Cerium dioxide

Short-term toxicity to fish

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

short-term toxicity to fish

Type of information:

experimental study

Adequacy of study:

key study

Study period:

from 30-OCT-2000 to 29-NOV-2000

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, but the GLP are not stated, and no analytics were performed.

Qualifier:

according to guideline

Guideline:

OECD Guideline 203 (Fish, Acute Toxicity Test)

Deviations:

no

GLP compliance:

no

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: The substance practically insoluble in water was introduced in the test medium by weighed adequate quantity and was dispersed by stirring. The dissolution was continued during a period of 168 hours to be sure that the equilibrium was reached and "soluble fraction" stable during the test. After correction of evaporation by addition of deionised water, stirring was stopped and the different suspensions were decanted for a resting period of 4 hours.
- Controls: yes, test water without test item
- Evidence of undissolved material (e.g. precipitate, surface film, etc): no

Test organisms (species):

Danio rerio (previous name: Brachydanio rerio)

Details on test organisms:

TEST ORGANISM
- Common name: Zebrafish
- Source: Pisciculture Exotique - Dourdan, 91, France
- size/weight: 30.4 mm, 0.3 g;
- Method of breeding: The fish were bred in reconstituted water (ISO 7346) with continual aeration and filtering device
- Food: TetraMin Tetra during breeding (no feeding during the test);

ACCLIMATION
- Acclimation period: 2 weeks
- Acclimation conditions: same as test
- Health during acclimatation: mortality less than 1% within the adaptation period.

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

96 h

Hardness:

250 ± 25 mg/L as CaCO3.

Test temperature:

24 ± 1°C

pH:

7.17 - 7.87

Dissolved oxygen:

4.5 - 8.2 mg/L

Salinity:

not applicable

Nominal and measured concentrations:

100 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel:
- Type : 5 litres glass beakers
- Fill volume: 4 L of reconstituted water
- Aeration: none during the test, but dilution water was previously saturated with oxygen before the start of the test
- No. of organisms per vessel: 10
- No. of vessels per concentration (replicates): 1
- No. of vessels per control (replicates): 1
- Biomass loading rate: 0.76 g/L

WATER PARAMETERS
- Source: reconstituted water-ISO 7346
- Conductivity: < 5 µs/cm
- Intervals of water quality measurement : pH and dissolved oxygen were measured after 0, 24, 48, 72 and 96 h of exposure
- No further data

OTHER TEST CONDITIONS
- Photoperiod: about 12 h light daily
- Light intensity: natural diffused lighting

EFFECT PARAMETERS MEASURED : Immobility and absence of respiration motion observed after 3, 24, 48, 72 and 96 h of exposure

Reference substance (positive control):

yes

Remarks:

potassium dichromate

Key result

Duration:

96 h

Dose descriptor:

LL50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality (fish)

Key result

Duration:

96 h

Dose descriptor:

NOELR

Effect conc.:

>= 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality (fish)

Details on results:

No mortality was observed during the test, either in control or test groups.
No abnormal response of the fish was observed during the test period.

Results with reference substance (positive control):

- Results with reference substance valid? yes
- Mortality: no data
- 24h LC50: 226 mg/L (K2Cr2O7). This calculated value was between the interval (200-400 mg/L) formely defined by the method, and was used to validate the selected fish batch.

Validity criteria fulfilled:

yes

Conclusions:

Using a limit test at 100 mg/L, cerium dioxide had no acute toxic effect on the fish Danio rerio.

Executive summary:

The 96hr-acute toxicity of cerium dioxide to Brachydanio rerio was studied under static conditions according to OECD Guideline 203. Brachydanio rerio were exposed to control and test chemical at nominal concentration of 100 mg /L. Mortality/immobilization were observed daily. No mortality was observed during the test, neither in the control nor in the group exposed to the test item. The 96 hour LL50 and NOELR were thus > 100 mg/L.

Reference 2

Endpoint:

short-term toxicity to fish

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

From JAN 2007 to 26 APR 2007

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

test procedure in accordance with national standard methods with acceptable restrictions

Remarks:

The study was conducted according to an american guideline, without reference to the application of GLP and without analytical monitoring of the test substance. 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

Reason / purpose for cross-reference:

reference to same study

Qualifier:

according to guideline

Guideline:

other: U.S. Environmental Protection Agency. 2002a. Methods for Measuring the Acute Toxicity of Effluents and Receiving Waters to Freshwater and Marine Organisms. EPA-821-R-02-012. Office of Water, Washington D.C.

