Ditantalum pentaoxide

Repeated dose toxicity: oral

Administrative data

Endpoint:

sub-chronic toxicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2021-12-24 to 2022-09-14

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

OECD 408

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2022

Report date:

2022

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 408 (Repeated Dose 90-Day Oral Toxicity Study in Rodents)

Deviations:

yes

Remarks:

Concentration, stability, and homogeneity of test item formulations were not determined in this study, as no feasible analytical method is available.

GLP compliance:

yes (incl. QA statement)

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Ditantalum pentaoxide

EC Number:

215-238-2

EC Name:

Ditantalum pentaoxide

Cas Number:

1314-61-0

Molecular formula:

O5Ta2

IUPAC Name:

ditantalum(5+) pentaoxidandiide

Specific details on test material used for the study:

SOURCE OF TEST MATERIAL
- Source (i.e. manufacturer or supplier) and lot/batch number of test material: Taniobis GmbH, Batch (LOT) Number: 210515
- Physical Description: White powder
- Purity: 99.9%
- Expiry date: 12 November 2026 (shelf life)

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: At room temperature (21° C, protected from light)
- Stability and homogeneity of the test material in the vehicle/solvent under test conditions (e.g. in the exposure medium) and during storage: The test item dosing formulations were prepared with corn oil. The substance is a metal compound that does not dissolve in concentrated acid. Furthermore, the test item is also not expected to react with any oil-like substance like corn oil. Therefore, it is expected that the compound is stable in corn oil for the period from formulation until administration.

TREATMENT OF TEST MATERIAL PRIOR TO TESTING
- During the current study, the test item dosing formulations were prepared with corn oil. Preparations were visually inspected for homogeneity prior to use and all preparations were used within 2 hours after completion of the preparation of the test item. Additionally, test item formulations were stored protected from light.

Test animals

Species:

rat

Strain:

Wistar

Details on species / strain selection:

Strain: Crl: WI(Han)
Condition: Outbred, SPF-Quality

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Deutschland, Sulzfeld, Germany or Charles River Laboratories France, L'Arbresle Cedex, France.
- Age at study initiation: At least 6 weeks
- Weight at study initiation: 137 to 187 g (males) / 117 to 146 g (females)
- Housing: Polycarbonate cages (Makrolon type IV, height 18 cm or Makrolon type 2000P, height 21.5 cm) containing sterilized wooden fibers as bedding material (Lignocel S 8-15, JRS - J.Rettenmaier & Söhne GmbH + CO. KG, Rosenberg, Germany) equipped with water bottles.
Up to 5 animals of the same sex and same dosing group together.
During locomotor activity monitoring, animals are housed individually in a Hi-temp polycarbonate cage (Ancare corp., USA; dimensions: 48.3 x 26.7 x 20.3 cm) without cage-enrichment, bedding material, food and water. These housing conditions will be maintained unless deemed inappropriate by the Study Director and/or Clinical Veterinarian. The room(s) in which the animals will be kept will be documented in the study records. Cages will be arranged on the racks according to a Latin-square model.
- Diet (e.g. ad libitum): SM R/M-Z from SSNIFF® Spezialdiäten GmbH, Soest, Germany,ad libitum, except during designated procedures (During motor activity measurements, animals do not have access to food for a maximum of 2 hours)
- Water (e.g. ad libitum): Municipal tap water, ad libitum
- Acclimation period: at least 5 days before the commencement of dosing

DETAILS OF FOOD AND WATER QUALITY:

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 18 - 24 °C
- Humidity (%): 40 - 70%
- Air changes (per hr): ten or more
- Photoperiod (hrs dark / hrs light): 12/12 (except during designated procedures)

Administration / exposure

Route of administration:

oral: gavage

Details on route of administration:

The first day of dosing will be designated as Day 1 (exception: Alternate animals used for replacement after Day 1 will assume the day of the animal being replaced). The dose formulations will be stirred continuously during dosing and dosed within 2 hours after adding the vehicle to the test item. The doses will be given using a plastic feeding tube.

