lambda4-cerium(4+) zirconium(4+) tetraoxidandiide

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:

key study

Study period:

from 30-NOV-2007 to 19-DEC-2008

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:

- Concentrations: Triplicate samples were taken from each treatment (control and loading rate of 100 mg/L) before the start of the test and at the end of the test after 48 hours.
- Sampling method: no data
- Sample storage conditions before analysis: Immediately after sampling, the samples were acidified with 10% (v/v) nitric acid (HNO3, 65% Suprapur®, Merck) to stabilise the samples during the storage period. Then the samples were stored at room temperature in the dark.

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
- Method:
The test item is a multi-constituent substance containing different sparingly soluble components. In order to assess its toxicity, a water accommodated fraction (WAF) was prepared. The test method was based on the OECD Guidance Document on Aquatic Toxicity Testing of Difficult Substances and Mixtures.
The WAF with the loading rate of 100 mg/L was prepared just before introduction of the daphnids (i.e., start of the test) as follows:
A dispersion of the test item was prepared in the test water by mixing 200.9 mg of test item into 2000 mL of test water using ultrasonic treatment for 15 minutes. No auxiliary solvent or emulsifier was used.
The dispersion was stirred on a magnetic stirrer for 6 days at room temperature in the dark to dissolve a maximum amount of the different sparingly soluble components of the test item in the dispersion. Then, stirring was stopped and after another day the undissolved test item had completely settled down on the bottom of the stirring vessel. The contact time of the test item and test water for equilibration (i.e., stirring time and deposition period) was 7 days. The clear equilibrated supernatant was carefully separated from the non-dissolved test item and was used as test medium. The maximum contact time of 7 days was chosen according to the results of a pre-test (non-GLP) in which the concentration of dissolved cerium was below the limit of quantification during the stirring period of 7 days. The deposition time of one day was necessary to allow a maximum amount of the undissolved test item to deposit.
- Controls: blank (test water without addition of the test item)
- Evidence of undissolved material (e.g. precipitate, surface film, etc): yes, on the bottom of the stirring vessel, but not in the final test solution

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Common name: water flea
- Strain: defined by the supplier as clone 5
- Source: Originally supplied by the University of Sheffield / UK in 1992. Since that time, the clone has been bred at Harlan Laboratories.
- Age at study initiation (mean and range, SD): The organisms used in the test were 6-24 hours old and were not first brood progeny.
- Weight and length at study initiation: no data
- Method of breeding: in reconstituted water of the quality identical to the water quality used in the tests (in respect to pH, main ions, and total hardness) and under temperature and light conditions identical to those of the tests
- Feeding during test: no

ACCLIMATION
- Acclimation period: no

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

48 h

Hardness:

2.5 mmol/L (= 250 mg/L as CaCO3)

Test temperature:

20°C

pH:

7.7-7.8

Dissolved oxygen:

8.6-8.9 mg/L

Salinity:

not applicable

Nominal and measured concentrations:

Nominal loading rate: 100 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel type: closed to reduce the loss of water by evaporation and to avoid the entry of dust into the solutions
- Material, size, headspace, fill volume: The test was performed in 100-mL glass beakers filled with 50 mL of test medium.
- Aeration: The test water was aerated prior to the start of the study until oxygen saturation was reached, but was not aerated during the test period.
- Type of flow-through (e.g. peristaltic or proportional diluter): none (static test)
- Renewal rate of test solution (frequency/flow rate): no renewal (static test)
- No. of organisms per vessel: 5
- No. of vessels per concentration (replicates): 4
- No. of vessels per control (replicates): 4
- Biomass loading rate: 10 mL test medium per daphnia

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Reconstituted test water: analytical grade salts dissolved in purified water
- Total organic carbon: no data
- Particulate matter: no data
- Metals, Pesticides, Chlorine: no data
- Alkalinity: 0.8 mmol/L
- Ca/mg ratio: 4:1 (based on molarity)
- Na/K ratio: 10:1 (based on molarity)
- Conductivity: no data
- Culture medium different from test medium: no
- Intervals of water quality measurement: At the start and at the end of the test, the pH values, the dissolved oxygen concentrations and the water temperature were determined at each test concentration and in the control.
The appearance of the test media was visually recorded at the start of the test and after 24 and 48 hours.

OTHER TEST CONDITIONS
- Adjustment of pH: no
- Photoperiod: A 16-hour light to 8-hour dark cycle with a 30 minute transition period was used.
- Light intensity: between approximately 490 and 650 Lux

EFFECT PARAMETERS MEASURED
The daphnids were observed for immobility after 24 and 48 hours of exposure (daphnids not being able to swim within 15 seconds after gentle agitation of the test beaker are considered to be immobilised).
The NOELR and EL0 were determined directly from the raw data.
The EL50 and the EL100 could not be determined due to the absence of a toxic effect of the test item in this test.

