Cerium

Repeated dose toxicity: inhalation

Administrative data

Endpoint:

sub-chronic toxicity: inhalation

Type of information:

migrated information: read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Study period:

August - December 1993

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP OECD 413 TG compliant study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1994

Report date:

1994

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 413 (Subchronic Inhalation Toxicity: 90-Day Study)

GLP compliance:

yes

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Dicerium tricarbonate

EC Number:

208-655-6

EC Name:

Dicerium tricarbonate

Cas Number:

537-01-9

IUPAC Name:

dicerium tricarbonate

Test animals

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Canada Inc., St Constant, Quebec, Canada
- Age at study initiation: 7 weeks old
- Weight at study initiation: 206 - 270 g (males) / 135 - 179 g (females)
- Fasting period before study: no
- Housing: individually in stainless-stell wire mesh-bottomed cages
- Diet: ad libitum (except during exposure, urinalysis, prior to bleeding and prior to necropsy)
- Water: ad libitum
- Acclimation period: 2 (males) or 3 (females) weeks


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 +/- 3
- Humidity (%): 50 +/- 20
- Air changes (per hr): 12 - 15
- Photoperiod (hrs dark / hrs light): 12 / 12


IN-LIFE DATES: From: August 31, 1993 To: December 20, 1993

Administration / exposure

Route of administration:

inhalation: aerosol

Type of inhalation exposure:

nose only

Vehicle:

other: unchanged (no vehicle)

Remarks on MMAD:

MMAD / GSD: Mass Median Aerodynamic Diameter (MMAD) +/- Gravimetric Standard Deviation (GSD):
- Males at 0.0050 mg/L = 1.9 +/- 1.9
- Females at 0.0050 mg/L = 1.8 +/- 1.9
- Males at 0.0505 mg/L = 2.0 +/- 1.9
- Females at 0.0505 mg/L = 2.0 +/- 1.9
- Males at 0.5082 mg/L = 2.2 +/- 1.8
- Females at 0.5068 mg/ L = 2.2 +/- 1.8

Details on inhalation exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: Four standard stainless-steel cylindrical "flow-through" nose-only inhalation chambers (approx. 80.6 L per chamber)
- Method of holding animals in test chamber: polycarbonate restraint cones
- Source and rate of air: laboratory compressed air supply
- Method of conditioning air: predried compressed air
- System of generating particulates/aerosols: Venturi T-section (connected to powder feed nozzle and compressed air system)
- Temperature, humidity, pressure in air chamber: 20-24°C, 30-70% relative humidity, at least 19% O2
- Air flow rate: set at a level determined in preliminary work to be adequate to maintain chamber environment conditions
- Air change rate: at least 10 per hour
- Method of particle size determination: Andersen 1 ACFM cascade impactor operated at a flow rate of 28.3 L/min
- Treatment of exhaust air: purifying system


TEST ATMOSPHERE
- Brief description of analytical method used: Gravimetric aerosol concentrations measured hourly using vertically oriented open-faced glass fiber filters. Test atmosphere continually monitored throughout exposure period by a precalibrated real-time aerosol monitor.
- Samples taken from breathing zone: yes


VEHICLE
Not applicable

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Filters from 2nd day of exposure and monthly thereafter used for chemical analysis by Sponsor.

Duration of treatment / exposure:

13 weeks

Frequency of treatment:

6 hours a day, 5 days a week

Doses / concentrations

Remarks:

Doses / Concentrations:
0.0050, 0.0505 and 0.5075 mg/L
Basis:
other: mean nominal chamber concentrations determined by dividing the amount of CeO2 powder used by the total volume of air passing the chamber during the generation period

No. of animals per sex per dose:

15

Control animals:

yes

Details on study design:

- Dose selection rationale: Not specified
- Rationale for animal assignment (if not random): computer-based randomization procedure based on bodyweight (males and females separately)
- Rationale for selecting satellite groups: Not applicable
- Post-exposure recovery period in satellite groups: Not applicable