Vehicle:

corn oil

Remarks:

specific gravity 0.92

Details on oral exposure:

PREPARATION OF DOSING SOLUTIONS:
During the current study, the test item dosing formulations were prepared with corn oil. The substance is a metal compound that does not dissolve in concentrated acid. Furthermore, the test item is also not expected to react with any oil-like substance like corn oil. Therefore, it is
expected that the compound is stable in corn oil for the period from formulation until administration.
In addition, to limit the impact, the test item preparation was performed with approved procedures and documented in detail. Preparations were made daily visually inspected for homogeneity prior to use and all preparations were used within 2 hours after completion of the preparation of the test item. Additionally, test item formulations were stored protected from light.

VEHICLE
- Justification for use and choice of vehicle (if other than water): Trial preparations were performed to select the suitable vehicle and to establish a suitable formulation procedure.
- Concentration in vehicle: Low dose (100 mg/kg bw/day) 25 mg/ml
Medium dose (300 mg/kg bw/day) 75 mg/ml
High Dose (1000 mg/kg bw/day): 250 mg/ml
- Amount of vehicle (if gavage): 4 ml

Analytical verification of doses or concentrations:

no

Remarks:

no feasible analytical method available

Details on analytical verification of doses or concentrations:

Analysis of test item in vehicle for concentration, homogeneity, and stability were not performed, as no feasible analytical method is available. In theory metal ions, such as ditantalum pentaoxide, can be analysed by ICP-MS, if the ditantalum pentaoxide can be dissolved in an aqueous solution. However, ditantalum pentaoxide does not dissolve in aqueous solutions and also not in concentrated hydrofluoric acid, not even after addition of nitric acid and heating overnight at 60°C, as was tested in Test Facility Reference No. 20326971.
The test item is not expected to react with any oil-like substance like corn oil. Therefore, it is expected that the compound is stable in corn oil for the period from formulation until administration.
To limit the impact, the test item preparation was performed with approved procedures and documented in detail. Preparations were visually inspected for homogeneity prior to use and all preparations were used within 2 hours after completion of the preparation of the test item. Additionally, test item formulations were stored protected from light.
This GLP exception was therefore considered as being minor with no impact on the outcomes and the integrity and the achievement of the objective of the study.

Duration of treatment / exposure:

90 days

Frequency of treatment:

Once daily

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

0 mg/kg bw/day (nominal)

Doses / concentrations 2

Dose / conc.:

100 mg/kg bw/day (nominal)

Doses / concentrations 3

Dose / conc.:

300 mg/kg bw/day (nominal)

Doses / concentrations 4

Dose / conc.:

1 000 mg/kg bw/day (nominal)

No. of animals per sex per dose:

10

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale: The set of publicly available information from toxicological studies on ECHA’s dissemination page includes data from an acute toxicity study, which concluded that tantalum oxide is non-toxic when administered orally (Cochran, 1950). An LD0 of ≥ 8,000 mg/kg bw after single dose administration was specified in the registration dossier.
In addition, study information on in vivo skin irritation (according to OECD 404, rated Klimisch 1) and in vivo eye irritation (according to OECD 405, rated as Klimisch 1) provide no evidence of local effects relevant for the classification of the substance Ditantalum pentaoxide.
Based on the practical insolubility of ditantalum pentaoxide and the available toxicological information, it is assumed that no relevant potential for systemic toxicity can be expected for the test substance, even for longer term studies.
Therefore, the high dose level was set to the maximum dose recommended in OECD TG 408, i.e. 1000 mg/kg bw/day. The mid dose (MD) and low dose (LD) level were spaced by approximately a factor of 3 in order to obtain 300 (MD) and 100 (LD) mg/kg bw/day.
- Fasting period before blood sampling for clinical biochemistry: Overnight with a maximum of 24 h

Positive control:

no

Examinations

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: At least once daily from Day 1 during dosing

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: Weekly; from Week 1 and throughout the study, and on the day of necropsy

BODY WEIGHT: Yes
- Time schedule for examinations: Weekly; from at least Day 1 and throughout the study. In order to monitor the health status, animals may be weighed more often.

