Magnesium zirconium oxide

Short-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

September 23-25, 2005

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Not a GLP study. Also, test material is diluted to 60% in aqueous suspension so the results were recalculated to represent 100% magnesium hydroxide.

Qualifier:

according to guideline

Guideline:

other: Methods for measuring the acute toxicity of effluents and receiving waters to freshwater and marine organisms. 5th ed., October 2002, EPA Volume 821-R-02-012. Test method 2021.0, Daphnia pulex and Daphnia magna acute toxicity tests.

GLP compliance:

no

Vehicle:

no

Test organisms (species):

Daphnia magna

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

48 h

Test temperature:

20 +/- 1°C

Nominal and measured concentrations:

A control plus seven chemical concentration exposures were tested: 96.88 mg/L; 193.75 mg/L; 387.5 mg/L; 775 mg/L; 1550 mg/L; 3100 mg/L; and 6200 mg/L.

Details on test conditions:

TEST SYSTEM
- Test vessel: cups
- Type (delete if not applicable): open
- Material, size, headspace, fill volume: 30-mL plastic cups, fill volume 25 mL
- Renewal rate of test solution (frequency/flow rate): 24 h
- No. of organisms per vessel: 5
- No. of vessels per concentration (replicates): 4
- No. of vessels per control (replicates): 4

TEST MEDIUM / WATER PARAMETERS
- Intervals of water quality measurement: daily

OTHER TEST CONDITIONS
- Photoperiod: 16L:8D
- Light type: fluorescent lighting

EFFECT PARAMETERS MEASURED (with observation intervals if applicable): survival, daily

Duration:

48 h

Dose descriptor:

LC50

Effect conc.:

284.76 mg/L

Conc. based on:

test mat.

Basis for effect:

mortality

Remarks on result:

other: for test material with 60% Mg(OH)2

Duration:

96 h

Dose descriptor:

LC50

Effect conc.:

170.86 mg/L

Conc. based on:

act. ingr.

Basis for effect:

mortality

Remarks on result:

other: recalculated to 100% Mg(OH)2

Survival of D. magna was 100 percent in the control exposure. After 48 hours of exposure to serial dilutions of the test solution, survival of D. magna in the test exposures ranged from 0 percent (concentration 6200 mg/L test substance) to 95 percent (96.88 mg/L test substance).

Table 1. Percent survival of D. magna at the conclusion of acute toxicity tests using dilutions of the test substance

Control or chemical exposure	Concentration of test substance (mg/L)	Survival (%) after 48 hours	mg/L LC50
Control	0	100	284.76
Test substance	96.88	95
Test substance	193.75	70
Test substance	387.5	25
Test substance	775	5
Test substance	1550	15
Test substance	3100	5
Test substance	6200	0

 

Water quality measurements remained within acceptable ranges throughout the duration of both toxicity

tests in virtually all replicates. Occasional deviations in temperature were observed during the test but these minor deviations did not appear significant. The LC50 (48h) for D. magna was recalculated to give a more accurate result with 100% concentration of magnesium hydroxide as the original LC50 was calculated with a 60% magnesium hydroxide concentration. The recalculated LC50 (48h) for D. magna was determined to be 170.86 mg/L.

Conclusions:

In a 48 hour acute static definitive toxicity test with Daphnia magna, the LC50 value was determined to be 284.76 mg of test substance (60% Mg(OH)2 aqueous suspension). The recalculated LC50 (48h) with pure magnesium hydroxide for D. Magna was determined as 170.86 mg/L.

Reference 2

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

from 08 AUG 1994 to 18 OCT 1994

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: The study was conducted according to the EU method C.2 and was GLP-compliant. However, no analytics were performed.

Qualifier:

according to guideline

Guideline:

EU Method C.2 (Acute Toxicity for Daphnia)

Deviations:

not specified

GLP compliance:

yes

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: Stock solutions were prepared by dissolving 100 mg of substance in 1000 g of test medium. The flasks were magnetically stirred for 24h at 30°C, then for 24h at 20°C and finally centrifugated at circa 9000 g for 20 min. The extracted solution was then used as test solution. The concentration of this test solution was expressed in percentage of dilution of the extracted solution. Here, only the undiluted extracted solution was tested (concentration = 100%)
- Controls: yes, test water without test item
- Evidence of undissolved material: no data

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Common name: Water flea
- Strain: Daphnia magna strauss 1820
- Source: IRCHA-INERIS (Daphnia breeding in Décines Rhône-Poulenc laboratory)
- Age at study initiation: no data
- Weight at study initiation: no data
- Length at study initiation: 560 µm- Method of breeding: no data
- Feeding during test: no data

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

48 h

Hardness:

no data

Test temperature:

20.1-20.4°C

pH:

8.4

Dissolved oxygen:

92-96%

Salinity:

not applicable

Nominal and measured concentrations:

100 mg/L (nominal loading rate)

Details on test conditions:

TEST SYSTEM
- Test vessel: 100 mL glass beaker
- Type: open
- Material, size, headspace, fill volume: 100 mL filled with 40 g of solution
- Aeration: The test medium was aerated with compressed air before the start of the test
- No. of organisms per vessel: 20
- No. of vessels per concentration (replicates): 2
- No. of vessels per control (replicates): 1
- Biomass loading rate: 1 daphnia per 2 g of tested solution

