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Administrative data

Description of key information

Repeated Dose Toxicity - Oral Route:


No oral repeated dose toxicity data of sufficient quality are available for tungsten carbide (target substance). However, repeated oral dose toxicity data are available for sodium tungstate (source substance), which are used for read-across. Due to lower water solubility and lower toxicity for the target substance compared to the source substance, the resulting read-across from the source substance to the target substance is appropriate as a conservative estimate of potential toxicity for this endpoint. In addition, read-across is appropriate because the classification and labelling is more protective for the source substance than the target substance, the PBT/vPvB profile is the same, and the dose descriptors are, or are expected to be, lower for the source substance. For more details, refer to the read-across category approach included in the Category section of this IUCLID submission on Annex 3 in the CSR.


The read-across study on sodium tungstate was sponsored conducted the United States Army Center for Health Promotion and Preventive Medicine and published byMcCain et al (2015). The 90-day oral toxicity study was conducted in rats according to the procedure described in the Environmental Protection Agency (EPA) Health Effects Testing Guidelines (40 CFR, Part 798.2650) in compliance with Good Laboratory Practice. Briefly, this study of the subchronic toxicity of sodium tungstate dihydrate aqueous solution in male and female Sprague-Dawley rats was evaluated by daily oral gavage of 0, 10, 75, 125, or 200 mg/kg bw/d for 90 days. Measured parameters included food consumption, body weight measurements, hematology, clinical chemistry, and histopathological changes. There was a significant decrease in food consumption and body weight gain in males at 200 mg/kg bw/d from days 77 to 90; however, there was no effect in food consumption and body weights in females. There were no changes in the hematological and clinical parameters studied. Histopathological changes were seen in kidney of male and female and epididymis of male rats. The histopathological changes observed in the kidneys of male and female rats dosed at 125 or 200 mg/k/d consisting of mild to severe cortical tubule basophilia in 2 high-dose groups. Histological changes in epididymides included intraluminal hypospermia with cell debris in the 200 mg/kg bw/day dosed male rats. Histopathological changes were observed in the glandular stomach including inflammation and metaplasia in the high-dose groups (125 or 200 mg/kg bw/day) of both sexes of rats. Based on histopathology effects seen in the kidneys, the lowest observable adverse effect level was 125 mg/kg bw/d and the no observable adverse effect level was 75 mg/kg bw/d in both sexes of rats for oral subchronic toxicity. The US EPA’s Benchmark Dose Software (BMDS, Version 1.4.1) was used to model the data to derive a BMDL10. The lowest (most precautionary) BMDL10 from the renal toxicity endpoint in the 90-day oral toxicity study was 102 mg/kg bw/d.


In addition to McCain et al (2015) rat oral 90-day repeated dose study, the US National Toxicology Program (NTP) has conducted two additional 90-day drinking water studies, one in Sprague-Dawley rats and a second one in B6C3F1 mice (10/sex/species/dose). The study design included doses of 0, 125, 250, 500, 1000, or 2000 mg/L. 


There were no early deaths during the 3-month rat study. When compared to the vehicle control group, final mean body weights were lower for the 1,000 and 2,000 mg/L males and 2,000 mg/L females. Water consumption was lower for the 1,000 and 2,000 mg/L males and females. The urine xanthine/creatinine ratios were significantly increased in all male and female exposed groups. Serum insulin concentrations were significantly decreased in the 2,000 mg/L males relative to the vehicle control males. Significantly decreased absolute weights were observed in several organs but were considered secondary to body weights reductions. Exposure-related histological lesions were limited to the kidneys and included increased incidences of renal tubule regeneration in the 1,000 and 2,000 mg/L males and females; the increases in the 2,000 mg/L groups were significant relative to the vehicle control group.


In the mice study, a decreased water consumption was observed in 1000 (11%) and 2000 mg/L (16%) male mice. During the 13-week phase of the study, there was no effect on survival, hematology, or organ weights in mice. Renal tubule regeneration was characterized by hyperplasia of tubular epithelial cells with cytoplasmic basophilia, nuclear crowding, karyomegaly, and occasional mitotic figures. Total tungsten concentrations were generally dose proportional in blood and urine. The micronucleus assay was negative in mice. The Comet assay was positive in the liver and ileum of male mice and negative in the blood and kidney of mice. The kidney appeared to be the only major target organ following exposure of mice to sodium tungstate dihydrate at water concentrations of 1000 and 2000 mg/L.


Repeated Dose Toxicity - Inhalation Route:


A 90-day repeat dose inhalation toxicity study was identified for tungsten carbide (WC) in which one dose of WC (15 mg/m3) was administered to rats and mice, whole body inhalation exposure, 5 days/week for 13 weeks. The LOEL was deemed to be 15 mg/m3in rats based on mild histopathological alterations in the lungs (focal reactions around the end airways) and chronic rhinitis, and in mice based on chronic rhinitis. However, because only one dose was evaluated, this dose did not result in any effects on which a DNEL would be derived or classification would be based, and using this dose would result in an inaccurate DNEL and classification, the 28-day inhalation toxicity study on tungsten oxide are used for read-across.


No inhalation repeated dose toxicity data of sufficient quality are available for tungsten carbide however, data are available for tungsten oxide, which are used for read-across.


No inhalation repated dose toxicity data of sufficient quality are available for tungsten carbide (target substance). However, inhalation repeated dose toxicity data are available for tungsten oxide (source substance), which are used for read-across. Due to lower water solubility and similar toxicity for the target substance compared to the source substance, the resulting read-across from the source substance to the target substance is appropriate. In addition, rea- across is appropriate because the classification and labelling is similar for the source substance than the target substance, the PBT/vPvB profile is the same, and the dose descriptors are, or are expected to be, lower for the source substance. For more details, refer to the read-across category approach in Annex 3 in the CSR.


A 28-day inhalation toxicity study conducted according to OECD 412 is available on tungsten oxide (also known as tungsten blue oxide or TBO), which is considered the key repeated dose study. In this study, 5 rats/sex/dose were given TBO nose-only for 6 hours per day, 7 days/week, for 28 days (with a 14-day recovery period) at doses of 0 (control), 0.08, 0.325, and 0.65 mg/L air. The NOAEC was deemed to be > 0.65 mg/L air (650 mg/m3), as no significant effects were reported.

Key value for chemical safety assessment

Toxic effect type:
concentration-driven

Repeated dose toxicity: via oral route - systemic effects

Link to relevant study records

Referenceopen allclose all

Endpoint:
sub-chronic toxicity: oral
Type of information:
read-across based on grouping of substances (category approach)
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
comparable to guideline study with acceptable restrictions
Justification for type of information:
REPORTING FORMAT FOR THE CATEGORY APPROACH

1. HYPOTHESIS FOR THE CATEGORY APPROACH: The hypothesis is that properties are likely to be similar or follow a similar pattern because of the presence of a common metal ion, in this case tungstate.
2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES):
Source: Sodium Tungstate
Target: Tungsten Carbide
3. CATEGORY APPROACH JUSTIFICATION: See Annex 3 in CSR
4. DATA MATRIX: See Annex 3 in CSR
Reason / purpose for cross-reference:
reference to same study
Reason / purpose for cross-reference:
read-across: supporting information
Qualifier:
equivalent or similar to guideline
Guideline:
EPA OPPTS 870.3100 (90-Day Oral Toxicity in Rodents)
GLP compliance:
yes
Limit test:
no
Species:
rat
Strain:
Sprague-Dawley
Details on species / strain selection:
SD
Sex:
male/female
Details on test animals or test system and environmental conditions:
Groups of 10 F1 rats per sex continued on in the study after weaning and were provided drinking water containing the same respective sodium tungstate concentration for 3 months. For all exposure concentrations, except the 2,000 mg/L group, two pups per sex from five randomly selected litters per exposure group were chosen. For the 2,000 mg/L group, a third male pup was selected from two of the four available litters and a third female pup was selected from the other two litters to obtain the complete number of animals needed for the study. After assignments to the 3-month study were complete, five pups per sex from the remaining vehicle control pups were randomly selected as the end-of-study sentinel animals. On the day the last litter reached PND 21, dams were removed, and the pups were weaned. Weaning marked the beginning of the 3-month study.
After weaning, F1 rats were housed five per cage. Feed and dosed water were available ad libitum. Water consumption was measured weekly for 3 months. Cages were changed weekly though PND 4, then changed twice weekly. Racks were changed and rotated at least every 2 weeks.