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study):
- Food consumption quantitatively measured weekly for each cage in 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 AND COMPOUND INTAKE (if drinking water study): Yes
- Time schedule for examinations: Regular basis throughout the study.

OPHTHALMOSCOPIC EXAMINATION: Yes
- Time schedule for examinations: Pretreatment Period - All animals once (including spare animals), Dosing Period - All Group 1 and 4 animals during Week 13
- Dose groups that were examined: All animals once

HAEMATOLOGY: Yes
- Time schedule for collection of blood: On days of scheduled or unscheduled necropsy
- Anaesthetic used for blood collection: Yes (isoflurane (Abbott B.V., Hoofddorp, The Netherlands))
- Animals fasted: Yes, overnight
- How many animals: All animals
- the following parameters were examined:
White Blood Cell (WBC)
Neutrophils (absolute)
Lymphocytes (absolute)
Monocytes (absolute)
Eosinophils (absolute)
Basophils (absolute)
Large unstained cells (LUC) (absolute)
Red Blood Cell (RBC)
Reticulocytes (absolute)
Red Blood Cell Distribution Width (RDW)
Hemoglobin
Hematocrit
Mean corpuscular volume (MCV)
Mean corpuscular hemoglobin (MCH)
Mean corpuscular hemoglobin concentration (MCHC)
Platelets
Prothrombin time (PT)
Activated partial thromboplastin time (APTT)

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: On days of scheduled or unscheduled necropsy
- Animals fasted: Yes
- How many animals: All animals
- the following parameters were examined
Alanine aminotransferase (ALT), Triglycerides, Aspartate aminotransferase (AST), HDL and LDL Cholesterol, Alkaline Phosphatase (ALP), Sodium, Total protein, Potassium, Albumin, Chloride, Total Bilirubin, Calcium, Urea, Inorganic Phosphate (Inorg. Phos), Creatinine, Triiodothyronine (T3), Glucose, Thyroxine (T4), Cholesterol, Thyroid-Stimulating Hormone (TSH)

PLASMA/SERUM HORMONES/LIPIDS: Yes
- Time of blood sample collection: On days of scheduled or unscheduled necropsy
- Animals fasted: Yes
- How many animals: All animals

URINALYSIS: No

NEUROBEHAVIOURAL EXAMINATION: Yes
- Time schedule for examinations: not specified
- Dose groups that were examined: not specified
- Battery of functions tested: sensory activity / grip strength / motor activity / other: excitability

IMMUNOLOGY: Not specified

Sacrifice and pathology:

GROSS PATHOLOGY: Yes (see section "Any other information on materials and methods incl. tables" for more details)
- Unscheduled Euthanasia: Animals will be deeply anesthetized using isoflurane and subsequently exsanguinated. If necessary, animals will be refrigerated to minimize autolysis.
- Scheduled Euthanasia: Animals surviving until scheduled euthanasia will have a terminal body weight recorded and will be deeply anesthetized using isoflurane and subsequently exsanguinated and subjected to a full post mortem examination. Animals will be fasted (overnight with a maximum of 24 hours) before their scheduled necropsy.
- Animals will be subjected to a complete necropsy examination, which will include evaluation of the carcass and musculoskeletal system; all external surfaces and orifices; cranial cavity and external surfaces of the brain; and thoracic, abdominal, and pelvic cavities with their associated organs and tissues.
- Representative samples of tissues will be collected and preserved in 10% neutral buffered formalin or modified Davidson's solution as detailed in Test Facility SOPs.

HISTOPATHOLOGY: Yes (see section "Any other information on materials and methods incl. tables" for more details)
- Tissues were embedded in paraffin, sectioned, mounted on glass slides, and stained with hematoxylin and eosin.
- Tissues were evaluated histopathologically by a board-certified toxicological pathologist with training and experience in laboratory animal pathology.

