Cerium dioxide

Toxicity to soil macroorganisms except arthropods

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

toxicity to soil macroorganisms except arthropods: short-term

Type of information:

experimental study

Adequacy of study:

key study

Study period:

from 21-JUN-1996 to 11-DEC-1996

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 207 (Earthworm, Acute Toxicity Tests)

Deviations:

yes

Remarks:

25 g of sand was used instead of 10 g as stated in the OECD Guideline n° 207. The deviation was not affected the results of this study

GLP compliance:

yes

Analytical monitoring:

no

Details on sampling:

no data

Vehicle:

no

Details on preparation and application of test substrate:

Details on preparation and application of test substrate:
- Method of mixing into soil: Quantities of 501.3, 501.6, 501.4, 501.8 and 500.9 mg of the test substance cerium oxide were weighed out accurately and each portion was mixed thoroughly with 25 g of M32 sand. On the day the test was started, this mixture was mechanically mixed with 650 g of wet artificial soil (481.5 g of dry artificial soil and 168.5 g moisture) and 100 ml of distilled water.
- Controls: controls were prepared in a similar way and did not contain test item.

Test organisms (species):

Eisenia fetida

Animal group:

annelids

Details on test organisms:

TEST ORGANISM
- Common names: redworm, brandling worm, tiger worm, red wiggler worm
- Source: obtained from the commercial hatchery Blades Biological, Cowden, Edenbridge, Kent, England
- Age at test initiation: no data
- Weight at test initiation: 0.312 to 0.512 g
- Method of cultivation: cultured in TNO laboratory under standard conditions in a horse-manure, garden soil mixture (1:1) at about 25°C

ACCLIMATION
no data

Study type:

laboratory study

Substrate type:

artificial soil

Limit test:

yes

Total exposure duration:

14 d

Post exposure observation period:

none

Test temperature:

20.3 - 20.7°C

pH:

5.8

Moisture:

51.4 - 52.5% (based on dry constituents)

Details on test conditions:

TEST SYSTEM
- Test container (material, size): One-litre all glass jars, provided with a glass lid (domestic preserving jars).
- Amount of soil: ca. 775 g wet weight
- No. of organisms per container (treatment): ten worms
- No. of replicates per treatment group: 4 + 1 replicate without worm for pH and moisture content measurements
- No. of replicates per control: 4 + 1 replicate without worm for pH and moisture content measurements

SOURCE AND PROPERTIES OF SUBSTRATE
- Geographic location: Sphagnum peat: Oosteinderweg 357, Aalsmeer, The Netherlands; Fine industrial sand: Wierselaan 121, Vreeswijk, The Netherlands; Kaolin clay: Provincialeweg West 44, Haastrecht, The Netherlands
- Soil texture of the mixture
- % sand: 70%
- % silt: 10%
- % clay: 20%
- Composition: The artificial soil consisted of finely ground sphagnum peat (no visible plant remains), kaolin clay and fine industrial sand at a ratio of 1:2:7 (based on dry weight) respectively.
- Pretreatment of soil: the components were mixed with distilled water and calcium carbonate in a polyethylene bag.
- Storage (condition, duration): no data except that sphagnum peat, fine industrial sand and kaolin clay arrived at TNO on March 1993, February 1993 and February 1990, respectively.
- No further data

OTHER TEST CONDITIONS
- Photoperiod: continuous low intensity illumination
- Light intensity: 688 to 742 lux

EFFECT PARAMETERS MEASURED: After 7 and 14 days, the number of surviving worms was determined and the condition of the worms with respect to appearance and behaviour was visually assessed. The worms were individually weighed at the start of the experiment. At the end of the test, the total weight of the surviving worms was determined for each replicate container.

TEST CONCENTRATIONS
- Spacing factor for test concentrations: not relevant (limit test)
- Justification for using less concentrations than requested by guideline: Because no adverse effect were to be expected, a combined range finding/limit test with a highest dose of 1000 mg of test substance per kg of dry soil was carried out.
- Range finding study: yes, realization of a combined range finding/limit test.
- Test concentrations: 1000 mg/kg of dry soil
- Results used to determine the conditions for the definitive study: As no effects were observed, the combined ranged finding/limit test is considered as the final test.

Nominal and measured concentrations:

0 and 1000 mg/kg dry soil nominal

Reference substance (positive control):

no

Key result

Duration:

14 d

Dose descriptor:

LC50

Effect conc.:

> 1 000 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality

Key result

Duration:

14 d

Dose descriptor:

NOEC

Effect conc.:

>= 1 000 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: mortality, appearance, behaviour, weight

Details on results:

At 1000 mg/kg dry soil, there was no significant effect with respect to survival (5% significance level) or to weight (1% significance level) or any other adverse effect with respect to the condition of the test animals. However, at 1000 mg/kg, one animal died. Because 10% mortality is allowed (for the control), this mortality is not taken into account to establish the NOEC value for mortality.

Results with reference substance (positive control):

none

Reported statistics and error estimates:

The LC50 is not determined because no effect was observed at the single concentration tested.
The NOEC values were estimated by comparing effects with regard to survival, weight, appearance and behaviour (the latter two visually assessed) of the exposed animals with those of the control animals. The NOEC is qualified according to the duration of exposure. To determine the NOEC for survival, the survival rates at each concentration were compared pair-wise with those in the control using a binomial test. A significance level of 5% was employed. To determine the NOEC for weight, a multiple comparaison was made between the average weight increase of the worms per container at each container and the average weight increase in the controls using a two-tailed Dunnett test. A significance level of 1% and 5% was employed. In case of 1% significance only that significance is given. The NOEC for behaviour and appearance was not determined statistically.

Table 1: Number of living animals in the control and several test concentrations after exposure to several concentrations of cerium dioxide

Time (d)	Nominal concentration of test substance (mg/kg dry soil)
	0	100
0 7 14	40a 40a 40a	40a 40b 39b

a) condition of all test animals, visually assessed, normal (good)

b) condition of all test animals visually assessed, equal to that of the control animals

Validity criteria fulfilled:

yes

Conclusions:

The NOEC is equal or higher than 1000 mg/kg dry soil. Cerium dioxide is considered as not harmful to Eiseinia fetida under the tested conditions.

Executive summary:

Cerium Dioxide has been tested for acute toxicity to Eisenia foetida. The study was carried out according to the OECD Guideline 207 and in compliance with the principles of Good Laboratory Practices.

Worms were exposed to cerium dioxide mixed with artificial soil at a concentration of 1000 mg/kg of dry soil for a 14-day period.

No significant effect with respect to survival, weight, behaviour or appearance was observed.The NOEC is equal or higher than 1000 mg/kg dry soil. The cerium dioxide is considered as not harmful to the tested terrestrial organism.

Reference 2

Endpoint:

toxicity to soil macroorganisms except arthropods: long-term

Data waiving:

other justification

Justification for data waiving:

other:

Description of key information

The 14-day NOEC (Eiseinia fetida) of the bulk form of cerium dioxide was ≥ 100 mg/kg dry soil based on the mortality, the appearance, the behaviour and the weight. Hence, the bulk form of cerium dioxide is considered as not harmful to Eiseinia fetida under the tested conditions.

Additional information

One experimental study, scored as Klimisch 1, was available and selected as a key study (TNO, 1996). It revealed that the bulk form of cerium dioxide was not harmful to earthworms.