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Description of key information

Oral: NOEL = 150 mg/kg/day, 28 days rat male/female, OECD 422, CIT 2008.

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Link to relevant study records
Reference
Endpoint:
short-term repeated dose toxicity: oral
Remarks:
combined repeated dose and reproduction / developmental screening
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Study period:
16 July 2007 to 31 October 2008
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Study conducted to GLP in compliance with agreed protocols, with no or minor deviations from standard test guidelines and/or minor methodological deficiencies, which do not affect the quality of the relevant results.
Qualifier:
according to
Guideline:
OECD Guideline 422 (Combined Repeated Dose Toxicity Study with the Reproduction / Developmental Toxicity Screening Test)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Limit test:
no
Species:
rat
Strain:
Sprague-Dawley
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS
- Age at study initiation: approximately 10 weeks old at the beginning of the treatment period
- Weight at study initiation: at the beginning of the treatment period, the animals had a mean body weight of 419 g (range: 392 g to 442 g) for the males and 263 g (range: 239 g to 283 g) for the females
- Fasting period before study: no
- Housing: The males were individually housed, except during pairing, in wire-mesh cages (43.0 x 21.5 x 18.0 cm). The females were individually housed, except during pairing, until late gestation in wire-mesh cages (43.0 x 21.5 x 18.0 cm). The females were individually housed from late gestation, and with their litter during lactation, in polycarbonate cages (43.0 x 21.5 x 20.0 cm).
- Diet: ad libitum
- Water: free access to bottles containing tap water (filtered with a 0.22 µm filter)
- Acclimation period: the animals were acclimated to the study conditions for a period of 7 days before the beginning of the treatment period.


ENVIRONMENTAL CONDITIONS
- Temperature: 22 ± 2°C
- Humidity: 50 ± 20%
- Air changes: about 12 cycles/hour of filtered, non-recycled air
- Photoperiod: 12 hrs dark / 12 hrs light


IN-LIFE DATES: From 14 August 2007 to 10 October 2007
Route of administration:
oral: gavage
Vehicle:
other: 0.5 % aqueous methylcellulose solution
Details on oral exposure:
PREPARATION OF DOSING SOLUTIONS:
The test material was administered as a suspension in the vehicle. The test material was ground to fine powder using a mortar and pestle, suspended in the vehicle in order to achieve the concentrations of 30, 90 and 200 mg/mL and then homogenized using a magnetic stirrer. The test material dosage forms were prepared at a frequency based on stability data (up to 9 days) and were stored at +4 °C, protected from light, prior to use.


VEHICLE
- Justification for use and choice of vehicle (if other than water): aqueous suspension, as recommended in the guideline
- Concentration in vehicle: 30, 90 and 200 mg/mL
- Amount of vehicle (if gavage): a constant volume of 5 mL/kg/day was used
- Lot/batch no. (if required): methylcellulose batch No. 017K0052, supplied by Sigma
- Purity: data not available
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
During a pre-study period, the homogeneity, stability and concentration of two dosage forms prepared at the lowest and highest concentrations of the present study (30 and 200 mg/mL) were checked using ICP-OES (Inductively Coupled Plasma/Optical Emission Spectrometry) after validation of the analytical method. The results showed acceptable homogeneity and stability of both concentrations over 9 days at +4 °C.

During the study, the concentration of the test material and homogeneity of the dosage forms was determined in samples of each control and test material dosage form prepared for use in weeks 1, 3 and 6. The results showed acceptable homogeneity and concentration of all dosage forms analyzed. Precision (RSD =< 10 %) and accuracy (100 ± 10 %) of the method were found to be satisfactory.
Duration of treatment / exposure:
- In males: 15 days before mating, during the mating period (up to 3 weeks), until sacrifice (i.e. at least 4 weeks in total)
- In females: 15 days before mating, during the mating period (up to 3 weeks), during pregnancy, during lactation until day 5 post-partum inclusive
Frequency of treatment:
Each animal was given the appropriate dosage form once a day, at approximately the same time each day, 7 days a week.
Remarks:
Doses / Concentrations:
0, 150, 450 and 1000 mg/kg
Basis:
other: nominal conc. corrected from the water content
No. of animals per sex per dose:
10 males and 10 females per group
Control animals:
yes, concurrent vehicle
Details on study design:
- Dose selection rationale: on the basis of a previous 14-day toxicity study in the rat in which the dose-levels of 150, 450 and 1000 mg/kg/day elicited no clear treatment-related effects.
- Rationale for animal assignment: during the pre-treatment period, the required number of animals (40 males and 40 females) was selected according to body weight and clinical condition and allocated to the groups (by sex), according to a computerized stratification procedure, so that the average body weight of each group was similar.
Positive control:
not used
Observations and examinations performed and frequency:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: From arrival, the animals were observed once a day as part of routine examinations. From the start of treatment period, each animal was observed once a day, at approximately the same time for the recording of clinical signs.


DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: on all animals outside the home cage, in a standard arena, once before the beginning of the treatment period and then once a week until the end of the study.
Observations included (but were not limited to) changes in the skin, fur, eyes, mucous membranes, occurrence of secretions and excretions and autonomic activity (e.g. lachrymation, piloerection, pupil size, unusual respiratory pattern). Changes in gait, posture and response to handling as well as the presence of clonic or tonic movements, stereotypes (e.g. excessive grooming, repetitive circling) or bizarre behavior (e.g. self-mutilation, walking backwards) were also recorded.


BODY WEIGHT: Yes
- Time schedule for examinations: the body weight of each male was recorded on the first day of treatment (day 1), then once a week until sacrifice. The body weight of each female was recorded on the first day of treatment (day 1), then once a week until mated (or until sacrifice) and on days 0, 7, 14 and 20 post-coitum and days 1 and 5 post-partum.


FOOD CONSUMPTION: Yes
The quantity of food consumed by each male was recorded once a week, over a 7 day period, from the first day of treatment until sacrifice. The quantity of food consumed by each female was recorded once a week, over a 7 day period, from the first day of treatment through gestation (days 0-7, 7-14 and 14-20 post-coitum intervals) and lactation (days 1-5 post-partum intervals) until sacrifice. During the pairing period, food consumption was not recorded for males or females.


WATER CONSUMPTION: No


OPHTHALMOSCOPIC EXAMINATION: No


HAEMATOLOGY: Yes
- Time schedule for collection of blood: on the day of sacrifice
- Anaesthetic used for blood collection: Yes (isoflurane)
- Animals fasted: Yes
- How many animals: the last five males and females of each group
- The following parameters were determined: Erythrocytes, Hemoglobin, Mean cell volume, Packed cell volum, Mean cell hemoglobin concentration, Mean cell hemoglobin, Thrombocytes, Leucocytes, Differential white cell count with cell morphology (neutrophils, eosinophils, basophils, lymphocytes and Large Unstained Cells), monocytes, Reticulocytes, Prothrombin time, Activated partial thromboplastin time, Fibrinogen.


CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: on the day of sacrifice
- Animals fasted: Yes
- How many animals: the last five males and females of each group
- The following parameters were determined: Sodium, Potassium, Chloride, Calcium, Inorganic phosphorus, Glucose, Urea, Creatinine, Total bilirubin, Total proteins, Albumin, Albumin/globulin ratio, Total cholesterol, Triglycerides, Alkaline phosphatase, Aspartate aminotransferase, Alanine aminotransferase, Lactate dehydrogenase, Bile acids.


URINALYSIS: No


NEUROBEHAVIOURAL EXAMINATION: Yes
- Time schedule for examinations: once at the end of the treatment period
- Dose groups that were examined: on the first five males and the first five females from each group
- Battery of functions tested: detailed clinical examination, measurement of reactivity to manipulation or to different stimuli and motor activity


OTHER: MORTALITY AND MORBIDITY: each animal was checked for mortality or signs of morbidity at least twice a day during the treatment period.
Sacrifice and pathology:
GROSS PATHOLOGY: Yes. A complete macroscopic post-mortem examination was performed on all animals. This included examination of the external surfaces, all orifices, the cranial cavity, the external surfaces of the brain, the thoracic, abdominal and pelvic cavities with their associated organs and tissues and the neck with its associated organs and tissues. Special attention was paid to the reproductive organs. The numbers of corpora lutea and implantation sites were also recorded.
HISTOPATHOLOGY: Yes (see table 1)
Statistics:
Mean values were compared by one-way variance analysis and Dunnett test, (mean values being considered as normally distributed, variances being considered as homogeneous). Percentage values were compared by Fisher exact probability test.
Clinical signs:
no effects observed
Mortality:
no mortality observed
Body weight and weight changes:
no effects observed
Food consumption and compound intake (if feeding study):
no effects observed
Food efficiency:
not examined
Water consumption and compound intake (if drinking water study):
not examined
Ophthalmological findings:
not examined
Haematological findings:
effects observed, treatment-related
Description (incidence and severity):
See "Details on results" for information
Clinical biochemistry findings:
effects observed, treatment-related
Description (incidence and severity):
See "Details on results" for information
Urinalysis findings:
not examined
Behaviour (functional findings):
effects observed, treatment-related
Description (incidence and severity):
See "Details on results" for information
Organ weight findings including organ / body weight ratios:
no effects observed
Gross pathological findings:
no effects observed
Histopathological findings: non-neoplastic:
effects observed, treatment-related
Description (incidence and severity):
See "Details on results" for information
Histopathological findings: neoplastic:
no effects observed
Details on results:
CLINICAL SIGNS AND MORTALITY: there were no treatment-related mortalities or clinical signs.