Route of administration:
oral: drinking water
Details on route of administration:
deionized drinking water
Vehicle:
water
Details on oral exposure:
- 90 days for dosed-feed and dosed-water studies
Analytical verification of doses or concentrations:
not specified
Duration of treatment / exposure:
90-days
Frequency of treatment:
Daily
Dose / conc.:
0 mg/L drinking water
Dose / conc.:
125 mg/L drinking water
Remarks:
Approximately 11.8 mg/kg/day for males and 14.0 mg/kg/day for females.
Dose / conc.:
250 mg/L drinking water
Remarks:
Approximately 24.3 mg/kg/day for males and 26.1 mg/kg/day for females.
Dose / conc.:
500 mg/L drinking water
Remarks:
Approximately 48.9 mg/kg/day for males and 54.4 mg/kg/day for females.
Dose / conc.:
1 000 mg/L drinking water
Remarks:
Approximately 91.8 mg/kg/day for males and 101.4 mg/kg/day for females.
Dose / conc.:
2 000 mg/L drinking water
Remarks:
Approximately 157.2 mg/kg/day for males and 160.5 mg/kg/day for females.
No. of animals per sex per dose:
Each group per sex per species contains five animals
Control animals:
yes, concurrent vehicle
Details on study design:
On the day the last litter (exposed from GD 6 to GD21) reached PND 20, pups were randomly assigned to the 3-month study. For all exposure concentrations, except the 2,000 mg/L group, two pups per sex from five randomly selected litters per exposure group were chosen. For the 2,000 mg/L group, a third male pup was selected from two of the four available litters and a third female pup was selected from the other two litters to obtain the complete number of animals needed for the study. After assignments to the 3-month study were complete, five pups per sex from the remaining vehicle control pups were randomly selected as the end-of-study sentinel animals. On the day the last litter reached PND 21, dams were removed, and the pups were weaned. Weaning marked the beginning of the 3-month study.
After weaning, F1 rats were housed five per cage. Feed and dosed water were available ad libitum. Water consumption was measured weekly for 3 months. Cages were changed weekly though PND 4, then changed twice weekly. Racks were changed and rotated at least every 2 weeks.
Positive control:
Not applicable
Observations and examinations performed and frequency:
Animals are individually weighed on days one, seven, and at weekly periods thereafter. All animals are observed twice daily for clinical signs of declining health, or death. Animals found near death or showing clinical signs of pain or distress are humanely euthanized. Formal clinical observations are performed and recorded weekly. Food consumption/water consumption is measured and recorded weekly.

Clinical Laboratory Studies
Blood is collected from both sexes of "special study" rats, at days 4 ± 1 and 21 ± 2 and from the core study rats at the end of the study. These are processed for hematology and clinical chemistry determinations. Blood is collected from core study mice at the end of the study for hematology determinations. See clinical measurements:

1. Hematology:
Erythrocyte count
Mean corpuscular volume
Hemoglobin
Packed cell volume
Mean corpuscular hemoglobin
Mean corpuscular hemoglobin concentration
Erythrocyte morphologic assessment
Leukocyte count
Leukocyte differential
Reticulocyte count
Platelet count and morphologic assessment

2. Clinical Chemistry:
Sorbitol dehydrogenase (SDH)
Alkaline Phosphatase (ALP)
Creatine Kinase (CK)
Creatinine
Total Protein
Albumin
Urea Nitrogen (BUN)
Total Bile Acids
Alanine Aminotransferase (ALT)
Glucose
Cholesterol
Triglycerides
Sacrifice and pathology:
- Liver, thymus, right kidney, right testis, heart, and lung weights are recorded from all animals surviving until the end of the study.
- A complete necropsy is performed on all treated and control animals, and all tissues required for complete histopathology are trimmed, embedded, sectioned, and stained with hematoxylin and eosin for histopathologic evaluation. See necropsy list:

A complete gross necropsy is an external examination of the animal including body orifices and examination and fixation of all of the following organs/tissues from animals from all treatment groups for histopathologic examination.
Adrenal glands
Brain
Clitoral glands
Esophagus
Eyes
Femur
Gallbladder (mouse)
Gross lesions
Harderian glands
Heart and aorta
Intestine, large (cecum, colon, rectum)
Intestine, small (duodenum, jejunum, ileum)
Kidneys
Liver
Lungs and mainstem bronchi
mandibular and mesenteric
bronchial mediastinal (inhalation studies)
Mammary gland with adjacent skin
Muscle, thigh
Nerve, sciatic
Nasal cavity and nasal turbinates
Oral cavity, larynx, and pharynx
Ovaries
Pancreas
Parathyroid glands
Pituitary gland
Preputial glands
Prostate
Salivary glands
Seminal vesicles
Skin, site of application (dermal studies)
Spinal cord
Spleen
Stomach (forestomach and glandular)
Testes, epididymides, and vaginal tunics of testes
Thymus
Thyroid gland
Tissue masses
Tongue
Trachea
Urinary bladder
Uterus
Vagina
Zymbal glands

- A complete histopathologic evaluation inclusive of treatment-related gross lesions shall be done on all animals. Treatment-related lesions for target organs shall be identified and these organs plus gross lesions shall be examined to a no-effect level. TIssues examined:
Adrenal glands
Brain (3 sections including frontal cortex and basal ganglia, parietal cortex and thalamus, and cerebellum and pons)
Clitoral glands
Esophagus
Eyes
Femur, including diaphysis with marrow cavity and epiphysis (femoral condyle with epiphyseal cartilage plate, articular cartilage and articular surface)
Gallbladder (mouse)
Gross lesions
Harderian glands
Heart and aorta
Intestine, large (cecum, colon, rectum)
Intestine, small (duodenum, jejunum, ileum)
Kidneys
Larynx (inhalation studies)
Liver (2 sections including left lateral lobe and median lobe)
Lungs and mainstem bronchi
Lymph nodes
mandibular and mesenteric
bronchial & mediastinal (inhalation studies)
Mammary gland with adjacent skin
Muscle, thigh (only if neuromuscular signs were present)
Nasal cavity and nasal turbinates (3 sections)
Ovaries
Pancreas
Parathyroid glands
Pituitary gland
Preputial glands
Prostate
Salivary glands
Seminal vesicle
Skin, site of application (dermal studies)
Spinal cord and sciatic nerve (if neurologic signs were present)
Spleen
Stomach (forestomach and glandular)
Testes with epididymides
Thymus
Thyroid gland
Tissue masses
Trachea
Urinary bladder
Uterus
Other examinations:
- Tungsten concentrations in blood and urine
- Genotoxicity (micronucleus and Comet assay): Blood for Micronuclei samples were taken from rats at study termination for micronuclei determinations.
Clinical signs:
effects observed, non-treatment-related
Description (incidence and severity):
There were no clinical observations related to exposure, and all exposed animals were similar in overt behavior and general appearance to the vehicle control animals
Mortality:
no mortality observed
Description (incidence):
There were no early deaths during the 3-month study
Body weight and weight changes:
effects observed, treatment-related
Description (incidence and severity):
Initial mean body weights were 9% and 16% below those of the vehicle control group for the 1,000 and 2,000 mg/L males, respectively; and 14%, 11%, and 13% below those of the vehicle control group for the 500, 1,000, and 2,000 mg/L females, respectively. Final mean body weights were lower for the 1,000 and 2,000 mg/L males and females, with the 2,000 mg/L males weighing approximately 29% less than the vehicle control group and the 2,000 mg/L females weighing approximately 18% less than the vehicle control group.