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: bidistillated water
- Total organic carbon: no data
- Particulate matter: no data
- Metals: no data
- Pesticides: no data
- Chlorine: no data
- Alkalinity: NaHCO3: 0.2 g/L
- Ca/mg ratio: CaCl2.2H2O: 0.297 g/L; MgCl2.6H2O: 0.167 g/L
- other: K2SO4: 0.026 g/L
- Conductivity: 0.90 µS/cm (of the bidistillated water)
- Culture medium different from test medium: no data
- Intervals of water quality measurement: The concentration of dissolved oxygen and the pH were measured after 48 h in each test flask


OTHER TEST CONDITIONS
- Adjustment of pH: no
- Photoperiod: exposure in the dark
- Light intensity: no

EFFECT PARAMETERS MEASURED (with observation intervals if applicable): The measured effect is the mortality of the daphnids estimated through their immobilisation after 24 and 48 hours of exposure


TEST CONCENTRATIONS
- Spacing factor for test concentrations: not applicable (limit test)
- Justification for using less concentrations than requested by guideline: not applicable (limit test)
- Range finding study : no

Reference substance (positive control):

yes

Remarks:

potassium dichromate (K2Cr2O7).

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

> 100 other: % saturated solution (initial loading rate = 100 mg/L)

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Details on results:

No further details given on the study results.

Results with reference substance (positive control):

The 24-h EC50 for potassium dichromate was 1.4 ppm (w/w) (1.3-1.5 ppm (w/w)).

Reported statistics and error estimates:

Not necessary as no adverse effect was observed.

Effect of Zirconium dioxide on the Mobility of Daphnia magna:

Treatment (Loading rate)	No. of daphnids tested	Immobilized daphnids after 24 hours           No.                   %		Immobilized daphnids after 48 hours           No.                   %
Control	20	0	0	0	0
100 mg/L	20	0	0	0	0
100 mg/L	20	0	0	1	5

Validity criteria fulfilled:

not specified

Conclusions:

Zirconium dioxide had no acute effect on Daphnia magna at an initial loading rate of 100 mg/L.

Executive summary:

The acute toxicity of zirconium dioxide to Daphnia magna was studied under static conditions according to EU method C.2. Daphnids were exposed to control and test chemical at an initial loading rate of 100 mg/L for 48 hours. Mortality and immobilization were observed after 24 and 48 hours.

No significant immobilization was observed with the loading rate of 100 mg/L. The 48-h NOEC and 48-h EC50 were thus superior to this value.

Reference 3

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

weight of evidence

Justification for type of information:

Read across from a study performed with zirconium dioxide in combination with one study performed with magnesium dihydroxide. The read across justification document is attached in IUCLID Section 13.

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across source

Key result

Remarks on result:

other: Magnesium zirconium oxide is not considered to be toxic or harmful to aquatic invertebrates.

Remarks:

This conclusion was based on the results of the study from Bazin (1994) with zirconium dioxide, the results of the study of Heinen et al. (2005) with magensium dihydroxide, and the limited water solubility of magnesium zirconium oxide.

Description of key information

The endpoint is covered by a weight of evidence approach including one short-term study for zirconium dioxide (Bazin, 1994) and one short-term study for magnesium hydroxide (Heinen, 2005). Zirconium dioxide did not cause any adverse effects in daphnids up to and including the limit test concentration of 100 mg/L (nominal loading rate). The study performed with magnesium hydroxide is considered relevant for magnesium oxide because magnesium oxide, upon dissolution in water, is transformed to magnesium hydroxide. The LC50 for Mg(OH)2 was determined to be 170.86 mg/L. Taking into account these key data for zirconium dioxide and magnesium hydroxide, magnesium zirconium oxide can be concluded to be not toxic or harmful to aquatic invertebrates either.

Additional information

1. Information on zirconium dioxide

In a study from Bazin (1994), the acute toxicity of zirconium dioxide to Daphnia magna was studied under static conditions according to EU method C2. Daphnids were exposed to control and test chemical at an initial loading rate of 100 mg/L for 48 hours. No significant immobilization was observed up to and including the loading rate of 100 mg/L. The 48-h EC50 was thus superior to this value.

2. Information on magnesium oxide

For magnesium oxide, data obtained from a test performed with magnesium hydroxide were added to the dossier. The rationale behind this is that in the environment, MgO will result in Mg(OH)2 formation when in contact with water, according to the following (general) reaction:

MgO + H2O <--> Mg(OH)2

A study performed with a 60% aqueous solution of Mg(OH)2 was added to the weight of evidence approach. The study is a short-term toxicity test with Daphnia magna (Heinen, 2005) which was carried out according to a US EPA test method. The recalculated 48-h LC50 for pure Mg(OH)2 was determined to be 170.86 mg/L.

3. Conclusion on magnesium zirconium oxide

Magnesium zirconium oxide is zirconium dioxide with magnesium partly replacing zirconium in the crystal lattice. Since both zirconium dioxide and magnesium hydroxide (which is formed when magnesium oxide is in contact with water) are - based on the results of the available key studies for these substances - not to be classified as toxic or harmful to aquatic invertebrates, it was concluded that magnesium zirconium oxide is not expected to be toxic or harmful to aquatic invertebrates either. This confirms the read across assumption that the addition of magnesium (oxide) to the crystal lattice of zirconium dioxide does not alter the unhazardous character of zirconium dioxide.