BODY WEIGHT AND WEIGHT GAIN: Females had lower mean body weight gains during pregnancy and lactation and lower food consumption during lactation but this may be related to the higher number of fetuses/pups in the control group. There were no effects during the pre-mating period and no effects on mean male body weight or food consumption.

HAEMATOLOGY: Males and females treated at 1000 mg/kg/day had a decrease in white blood cell count (approximately 12 %) when compared with controls (See Table 3).

CLINICAL CHEMISTRY: Females treated at 1000 mg/kg/day had a decrease in chloride concentration and an increase in glucose, potassium, inorganic phosphorus and urea concentrations.

NEUROBEHAVIOUR: A majority of animals treated at 1000 mg/kg/day had an increased number of horizontal movements during the 1-hour motor activity test but there were no other effects of treatment observed during the tests performed in the functional observation battery.

HISTOPATHOLOGY: NON-NEOPLASTIC: There was microscopic treatment related in the stomach that consisted of increased incidence and/or severity of submucosal eosinophil infiltration and pyloric gland hyperplasia in rats from both sexes treated at 1000 mg/kg/day and 450 mg/kg/kg. See detailed values in Table 2.
No microscopic treatment related changes were observed in the testes and ovaries.
Dose descriptor:
NOEL
Effect level:
150 mg/kg bw/day (nominal)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: based on microscopic effects observed in the stomach
Critical effects observed:
not specified

Table 2: incidence and grading at microscopic findings in the stomach of rats given Cerium carbonate 99 humide

Sex

Male 

Female

Group

1

2

3

4

1

2

3

4

Dose-level (mg/kg/day)

0

150

450

1000

0

150

450

1000

STOMACH

- Increased submucosal eosinophil infiltration

Grade 1

3

2

4

0

1

1

2

3

Grade 2

0

1

1

4

0

0

0

0

Grade 3

0

0

0

1

0

0

0

0

Total affected

3/5

 3/5

5/5 

5/5

1/5

 1/8

2/6 

3/5

-Pyloric glands hyperplasia

Grade 1

0

0

5

2

0

0

0

2

Grade 2

0

0

0

2

0

0

0

0

Total affected

0/5

 0/5

 5/5

4/5

0/5

 0/5

 0/5

2/5

 

Table 3: Hematology - concentration in Monocytes

Dose (mg/kg/d)

0

150

450

1000

Monocytes (G/L)

Males

M

0.61

0.44

0.43

0.37 **

SD

0.104

0.143

0.046

0.053

n

4

4

4

5

Females

M

0.3

0.38

0.4

0.54 *

SD

0.139

0.073

0.101

0.172

n

5

5

5

5

 

M : Mean value

SD : Standard Deviation

N : number of animals

*  P < 0.05

** P < 0.01

Table 4 : Blood biochemistry

Sex                                                           Male                                                      Female

Dose-level (mg/kg/day)                 0       150      450    1000               0       150     450      1000

Potassium (mmol/L)                    4.11   3.80      4.02    4.12              4.00    4.17    4.16     4.70

Chloride (mmol/L)                   104.2  105.0   103.9 104.7            102.1  101.3  100.8    99.6**

Glucose (mmol/L)                    8.13    9.71    8.73     8.53            6.60     7.10    7.41    8.79**

In. phosphorus

(mmol/L)              2.22    2.16     2.11    2.17             2.12   2.15    2.29    2.39

Urea

(mmol/L)                    5.3      5.7       5.2       5.9               6.6      7.4      6.4       7.9

** p <0.01

 

Conclusions:
Based on the experimental conditions of this study, the NOEL for parental toxicity was considered to be 150 mg/kg/day in female and male rats.
Executive summary:

The repeated dose toxicity of the test material was investigated in a GLP study which was conducted in accordance with the standardised guideline OECD 422, During the study test material was administered daily by oral gavage to male and female Sprague-Dawley rats, for 2 weeks before mating, during mating, gestation and until day 5 post-partum, at dose-levels of 150, 450 or 1000 mg/kg/day.

There were no adverse effects of treatment at any dose-level on mortality, clinical signs, body weight or food consumption. Animals treated at 1000 mg/kg/day had lower white blood cell counts and females in this group had lower chloride concentration and higher glucose, potassium, inorganic phosphorus and urea levels. There were microscopic treatment related findings in the stomach that consisted of increased incidence and/or severity of submucosal eosinophil infiltration and pyloric gland hyperplasia in rats from both sexes treated at 1000 mg/kg/day and 450 mg/kg/kg. No test material-related microscopic findings were observed at 150 mg/kg/day. No microscopic treatment related changes were observed in the testes and ovaries.