Food consumption and compound intake (if feeding study):
not specified
Food efficiency:
not specified
Water consumption and compound intake (if drinking water study):
effects observed, treatment-related
Description (incidence and severity):
Water consumption was lower for the 1,000 and 2,000 mg/L males and females, with overall reductions of 27% and 42% for males and females, respectively, in the 2,000 mg/L groups compared to the respective vehicle control groups.
Ophthalmological findings:
not specified
Haematological findings:
effects observed, treatment-related
Description (incidence and severity):
In female rats, there was a mild (<10%) significant decrease in the erythron characterized by a significant decrease in the hemoglobin concentration in the 2,000 mg/L group and a significant negative trend in the hematocrit concentration, hemoglobin concentration, and erythrocyte count with increasing exposure. Although there were no significant pairwise changes observed in the male erythron, there were significant negative trends in hematocrit concentration, hemoglobin concentration, and erythrocyte count with increasing exposure concentration. The reticulocyte count was unchanged in both males and females. These mild erythron changes were most likely due to the stress of exposure,
which is supported by the lower mean body weights
observed in the 2,000 mg/L groups.
Clinical biochemistry findings:
effects observed, treatment-related
Description (incidence and severity):
In male rats, blood urea nitrogen (BUN) was significantly increased, and the total protein, globulin concentrations, and insulin concentrations were significantly decreased in the 2,000 mg/L group. The BUN was likely increased due to the lower water consumption values in that exposure group. The toxicological relevance of the observed decreases in the total protein and globulins is uncertain; these changes could be a secondary effect of exposure.
Urinalysis findings:
effects observed, treatment-related
Description (incidence and severity):
The urine xanthine/creatinine ratios were significantly increased in all male and female exposed groups relative to the vehicle control groups
Behaviour (functional findings):
not specified
Immunological findings:
not specified
Organ weight findings including organ / body weight ratios:
effects observed, treatment-related
Description (incidence and severity):
Absolute kidney weights were reduced in males in all exposed groups, relative to the vehicle control group, with a significant decrease observed in the 2,000 mg/L group (approximately 21%). Relative kidney weights were higher in 1,000 mg/L females and significantly increased in the 2,000 mg/L males and females, relative to the vehicle control group. Although the kidney was a target tissue, it is unlikely that the lesions observed were responsible for the differences in kidney weights; it is more likely that these organ weight differences are an effect of body weight differences.
When compared to vehicle control groups, significant differences were also observed in other organ weights, including decreased absolute heart and lung weights in males and females; decreased absolute liver weights in males and increased relative liver weights in females; decreased absolute thymus weights in males and increased relative testis weights. These changes were considered secondary to body weight reductions.
Rats administered 2,000 mg/L exhibited significantly decreased left cauda epididymis (14%) and epididymis (13%) weights, and lower testis weights (8%) compared to the vehicle control group.
Although these were significant (cauda and epididymis) and/or displayed a significant negative trend with increasing exposure concentration (right testis), rats in the 2,000 mg/L group displayed mean body weights that were 28% lower than the vehicle control group. There were no changes in reproductive parameters or alterations in contralateral testis and epididymis or in histopathology. Given the magnitude of the body weight effect and the absence of changes in other endpoints, the lower reproductive organ weights are likely secondary to effects on body weight.
Gross pathological findings:
no effects observed
Description (incidence and severity):
No exposure-related gross lesions were recorded
Neuropathological findings:
not specified
Histopathological findings: non-neoplastic:
effects observed, treatment-related
Description (incidence and severity):
Exposure-related histological lesions were found in the kidneys. Renal tubule regeneration was increased in the male and female 1,000 and 2,000 mg/L groups; the increases in the 2,000 mg/L groups were significant relative to the vehicle control groups. The lesion was characterized by hyperplasia of proximal convoluted tubular epithelial cells that manifested as cytoplasmic basophilia, nuclear crowding, and occasional mitotic figures. Renal tubule regeneration occurs as a response to previous degeneration or necrosis and is one of the most common exposure-related lesions in the kidney.90
Degeneration and necrosis were not present in this study, perhaps due to the fact that by the time of necropsy, the response of the kidney had progressed from degeneration to regeneration. Renal tubule regeneration differed from chronic progressive nephropathy (CPN) by the lack of thickened basement membranes, associated inflammatory cells, proteinaceous casts, and cytoplasmic pigment—all features typically seen with CPN. The incidences and severities of CPN were not increased in exposed groups of animals.

Histopathological findings: neoplastic:
no effects observed
Description (incidence and severity):
Neoplasms were not identified in male or female rats
Other effects:
effects observed, treatment-related
Description (incidence and severity):
Although the weights of the left epididymis and the left cauda were significantly decreased in the 2,000 mg/L males, there were no corresponding changes in sperm parameters, including number of sperm/mg cauda epididymis, total number of sperm/cauda, sperm motility, number of homogenization-resistant spermatids/mg testis, or total number of spermatids.
Key result
Dose descriptor:
LOAEL
Effect level:
ca. 1 000 mg/L drinking water
Based on:
test mat.
Sex:
male/female
Basis for effect level:
histopathology: non-neoplastic
Key result
Dose descriptor:
NOAEL
Effect level:
ca. 500 mg/L drinking water
Based on:
test mat.
Sex:
male/female
Basis for effect level:
histopathology: non-neoplastic
Key result
Critical effects observed:
yes
Lowest effective dose / conc.:
1 000 mg/L drinking water
System:
urinary
Organ:
kidney
Treatment related:
yes
Dose response relationship:
yes
Relevant for humans:
yes

In both males and females, the total tungsten concentration in blood increased proportionally to the exposure concentration with no observed sex difference. The blood tungsten concentration in vehicle control animals was below the limit of detection (LOD; 0.0016 μg/g) of the assay. The urine tungsten concentration is presented as both μg/g of urine and after correcting for urinary creatinine concentrations (μg/mg creatinine). Low concentrations of tungsten were detected in urine from vehicle control male and female groups. The concentrations of creatinine-corrected tungsten in urine increased proportionally to the exposure concentration in both males and females and were significantly increased in all exposed groups compared to the corresponding vehicle control groups. As with blood, there was no observed sex difference in urinary tungsten concentrations.
The micronucleus assay was negative in rats. The Comet assay was positive in the liver of rats but negative in the blood and kidney.