TEST CONCENTRATIONS
- Spacing factor for test concentrations: not relevant (limit test)
- Range finding study: yes
- Test concentrations of the range finding study: no data
- Results used to determine the conditions for the definitive study: no mortality at the undiluted loading rate

Reference substance (positive control):

yes

Remarks:

potassium dichromate

Key result

Duration:

48 h

Dose descriptor:

EL50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Duration:

48 h

Dose descriptor:

NOELR

Effect conc.:

>= 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Details on results:

APPEARANCE OF THE TEST MEDIUM
No remarkable observations were made concerning the appearance of the test medium. The test medium was a clear solution throughout the whole test duration.

ANALYTICAL MONITORING
In the analysed test medium samples from the start of the test, the measured cerium concentration was 6.4 µg/L. During the test period of 48 hours, the cerium concentration decreased to < 0.8 µg/L (Limit of Quantification). The mean measured cerium concentration, calculated as geometric mean between the measurement at test start and at test end (half of LOQ) was 1.6 µg/L, corresponding to 3.3 µg/L test item.

Results with reference substance (positive control):

- Results with reference substance valid? yes
- Mortality: no data
- 48h-EC50: 0.53 mg/L (acceptance range: 0.53-1.1 mg/L) (potassium dichromate)

Reported statistics and error estimates:

None as no adverse effect was observed.

Effect of the test item on the mobility of Daphnia magna: Loading rate (mg/L) Mean measured test item concentration (µg/L) No. of daphnids tested Immobilised daphnids after 24 hours           No.                   % Immobilised daphnids after 48 hours           No.                   % Control -- 20 0 0 0 0 100 3.3 20 0 0 0 0

Validity criteria fulfilled:

yes

Conclusions:

The test item had no acute toxic effects on Daphnia magna up to the highest concentration which could be tested at a loading rate of 100 mg/L.

Executive summary:

The acute toxicity of the reaction mass of cerium dioxide and zirconium dioxide to Daphnia magna was determined in a 48-hour static test according to the EU Commission Directive 92/69/EEC, Part C.2 (1992) and the OECD Guideline for Testing of Chemicals, No. 202 (2004).

Daphnids were exposed to control and test chemical at a nominal loading rate of 100 mg dry substance/L for 48 hours. Mortality/immobilisation were observed daily. In the control and the test solution (loading rate of 100 mg/L), no immobilised test organisms were observed during the period of 48 h. The 48 hour EL50 and NOELR were thus > 100 mg/L.

Reference 2

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study without detailed documentation

Reason / purpose for cross-reference:

reference to same study

Qualifier:

according to guideline

Guideline:

OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)

Deviations:

no

GLP compliance:

not specified

Analytical monitoring:

no

Details on sampling:

No analytical monitoring of the test substance concentration during the test.

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: Nano cerium oxide was poorly soluble in water. According the Guidance Document on Aquatic Toxicity Testing of Difficult Substances and Mixtures (2002), a saturated solution of this high purity cerium oxide was prepared. No other details.
- Controls: yes (test water without test item)
- Evidence of undissolved material (e.g. precipitate, surface film, etc): no data
No further data

Test organisms (species):

Daphnia magna

Details on test organisms:

No data

Test type:

not specified

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

48 h

Hardness:

No data

Test temperature:

No data

pH:

No data

Dissolved oxygen:

No data

Salinity:

Not applicable

Nominal and measured concentrations:

Nominal concentration: 100% (v/v saturated solution) cerium oxide nanoparticles

Details on test conditions:

TEST SYSTEM
- Test vessel: no data
- Aeration: no data
- Type of flow-through (e.g. peristaltic or proportional diluter): no data
- Renewal rate of test solution (frequency/flow rate): no data
- No. of organisms per vessel: 10
- No. of vessels per concentration (replicates): 4
- No. of vessels per control (replicates): 4
- No. of vessels per positive control (replicates): 2
- Biomass loading rate: no data

TEST MEDIUM / WATER PARAMETERS
No data

EFFECT PARAMETERS MEASURED: The daphnids were observed for immobility after 24 and 48 hours of exposure.
The 48-hour EC50 and the 48-hour NOEC were determined.

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: none

Reference substance (positive control):

yes

Remarks:

potassium dichromate (0.32; 0.56; 1.0 mg/l)

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

> 100 other: % (v/v) saturated solution of cerium oxide nanoparticle

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

>= 100 other: % (v/v) saturated solution of cerium oxide nanoparticle

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Details on results:

There were no toxic effects observed i.e. no immobilisation occurred at any time period during the test.