Based on the experimental conditions of this study, the No Observed Effect Level (NOEL) for parental toxicity was considered to be 150 mg/kg/day in female and male rats.

Endpoint conclusion
Endpoint conclusion:
adverse effect observed
Study duration:
subacute
Species:
rat

Repeated dose toxicity: inhalation - systemic effects

Endpoint conclusion
Endpoint conclusion:
no study available

Repeated dose toxicity: inhalation - local effects

Endpoint conclusion
Endpoint conclusion:
no study available

Repeated dose toxicity: dermal - systemic effects

Endpoint conclusion
Endpoint conclusion:
no study available

Repeated dose toxicity: dermal - local effects

Endpoint conclusion
Endpoint conclusion:
no study available

Additional information

Oral Toxicity

The repeated dose toxicity of the test material was investigated in a GLP study which was conducted in accordance with the standardised guideline OECD 422, During the study test material was administered daily by oral gavage to male and female Sprague-Dawley rats, for 2 weeks before mating, during mating, gestation and until day 5 post-partum, at dose levels of 150, 450 or 1000 mg/kg/day. There were no adverse effects of treatment at any dose level on mortality, clinical signs, body weight or food consumption. Animals treated at 1000 mg/kg/day had lower white blood cell counts and females in this group had lower chloride concentration and higher glucose, potassium, inorganic phosphorus and urea levels. There were microscopic treatment related findings in the stomach that consisted of increased incidence and/or severity of submucosal eosinophil infiltration and pyloric gland hyperplasia in rats from both sexes treated at 1000 mg/kg/day and 450 mg/kg/kg. No test material-related microscopic findings were observed at 150 mg/kg/day. No microscopic treatment related changes were observed in the testes and ovaries. Based on the experimental conditions of this study, the No Observed Effect Level (NOEL) for parental toxicity was considered to be 150 mg/kg/day in female and male rats.  

This is the only reliable study on repeated dose toxicity that is available for the substance. It has been performed on a structural analogue, cerium carbonate. The similar toxicological profiles of cerium carbonate and cerium oxalate, along with the structural similarity, mean that this is considered to be an acceptable read-across approach. The study was performed in line with a recognised OECD guideline and to GLP standard. It is assigned a score of 2 in line with the reliability scoring system of Klimisch et al (1997), based on the fact that a read across approach has been used.

In accordance with Section 1 of Annex XI a subchronic toxicity study, as required under section 8.6.2 of Annex IX does not appear scientifically necessary. The existing oral data is considered to adequately address the repeated dose toxicity endpoint and a further 90-day study is regarded as unnecessary.

Inhalation Toxicity

In accordance with section 1 of REACH Annex XI, the repeat dose toxicity study via the inhalation route (required in section 8.6.1 of Annex VIII) does not need to be conducted if the study does not appear to be scientifically necessary. An oral study conducted to OECD Guideline 422 (Combined Repeated Dose Toxicity Study with the Reproduction / Developmental Toxicity Screening Test) already sufficiently addresses the repeat dose toxicity data requirements.

Dermal Toxicity

In accordance with section 1 of REACH Annex XI, the repeat dose toxicity study via the dermal route (required in section 8.6.1 of Annex VIII) does not need to be conducted if the study does not appear to be scientifically necessary. An oral study conducted to OECD Guideline 422 (Combined Repeated Dose Toxicity Study with the Reproduction / Developmental Toxicity Screening Test) already sufficiently addresses the repeat dose toxicity data requirements. Furthermore, dermal exposure of the substance is considered unlikely.


Justification for selection of repeated dose toxicity via oral route - systemic effects endpoint:
Only one study available.

Justification for selection of repeated dose toxicity inhalation - systemic effects endpoint:
A data waiver has been submitted for this endpoint.

Justification for selection of repeated dose toxicity inhalation - local effects endpoint:
A data waiver has been submitted for this endpoint.

Justification for selection of repeated dose toxicity dermal - systemic effects endpoint:
A data waiver has been submitted for this endpoint.

Justification for selection of repeated dose toxicity dermal - local effects endpoint:
A data waiver has been submitted for this endpoint.

Justification for classification or non-classification

In accordance with with criteria for classification as defined in Annex I, Regulation 1272/2008, the test material does not require classification for specific organ toxicity, repeated dose. The effects observed in the main study are not considered to be toxicologically significant and do not indicate any signs of organ dysfunction.