Conclusions:
There were no early deaths during the 3-month study. When compared to the vehicle control group, final mean body weights were lower for the 1,000 and 2,000 mg/L males and 2,000 mg/L females. Water consumption was lower for the 1,000 and 2,000 mg/L males and females. The urine xanthine/creatinine ratios were significantly increased in all male and female exposed groups. Serum insulin concentrations were significantly decreased in the 2,000 mg/L males relative to the vehicle control males. Significantly decreased absolute weights were observed in several organs but were considered secondary to body weights reductions. Exposure-related histological lesions were limited to the kidneys and included increased incidences of renal tubule regeneration in the 1,000 and 2,000 mg/L males and females; the increases in the 2,000 mg/L groups were significant relative to the vehicle control group.
Executive summary:

No oral repeated dose toxicity data of sufficient quality are available for tungsten carbide (target substance). However, oral repeated dose toxicity data are available for sodium tungstate (source substance), which is used for read-across. Due to lower water solubility and lower toxicity for the target substance compared to the source substance, the resulting read-across from the source substance to the target substance is appropriate as a conservative estimate of potential toxicity for this endpoint. In addition, read-across is appropriate because the classification and labelling is more protective for the source substance than the target substance, the PBT/vPvB profile is the same, and the dose descriptors are, or are expected to be, lower for the source substance. For more details, refer to the tungstate read-across category approach in the Category section or Annex 3 in the CSR.

Endpoint:
sub-chronic toxicity: oral
Type of information:
read-across based on grouping of substances (category approach)
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
comparable to guideline study with acceptable restrictions
Justification for type of information:
REPORTING FORMAT FOR THE CATEGORY APPROACH

1. HYPOTHESIS FOR THE CATEGORY APPROACH: The hypothesis is that properties are likely to be similar or follow a similar pattern because of the presence of a common metal ion, in this case tungstate.
2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES):
Source: Sodium Tungstate
Target: Tungsten Carbide
3. CATEGORY APPROACH JUSTIFICATION: See Annex 3 in CSR
4. DATA MATRIX: See Annex 3 in CSR
Reason / purpose for cross-reference:
reference to same study
Reason / purpose for cross-reference:
read-across: supporting information
Qualifier:
equivalent or similar to guideline
Guideline:
EPA OPPTS 870.3100 (90-Day Oral Toxicity in Rodents)
GLP compliance:
yes
Limit test:
no
Species:
mouse
Strain:
B6C3F1
Sex:
male/female
Details on test animals or test system and environmental conditions:
Male and female B6C3F1/N mice were 4 to 5 weeks old upon receipt and were quarantined for 11 days before study start. Mice were randomly assigned to one of six exposure groups (n = 10 mice/sex/group).
Mice were housed individually (males) or five per cage (females). Feed and dosed water were available ad libitum. Water consumption was measured weekly for 3 months. Cages were changed at least once weekly (males) or twice weekly (females) and rotated every 2 weeks. Racks were changed and rotated every 2 weeks.
Route of administration:
oral: drinking water
Details on route of administration:
deionized drinking water
Vehicle:
water
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
Dose formulations were stable for 42 days at room temperature. Preadministration and postadministration (animal room) analyses of dose formulations were conducted monthly throughout the 3-month studies.ll preadministration formulations in the 3-month mouse studies were within 10% of the target concentration. In the 3-month mouse study, four postadministration samples were more than 10% below the target concentration, with the largest difference being 12.8% below the target. Three postadministration samples collected from carboys or bottles for the 125, 500, and 2,000 mg/L dose formulations in the 3-month rat study were 10.8% to 12.3% below the corresponding target concentration.
Duration of treatment / exposure:
90 days (3-months)
Frequency of treatment:
Daily
Dose / conc.:
0 mg/L drinking water
Dose / conc.:
125 mg/L drinking water
Remarks:
Average daily sodium tungstate dose of approximately 14 mg/kg/day for males and females.
Dose / conc.:
250 mg/L drinking water
Remarks:
Average daily sodium tungstate dose of approximately 27 mg/kg/day for males and 29 mg/kg/day for females.
Dose / conc.:
500 mg/L drinking water
Remarks:
Average daily sodium tungstate dose of approximately 57 mg/kg/day for males and 58 mg/kg/day for females.
Dose / conc.:
1 000 mg/L drinking water
Remarks:
Average daily sodium tungstate dose of approximately 108 mg/kg/day for males and 113 mg/kg/day for females.
Dose / conc.:
2 000 mg/L drinking water
Remarks:
Average daily sodium tungstate dose of approximately 212 mg/kg/day for males and 202 mg/kg/day females.
No. of animals per sex per dose:
Each group per sex per species contains five animals
Control animals:
yes, concurrent vehicle
Positive control:
Not applicable
Observations and examinations performed and frequency:
Animals are individually weighed on days one, seven, and at weekly periods thereafter. All animals are observed twice daily for clinical signs of declining health, or death. Animals found near death or showing clinical signs of pain or distress are humanely euthanized. Formal clinical observations are performed and recorded weekly. Food consumption/water consumption is measured and recorded weekly.

Clinical Laboratory Studies
Blood is collected from both sexes of "special study" rats, at days 4 ± 1 and 21 ± 2 and from the core study rats at the end of the study. These are processed for hematology and clinical chemistry determinations. Blood is collected from core study mice at the end of the study for hematology determinations. See clinical measurements:

1. Hematology:
Erythrocyte count
Mean corpuscular volume
Hemoglobin
Packed cell volume
Mean corpuscular hemoglobin
Mean corpuscular hemoglobin concentration
Erythrocyte morphologic assessment
Leukocyte count
Leukocyte differential
Reticulocyte count
Platelet count and morphologic assessment

2. Clinical Chemistry:
Sorbitol dehydrogenase (SDH)
Alkaline Phosphatase (ALP)
Creatine Kinase (CK)
Creatinine
Total Protein
Albumin
Urea Nitrogen (BUN)
Total Bile Acids
Alanine Aminotransferase (ALT)
Glucose
Cholesterol
Triglycerides
Sacrifice and pathology:
A complete gross necropsy is an external examination of the animal including body orifices and examination and fixation of all of the following organs/tissues from animals from all treatment groups for histopathologic examination.
Adrenal glands
Brain
Clitoral glands
Esophagus
Eyes
Femur
Gallbladder (mouse)
Gross lesions
Harderian glands
Heart and aorta
Intestine, large (cecum, colon, rectum)
Intestine, small (duodenum, jejunum, ileum)
Kidneys
Liver
Lungs and mainstem bronchi
mandibular and mesenteric
bronchial mediastinal (inhalation studies)
Mammary gland with adjacent skin
Muscle, thigh
Nerve, sciatic
Nasal cavity and nasal turbinates
Oral cavity, larynx, and pharynx
Ovaries
Pancreas
Parathyroid glands
Pituitary gland
Preputial glands
Prostate
Salivary glands
Seminal vesicles
Skin, site of application (dermal studies)
Spinal cord
Spleen
Stomach (forestomach and glandular)
Testes, epididymides, and vaginal tunics of testes
Thymus
Thyroid gland
Tissue masses
Tongue
Trachea
Urinary bladder
Uterus
Vagina
Zymbal glands

