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Short-term toxicity to aquatic invertebrates

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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 studies performed with zirconium dichloride oxide and zirconium dioxide. The read across justification document is attached to IUCLID Section 13.
Reason / purpose for cross-reference:
read-across source
Reason / purpose for cross-reference:
read-across source
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
anhydrous zirconium dinitrate oxide
Basis for effect:
mobility
Remarks on result:
other: Based on the studies performed with zirconium dichloride oxide and zirconium dioxide, it can be concluded that no immobilisation is to be expected at the limit test concentration (nominal loading rate of 100 mg/L, anhydrous zirconium dinitrate oxide).
Endpoint:
short-term toxicity to aquatic invertebrates
Type of information:
experimental study
Adequacy of study:
weight of evidence
Study period:
27 Nov 2012 - 21 Jan 2013
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
GLP compliance:
yes (incl. QA statement)
Analytical monitoring:
yes
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
Pre-study solubility work showed that the test item was insoluble in water using the traditional methods of preparation, e.g. ultrasonication. Based on this information the test item was categorized as being a ‘difficult substance’ as defined by the OECD Guidance Document on Aquatic Toxicity Testing of Difficult Substances and Mixtures (OECD 2000). Therefore a media preparation trial was conducted in order to determine the solubility of the test item under test conditions.

- Method of the media preparation trial: An amount of test item (250 mg) was added to the surface of 5 liters of reconstituted water and stirred vigorously using a magnetic stirrer for 10 minutes. The pH of the media was adjusted to 7.8 and the stirring restarted for a further 24 hours. After stirring, any undissolved test item was removed by filtration through a 0.2 µm Gelman Acrocap filter (initial 500 mL discarded) to give the 100% v/v saturated test solution from which serial dilutions were made to obtain the remaining test concentrations of 0.10, 1.0 and 10% v/v saturated solution. The test item used represents a solution containing 29.2% anhydrous zicronium dichloride oxide. Given the low aqueous solubility it was considered that a loading rate of 50 mg test item/L, which corresponds to 14.6 mg zirconium dichloride oxide/L, was sufficient to ensure 100% saturation of the test media.
Test organisms (species):
Daphnia magna
Details on test organisms:
TEST ORGANISM
- Common name: Water flea, Daphnia magna
- Age at study initiation (mean and range, SD): < 24 h old (first instar)
- Strain: not reported, in-house laboratory culture

ACCLIMATION
- Acclimation conditions (same as test or not): Adult Daphnia were maintained in 150 mL glass beakers containing Elendt M7 medium in a temperature controlled room at approximately 20°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.
- Type and amount of food: Each culture was fed daily with a mixture of algal suspension (Desmodesmus subspicatus) and Tetramin® flake food suspension
- Feeding frequency:daily
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
48 h
Hardness:
250 mg/L as CaCO3
Test temperature:
20-21°C
pH:
24 hours: 7.7-7.8
48 hours: 8.1
Dissolved oxygen:
air-saturation level
Salinity:
not applicable
Nominal and measured concentrations:
Nominal:
Range-finder: 0.10, 1.0, 10 and 100 % v/v saturated solution.
Measured: 100 % v/v saturated solution: < LOQ (0.051 mg Zr/L)
Details on test conditions:
TEST SYSTEM
- Type (delete if not applicable): closed
- Material, size, headspace, fill volume: 250 mL test and control vessel contained 200 mL of test media
- Aeration:no
- Renewal rate of test solution (frequency/flow rate): no renewal rate
- No. of organisms per vessel: 10
- No. of vessels per concentration (replicates): 1
- No. of vessels per control (replicates): 1

OTHER TEST CONDITIONS
- Adjustment of pH: adjusted from 6.8 to 7.8
- Photoperiod: 16 hours light, 8 hours dark with 20 minutes dawn and dusk transition period

EFFECT PARAMETERS MEASURED (with observation intervals if applicable): after 24 hours and 48 hours the number of immobilized Daphnia magna were recorded

