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Long-term toxicity to aquatic invertebrates

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Administrative data

Endpoint:
long-term toxicity to aquatic invertebrates
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
supporting study
Study period:
from 21-DEC-2007 to 27-FEB-2009
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: The study was performed according to an international test guideline and to GLP. As the data is used in a read-across approach, a maximal reliability score of 2 was attributed.

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2009
Report date:
2009

Materials and methods

Test guideline
Qualifier:
according to guideline
Guideline:
OECD Guideline 211 (Daphnia magna Reproduction Test)
Deviations:
no
GLP compliance:
yes (incl. QA statement)

Test material

Constituent 1
Chemical structure
Reference substance name:
Cerium dioxide
EC Number:
215-150-4
EC Name:
Cerium dioxide
Cas Number:
1306-38-3
Molecular formula:
CeO2
IUPAC Name:
cerium dioxide
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):
This chronic data on cerium dioxide was used in a read-across approach as this cerium compound is highly insoluble (water solubility < 0.123 µg/L at 20 °C) as reaction mass of lanthanum phosphate and cerium phosphate and terbium phosphate.

Sampling and analysis

Analytical monitoring:
yes
Details on sampling:
- Concentrations:
Triplicate samples were taken from the test media of all test concentrations (loading rate of 100 mg/L and dilutions 1:3.2, 1:10, 1:32 and 1:100) and from the control at the start of the first treatment period (Day 0), at a treatment period in the second week (Day 7), and at a treatment period in the last week (Day 16). The following samples were taken in triplicate at the end of two test medium renewal periods of 48 hours (Days 2 and 9) and at the end of one renewal period of 72 hours (Day 19):
a) Samples with food, taken from the actual test by combining the contents of the test beakers after the end of the treatment period.
b) Samples without food and test animals incubated during the renewal periods under the test conditions.
The concentrations of cerium were measured in two of the triplicate test media samples from the highest test concentration (loading rate of 100 mg/L) which was determined to be the 21-day NOELR.
- Sampling method: data not available
- Sample storage conditions before analysis: immediately after sampling, the samples were acidified with 10% (v/v) nitric acid (HNO3, 65% Suprapur, Merck) to stabilize the samples during storage. Then the samples were stored in PE flasks at ambient temperature and protected from light until analysis.

Test solutions

Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION
- Method:
Due to the low water solubility of the test item, a saturated solution of the test item with the loading rate of 100 mg/L was tested as the highest test concentration and was used as a stock solution for preparation of the test media of lower test concentrations (dilutions 1:3.2, 1:10, 1:32 and 1:100). Additionally, a control (test water without test item) was tested in parallel.
The test method is based on the OECD Guidance Document on Aquatic Toxicity Testing of Difficult Substances and Mixtures.
Seven days before the start of the test and seven days prior to each test medium renewal, a dispersion of the test item with the loading rate of 100 mg/L was prepared by dispersing 200 mg (effective weights: 200.0-201.4 mg) of the test item in 2000 mL of test water. The test item was mixed into the test water as homogeneously as possible using ultrasonic treatment for 15 minutes and intense stirring. No auxiliary solvent or emulsifier was used. The dispersions were stirred on magnetic stirrers at room temperature in the dark over six days. Then, the stirrers were switched off in order to allow the non-dissolved test item to deposit at the bottom of the stirring vessel. The contact time of the test item and the test water for equilibration (i.e. stirring time and deposition period) was 7 days.
The equilibrated test medium (saturated solution) was carefully separated from the non-dissolved test item. The saturated solution was used as the highest test concentration. Additionally, adequate volumes of the saturated solution were diluted with test water for the preparation of the test media with lower test item concentrations.
- Eluate: no
- Differential loading: yes
- Controls: test water without 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

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 of parental stock (mean and range, SD): < 24 hours. These daphnids originated from parental daphnids that were at least 14 days old but no older than 4 weeks, and were not first brood progeny.
- Feeding during test
- Food type: a food mixture containing a suspension of green algae of the species Scenedesmus subspicatus (freshly grown in the Harlan laboratories) and a fish food suspension.
- Amount:
The carbon contents of the algal and fish food suspensions were determined using a Shimadzu TOC 5000A Analyzer. The food amounts were based on the measured concentrations of total organic carbon (TOC) in the food suspensions and consisted of 50% algae and 50% fish food
(based on TOC). The amounts of TOC fed per test animal and day were as follows:
Day 0-4: 0.10 mg TOC / Daphnia
Day 5-13: 0.15 mg TOC / Daphnia
Day 14-20: 0.20 mg TOC / Daphnia
- Frequency: daily

ACCLIMATION
- Acclimation period: no

Study design

Test type:
semi-static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
22 d
Remarks on exposure duration:
It was expected at the observation of the test animals on Day 21 that some test animals would release their offspring from brood pouch in the next hours. Therefore the test was extended for 24 hours.
Post exposure observation period:
none