- A complete histopathologic evaluation inclusive of treatment-related gross lesions shall be done on all animals. Treatment-related lesions for target organs shall be identified and these organs plus gross lesions shall be examined to a no-effect level. TIssues examined:
Adrenal glands
Brain (3 sections including frontal cortex and basal ganglia, parietal cortex and thalamus, and cerebellum and pons)
Clitoral glands
Esophagus
Eyes
Femur, including diaphysis with marrow cavity and epiphysis (femoral condyle with epiphyseal cartilage plate, articular cartilage and articular surface)
Gallbladder (mouse)
Gross lesions
Harderian glands
Heart and aorta
Intestine, large (cecum, colon, rectum)
Intestine, small (duodenum, jejunum, ileum)
Kidneys
Larynx (inhalation studies)
Liver (2 sections including left lateral lobe and median lobe)
Lungs and mainstem bronchi
Lymph nodes
mandibular and mesenteric
bronchial & mediastinal (inhalation studies)
Mammary gland with adjacent skin
Muscle, thigh (only if neuromuscular signs were present)
Nasal cavity and nasal turbinates (3 sections)
Ovaries
Pancreas
Parathyroid glands
Pituitary gland
Preputial glands
Prostate
Salivary glands
Seminal vesicle
Skin, site of application (dermal studies)
Spinal cord and sciatic nerve (if neurologic signs were present)
Spleen
Stomach (forestomach and glandular)
Testes with epididymides
Thymus
Thyroid gland
Tissue masses
Trachea
Urinary bladder
Uterus
Other examinations:
Genotoxicity (micronucleus and Comet assay)
Clinical signs:
no effects observed
Mortality:
no mortality observed
Description (incidence):
There were no early deaths or exposure-related clinical observations in male or female B6C3F1/N mice exposed to sodium tungstate for 3 months
Body weight and weight changes:
effects observed, treatment-related
Description (incidence and severity):
Over the course of the study, group mean body weights were below 90% of the vehicle control group mean for the 250, 1,000, and 2,000 mg/L females and the 2,000 mg/L males. At study termination, the mean body weights of all exposed groups of males and females were within 10% of the vehicle control groups.
Food consumption and compound intake (if feeding study):
not specified
Food efficiency:
not specified
Water consumption and compound intake (if drinking water study):
effects observed, treatment-related
Description (incidence and severity):
Weekly mean water consumption was reduced slightly in the 1,000 mg/L male group (11%), the 2,000 mg/L males (16%), and the 2,000 mg/L females (11%), relative to the respective vehicle control groups
Ophthalmological findings:
not specified
Haematological findings:
effects observed, treatment-related
Description (incidence and severity):
In male mice, the white blood cell count was significantly decreased in the 1,000 and 2,000 mg/L groups relative to the vehicle control group (Table 36). These decreases were driven by a significant decrease in the lymphocyte count in the 1,000 and 2,000 mg/L groups and a significant decrease in the monocyte count in the 500 mg/L and higher groups. Additionally, the eosinophil counts were significantly decreased in all sodium tungstate-exposed male groups. These leukocyte changes are consistent with a stress leukogram (i.e., effects of chronic increase in endogenous corticosterone.
Clinical biochemistry findings:
not specified
Urinalysis findings:
not specified
Behaviour (functional findings):
not specified
Immunological findings:
not specified
Organ weight findings including organ / body weight ratios:
effects observed, treatment-related
Description (incidence and severity):
A higher group mean relative testis weight was observed in the 2,000 mg/L male group, relative to the vehicle control group, and was likely due to the lower mean body weights in that group. There were no histological lesions in the testes related to sodium tungstate exposure. In female mice, there were several sporadic increases in group mean organ weights, but they lacked an exposure concentration response or other supporting evidence that they represented anything but biological variation. Relative kidney weights were significantly increased in the 1,000 and 2,000 mg/L females and 2000 mg/L males but were most likely due to reduced mean body weights in those groups compared to the vehicle control group.
Gross pathological findings:
no effects observed
Description (incidence and severity):
No exposure-related gross lesions were recorded
Neuropathological findings:
not specified
Histopathological findings: non-neoplastic:
effects observed, treatment-related
Description (incidence and severity):
The only histological lesion associated with exposure was in the kidney. The incidences of renal tubule regeneration were higher in the 1,000 and 2,000 mg/L male and female groups compared to the respective vehicle control groups; the increases in the male groups were significant. The lesion consisted of hyperplastic tubules, predominantly in the deep cortical to medullary region, lined by epithelial cells with increased cytoplasmic basophilia, nuclear crowding, prominent nucleoli, marginated chromatin, and karyomegaly. There were occasional mitotic figures.
Histopathological findings: neoplastic:
no effects observed
Description (incidence and severity):
- No neoplasms were reported in exposed male or female mice.
Other effects:
no effects observed
Description (incidence and severity):
In male mice, no significant differences were observed between exposed groups and the vehicle control group in left testis weight, left epididymal weight, left cauda weight, or any of the sperm parameters, including number of sperm/mg cauda epididymis, total number sperm/cauda, sperm motility, number of homogenization-resistant spermatids/mg testis, and total number of spermatids. The testes and epididymides were evaluated to a no-effect level, and no histological findings associated with sodium tungstate exposure were present at 3 months. Under the conditions of this 3-month study, Sodium tungstate administration via drinking water did not exhibit the potential to be a reproductive toxicant in B6C3F1/N mice.

Key result
Dose descriptor:
LOAEL
Effect level:
ca. 1 000 mg/L drinking water
Based on:
test mat.
Sex:
male/female
Basis for effect level:
histopathology: non-neoplastic
Key result
Dose descriptor:
NOAEL
Effect level:
ca. 500 mg/L drinking water
Based on:
test mat.
Sex:
male/female
Basis for effect level:
histopathology: non-neoplastic
Key result
Critical effects observed:
yes
Lowest effective dose / conc.:
1 000 mg/L drinking water
System:
urinary
Organ:
kidney
Treatment related:
yes
Dose response relationship:
yes
Relevant for humans:
yes

Blood was collected from up to 10 animals per group on the morning of day 91. Total blood tungsten concentrations were determined using a validated analytical method. Tungsten was not detected in males in the vehicle control group above the LOD of the assay (0.0016 μg/g); however, low concentrations of tungsten were detected in females in the vehicle control group. In both males and females, the blood tungsten concentrations increased proportionally with the exposure concentration; there was no observed sex difference. In females, the tungsten concentrations in exposed groups were significantly higher than in the corresponding vehicle control group.


The micronucleus assay was negative in mice. The Comet assay was positive in the liver and ileum of male mice and negative in the blood and kidney of mice.

Conclusions:
Decreased water consumption was observed in 1000 (11%) and 2000 mg/L (16%) male mice. During the 13-week phase of the study, there was no effect on survival, hematology, or organ weights in mice. Renal tubule regeneration was characterized by hyperplasia of tubular epithelial cells with cytoplasmic basophilia, nuclear crowding, karyomegaly, and occasional mitotic figures. Total tungsten concentrations were generally dose proportional in blood and urine. The micronucleus assay was negative in mice. The Comet assay was positive in the liver and ileum of male mice and negative in the blood and kidney of mice. The kidney appeared to be the only major target organ following exposure of mice to sodium tungstate dihydrate at water concentrations of 1000 and 2000 mg/L.
Executive summary:

No oral repeated dose toxicity data of sufficient quality are available for tungsten carbide (target substance). However, oral repeated dose toxicity data are available for sodium tungstate (source substance), which is used for read-across. Due to lower water solubility and lower toxicity for the target substance compared to the source substance, the resulting read-across from the source substance to the target substance is appropriate as a conservative estimate of potential toxicity for this endpoint. In addition, read-across is appropriate because the classification and labelling is more protective for the source substance than the target substance, the PBT/vPvB profile is the same, and the dose descriptors are, or are expected to be, lower for the source substance. For more details, refer to the tungstate read-across category approach included in the Category section or Annex 3 in the CSR.