Results with reference substance (positive control):

- Results with reference substance valid? yes
- The 48h-EC50 was not calculated in the publication. It should be noticed that no adverse effect was observed at 0.56 mg/L, while 100% immobility was observed at the highest tested (1.0 mg/L) (potassium dichromate)

Reported statistics and error estimates:

No data

 Table 1: Effect of cerium oxide on the mobility of Daphnia magna

Nominal concentration (% v/v saturated solution)	No. of daphnids tested	Immobilised daphnids after 24 hours         No.                   %		Immobilised daphnids after 48 hours         No.                   %
Control	40	0	0	0	0
100% nano cerium oxide	40	0	0	0	0

Validity criteria fulfilled:

not specified

Conclusions:

Cerium oxide nanoparticles had no acute toxic effects on Daphnia magna at 100% (v/v) saturated solution.

Executive summary:

The 48hr-acute toxicity of cerium oxide nanoparticles to Daphnia magna was studied according to the OECD Guideline for Testing of Chemicals, N°202 (2004). Daphnids were exposed to control and test chemical at 100% (v/v) saturated solution for 48 hr. Immobilisation was monitored daily during the test. In the control and at 100% (v/v) saturated solution, no immobilised test organisms were observed during the test period of 48 h. Thus, the 48 hour EC₅₀ and the 48 hour NOEC were > 100% (v/v) saturated solution.

Reference 3

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Remarks:

The study was conducted according to the OECD internationally recognised guideline, without reference to the application of GLP and without analytical monitoring of the test material. However, the experimental details and results were well described.

Reason / purpose for cross-reference:

reference to same study

Reason / purpose for cross-reference:

reference to same study

Qualifier:

according to guideline

Guideline:

OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)

Deviations:

no

GLP compliance:

not specified

Analytical monitoring:

no

Details on sampling:

No analytical monitoring of the test substance concentration during the test.

Vehicle:

no

Details on test solutions:

- Method: Experimental test concentrations were prepared by dropwise addition of the cerium dioxide nanoparticles stock suspensions to the test medium adjusted to pH 4 using a 1 M HCl solution, while stirring. Subsequently, the pH of the test suspension was adjusted to 7.4.
- Controls: yes (test water without test item)
No further data

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Common name: Water flea
- Source: no data
- Age at study initiation: < 24h old
- Feeding during test: no
No further data

ACCLIMATION
No data

Test type:

not specified

Water media type:

freshwater

Limit test:

no

Total exposure duration:

48 h

Hardness:

No data

Test temperature:

20 +/- 1°C

pH:

7.4

Dissolved oxygen:

No data

Salinity:

Not applicable

Nominal and measured concentrations:

Nominal concentrations ranging from 10 to 1000 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: polyethylene cups containing 25 mL of control solution or test suspension
- No. of organisms per vessel: 10
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 3
No further data.

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Elendt M4 medium
No further data

OTHER TEST CONDITIONS
- Adjustment of pH: The pH of the stock suspension was adjusted to 7.4, before introduction in the test vessel. The test vessels were not subjected to pH adjustment.
- Photoperiod: 12-hour photoperiod
- Light intensity: no data

EFFECT PARAMETERS MEASURED (with observation intervals if applicable): after 48 hours the number of immobile organisms was counted
The 48-hour EC50 and the 48-hour NOEC were determined.

TEST CONCENTRATIONS
no data

Reference substance (positive control):

no

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: immobility

Remarks on result:

other: regardless the nanoparticles diameter (14, 20 or 29 nm)

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

>= 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: immobility

Remarks on result:

other: regardless the nanoparticles diameter (14, 20 or 29 nm)

Details on results:

- Characterisation of nanoparticles:
The suspensions appear turbid within an hour of suspension preparation, indicating particle aggregation to diameters ranging from 425 to 529 nm. Hence, the organisms were exposed to cerium dioxide nanoparticles aggregates.

- Biological results:
No immobilised organism was observed up to 1000 mg/L.

Validity criteria fulfilled:

not specified

Conclusions:

Cerium dioxide nanoparticles had no acute toxic effects on juvenile daphnids at 1000 mg/L.

Executive summary:

The 48hr-acute toxicity of cerium dioxide nanoparticles to Daphnia magna was studied according to the OECD guideline for Testing of Chemicals, n°202 (2004). Daphnids were exposed to control and test chemicals at concentrations ranging from 10 to 1000 mg/L for 48 hr at three nanoparticles sizes (14, 20 and 29 nm). Immobilisation was monitored during the test. In the control and in the tested groups, no immobilised test organisms were observed during the test period of 48 hours. Thus, the 48 hour EC₅₀ and the 48 hour NOEC were > 1000 mg/L regardless the nanoparticle diameter.