Positive control:

Not applicable

Examinations

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: twice daily (within the cage) and immediately before, during (hourly) and after exposure (outside the cage)


DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: weekly


BODY WEIGHT: Yes
- Time schedule for examinations: weekly, commencing on the day of randomization and extending through the treatment period (+ on days of behavioral testing and immediately before sacrifice)


FOOD CONSUMPTION:
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: Yes


FOOD EFFICIENCY:
- Body weight gain in kg/food consumption in kg per unit time X 100 calculated as time-weighted averages from the consumption and body weight gain data: No


WATER CONSUMPTION: No


OPHTHALMOSCOPIC EXAMINATION: Yes
- Time schedule for examinations: during acclimation and at study termination
- Dose groups that were examined: low and high dose-groups


HAEMATOLOGY: Yes
- Time schedule for collection of blood: in week 6 and at study termination
- Anaesthetic used for blood collection: No
- Animals fasted: Yes (overnight)
- How many animals: all surviving animals
- Parameters examined: red blood cell count, hemoglobin, hematocrit, erythrocyte indices, platelet count, mean platelet volume, withe blood cell count (total and differential), prothrombin time, blood cell morphology


CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: in week 6 and at study termination
- Animals fasted: Yes (overnight)
- How many animals: all surviving animals
- Parameters examined: ALP, ALT, AST, total bilirubin, cholesterol, triglycerides, glucose, blood urea nitrogen, creatinine, total proteins, albumin, globulin, albumin/globulin ratio, sodium, chloride, potassium, calcium, inorganic phosphorus


URINALYSIS: Yes
- Time schedule for collection of urine: in week 6 and at study termination
- Metabolism cages used for collection of urine: Yes
- Animals fasted: Yes (overnight)
- Parameters examined: color and appearance, pH, glucose, ketones, hemoglobin, volume, specific gravity, bilirubin, urobilinogen, proteins, nitrite, microscopy of centrifuged deposit


NEUROBEHAVIOURAL EXAMINATION: Yes (Functional Observational Battery)
- Time schedule for examinations: during acclimation, on day 1 (post dosing) and once during each of weeks 4, 8 and 13
- Dose groups that were examined: all animals
- Battery of functions tested: sensory activity / grip strength / motor activity / other: body temperature

Sacrifice and pathology:

GROSS PATHOLOGY: Yes (external examination, including identification of all clinically recorded lesions, and detailed internal examination)
ORGAN WEIGHTS: Yes (adrenals, brain, heart, kidneys, liver, lungs, ovaries or testes, pituitary, prostate, spleen, thymus, thyroid, uterus)
HISTOPATHOLOGY: Yes (standard extensive list of tissues)

Other examinations:

Not applicable

Statistics:

- Group mean values (with standard deviations) analyzed for homogeneity of variance using Bartlett's test
- Homogeneous data analyzed using Analysis of Variance and differences from controls assessed using Dunnett's 't' test
- Heterogeneous data analyzed using Kruskal-Wallis test and differences from controls assessed using Dunn's test
- Frequency data, gross pathology and histopathology findings analyzed using Fisher's exact probability test

Results and discussion

Results of examinations

Clinical signs:

no effects observed

Mortality:

no mortality observed

Body weight and weight changes:

effects observed, treatment-related

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Food efficiency:

not examined

Water consumption and compound intake (if drinking water study):

not examined

Ophthalmological findings:

no effects observed

Haematological findings:

effects observed, treatment-related

Clinical biochemistry findings:

no effects observed

Urinalysis findings:

no effects observed

Behaviour (functional findings):

no effects observed

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Gross pathological findings:

effects observed, treatment-related

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Histopathological findings: neoplastic:

no effects observed

Details on results:

The following relevant changes (considered test-article related) were observed:

BODY WEIGHT AND WEIGHT GAIN
- Statistically significant lower mean body weight gains in high-dose males when compared to controls in weeks 2 and 8
- Overall body weight gain of high-dose group marginallyinferior to that of controls

FOOD CONSUMPTION
Food consumption of high-dose males marginally lower than that of controls

HAEMATOLOGY
- Statistically significant elevated segmented neutrophil counts (when expressed as percentages of white blood cells) in low-dose and mid-dose females and high-dose males and females at weeks 6 and/or 13 compared to controls
- When expressed in absolute terms, segmented neutrophil counts in low-dose females and mid-dose and high-dose males and females elevated at weeks 6 and 13 compared to controls

ORGAN WEIGHTS
- Statistically significant higher lung (absolute and relative) weights in mid-dose and high-dose groups compared to controls
- Change in lung weight seen in all treated groups, although not always statistically significant
- Statistically significant higher spleen (relative) weights and higher spleen (absolute) weights in high-dose males compared to controls

GROSS PATHOLOGY
- Lungs: discoloration or pale areas (30 rats each in mid-dose and high-dose groups), pale foci (4 rats in low-dose group), uncollapsed parenchyma (2 rats in mid-dose group and 30 in high-dose group)
- Lymph nodes: enlargement and/or pale discoloration of the bronchial lymph nodes (28 rats in low-dose group, 30 each in mid-dose and high-dose groups), mediastinal lymph nodes (1 rat in control group, 12 in low-dose group, 18 in mid-dose group and 20 in high-dose group), pancreatic lymph nodes (3 rats in control group, 1 each in mid-dose and high-dose groups)

HISTOPATHOLOGY: NON-NEOPLASTIC
- Pigment accumulation and/or alveolar epithelial/lymphoid hyperplasia in the lungs (in low-dose, mid-dose and high-dose groups)
- Lymphoid hyperplasia of the bronchial or mediastinal (in low-dose, mid-dose and high-dose groups) and pancreatic (in mid-dose group) lymph nodes
- Metaplasia and/or pigment accumulation in larynx (in low-dose, mid-dose and high-dose groups)
- Pigment accumulation in bronchial or mediastinal lymph nodes, nasal cavity and bronchi (in low-dose, mid-dose and high-dose groups), in trachea and pancreatic lymph nodes (in mid-dose and high-dose groups), and in liver, mandibular lymph nodes and spleen (high-dose group only)

Effect levels

1

Dose descriptor:

NOEC

Effect level:

< 0.005 mg/L air

Sex:

male

Basis for effect level:

other: gross pathology; organ weights; histopathology

2

Dose descriptor:

NOEC

Effect level:

< 0.005 mg/L air

Sex:

female

Basis for effect level:

other: haematology; gross pathology; organ weights; histopathology

Target system / organ toxicity

Critical effects observed:

not specified

Any other information on results incl. tables

Tissue/Lesion	Incidence of microscopic findings (/No. of animals examined)
	0 mg/L		0.005 mg/L		0.0505 mg/L		0.5075 mg/L
	Males	Females	Males	Females	Males	Females	Males	Females
Bronchi:
- Pigment accumulation	0/15	0/15	1/15	0/15	5/15*	4/15*	15/15*	15/15*
Nasal cavity:
- Goblet cell hypertrophy and/or hyperplasia	0/15	0/15	0/15	1/15	0/15	0/15	1/15	2/15
- Pigment accumulation	0/15	0/15	12/15*	3/15	15/15*	11/15*	15/15*	15/15*
Larynx:
- Metaplasia	0/15	0/15	3/15	3/15	9/15*	6/15*	13/15*	9/15*
- Pigment accumulation	0/15	0/15	6/15*	0/15	9/15*	7/15*	12/15*	9/15*
Liver:
- Pigment accumulation	0/15	0/15	0/9	0/1	0/7	0/5	6/15*	5/15*
Lungs:
- Pigment accumulation	0/15	0/15	15/15*	15/15*	15/15*	15/15*	15/15*	15/15*
- Alveolar epithelial hyperplasia	0/15	0/15	1/15	0/15	11/15*	5/15*	14/15*	15/15*
- Lymphoid hyperplasia	0/15	0/15	0/15	0/15	0/15	1/15	12/15*	7/15*
Mandibular lymph nodes:
- Pigment accumulation	0/15	0/15	0/3	0/5	0/5	0/3	6/15*	6/15*
Spleen:
- Pigment accumulation	0/15	0/15	0/1	0/0	0/0	0/0	6/15*	3/15
Trachea:
- Pigment accumulation	0/15	0/15	0/15	0/15	1/15	1/15	14/15*	14/15*
Bronchial lymph nodes:
- Pigment accumulation	0/15	0/15	13/13*	14/15*	15/15*	15/15*	15/15*	15/15*
- Lymphoid hyperplasia	0/15	0/15	11/13*	13/15*	15/15*	15/15*	15/15*	15/15*
Mediastinal lymph nodes:
- Pigment accumulation	0/0	0/1	2/2	10/10	8/10	9/9	9/9	9/10
- Lymphoid hyperplasia	0/0	0/1	2/2	10/10	9/10	9/9	9/9	9/10
Pancreatic lymph nodes:
- Pigment accumulation	-	0/2	-	0/0	-	1/1	-	1/1
- Lymphoid hyperplasia	-	0/2	-	0/0	-	1/1	-	0/1

* p< 0.05

Applicant's summary and conclusion

Conclusions:

An overall NOEC could not be established based on changes in hematology (females only), organ weights, macroscopic observations at necropsy and histopathology at the lowest concentration tested, i.e. 0.005 mg/L.

Executive summary:

In an OECD TG 413-compliant study, the potential general toxicity of Cerium Oxide was tested following repeated nose-only inhalation to 7-week old Sprague-Dawley rats (15/sex) for 6 hours a day, 5 days a week, for 13 weeks, at the concentrations of 0 (air), 0.005, 0.0505 or 0.5075 mg/L.

 

No treatment-related deaths or clinical signs occurred during the study. There were no effects on ophthalmology, blood chemistry or urinalysis at any dose level. No behavioral changes following either acute or subchronic exposure and no significant differences in motor activity were observed in treated groups in a Functional Observational Battery assessment.

 

Treatment-related changes included changes in hematology, organ weights, macroscopic observations at necropsy and histopathology. Higher segmented neutrophil counts at weeks 6 and 13 were seen in females at 0.005 mg/L and above and in males at 0.0505 mg/L and above. A trend for higher lung weights was observed at 0.005 mg/L and above, and higher spleen weights were noted in males exposed to 0.5075 mg/L. Discoloration of the lungs and discoloration/enlargement of lymph nodes were observed in all treated groups. Microscopically, pigmented material accumulation in the lungs, bronchial, mandibular and mediastinal or pancreatic lymph nodes, trachea, bronchi, larynx, nasal cavity, liver and spleen, as well as alveolar epithelial hyperplasia in the lungs, metaplasia in larynx, and lymphoid hyperplasia in lymph nodes and lungs, correlating with the presence of pigment in these tissues, were seen in all treated groups with a clear dose-response relationship. Systemic dissemination of the test substance to tissues other than respiratory tract was evident at the highest concentration of 0.5075 mg/L.

 

Based on changes in hematology, organ weights, macroscopic observations at necropsy and histopathology at 0.005 mg/L, no NOEC could not be established.

 

No classification for repeat-dose toxicity is warranted based on the absence of toxicologically relevant effects in this study, according to the criteria of Annex VI Directive 67/748/EEC or UN/EU GHS.

 

This study is classified as acceptable. It satisfies the OECD 413 guideline requirements on subchronic inhalation toxicity.