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 10
- Justification for using less concentrations than requested by guideline: spacing factor was 10 as test was range finder study (no definitive study performed as no effects were seen in 100% v/v saturated solution)
- Range finding study: yes
- Test concentrations: 0.1-1.0-10 and 100% v/v saturated solutions
- Results used to determine the conditions for the definitive study: No immobility was observed at a loading of 100% v/v saturated solution, therefore, and because dissolved Zr levels were < LOQ in all treatments, no definitive study was performed.
Reference substance (positive control):
yes
Remarks:
potassium dichromate
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
> 100 other: % v/v saturated solution
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mobility
Remarks on result:
other: no measurable dissolved zirconium present in the range finder study
Details on results:
No mortality was observed in the preliminary test up to the highest test dose (100% v/v saturated solution).
Results with reference substance (positive control):
EC50 after 24 hours: 0.75 mg/L (CI: 0.56-1.0)
EC50 after 48 hours: 0.45 mg/L (CI: 0.42-0.48)
NOEC after 24 hours and 48 hours: 0.56 and 0.32 mg/L
Results of positive control with potassium dichromate were within the normal range for this reference item.

Chemical analysis of the test preparations at 0 and 48 hours showed measured dissolved zirconium concentrations of less than the limit of quantitation (LOQ) of the analytical method employed (which was determined to be 0.051 mg Zr/L). As a result,

it was considered unnecessary to carry on to the definitive stage of testing.

Validity criteria fulfilled:
yes
Conclusions:
The acute toxicity of the test item (zirconium dichloride oxide) to the freshwater invertebrate Daphnia magna has been investigated and yielded a 48-h EC50 value of greater than 100% v/v saturated solution. No mortality was observed up to and including at the highest test dose. No measurable dissolved zirconium was present in any of the test solutions (dissolved Zr < LOQ = 51 µg Zr/L). Therefore, no definitive toxicity test was conducted for zirconium dichloride oxide.
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:
guideline study with acceptable restrictions
Remarks:
The study was conducted according to the EU method C2 and the GLP. A reliability score of Klimisch 2 (reliable with restrictions) was assigned because 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
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 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 C2. 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 at the loading rate of 100 mg/L. The 48-h NOEC and 48-h EC50 were thus superior to this value.

Description of key information

The endpoint was covered using a weight of evidence approach including a study performed with the read across substance zirconium dichloride oxide (Harris, 2014) and another study performed with the read across substance zirconium dioxide (Bazin, 1994). These studies indicate that zirconium is not harmful or toxic to aquatic invertebrates, with the EC50 values being > 100% v/v saturated solution (Harris, 2014) or > 100 mg/L (initial loading rate, Bazin, 1994). Zirconium dinitrate oxide is a water soluble compound (when pH is not adjusted). However, zirconium precipitates out of solution at environmentally relevant pH levels. This behaviour is similar to that of other water soluble zirconium compounds such as zirconium dichloride oxide, justifying read across from this substance. The study on zirconium dioxide (which is an insoluble zirconium compound) is added to the read across approach to demonstrate the similarity in the ecotoxicological behaviour of 'water soluble' and insoluble zirconium compounds.

Key value for chemical safety assessment

Additional information

Two relevant read across studies were identified and were used in a weight of evidence approach to cover this endpoint.

In the study of Harris (2014), a range finding study was performed in which the highest test concentration was a 100% v/v saturated solution of zirconium dichloride oxide (nominal loading rate of 50 mg anhydrous zirconium dichloride oxide/L). No immobility was observed after 48 hours, which leads to an EC50 > 100% v/v saturated solution. Dissolved zirconium concentration was < LOQ (i.e. 0.051 mg Zr/L) in all treatments. Because zirconium was not available to cause effects in Daphnia magna, no further testing was performed.

Similar results would be expected with zirconium dinitrate oxide, which is also a 'water soluble' zirconium compound in pure water in the absence of pH adjustment but with a similar precipitation behaviour as zirconium dichloride oxide in natural aqueous media. Because of the precipitation of zirconium at environmentally relevant conditions, it is considered justified to also perform read across from insoluble zirconium substances such as zirconium dioxide (for further argumentation reference can be made to the read across document attached to IUCLID Section 13). Therefore, the study from Bazin (1994) performed with zirconium dioxide (an insoluble zirconium compound) was included in the weight of evidence approach. In this study, the acute toxicity of zirconium dioxide to Daphnia magna was studied under static conditions according to EU method C2. No significant immobilisation was observed at a nominal loading rate of 100 mg/L (ZrO2). The 48-h EC50 was thus superior to this value.

In conclusion, at environmentally relevant pH values, zirconium dinitrate oxide is not expected to cause any acute adverse effects in aquatic invertebrates.