Other examinations:

- Estrous stage determination: At the End of Treatment on the day of necropsy, a vaginal smear will be taken to determine the stage of estrus from all Study animals. This will be done for all females, except for females that have to be euthanized in extremis or die spontaneously. Estrous stage will be evaluated by examining the vaginal cytology of the samples obtained by vaginal smears procedures.
- Organ weights: The organs detailed under section "Any other information on materials and methods incl. tables" will be weighed at necropsy. Paired organs will be weighed together. In the event of gross abnormalities, in addition to the combined weight, the weight of each organ of a pair may be taken and entered as a tissue comment. Organ weight as a percent of body weight (using the terminal body weight) will be calculated.

Statistics:

All statistical analyses were performed within the respective study phase, unless otherwise noted. Numerical data collected on scheduled occasions were summarized and statistically analyzed as indicated below according to sex and occasion.

Constructed Variables
Body Weight Gains: Calculated between each scheduled interval.
Mean Overall Body Weight Gain: Calculated over the complete Dosing Period.
Food Consumption: Calculated between each scheduled interval.
Mean Overall Food Consumption: Calculated over the complete Dosing Period.
Organ Weight Relative to Body Weight: Calculated against the terminal body weight

Descriptive Statistical Analyses
Means, standard deviations (or % coefficient of variation or standard error, when deemed appropriate), percentages, numbers, and/or incidences will be reported as appropriate by dataset.

Inferential Statistical Methods
All statistical tests were conducted at the 5% significance level. All pairwise comparisons were conducted using two sided tests and will be reported at the 1% and 5% levels, unless otherwise noted.

The pairwise comparisons of interest are listed below:
Group 2 vs. Group 1
Group 3 vs. Group 1
Group 4 vs. Group 1
Analyses will be performed according to the matrix below when possible, but will exclude any group with less than 3 observations.

Results and discussion

Results of examinations

Clinical signs:

effects observed, non-treatment-related

Description (incidence and severity):

Any clinical signs noted during the Treatment Period occurred within the range of background findings to be expected for rats of this age and strain which are housed and treated under the conditions in this study and did not show any apparent dose-related trend. At the incidence observed, these were considered to be unrelated to treatment with the test item.

Mortality:

mortality observed, non-treatment-related

Description (incidence):

Male No. 37 (1000 mg/kg/day) was found dead on Day 33 of the Treatment Period. On the day prior to its death, the animal was noted to have erected fur and a labored breathing. Main findings recorded at necropsy included the presence of white oil-like fluid in the thoracic cavity, fluid in the pericardium and a perforation of the trachea. At microscopic examination, black appearing foreign material (presumably the solid test material) was present in the mediastinal area bordering the lung and a mixed cell inflammation was present in the pericardium of the left atrium of the heart. These macroscopic and microscopic findings were consistent with a gavage procedure-related cause of death.

Body weight and weight changes:

no effects observed

Description (incidence and severity):

Body weights and body weight gain of treated animals remained in the same range as controls over the study period

Food consumption and compound intake (if feeding study):

effects observed, non-treatment-related

Description (incidence and severity):

Food consumption in females was similar to the control level over the study period. Only in males food consumption was slightly lower at all dose levels from Day 50 of treatment period (not statistically significant). Without dose dependency and without effect on bw gain it was considered not treatment related.

Food efficiency:

not examined

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

not examined

Ophthalmological findings:

effects observed, non-treatment-related

Description (incidence and severity):

Ophthalmology findings noted during the pretreatment period and/or in week 13 was similar among the groups, and occurred within the range considered normal for rats of this age and strain. These findings were therefore considered to be unrelated to treatment with the test material.

Haematological findings:

effects observed, non-treatment-related

Description (incidence and severity):

Changes in eosinophil counts in all treated female groups were considered to have arisen as a result of a slightly high mean control value when compared to historical control data. These changes were regarded as unrelated to treatment with the test material.
Decreases in basophil and large unstained cell count in all treated female groups were considered to be unrelated to treatment with the test material as individual values remained within control range and no dose-response relationship could be observed.

Clinical biochemistry findings:

effects observed, treatment-related

Description (incidence and severity):

No treatment related effects in animals up to 300 mg/kg bw/d. Clinical chemistry changes at 1000 mg/kg/day comprised increased cholesterol, HDL and LDL levels in males (1.21, 1.19 and 1.25x of control, respectively), and decreased chloride concentration in females (0.98x of control). Considering the small magnitude of changes and absence of any histopathological correlation, these clinical chemistry changes were considered to be non-adverse.