Reference 4

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Remarks:

Test procedures were in accordance with generally accepted scientific standards and described in sufficient details.

Reason / purpose for cross-reference:

reference to same study

Reason / purpose for cross-reference:

reference to same study

Qualifier:

no guideline available

Principles of method if other than guideline:

24h-mortality test with instar II-III larvae of the crustacean Thamnocephalus platyurus using the toxicity test kit Thamnotoxkit F (MicroBioTests, Mariakerke, Belgium).

GLP compliance:

not specified

Analytical monitoring:

no

Details on sampling:

No analytical monitoring of the test substance concentration during the test.

Vehicle:

no

Details on test solutions:

- Method: Experimental test concentrations were prepared by dropwise addition of the cerium dioxide nanoparticles stock suspensions to the test medium adjusted to pH 4 using a 1 M HCl solution, while stirring. Subsequently, the pH of the test suspension was adjusted to 7.4.
- Control: yes (test water without test item)
No further data

Test organisms (species):

other aquatic crustacea: Thamnocephalus platyurus

Details on test organisms:

TEST ORGANISM
- Common name: fairy shrimp
- Source: The test organisms were provided in the THAMNOTOXKIT FTM (MicroBioTests, Mariakerke, Belgium) as dormant eggs (cysts).
- Age at study initiation: The test was performed on instar II-III larvae hatched from cysts mentioned above.
- Method of hatching: The hatching is experimentally induced by the authors 24 hours before the start of the toxicity test. The tube containing cysts was filled with 1 mL hatching medium prepared by transferring 2.5 mL Standard Freshwater into a vial and adding 17.5 mL deionised water. Then, the tube was closed and shaked at regular intervals for approximately 30 minutes. After this pre-hydration, cysts were transferred into Petri dishes containing 10 mL hatching medium. To promote hatching, the Petri dishes were covered and incubated at 25°C for 20 to 22 hours under continuous illumination (3000 – 4000 lux).
No further data.

ACCLIMATION
No

Test type:

semi-static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

24 h

Hardness:

No data

Test temperature:

25°C

pH:

No data

Dissolved oxygen:

No data

Salinity:

Not applicable

Nominal and measured concentrations:

Nominal concentrations: 100, 500, 1000, 3000 and 5000 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: 24-well plate covered with a strip of Parafilm.
- No. of organisms per vessel: 10 larvae per well.
- No. of vessels per concentration (replicates): 3 wells per concentration.
- No. of vessels per control (replicates): 3 wells per control.
- No. of replications of the assay: 2 for the 20 and 29-nm particles, and 3 for the 14-nm particles.
No further data.

TEST MEDIUM / WATER PARAMETERS
All test suspensions were prepared in EPA medium.

OTHER TEST CONDITIONS
- Adjustment of pH: The pH of the stock suspension was adjusted to 7.4 before introduction in the wells. The test wells were not subjected to pH adjustment.
- Photoperiod: in the dark

EFFECT PARAMETERS MEASURED: after 24 h of incubation, mortality was determined.
The 24-hour LC50 and the 24-hour NOEC were determined.

TEST CONCENTRATIONS
no data

Reference substance (positive control):

no

Duration:

24 h

Dose descriptor:

NOEC

Effect conc.:

>= 5 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality

Remarks on result:

other: regardless the nanoparticles diameter (14, 20 and 29 nm)

Duration:

24 h

Dose descriptor:

LC50

Effect conc.:

> 5 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality

Remarks on result:

other: regardless the nanoparticles diameter (14, 20 and 29 nm)

Details on results:

- Characterisation of nanoparticles:
The suspensions appear turbid within an hour of suspension preparation, indicating particles aggregation to diameters ranging from 467 to 758 nm. Hence, the organisms were exposed to cerium dioxide nanoparticle aggregates.

- Biological results:
After a 24-hour exposure of Thamnocephalus platyurus to 5000 mg/L 14, 20 and 29 nm cerium dioxide particles, only 12, 10 and 7% mortality was noted, respectively. These mortality values were not significant.

Validity criteria fulfilled:

yes

Remarks:

control mortality was not exceeded 10%.

Conclusions:

Cerium dioxide nanoparticles had no acute effects on Thamnocephalus platyurus at 5000 mg/L.

Executive summary:

The 24hr-acute toxicity of cerium dioxide nanoparticles to Thamnocephalus platyurus was studied using the toxicity test-kit Thamnotoxkit F according to the standard operational procedure. Instar II-III larvae were exposed to 100, 500, 1000, 3000 and 5000 mg nano-cerium dioxide / L in well plates for 24 hours at three nanoparticles sizes (14, 20 and 29 nm). The mortality was observed at the end of the test.

