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Short-term toxicity to aquatic invertebrates

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Endpoint:
short-term toxicity to aquatic invertebrates
Type of information:
experimental study
Adequacy of study:
weight of evidence
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
Duration:
48 h
Dose descriptor:
LL50
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

g/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 NOEL were thus > 100 mg/L.

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.

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 the reaction mass of cerium dioxide and zirconium dioxide, praseodymium(III,IV) 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
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: The reaction mass of cerium dioxide, praseodymium(III,IV) oxide and zirconium dioxide is not considered to be toxic or harmful to aquatic invertebrates.
Remarks:
This conclusion is based on the experimental results available for zirconium dioxide (Bazin, 1994), praseodymium(III,IV) oxide (Bätscher, 2008a) and the reaction mass of cerium dioxide and zirconium dioxide (Bätscher, 2008b). In all these studies, no acute toxic effects were observed in Daphnia magna at a nominal loading rate of 100 mg/L.
Endpoint:
short-term toxicity to aquatic invertebrates
Type of information:
experimental study
Adequacy of study:
weight of evidence
Study period:
3 December 2007 - 19 December 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 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 material is a sparingly soluble substance. In order to assess its toxicity, a saturated solution was prepared and tested. The test method was based on the OECD Guidance Document on Aquatic Toxicity Testing of Difficult Substances and Mixtures. The test medium with a 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 material was prepared in the test water by mixing 200.2 mg of test material into 2000 mL of test water using ultrasonic treatment for 15 minutes and intense stirring. No auxiliary solvent or emulsifier was used.
The dispersion was stirred by a magnetic stirrer at room temperature in the dark for 24 hours. Then, stirring was stopped and after another 24 hours the non-dissolved test material had completely settled down on the bottom of the stirring vessel. The clear equilibrated supernatant was carefully separated from the non-dissolved test material and was used as test medium. The stirring and settling periods were chosen according to the results of pre-experiments (non-GLP). In this pre-experiment, the maximum concentration of dissolved test material was reached after a stirring period of 24 hours. The deposition time of one day was necessary to allow a maximum amount of the test material to deposit.
- Controls: blank (test water without addition of the test material)
- 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
- 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 at study initiation (mean and range, SD): no data
- Length at study initiation (length definition, mean, range and SD): 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
- Source: Originally supplied by the University of Sheffield, UK in 1992. Since that time, the clone has been bred at the laboratory.

ACCLIMATION
- Acclimation period: no
Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
48 h
Post exposure observation period:
none
Hardness:
2.5 mmol/L (= 250 mg/L as CaCO3)
Test temperature:
20°C
pH:
7.8 - 8.0
Dissolved oxygen:
8.5 - 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 (delete if not applicable): closed to reduce the loss of water by evaporation and to avoid the entry of dust into the solution
- Material, size, headspace, fill volume: The test was performed in 100 mL glass beakers filled with 50 mL of test medium. The test vessels were covered with glass plates to reduce the loss of water by evaporation and to avoid the entry of dust into the solutions.
- 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
- Alkalinity: 0.8 mmol/L
- Ca/mg ratio: 4:1 (based on molarity)
- 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 were 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
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 RESULTS:
In the analysed test medium samples from the start of the test, the measured praseodymium concentration was 0.13 mg/L. During the test period of 48 hours, the praseodymium concentration decreased to 0.039 mg/L. The mean measured praseodymium concentration (calculated as geometric mean between the measurement at test start and test end) was 0.070 mg/L, corresponding to a test material concentration of 0.085 mg/L. The solubility limit reached during this test was thus different from that obtained during the water solubility test (see IUCLID section 4.8). Such contrasting results could be explained by the different water media used in the water solubility test and ecotoxicological studies (media containing analytical grade salts).
Results with reference substance (positive control):
- Results with reference substance valid? yes
- Mortality: no data
- EC50 48h: 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

Table 1 Summary of the Effect of the Test Material on the Mobility of Daphnia magna

Loading Rate (mg/L)

Mean Measured Test Material Concentration (mg/L)

No. of Daphnids Tested

Immobilised Daphnids After 24 Hours

  

Immobilised Daphnids After 48 Hours

No.

%

No.

%

Control

-

20

0

0

0

0

100

0.085

20

0

0

0

0

 

Validity criteria fulfilled:
yes
Conclusions:
The test material 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 conditions of the test. The 48 hour EL50 and NOELR were thus > 100 mg/L and ≥ 100 mg/L, respectively.

Description of key information

The endpoint is covered by a weight of evidence approach including three short-term toxicity studies performed with zirconium dioxide (Bazin, 1994), praseodymium(III,IV) oxide (Bätscher, 2008a) and the reaction mass of cerium dioxide and zirconium dioxide (Bätscher, 2008b). None of these substances caused adverse effects in Daphnia magna at a nominal loading rate of 100 mg/L. Taking into account the results of the available studies for its individual constituents, the reaction mass of these three substances can be concluded not to be toxic or harmful to aquatic invertebrates either.

Key value for chemical safety assessment

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 immobilisation was observed up to and including at the loading rate of 100 mg/L. The 48-h EC50 was thus superior to this value.

2. Information on the reaction mass of cerium dioxide and zirconium dioxide

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) (Bätscher, 2008b). 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 and >= 100 mg/L, respectively.

3. Information on praseodymium(III,IV) oxide

The acute toxicity of the test material to Daphnia magna was determined in a 48-hour static test conducted in accordance with the standardised guidelines OECD 202 and EU Method C.2 (Bätscher, 2008a). Daphnids were exposed to a control and the test material at a nominal loading rate of 100 mg/L for 48 hours. Mortality and 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 hours. The 48-hour EL50 and NOELR were thus > 100 mg/L and ≥ 100 mg/L, respectively. The mean measured concentration of the test item in the solution was determined to be 0.085 mg/L.

4. Conclusion on the reaction mass of cerium dioxide, praseodymium(III,IV) oxide and zirconium dioxide

Since all constituents of the reaction mass, i.e. cerium dioxide, praseodymium(III,IV) oxide and zirconium dioxide 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 the reaction mass of cerium dioxide, praseodymium(III,IV) oxide and zirconium dioxide is not toxic or harmful to aquatic invertebrates either. This confirms the read across assumption that the addition of cerium dioxide and praseodymium(III,IV) oxide to zirconium dioxide does not alter the unhazardous character of zirconium dioxide.