Endpoint:
sub-chronic toxicity: oral
Type of information:
read-across based on grouping of substances (category approach)
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Remarks:
Well documented, scientifically sound study that was conducted according to EPA OTS 798.2650 (90-Day Oral Toxicity in Rodents)
Justification for type of information:
1. HYPOTHESIS FOR THE CATEGORY APPROACH: The hypothesis is that properties are likely to be similar or follow a similar pattern because of the presence of a common metal ion, in this case tungstate.
2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES):
Source: Sodium tungstate
Target: Tungsten Carbide
3. CATEGORY APPROACH JUSTIFICATION: See Annex 3 in CSR
4. DATA MATRIX: See Annex 3 in CSR
Reason / purpose for cross-reference:
assessment report
Reason / purpose for cross-reference:
read-across: supporting information
Qualifier:
according to guideline
Guideline:
EPA OTS 798.2650 (90-Day Oral Toxicity in Rodents)
Deviations:
no
GLP compliance:
yes
Limit test:
no
Specific details on test material used for the study:
Sodium tungstate dihydrate (Tungstic acid sodium salt dihydrate, Na2WO42H2O, CAS # 10213-10-2, Batch # 12330JO) 99% pure
Species:
rat
Strain:
other: SD
Details on species / strain selection:
5-week-old SD rats were purchased from Charles River Laboratories, Raleigh, North Carolina
Sex:
male/female
Details on test animals or test system and environmental conditions:
Animals were held for 1 week in quarantine prior to initiation of treatments. At the start of testing, rats weighed between 199 and 230 g. Test animals were identified by individual cage cards and microchip implants and were individually housed in polycarbonate cages. Bedding was placed in the bottom of each cage and replaced twice weekly. Drinking quality water and a certified laboratory diet were available ad libitum. Animal rooms were maintained at 64 F to 79 F, with relative humidity of 30% to 70% and a 12-hour light–dark cycle.
Route of administration:
oral: drinking water
Details on route of administration:
Sodium tungstate dihydrate was solubilized with DI water to produce 4 dosing solutions
Vehicle:
water
Details on oral exposure:
The dose levels were selected on the basis of our previous studies where the highest dose used was 200 mg/kg/ d in a subchronic toxicity study. Sodium tungstate dihydrate was solubilized with DI water to produce 4 dosing solutions of 200, 125, 75, and 10 mg Na2WO4/mL.
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
Tungstate concentrations of the dosing solutions were verified by the Aberdeen Test Center and found to be consistent for purity and stability during the study period
Duration of treatment / exposure:
A 90-day oral toxicity study
Frequency of treatment:
Test chemical solutions were administered daily (7 days per week) for 90 days. A 16 GA 2-in stainless steel gavage needle
Dose / conc.:
10 mg/kg bw/day (actual dose received)
Dose / conc.:
75 mg/kg bw/day (actual dose received)
Dose / conc.:
125 mg/kg bw/day (actual dose received)
Dose / conc.:
200 mg/kg bw/day (actual dose received)
No. of animals per sex per dose:
Following 1-week quarantine/acclimatization period, 50 male and 50 female SD rats were randomly distributed
Control animals:
yes, concurrent vehicle
Details on study design:
Sodium tungstate dihydrate was solubilized with DI water to produce 4 dosing solutions of 200, 125, 75 and 10 mg Na2WO4/mL.
Observations and examinations performed and frequency:
A clinical examination was made for each animal prior to initiation of treatment and once weekly during treatment. Observations included but were not limited to changes in skin and fur, eyes, mucous membranes, occurrence of secretions and excretions, and autonomic activity (eg, lacrimation, piloerection, pupil size, and unusual respiratory pattern). Changes in gait, posture, and response to handling as well as the presence of clonic or tonic movements, stereotypes (eg, excessive grooming, repetitive circling), or bizarre behavior (eg, selfmutilation, walking backward) were recorded according to testing guidelines. Body and feeder weights were recorded on days .3, .1, 0 (first day of dosing), 7, and weekly thereafter. Doses were adjusted weekly to reflect the change in individual body weights. Animals were observed daily for any toxic signs.
Sacrifice and pathology:
Blood was collected. Each rat was then submitted for complete necropsy. The brain, heart, liver, kidneys, spleen, adrenals, thymus, epididymis/uterus, and testes/ovaries were removed and weighed for absolute organ weights. The tissues harvested for histopathological evaluation included the brain, pituitary, thyroid with parathyroid gland, thymus, lungs, trachea, heart, bone marrow, salivary gland, liver, spleen, kidney, adrenal gland, pancreas, testis, ovaries, uterus, aorta, esophagus, stomach, duodenum, jejunum, ileum, caecum, colon, urinary bladder, salivary lymph node peripheral nerve (siatic), thigh musculature (vastus lateralis), eye, spinal cord (3 levels), and exorbital lachrymal gland.

Hematology parameters included white blood cell count, neutrophils, lymphocytes, monocytes, eosinophils, basophils, red blood cell count, hemoglobin, hematocrit, mean cell volume, mean cell hemoglobin, mean cell hemoglobin concentration, red blood cell distribution width, platelets, and mean platelet volume.

Clinical chemistry parameters measured included The clinical chemistry analytes ialkaline phosphatase, alanine aminotransferase, aspartate aminotransferase, blood urea nitrogen, calcium, cholesterol, creatinine kinase, creatinine, glucose (GLU; nonfasting), lactate dehydrogenase, total bilirubin, total protein, triglycerides, Na, K, and Cl

Urinalysis included appearance, pH, specific gravity, GLU, bilirubin, urobilinogen, ketone, blood, protein, nitrite, and leukocytes.
Other examinations:
Ophthalmic examinations were performed on all control and treated animals prior to the scheduled start of the study and within a week of the scheduled 90-day necropsies. Urinalysis was also performed on 8 of 10 animals from all dose
groups (including negative control) within 2 weeks of the final (90-day) necropsies
Statistics:
Food consumption, body weights, and absolute organ weights were compared among dosage groups and controls using ANOVA. When significance was observed, the data were further analyzed using a Dunnett test to compare the doses to the control group. Statistical significance was defined at the P <05 level. Clinical chemistry, hematology, and urinalysis data were analyzed with ANOVA and Bonferroni post hoc test to compare dosage groups to the control group.
Clinical signs:
no effects observed
Description (incidence and severity):
- No evidence of overt toxicity and no treatment-related clinical signs were seen in any dose levels.
- Results showed that rats dosed with sodium tungstate in water for 90 consecutive days had no abnormal clinical signs at any of the dose levels
Mortality:
mortality observed, non-treatment-related
Description (incidence):
No unscheduled deaths (a single male rat in 200 mg/kg/d dose group was moribund and was euthanized on day 79; a few tissues from this rat were submitted for histopathological examination and death was determined to be not compound related
Body weight and weight changes:
effects observed, treatment-related
Description (incidence and severity):
There were significant decreases in food consumption in male rats at 200 mg/kg/d from weeks of 4 to 13, while there was no change in food consumption in female rats during the 90-day study
Food consumption and compound intake (if feeding study):
effects observed, treatment-related
Description (incidence and severity):
There were significant decreases in food consumption in male rats at 200 mg/kg/d from weeks of 4 to 13, while there was no change in food consumption in female rats during the 90-day study changes in female rats in any dose groups throughout study
period when compared to control rats.
Food efficiency:
not specified
Water consumption and compound intake (if drinking water study):
not specified
Ophthalmological findings:
no effects observed
Description (incidence and severity):
Ophthalmic examinations prior to study initiation and within
a week of the scheduled necropsies revealed no abnormalities
Haematological findings:
no effects observed
Description (incidence and severity):
Male and female rats showed no significant differences in any hematological parameters at any dose levels of sodium tungstate
Clinical biochemistry findings:
no effects observed
Description (incidence and severity):
The results of clinical chemistry parameters studied in rats showed no significant changes in any dose levels of sodium tungstate in rats. The parameters studied showed some changes in levels that were not dose related and insignificant and considered within normal range limits when compared to controls. All other parameters were found to be similar to control rats.