Endocrine findings:

no effects observed

Description (incidence and severity):

Serum levels of T3, T4 and TSH were considered unaffected by treatment with the test material.

Urinalysis findings:

not examined

Behaviour (functional findings):

effects observed, non-treatment-related

Description (incidence and severity):

Functional observations (activity, autonomic response, excitability as well as physiological, sensorimotor and neuromuscular observations) were considered to be unaffected by treatment with the test material. The lower hindlimb grip strength in males from 100 mg/kg/day onwards was considered to derive from a relatively high concurrent mean control value when compared with historical control data. Therefore, this difference was considered to be unrelated to treatment with the test material. Any observations noted occurred within the range of background findings to be expected for rats of this age and strain which are housed and treated under the conditions in this study and did not show any apparent dose-related trend. Motor activity was similar between treated and control groups in both sexes. All groups showed a similar motor activity habituation profile with a decreasing trend in activity over the duration of the test period.

Immunological findings:

no effects observed

Organ weight findings including organ / body weight ratios:

effects observed, non-treatment-related

Description (incidence and severity):

There were no test material-related alterations in organ weights.
The statistically significant lower seminal vesicle weight at 100 mg/kg/day (absolute and relative to body weight) and at 1000 mg/kg/day (relative to body weight) lacked a dose related pattern and was regarded unrelated to the treatment with the test material.

Gross pathological findings:

no effects observed

Description (incidence and severity):

There were no test material-related gross observations.
All of the recorded macroscopic findings were within the range of background gross observations encountered in rats of this age and strain.

Neuropathological findings:

not specified

Histopathological findings: non-neoplastic:

effects observed, non-treatment-related

Description (incidence and severity):

Male No. 36 and Female No. 78 showed a focal area with foreign material (black, amorphous) in the bronchi/alveoli of the lung. This black appearing material was considered to represent the solid test material, which might have been aspirated during the gavage procedure. The remainder of the recorded microscopic findings in the animals at scheduled necropsy were within the range of background pathology encountered in rats of this age and strain. There was no test material-related alteration in the prevalence, severity, or histologic character of those incidental tissue alterations.

Histopathological findings: neoplastic:

no effects observed

Other effects:

not specified

Effect levels

Key result

Dose descriptor:

NOAEL

Effect level:

> 1 000 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: No adverse effects observed

Target system / organ toxicity

Key result

Critical effects observed:

no

Applicant's summary and conclusion

Conclusions:

Clinical chemistry changes at 1000 mg/kg/day comprised increased (HDL and LDL) cholesterol levels in males and decreased chloride concentration in females. Considering the small magnitude of changes and absence of any histopathological correlation, these clinical chemistry changes were considered to be non-adverse. In conclusion, based on the results of this 90-day study in Wistar Han rats, the No Observed Adverse Effect Level (NOAEL) of Ta2O5 CERAMIC Grade was considered to be at least 1000 mg/kg/day.

Executive summary:

In a subchronic toxicity study Ta2O5 CERAMIC Grade (99.9%) was administered to 10 Wistar Han rats/sex/dose by gavage at dose levels of 0, 100, 300, 1000 mg/kg bw/day.

There were no compound related effects in mortality, clinical signs, body weight, food consumption, hematology, clinical chemistry, organ weights, or gross and histologic pathology. There were changes in clinical chemistry at 1000 mg/kg/day comprising increased cholesterol, HDL and LDL levels in males (1.21, 1.19 and 1.25x of control, respectively), and decreased chloride concentration in females (0.98x of control). However, considering the small magnitude of changes and absence of any histopathological correlation, these clinical chemistry changes were considered to be non-adverse. Therefore, the NOAEL is 1000 mg/kg bw/d.

This subchronic toxicity study in the rats is acceptable and satisfies the guideline requirement for a subchronic oral study (OPPTS 870.3100; OECD 408) in rats.