Test conditions

Hardness:
2.5 mmol/L (= 250 mg/L as CaCO3)
Test temperature:
20°C
pH:
between 7.5 to 8.0
Dissolved oxygen:
at least 7.9 mg/L
Salinity:
not applicable
Nominal and measured concentrations:
initial loading rate: 100 mg/L and dilutions 1:3.2, 1:10, 1:32 and 1:100
mean measured concentration: below the limit of quantification for the 100 mg/L loading rate
Details on test conditions:
TEST SYSTEM
- Test vessel:
- Type : 100 mL glass beakers covered with glass plates to reduce the loss of water by evaporation and to avoid the entry of dust into the solutions
- Material, size, headspace, fill volume: vessels containing 80 mL of test medium
- Aeration: Before use, the test water was aerated until oxygen saturation. During the test, the test media were not aerated.
- Type of flow-through (e.g. peristaltic or proportional diluter): none (semi-static test)
- Renewal rate of test solution (frequency/flow rate): three times per week
- No. of organisms per vessel: Each test animal was kept individually in test vessel
- No. of vessels per concentration (replicates): 10
- No. of vessels per control (replicates): 10
- Biomass loading rate: 80 ml of medium per parental daphnid.

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: reconstituted test water : analytical grade salts dissolved in purified water
- Alkalinity: 0.9 mmol/L
- Ca/Mg ratio (mol): no data
- Culture medium different from test medium: no
- Intervals of water quality measurement: At the beginning and end of each test medium renewal period, the pH and dissolved oxygen concentrations were measured in one replicate of each test concentration and the control. At the same time, the water temperature was measured in one of the control replicates. Additionally, the room temperature was continuously monitored. The appearance of the test media was recorded at the beginning and end of each test medium renewal period.
- 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 500 and 630 lux

EFFECT PARAMETERS MEASURED :
Each working day, the test replicates were observed for mortality of the parental daphnids and the presence of juveniles. The offspring were counted and removed three times per week at the renewal of the test media. At the same dates, the test beakers were also checked for the presence of aborted eggs or dead offspring.
The reproduction rate was calculated as the total number of living offspring produced per parent female surviving until the end of the test.
The mean reproduction rates of the daphnids at the test concentrations were compared to the control by multiple Williams’ tests. No EL values for the inhibition of the reproduction rate could be calculated since no effect was determined on the reproduction of the daphnids up to the highest concentration tested.

RANGE-FINDING STUDY
Test concentrations / Results used to determine the conditions for the definitive study: The choice of the test concentrations was based on the results of the acute toxicity test with Daphnia magna (RCC Study Number A17493). Concentrations of the test item far above the water solubility or loading rates above 100 mg/L were not tested in accordance with the test guidelines.
Reference substance (positive control):
no

Results and discussion

Effect concentrationsopen allclose all
Duration:
22 d
Dose descriptor:
NOELR
Effect conc.:
>= 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: survival and reproduction
Duration:
22 d
Dose descriptor:
LOELR
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: survival and reproduction
Details on results:
Analytical Results :
The concentration of cerium in test medium samples was below the limit of quantification of the analytical method (0.004 or 0.02 µg/L) with the exception of two samples taken at the end of the first test medium renewal period from the test medium of the actual test. In these samples concentrations of cerium of 0.2 mg/L were found.
The saturated solution used as test medium was prepared by sedimentation of the undissolved test item until the supernatant appeared to be a clear solution (24 hours). The test medium was not filtered on the request of the Sponsor. The wide range of measured concentrations of the test item was considered to be caused by very fine particles of the test item which were obviously still present in the supernatant after the deposition period. Thus, the test medium contained the maximum concentration of dissolved test item and very fine undissolved test item particles. The cerium found in the two samples was considered to originate from particles which were present in these samples.

Biological results:
In the control and at all test concentrations up to and including the loading rate of 100 mg/L, the survival of the test animals was at least 80% or higher at the end of the test. Thus, the survival of Daphnia magna over 21 days was not affected by the test item up to and including the highest test concentration (loading rate of 100 mg/L).
The first young offspring released from their parent animals were recorded in the control and at all test concentrations at observation on Day 8. Thus, the time of the first brood was not affected by the test item up to and including the loading rate of 100 mg/L.
The mean reproduction rate of the daphnids in the control was 100.4 ± 16.7 living offspring per adult (mean ± standard deviation). The mean reproduction rates of the exposed daphnids were between 104 and 121% of the reproduction in the control and no concentration-effect relationship was determined. No significant inhibitory effect of the test item on the mean reproduction rate was determined up to and including the highest test concentration (Williams’ test, one-sided, alpha = 0.05).
No visible abnormalities were observed in the test animals during the test.
No adverse effect, neither in terms of survival, nor in terms of reproduction, 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 does not exhibit any chronic toxicity to daphnids up to its solubility limit into water.

General results:
No remarkable observations were made concerning the appearance of the test media. All test media were clear throughout the test medium renewal periods.
Results with reference substance (positive control):
none
Reported statistics and error estimates:
The mean reproduction rates of the daphnids at the test concentrations were compared to the control by multiple Williams'test.