No significant acute toxicity was reported up to 5000 mg/L. Thus, the 24 hour EC₅₀ and the 24 hour NOEC were > 5000 mg/L regardless the nanoparticle diameter.

Reference 5

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

4 (not assignable)

Rationale for reliability incl. deficiencies:

documentation insufficient for assessment

Remarks:

The level of detail provided in the publication is considerably too low to conclude on its reliability.

Reason / purpose for cross-reference:

reference to same study

Principles of method if other than guideline:

No data except that daphnids were exposed for 96 hours to test chemical.

GLP compliance:

not specified

Analytical monitoring:

no

Details on sampling:

No analytical monitoring of the test substance concentration during the test

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: Particles were prepared by sonicating for 30 minutes in EPA water containing 0.01 - 10 µg/mL of particles.
- Controls: Yes, EPA water without the addition of particles.
No further data.

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Common name: Water flea
- Age at study initiation (mean and range, SD): no data, except that neonates were used.
No further data.

ACCLIMATION
No data.

Test type:

not specified

Water media type:

freshwater

Limit test:

no

Total exposure duration:

96 h

Hardness:

No data

Test temperature:

No data

pH:

No data

Dissolved oxygen:

No data

Salinity:

Not applicable

Nominal and measured concentrations:

Nominal concentrations: 0.01 to 10 mg/L

Details on test conditions:

TEST SYSTEM
No data

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: EPA medium
No further data

OTHER TEST CONDITIONS
No data

EFFECT PARAMETERS MEASURED (with observation intervals if applicable)
Endpoints assessed included lethality and shedding of the carapace.

TEST CONCENTRATIONS
- Spacing factor for test concentrations: No data
- Range finding study: No data

Duration:

96 h

Dose descriptor:

LC50

Effect conc.:

> 10 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality

Duration:

96 h

Dose descriptor:

NOEC

Effect conc.:

>= 10 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality

Details on results:

Biological results:
No mortality was observed among the daphnids exposed to 0.01 to 10 mg/L.

Characterisation of nanoparticles:
The measured sizes varied according to the techniques used. However, when comparing the size of nanoparticles to that of the bulk form, there are significant size differences. Solubility was below 1% fo all samples.

Validity criteria fulfilled:

not specified

Conclusions:

Based on the limited details provided, cerium dioxide nanoparticles do not cause acute toxicity to daphnids.

Executive summary:

The impacts of cerium dioxide nanoparticles (< 25 nm) were investigated on Daphnia magna assessing mortality when exposed for 96 hours to concentrations ranging from 0.01 to 10 mg/L. No mortality was observed among the daphnids exposed to the different concentrations.

Reference 6

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

from 11 SEP 2006 to 08 AUG 2007

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)

Version / remarks:

and EU Method C.2 (Acute toxicity for Daphnia)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

- Concentrations: triplicates samples from the test medium (loading rate of 100 mg/L) and from the control were taken just before test start and after 48 hours.
- Sampling method: no data
- Sample storage conditions before analysis: Immediately after sampling, the samples were acidified with 3% (v/v) nitric acid (HNO3, 65% Suprapur®, Merck) to stabilise the samples during the storage period. Then the samples were deep frozen and stored at about -20°C.

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: An undiluted filtrate of a supersaturated dispersion with the loading rate of 100 mg/L was tested. The dispersion with the loading rate of 100 mg/L was prepared by dispersing 50.3 mg of the test item in 500 mL of test water. The test item was mixed into the test water as homogeneously as possible using ultrasonic treatment for 15 min and intense stirring. The dispersion was stirred on a magnetic stirrer at room temperature in the dark for seven days. After the stirring period, the dispersion was filtered through a membrane filter (0.45 µm). The undiluted filtrate of the dispersion was used as the test medium.
- Differential loadings: No (limit test)
- Controls: blank (test water without test item)
- Evidence of undissolved material (e.g. precipitate, surface film, etc): no data

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Common name: Water flea
- Strain: clone defined as clone 5
- Source: supplied in 1992 by University of Sheffield/UK
- Age at study initiation: 6-24 hours, not first brood progeny
- Weight and length at study initiation (mean and range, SD): no data
- Method of breeding: Bred in RCC since 1992 in reconstituted water of the quality identical to the water used in the tests and under temperature and light conditions identical to those of the test.
- Feeding during test: No

ACCLIMATION
- Acclimation period: no

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

48 h

Hardness:

2.5 mmol/L (= 250 mg/L as CaCO3)

Test temperature:

20°C

pH:

7.8

Dissolved oxygen:

between 8.5 and 8.8 mg/L

Salinity:

not applicable

Nominal and measured concentrations:

Nominal loading rate: 100 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel:
- Type : 100-mL glass beakers
- Material, size, headspace, fill volume: vessels filled with 50 mL of test medium
- Aeration: The test water was aerated prior to the start of the study until oxygen saturation was reached. During the test period, the test water was not aerated.
- Type of flow-through (e.g. peristaltic or proportional diluter): none (static test)
- Renewal rate of test solution (frequency/flow rate): no renewal (static test)
- No. of organisms per vessel: 5
- No. of vessels per concentration (replicates): 4
- No. of vessels per control (replicates): 4
- Biomass loading rate: 2 mL of medium per daphnia

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: reconstituted test water: analytical grade salts dissolved in purified water
- Alkalinity: 0.8 mmol/L
- Ca/Mg ratio (mol): 4:1 (based on molarity)
- Na/ K ratio (mol): 10:1 (based on molarity)
- Culture medium different from test medium: no
- Intervals of water quality measurement: The pH values, the dissolved oxygen concentrations and the water temperature were determined at the start and at the end of the test in the control and the test medium. The appearance of the test medium was also recorded at the start of the test and after 24 and 48 hours.
- No further data

OTHER TEST CONDITIONS
- Adjustment of pH: No
- Photoperiod: a 16 hour light to 8 hour dark with a 30 minute transition period.
- Light intensity: between 470 and 640 lux

EFFECT PARAMETERS MEASURED :
The daphnids were observed for immobility after 24 and 48 hours of exposure (daphnids not being able to swim within 15 seconds after gentle agitation of the test beaker are considered to be immobilised).
The NOELR and EL0 were determined directly from the raw data. The EL50 and EL100 could not be determined due to the absence of a toxic effect of the test item in this test.

TEST CONCENTRATIONS
- Spacing factor for test concentrations: not relevant (limit test)
- Range finding study: yes
- Test concentrations of the range finding study: no data
- Results used to determine the conditions for the definitive study: no mortality at the undiluted loading rate.

Reference substance (positive control):

yes

Remarks:

potassium dichromate

Duration:

48 h

Dose descriptor:

EL50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Duration:

48 h

Dose descriptor:

NOELR

Effect conc.:

>= 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Details on results:

No adverse effect was observed at the highest loading rate tested (i.e. 100 mg/L), which corresponded to the maximum concentration of dissolved test item. As a result, cerium dioxide is not acutely toxic for daphnids up to its solubility limit into water.

The analytically measured concentrations of cerium in the test medium samples taken at the start and at the end of the test were below the LOQ (< 1 µg/L)

No remarkable observations concerning the appearance of the test medium.

Results with reference substance (positive control):

- Results with reference substance valid? yes
- 48h-EC50: 0.67 mg/L (acceptance range: 0.53 - 1.1 mg/L) (potassium dichromate)

Reported statistics and error estimates:

None as no adverse effect was observed

Effect of OPALINE DE POLISSAGE on the mobility of Daphnia magna

Treatment (Loading rate)	No. of daphnids tested	Immobilised daphnids after 24 hours	Immobilised daphnids after 48 hours
Control	20	No.: 0 %: 0	No.: 0 %: 0
Undiluted filtrate (100 mg/L)	20	No.: 0 %: 0	No.: 0 %: 0

Validity criteria fulfilled:

yes

Conclusions:

Cerium dioxide had no acute toxic effects on Daphnia magna up to its solubility limit in the test water at the loading rate of 100 mg/L under the present test conditions.

Executive summary:

The 48hr-acute toxicity of cerium dioxide to Daphnia magna was studied under static conditions according to the EU Commission Directive 92/69/EEC, Part C.2 (1992) and the OECD Guideline for Testing of Chemicals, N°202 (2004). Daphnids were exposed to control and test chemical at nominal concentration of 100 mg/L (loading rate) for 48 hr. Mortality/immobilisation were monitored daily. In the control and at the loading rate of 100 mg/L, no immobilised test organisms were determined during the test period of 48 h. Thus, the 48 hour EL50 and the 48 hour NOELR were > 100 mg/L. As no adverse effect was observed at the highest loading rate tested (i.e. 100 mg/L), which corresponded to the maximum concentration of dissolved test item, cerium dioxide is not acutely toxic for daphnids up to its solubility limit into water.