Urinalysis findings:
no effects observed
Description (incidence and severity):
Examination of urine samples taken approximately 1 week prior to necropsy revealed no significant changes in volume, specific gravity, or pH. No distinct dose-related trends were observed in GLU, bilirubin, ketone, blood, protein, urobilinogen,
nitrite, or leukocytes
Behaviour (functional findings):
no effects observed
Immunological findings:
not examined
Organ weight findings including organ / body weight ratios:
effects observed, treatment-related
Description (incidence and severity):
The body weights, absolute heart, liver, and thymus weights were significantly lower in male rats dosed at 200 mg/kg/d compared to control rat, but there were no effects on body weights and organ weights of female rats
Gross pathological findings:
not specified
Neuropathological findings:
not examined
Histopathological findings: non-neoplastic:
effects observed, treatment-related
Description (incidence and severity):
- Histopathology examination revealed effects on the urogenital system of the sodium tungstate-treated rats. Changes included mild to severe basophilia of renal cortical tubules in 1 of 9 and 10 of 10 males and 1 of 10 and 8 of 10 females in 2 high-dose
groups (125 and 200 mg/kg/d), respectively.
- Histopathological analysis of epididymides of rats dosed with sodium tungstate showed considerable effects in the high-dose group, Intraluminal cellular debris with and without hypospermia was noted in the epididymides of 3 of 10 males in the 200 mg/kg/d dose group. The lesion was not observed in the 10, 75, and 125 mg/kg/d dose groups.
- Histologic changes were also noted in the glandular stomach of males and females in high dosage groups. The changes included subacute inflammation consisting primarily of EOSs admixed with fewer mononuclear cells observed throughout the submucosa of 5 of 9, 4 of 10 males, and 8 of 10, 9 of 10 females in, 125 and 200 mg/kg/d dosage groups, respectively. Goblet cell metaplasia was also observed in the mucosa of the glandular stomach 8 of 9, 8 of 10 males and 8 of 10, 10 of 10
females of 125 and 200 mg/kg/d dosage groups, respectively. The gastric histologic findings in the lower dosed group were negative when compared to 2 high-dose groups
Histopathological findings: neoplastic:
no effects observed
Key result
Dose descriptor:
BMDL10
Effect level:
102 mg/kg bw/day (actual dose received)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
histopathology: non-neoplastic
Key result
Dose descriptor:
NOAEL
Effect level:
75 mg/kg bw/day (actual dose received)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
histopathology: non-neoplastic
Key result
Dose descriptor:
LOAEL
Effect level:
125 mg/kg bw/day (actual dose received)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
histopathology: non-neoplastic
Dose descriptor:
LOAEL
Effect level:
175 mg/kg bw/day (actual dose received)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
histopathology: non-neoplastic
Key result
Dose descriptor:
LOAEL
Effect level:
200 mg/kg bw/day (actual dose received)
Based on:
test mat.
Sex:
male
Basis for effect level:
food consumption and compound intake
Key result
Dose descriptor:
LOAEL
Effect level:
200 mg/kg bw/day (actual dose received)
Based on:
test mat.
Sex:
male
Basis for effect level:
body weight and weight gain
Key result
Dose descriptor:
NOAEL
Effect level:
200 mg/kg bw/day (actual dose received)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
clinical signs
haematology
Key result
Dose descriptor:
LOAEL
Effect level:
200 mg/kg bw/day (actual dose received)
Based on:
test mat.
Sex:
male
Basis for effect level:
histopathology: non-neoplastic
Key result
Critical effects observed:
yes
Lowest effective dose / conc.:
125 mg/kg bw/day (actual dose received)
System:
urinary
Organ:
kidney
Treatment related:
yes
Dose response relationship:
yes
Relevant for humans:
yes
Conclusions:
Subchronic toxicity of sodium tungstate was assessed in in male and female Sprague-Dawley rats by daily oral gavage of 0, 10, 75, 125, or 200 mg/kg/d for 90 days. There was a significant decrease in food consumption and body weight gain in males at 200 mg/kg/d from days 77 to 90; however, there was no effect in food consumption and body weights in females. There were no changes in the hematological and clinical parameters studied. Histopathological changes were seen in kidney of male and female and epididymis of male rats. Histopathological changes were observed in the kidneys of male and female rats dosed at 125 or 200 mg/k/d consisting of mild to severe cortical tubule basophilia in 2 high-dose groups. Histological changes in epididymides included intraluminal hypospermia with cell debris in the 200 mg/kg/d dosed male rats. Histopathological changes were observed in the glandular stomach including inflammation and metaplasia in the high-dose groups (125 or 200 mg/kg/d) of both sexes of rats. Based on histopathology effects seen in the kidneys, the lowest observable adverse effect level was 125 mg/kg/d and the no observable adverse effect level was 75 mg/kg/d in both sexes of rats for oral subchronic toxicity.
Executive summary:

No oral repeated dose toxicity data of sufficient quality are available for tungsten carbide (target substance). However, oral repeated dose toxicity data are available for sodium tungstate (source substance), which are used for read-across. Due to lower water solubility and lower toxicity for the target substance compared to the source substance, the resulting read-across from the source substance to the target substance is appropriate as a conservative estimate of potential toxicity for this endpoint. In addition, read-across is appropriate because the classification and labelling is more protective for the source substance than the target substance, the PBT/vPvB profile is the same, and the dose descriptors are, or are expected to be, lower for the source substance. For more details, refer to the tungstate read-across category approach in the Category section or Annex 3 in the CSR.

Endpoint:
short-term repeated dose toxicity: oral
Type of information:
read-across based on grouping of substances (category approach)
Adequacy of study:
other information
Study period:
Experiment start date (Animal arrival): 02 April 2015 - Completion date of experimental phase (Last day of necropsy): 27 April 2015
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment
Justification for type of information:
1. HYPOTHESIS FOR THE CATEGORY APPROACH: The hypothesis is that properties are likely to be similar or follow a similar pattern because of the presence of a common metal ion, in this case tungstate.
2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES):
Source: Sodium tungstate
Target: Tungsten Carbide
3. CATEGORY APPROACH JUSTIFICATION: See Annex 3 in CSR
4. DATA MATRIX: See Annex 3 in CSR
Reason / purpose for cross-reference:
read-across: supporting information
Qualifier:
no guideline required
Principles of method if other than guideline:
The objective of this study was to establish the maximum tolerated dose of the test item, Sodium Tungstate, in the non-pregnant female New Zealand White rabbit before conducting a preliminary study in mated females and a main developmental toxicity study.
GLP compliance:
no
Limit test:
no
Specific details on test material used for the study:
SOURCE OF TEST MATERIAL
- Source and lot/batch No.of test material: 2214
- Expiration date of the lot/batch: 01 March 2017

