen for further analysis if necessary.

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
*Stirring experiment:
Information provided by the Sponsor indicated that the test item was insoluble in pure water and that a saturated solution (SS) method of preparation was considered most appropriate. A nominal amount of test item (500 mg) was dispersed in 5 liters of test water with the aid of vigorous magnetic stirring for 96 hours. After 3, 24 and 96 hours, the pH of the media was checked and a sample taken for chemical analysis (i.e. dissolved tungsten) after filtration through a 0.2 µm Gelman Acrocap filter (initial 100 mL discarded). Dissolved tungsten concentrations were 0.112, 0.313 and 0.443 mg W/L after 3, 24 and 96 hours of stirring, respectively. Based on these results, the 96-h stirring period was selected for the combined range finder limit test.

*Combined Range Finder Limit Test:
A nominal amount of test item (500 mg) was dispersed in 5 liters of test water with the aid of vigorous magnetic stirring for 96 hours. After 96 hours the stirring was stopped and any undissolved test item was removed by filtration through a 0.2 µm Gelman Acrocap filter (first approximate 100 mL discarded in order to precondition the filter) to give a 100% v/v SS. A series of dilutions was made from this SS to give further test concentrations of 1.0 and 10% v/v SS. Each prepared concentration was inverted several times to ensure adequate mixing and homogeneity.
Evidence of undissolved material (e.g. precipitate, surface film, etc): At the start and throughout the test all control and test solutions were observed to be clear colorless solutions.

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Common name: Water flea, Daphnia magna
- Source: in-house laboratory culture
- Age at study initiation (mean and range, SD): < 24 h old
- Strain: not reported, in-house laboratory culture
- Culture conditions: Adult daphnids were maintained in 150-mL glass beakers containing 100 mL Elendt M7 medium in a temperature controlled room maintaining the water temperature at 18 to 22°C. The lighting cycle was controlled to give a 16 hours light and 8 hours darkness cycle with 20 minute dawn and dusk transition periods. Culture conditions ensured that reproduction was by parthenogenesis.
- Feeding during test: no
- Food type during culturing: Mixture of algal suspension (Desmodesmus subspicatus) and Tetramin® flake food suspension.
- Frequency of feeding during culturing: Each culture was fed daily.

Test type:

semi-static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

48 h

Hardness:

250 mg/L as CaCO3

Test temperature:

20-22°C

pH:

At t=0h: 7.9 - 8.0 (Fresh media)
At t=24h: 8.0 - 8.0 (Old media)
At t=24h: 7.8 - 8.0 (Fresh media)
At t=48h: 7.9 - 8.0 (Old media)

Dissolved oxygen:

At t=0h: 8.6 - 9.5 (Fresh media)
At t=24h: 8.5 - 8.8 (Old media)
At t=24h: 8.5 - 8.9 (Fresh media)
At t=48h: 8.9 - 9.1 (Old media)

Salinity:

not applicable

Nominal and measured concentrations:

Final test:
Nominal concentrations: 0, 1.0, 10 and 100% v/v saturated solution
Measured concentrations of dissolved zirconium were < LOQ in all test media at all sampling times.
Measured concentrations of dissolved tungsten (mg/L):
* t=0h (Fresh): < LOQ, 0.00538, 0.0529, 0.401
* t=24h (Old): < LOQ, 0.00614, 0.0391, 0.436
* t=24h (Fresh): < LOQ, 0.00763, 0.0213, 0.461
* t=48h (Old): < LOQ, 0.00287, 0.0374, 0.355

Details on test conditions:

TEST SYSTEM
- Test vessel: beaker
- Material, size, headspace, fill volume: 150-mL glass beaker filled with 100 mL of test medium
- Aeration: not during the test
- No. of organisms per vessel: 5
- No. of vessels per concentration (replicates): 4 (only 1 for the 1.0 and 10% v/v SS)
- No. of vessels per control (replicates): 4

OTHER TEST CONDITIONS
- Photoperiod: 16 h light and 8 h darkness daily, 20-min transition periods
- Light intensity: 777-1006 Lux

EFFECT PARAMETERS MEASURED (with observation intervals if applicable): Any immobilisation or adverse reactions to exposure were recorded at 24 and 48 hours after the start of exposure. The criterion of effect used was that daphnids were considered to be immobilised if they were unable to swim within 15 seconds after gentle agitation.

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 10

Reference substance (positive control):

yes

Remarks:

Potassium dichromate

Key result

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

> 100 other: % v/v SS with nominal loading rate 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Details on results:

- Mortality/immobilisation of control animals: none
- Other adverse effects in control animals: A single daphnid in the control group was observed to be trapped at the surface after 24 hours.
- Mortality of exposed animals: none
- Other adverse effects in exposed animals: none
- Abnormal responses: none

Results with reference substance (positive control):

- Results with reference substance valid? yes
- EC50/LC50: 48-h EC50 = 0.54 mg/L. The results from the positive control with potassium dichromate were within the normal range for this reference item.

Reported statistics and error estimates:

No statistics used (no EC50s needed to be calculated since no mortality/immobilisation was observed).

Validity criteria fulfilled:

yes

Conclusions:

The acute toxicity of tungsten zirconium hydroxide oxide to Daphnia magna was determined in a 48-hour semi-static test according to the OECD guideline 202. Daphnids were exposed to the test substance at 1.0, 10 and 100% v/v dilutions of a saturated solution with a nominal loading rate of 100 mg/L. No significant immobilisation was observed in any of the test media used. This study demonstrated that there were no toxic effects at saturation of the test solution.

Description of key information

The study of Ablitt (2018), investigating the acute toxicity of tungsten zirconium hydroxide oxide in Daphnia magna according to OECD guideline 202, was considered as the key study for endpoint coverage. In this semi-static test, no immobilisation was observed after 48 hours of exposure to 1.0, 10% and 100% v/v dilutions of a saturated solution with a nominal loading rate of 100 mg/L. Dissolved zirconium concentration were < LOQ (i.e. 0.002 mg Zr/L) in all test media at all sampling times, whereas dissolved tungsten concentrations were in the range of 0.0029-0.46 mg/L. Based on the results of this study it can be concluded that tungsten zirconium (hydroxide) oxide is not harmful to aquatic invertebrates.