Reference 7

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study without detailed documentation

Reason / purpose for cross-reference:

reference to same study

Qualifier:

according to guideline

Guideline:

OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)

Deviations:

no

GLP compliance:

not specified

Analytical monitoring:

no

Details on sampling:

none

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: Cerium oxide was poorly soluble in water. According the Guidance Document on Aquatic Toxicity Testing of Difficult Substances and Mixtures (2002), a saturated solution of this high purity cerium oxide was prepared. No other details.
- Controls: yes, test water without test item
- Evidence of undissolved material (e.g. precipitate, surface film, etc): no data
- No further data

Test organisms (species):

Daphnia magna

Details on test organisms:

No data

Test type:

not specified

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

48 h

Hardness:

No data

Test temperature:

No data

pH:

No data

Dissolved oxygen:

No data

Salinity:

No data

Nominal and measured concentrations:

Nominal concentration: 100% (v/v saturated solution) cerium oxide

Details on test conditions:

TEST SYSTEM
- Test vessel: no data
- Aeration: no data
- Type of flow-through (e.g. peristaltic or proportional diluter): no data
- Renewal rate of test solution (frequency/flow rate): no data
- No. of organisms per vessel: 10
- No. of vessels per concentration (replicates): 4
- No. of vessels per control (replicates): 4
- No. of vessels per positive control (replicates): 2
- Biomass loading rate: no data

TEST MEDIUM / WATER PARAMETERS
No data

EFFECT PARAMETERS MEASURED: The daphnids were observed for immobility after 24 and 48 hours of exposure.
The 48-hour EC50 and the 48-hour NOEC were determined.

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: none

Reference substance (positive control):

yes

Remarks:

potassium dichromate (0.32; 0.56; 1.0 mg/l)

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

> 100 other: % (v/v) saturated solution of cerium oxide

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

>= 100 other: % (v/v) saturated solution of cerium oxide

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Details on results:

There were no toxic effects observed i.e. no immobilisation occurred at any time period during the test.

Results with reference substance (positive control):

- Results with reference substance valid? yes
- The 48h-EC50 was not calculated in the publication. It should be noticed that no adverse effect was observed at 0.56 mg/L, while 100% immobility was observed at the highest tested (1.0 mg/L) (potassium dichromate)

Reported statistics and error estimates:

No data

Effect of cerium oxide on the mobility of Daphnia magna

Nominal concentration (% v/v saturated solution)	No. of daphnids tested	Immobilised daphnids after 24 hours	Immobilised daphnids after 48 hours
Control	40	No.: 0 %: 0	No.: 0 %: 0
100% cerium oxide	40	No.: 0 %: 0	No.: 0 %: 0

Validity criteria fulfilled:

not specified

Conclusions:

Cerium oxide (bulk sample) had no acute toxic effects on Daphnia magna at 100% (v/v) saturated solution.

Executive summary:

The 48hr-acute toxicity of cerium oxide to Daphnia magna was studied according to the OECD Guideline for Testing of Chemicals, N°202 (2004). Daphnids were exposed to control and test chemical at 100% (v/v) saturated solution for 48 hr. Immobilisation was monitored during the test. In the control and at 100% (v/v) saturated solution, no immobilised test organisms were observed during the test period of 48 h. Thus, the 48 hour EC50 and the 48 hour NOEC were > 100% (v/v) saturated solution.

Reference 8

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

4 (not assignable)

Rationale for reliability incl. deficiencies:

other: :

Remarks:

Some tables and figures of the publication report results on bulk cerium dioxide. However, the article primarily deals with the nanoparticle form, and no experimental detail is given concerning the experiment with the micrometric ones. Therefore, a reliability 4 was attributed to this data.

Reason / purpose for cross-reference:

reference to same study

Reason / purpose for cross-reference:

reference to same study

Principles of method if other than guideline:

No data are available on the bulk form. As results are presented concomittantly with those on nanoparticles, one can expect that the same experimental protocol was applied (i.e. OECD method 202).

GLP compliance:

not specified

Analytical monitoring:

not specified

Details on sampling:

No data on the analytical monitoring of concentrations of bulk cerium dioxide during the test.

Vehicle:

not specified

Details on test solutions:

No data are available on the bulk form.

Test organisms (species):

Daphnia magna

Details on test organisms:

No data are available concerning the organisms tested during the experiment on the bulk form.

Test type:

not specified

Water media type:

freshwater

Total exposure duration:

48 h

Hardness:

No data

Test temperature:

No data

pH:

No data

Dissolved oxygen:

No data

Salinity:

Not applicable

Nominal and measured concentrations:

No data are available on the bulk form.

Details on test conditions:

No data are available on the bulk form.

Reference substance (positive control):

not specified

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Details on results:

No further data.

Validity criteria fulfilled:

not specified

Conclusions:

Based on the limited details provided, (bulk) cerium dioxide does not cause acute toxicity to daphnids.

Executive summary:

In this publication primarily dealing with nanoparticulate cerium dioxide, some results are given concerning the bulk form. A 48-hour NOEC superior to 1000 mg/L based on immobility was reported, implying that bulk cerium dioxide does not cause acute toxicity to Daphnia magna.

Reference 9

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

4 (not assignable)

Rationale for reliability incl. deficiencies:

documentation insufficient for assessment

Remarks:

Test procedures were in accordance with generally accepted scientific standards and described in sufficient details.