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: Test solution was prepared by combining Cerium oxide with moderately hard reconstituted lab water. Cerium oxide was insoluble, which resulted in highly turbid solution. As a result, in order to eliminate any toxic effects due to high suspended solids, the solids were allowed to settle before using the solution in the test. The stock solution was prepared and allowed to mix for 24 hours. After 24 hours of mixing, it was removed from the stir plate and the suspended solid was allowed to settle for an additional 24 hours. The stock solution (100 g/L) was then decanted and used to prepare the tests solutions.
- Controls: yes, reconstituted water without test item
- Evidence of undissolved material (e.g. precipitate, surface film, etc): no data
- No further data

Test organisms (species):

Pimephales promelas

Details on test organisms:

TEST ORGANISM
- Common name: Fathead minnow
- Strain: no data
- Source: P. promelas were obtained from Aquatic BioSystems, Inc. (Fort Collins, CO).
- Age at study initiation : 6-8 days old (no age variation within the same test)
- Length / Weight at study initiation : no data
- Method of breeding: no data
- Feeding during test : Organisms were fed Artemia nauplii 2 hours prior to test initiation, and 2 hours prior to the 48 hour solution renewal.
- No further data

ACCLIMATION
- Acclimation period: no

Test type:

semi-static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

96 h

Hardness:

80 - 98 mg CaCO3/L

Test temperature:

20.0 ± 1.0°C

pH:

7.63 - 7.9

Dissolved oxygen:

6.2 - 7.9 mg O2/L

Salinity:

not applicable

Nominal and measured concentrations:

Nominal concentrations: 12500, 25000, 50000 mg/L

Details on test conditions:

The test was performed twice on the same day.

TEST SYSTEM
- Test vessel: 250 ml disposable plastic cup filled with 200 ml test solutions
- Aeration: no data
- Type of flow-through (e.g. peristaltic or proportional diluter): none (semi-static)
- Renewal rate of test solution (frequency/flow rate): after 24, 48 and 72 hours of exposure
- No. of organisms per vessel: 10
- No. of vessels per concentration (replicates): 4
- No. of vessels per control (replicates): 4
- Biomass loading rate: no data


TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: The reconstituted lab water was prepared using ultra-pure deionized water combined with reagent grade chemicals and followed the standard EPA recipe, with a slight modification to increase the hardness to approximately 100 mg/L.
- Alkalinity: 44-64 mg CaCO3/L
- Conductivity: 324-349 µmho/cm
- Total dissolved solids: 155-167 mg/L
- Ammonia: 0.12-0.32 mg NH3/L
- Intervals of water quality measurement: Total hardness (as mg CaCO3/L), pH, alkalinity (as mg CaCO3/L), conductivity, total dissolved solids, ammonia, and dissolved oxygen were measured in all concentrations at test initiation. Temperature, conductivity, pH, and dissolved oxygen were measured daily in each concentration.
- No further data

OTHER TEST CONDITIONS
- Photoperiod: 16L:8D light cycle
- Light intensity: 50-100 ft-c light intensity

EFFECT PARAMETERS MEASURED : The fathead minnow acute bioassay measure survivability to determine the Lethal Concentration for 50% of the organisms, also known as the LC50.

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 2
- Justification for using less concentrations than requested by guideline: no data
- Range finding study: yes
- Test concentrations: 12500, 25000, 50000 mg/L
- Results used to determine the conditions for the definitive study: no mortality at 12500, 25000, 50000 mg/L

Reference substance (positive control):

not specified

Remarks:

Reference toxicity tests were conducted monthly to ensure consistent organism quality. No further information.

Key result

Duration:

96 h

Dose descriptor:

LC50

Effect conc.:

> 50 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality (fish)

Results with reference substance (positive control):

no data

Reported statistics and error estimates:

no data

Sublethal observations / clinical signs:

Effect of Cerium oxide on the Mortality of Pimephales promelas

Nominal concentration (mg/L)	0	12500	25000	50000
Test A: Alive/Exposed % survival	39/40 97.5	40/40 100	39/40 97.5	40/40 100
Test B: Alive/Exposed % survival	39/40 97.5	40/40 100	39/40 97.5	40/40 100

Validity criteria fulfilled:

not specified

Conclusions:

Cerium oxide had no acute toxic effect on Pimephales promelas up to 50000 mg/L.

Executive summary:

The 96hr-acute toxicity of cerium oxide to Pimephales promelas was studied according to the US EPA method EPA-821 -R-02 -012 (2002).Pimephales promelas were exposed to control and test chemical at 12500, 25000 and 50000 mg/L for 96 hr. Mortality were observed during the test. No significant mortality was observed during the test period of 96 h at any concentrations tested. Thus, the 96 -hour LC50 was >50000mg/L.

Description of key information

The 96-hour LL50 (Fish: Brachydanio rerio) of the bulk form of cerium dioxide is > 100 mg/L. Hence, the bulk form of cerium dioxide is not harmful for the fish species tested.

Additional information

Two experimental studies, scored as Klimisch 2, are available (Bazzon, 2000 and Lambert, 2007). The first of them, conducted according to the OECD guideline was selected as a key study. The second, conducted according to an American guideline, gave consistent results and was flagged as a supporting study. Both studies concluded that the bulk form of cerium dioxide was not harmful to the fish species tested.