Any other information on results incl. tables

Number of surviving test animals :

 

 

Exposure day

Treatment / Dilution

 

Control

 

Dilution

1:100

 

Dilution

1:32

 

Dilution

1:10

 

Dilution

1:3.2

Saturated

Solution

(loading rate

100 mg/L)

0

1

2

5

6

7

8

9

12

13

14

15

16

19

20

21

22

10

10

10

10

10

10

10

10

9

9

9

9

9

9

9

8

8

10

10

10

10

10

10

10

10

10

10

10

10

10

10

10

10

10

10

10

10

10

10

10

10

10

10

10

9

9

9

9

9

9

9

10

10

10

10

10

10

10

10

10

10

10

10

10

10

10

10

10

10

10

10

10

10

10

9

9

9

9

9

9

9

9

9

9

9

10

10

10

10

10

10

10

10

10

10

10

10

10

10

10

10

10

% surviving on Day 22

80

100

90

100

90

100

 

 

Total number of living young daphnids produced by all adults (cumulative values):

 

 

Exposure day

Treatment / Dilution

 

Control

 

Dilution

1:100

 

Dilution

1:32

 

Dilution

1:10

 

Dilution

1:3.2

Saturated

Solution

(loading rate

100 mg/L)

0

1

2

5

6

7

8

9

12

13

14

15

16

19

20

21

22

0

0

0

0

0

0

172

172

428

475

475

615

618

719

719

789

884

0

0

0

0

0

0

160

160

422

479

480

666

670

842

842

915

1047

0

0

0

0

0

0

182

182

482

614

614

761

762

925

925

1056

1139

0

0

0

0

0

0

170

170

456

607

607

739

742

910

910

1053

1152

0

0

0

0

0

0

185

185

446

586

586

676

676

837

837

1012

1079

0

0

0

0

0

0

169

169

382

485

487

589

647

837

837

973

1094

% of control1

100.0

118.4

128.8

130.3

122.1

123.8

 

1: based on the value of the last exposure day

 

Number of living offspring produced per surviving adult after 22 days of exposure:

 

 

Replicate

N°.

Treatment / Dilution

 

Control

 

Dilution

1:100

 

Dilution

1:32

 

Dilution

1:10

 

Dilution

1:3.2

Saturated

Solution

(loading rate

100 mg/L)

1

2

3

4

5

6

7

8

9

10

110

*

75

110

111

119

*

75

104

99

100

105

137

112

103

126

105

110

114

35

130

137

100

129

137

122

*

108

113

114

125

121

81

115

133

135

135

106

97

104

123

125

121

120

108

94

118

113

*

135

119

106

96

119

124

126

101

86

112

105

Mean

SD

n

100.4

16.7

8

104.7

27.0

10

121.1

13.1

9

115.2

18.1

10

117.4

11.6

9

109.4

12.9

10

CV %

16.6

25.8

10.8

15.7

9.9

11.8

% of control

100.0

104.3

120.7

114.8

117.0

109.0

STAT

-

n.s.

n.s.

n.s.

n.s.

n.s.

 

SD: standard deviation

n: number of replicates (surviving adults)

CV %: coefficient of variation in %: (SDx/meanx)100%

*: test animal died during the test period

STAT: results of a Williams’ test with the mean values of living offspring

(one-sided, alpha= 0.05)

n.s.: mean value not significantly lower than in the control

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Remarks:
Control's survival rate = 80%, and control's mean reproduction rate > 60
Conclusions:
The test item Cerium dioxide had no toxic effect on survival and reproduction of Daphnia magna after the exposure period of 22 days up to the loading rate of 100 mg/L. Thus, the NOELR of the test item was determined to be at least the loading rate of 100 mg/L . The LOELR was above the loading rate of 100 mg/L.
Executive summary:

The effect of the test item Cerium dioxide on the survival and reproduction of Daphnia magna was investigated in a semi-static test over 22 days following the OECD Guidelines for Testing of Chemicals, No. 211 (1998) and the EU Commission Directive 92/69/EEC, C.20 (2001).Daphnids were exposed to control, and test chemical at nominal concentration of 100 mg of dry substance /L (loading rate) and the dilutions 1:3.2,1:10,1:32 and 1:100 of the saturated solution. The mortality and reproduction of the daphnids were compared with the corresponding parameters in the control and symptoms of toxicity were recorded.

 

The test item Cerium dioxide had no toxic effect on survival and reproduction of Daphnia magna after the exposure period of 22 days up to the loading rate of 100 mg/L. Thus, the NOELR of the test item was determined to be at least the loading rate of 100 mg/L. The LOELR was above the loading rate of 100 mg/L. As no adverse effect, neither in terms of survival, nor in terms of reproduction, 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 does not exhibit any chronic toxicity to daphnids up to its solubility limit into water.

 

This study is classified as acceptable and satisfies the guideline requirements for a chronic toxicity study with freshwater invertebrates.

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