Reason / purpose for cross-reference:

reference to same study

Principles of method if other than guideline:

No data except that daphnids were exposed for 96 hours to test chemical.

GLP compliance:

not specified

Analytical monitoring:

no

Details on sampling:

No analytical monitoring of the test substance concentration during the test

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: Particles were prepared by sonicating for 30 minutes in EPA water containing 0.01 - 10 µg/mL of particles.
- Controls: Yes, EPA water without the addition of particles.
No further data.

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Common name: Water flea
- Age at study initiation (mean and range, SD): no data, except that neonates were used.
No further data.

ACCLIMATION
No data.

Test type:

not specified

Water media type:

freshwater

Limit test:

no

Total exposure duration:

96 h

Hardness:

No data

Test temperature:

No data

pH:

No data

Dissolved oxygen:

No data

Salinity:

Not applicable

Nominal and measured concentrations:

Nominal concentrations: 0.01 to 10 mg/L

Details on test conditions:

TEST SYSTEM
No data

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: EPA medium
No further data

OTHER TEST CONDITIONS
No data

EFFECT PARAMETERS MEASURED (with observation intervals if applicable)
Endpoints assessed included lethality and shedding of the carapace.

TEST CONCENTRATIONS
- Spacing factor for test concentrations: No data
- Range finding study: No data

Duration:

96 h

Dose descriptor:

LC50

Effect conc.:

> 10 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality

Duration:

96 h

Dose descriptor:

NOEC

Effect conc.:

>= 10 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality

Details on results:

No mortality was observed among the daphnids exposed to 0.01 to 10 mg/L.

Validity criteria fulfilled:

not specified

Conclusions:

Based on the limited details provided, cerium dioxide (bulk sample) does not cause acute toxicity to daphnids.

Executive summary:

The impacts of cerium dioxide were investigated on Daphnia magna assessing mortality when exposed for 96 hours to concentrations ranging from 0.01 to 10 mg/L. No mortality was observed among the daphnids exposed to the different concentrations.

Reference 10

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

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

Adequacy of study:

supporting study

Justification for type of information:

Read across from studies performed with cerium dioxide (bulk and nano samples) and zirconium dioxide (bulk sample only). 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

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across source

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.

Basis for effect:

mobility

Remarks on result:

other: Based on the results from studies conducted with cerium dioxide (nano and bulk samples) and zirconium dioxide (bulk sample only), it can be concluded that no effects are expected for the reaction mass of cerium dioxide and zirconium dioxide.

Reference 11

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

supporting study

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 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	Immobilised daphnids after 24 hours           No.                   %		Immobilised 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 immobilisation were observed after 24 and 48 hours.

No significant immobilisation was observed with 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 48-hour EL50 (Daphnia magna) of the reaction mass of cerium dioxide and zirconium dioxide is > 100 mg/L based on mobility, revealing it is not harmful to daphnids. The test was carried out with a representative nanoform of the reaction mass, however the same conclusion is expected for any potential bulk form, should such form be placed on the market.

Additional information

A GLP-compliant study, scored as Klimisch 1 and flagged as key study, is available for the reaction mass, yielding a 48h-EL50 > 100 mg/L and revealing that the reaction mass is not harmful to Daphnia magna (Bätscher, 2008b).

Additionally, four experimental studies provide information on the toxicity to aquatic invertebrates of micrometric and nanometric cerium dioxide.

Micrometric cerium dioxide: One study (Bätscher, 2007a) is scored as Klimisch 1 and concluded that cerium dioxide is not acutely harmful to daphnids. The other studies of reliability 2 (Park et al, 2007) and 4 (Van Hoecke et al., 2009, Gaiser et al., 2009) yielded consistent results for micrometric cerium dioxide.

Nanometric cerium dioxide: Three literature studies are available on acute toxicity to aquatic invertebrates (Van Hoecke et al., 2009 (Klimisch 2); Park et al., 2007 (Klimisch 2); Gaiser et al., 2009 (Klimisch 4)). Van Hoecke et al. (2009) performed a study in D. magna in accordance with the OECD guideline, as well as a microplate study in Thamnocephalus platyurus. They did not observe any adverse effects in these test organisms, regardless of the particle size. The studies of Park et al. (2007) and Gaiser et al. (2009) in D. magna, yielded consistent results for nanometric cerium dioxide. All studies concluded that nanometric cerium dioxide is not acutely harmful to aquatic invertebrates.

Finally, zirconium dioxide (micrometric form tested only) was not found to be harmful to D. magna either (Bazin, 1994) in a Klimisch 2 study (48h-EL50 > 100 mg/L).

The studies on cerium dioxide and zirconium dioxide support the conclusion of the study on the reaction mass.