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: Test item formulations at concentrations of 0.5 mg/mL to 50 mg/mL in vehicle have been shown to be stable for up to seven days at room temperature, when stored refrigerated and when frozen (approximately -80 ºC).
Species:
rabbit
Strain:
New Zealand White
Details on species / strain selection:
The rabbit is the commonly used non-rodent species for developmental toxicity testing and is acceptable to regulatory authorities. The New Zealand White rabbit is sensitive to a number of known teratogens and Sequani have experience in the use of this species in embryo-foetal development studies.
Sex:
female
Details on test animals or test system and environmental conditions:
TEST ANIMALS
- Source: Covance Research Products Inc., 310 Swampbridge Road, Denver, PA 17517, USA
- Age at study initiation: The animals were approximately 5 months of age on arrival and on examination were found to be healthy.
- Weight at study initiation: On the first day of dosing they weighed 3.04 to 3.77 g.
- Housing: The animals were housed individually in perforated-floor cages suspended over paper-lined trays.
- Diet (e.g. ad libitum): A pelleted diet, STANRAB (P) SQC supplied by Special Diet Services (SDS) were freely available.
- Water (e.g. ad libitum): tap water was freely available
- Acclimation period: After at least seven days acclimatisation they were re-examined and confirmed to be suitable for use.

ENVIRONMENTAL CONDITIONS
- Temperature (°C): The target range for temperature was 16 °C to 20 °C. Recorded values were within these limits.
- Humidity (%): Humidity was not controlled but was recorded.
- Air changes (per hr): Room was air-conditioned
- Photoperiod (hrs dark / hrs light): The study room was illuminated by fluorescent light set to give a cycle of 12 hours light and 12 hours dark.

IN-LIFE DATES: From: 02 April 2015 To: 27 April 2015
Route of administration:
oral: gavage
Vehicle:
water
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
All test item formulations were analysed to assess achieved concentrations of sodium tungstate, using method C003-MP0023
Duration of treatment / exposure:
Seven consecutive days
Frequency of treatment:
Daily
Dose / conc.:
0 mg/kg bw/day (actual dose received)
Dose / conc.:
50 mg/kg bw/day (actual dose received)
Dose / conc.:
100 mg/kg bw/day (actual dose received)
Dose / conc.:
200 mg/kg bw/day (actual dose received)
Dose / conc.:
300 mg/kg bw/day (actual dose received)
No. of animals per sex per dose:
Two-females per group
Control animals:
yes, concurrent vehicle
Details on study design:
- Dose selection rationale:
- Rationale for animal assignment (if not random): Females were allocated arbitrarily to dose groups on arrival.
Observations and examinations performed and frequency:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: Animals were examined twice daily for mortality and morbidity.

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: Animals given a detailed clinical examination daily from the start of dosing.

BODY WEIGHT: Yes
- Time schedule for examinations: Body weights were recorded daily for five days before the start of dosing, and then daily until necropsy.

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study):
- Individual food intake was recorded daily for five days before the start of dosing, and then daily until necropsy.
Sacrifice and pathology:
GROSS PATHOLOGY: Yes

All surviving animals were killed by an intravenous overdose injection of sodium pentobarbitone and subjected to necropsy. Animals in Groups 2, 3 and 4 were killed on Day 8 of dosing and the surviving Group 5 animal was killed on Day 4 of dosing. The thoracic and abdominal cavities were opened by a ventral, mid-line incision and the major organs were examined. Organs or tissues showing macroscopic abnormalities were removed and retained in neutral buffered formaldehyde.
Clinical signs:
no effects observed
Description (incidence and severity):
No treatment-related clinical signs observed at 50, 100 or 200 mg/kg/day. Female 19, given 200 mg/kg/day, had reduced/no faeces during the treatment period, although this had been present for some of the pre-dose period; this was considered to be related to the minimal food intake recorded for this female, a likely cause of the red areas on the pyloric mucosa of the stomach, observed at necropsy.
Mortality:
no mortality observed
Description (incidence):
Female 130 (300 mg/kg/day) was found dead before dosing on Day 4 and the other female in this group (140) showed marked clinical signs on this day (most notably prostration, laboured breathing and coldness to the touch), and so was killed for humane reasons without receiving a fourth dose. Both decedents had shown inappetance and weight loss. There were no deaths related clinical signs observed at 50, 100 or 200 mg/kg/day.
Body weight and weight changes:
effects observed, treatment-related
Description (incidence and severity):
Animals given 200 mg/kg/day lost weight progressively from the start of treatment. Animals given 100 mg/kg/day showed some fluctuation in weight but remained above their Day -1 weight up to and including Day 7, with a subsequent dip on Day 8 being attributed to blood sampling on Day 7. Body weight gain at 50 mg/kg/day was comparable to that of Controls.
Food consumption and compound intake (if feeding study):
effects observed, treatment-related
Description (incidence and severity):
Female 19 (200 mg/kg/day) ate virtually none (6 g/day or less) of the pelleted diet from the onset of treatment and the other female given this dosage typically ate less than half of its pre-dose intake of pelleted diet. There was no effect of treatment with sodium tungstate on food intake at 100 or 50 mg/kg/day.
Food efficiency:
not specified
Water consumption and compound intake (if drinking water study):
not specified
Ophthalmological findings:
not specified
Haematological findings:
not specified
Clinical biochemistry findings:
not specified
Urinalysis findings:
not specified
Behaviour (functional findings):
not specified
Immunological findings:
not specified
Organ weight findings including organ / body weight ratios:
not specified
Gross pathological findings:
not specified
Description (incidence and severity):
Female 19 (200 mg/kg/day) had red areas on the pyloric mucosa of the stomach. There were no macroscopic changes for the remaining female at this dose, or for females given 100 or 50 mg/kg/day. At necropsy, Female 130 was moderately autolysed and Female 140 had a pale liver and red areas on the fundic mucosa of the stomach
Neuropathological findings:
not specified
Histopathological findings: non-neoplastic:
not specified
Histopathological findings: neoplastic:
not specified
Other effects:
not specified
Key result
Dose descriptor:
LOAEL
Effect level:
200 mg/kg bw/day (actual dose received)
Based on:
test mat.
Sex:
female
Basis for effect level:
body weight and weight gain
Key result
Dose descriptor:
NOAEL
Effect level:
100 mg/kg bw/day (actual dose received)
Based on:
test mat.
Sex:
female
Basis for effect level:
body weight and weight gain
Conclusions:
Death at 300 mg/kg/day and progressive weight loss at 200 mg/kg/day suggested that the maximum tolerated oral dose of sodium tungstate in the non-pregnant rabbit was less than 200 mg/kg/day. Doses of 100 or 50 mg/kg/day were generally well tolerated with only small fluctuations in body weight. A high dose level between 100 and 200 mg/kg/day is concluded to be appropriate for the subsequent dose-range finding study in the pregnant rabbit.
Executive summary:

No oral repeated dose toxicity data of sufficient quality are available for tungsten carbide (target substance). However, fertility toxicity data are available for sodium tungstate (source substance), which are used for read-across. Due to lower water solubility and lower toxicity for the target substance compared to the source substance, the resulting read-across from the source substance to the target substance is appropriate as a conservative estimate of potential toxicity for this endpoint. In addition, read-across is appropriate because the classification and labelling is more protective for the source substance than the target substance, the PBT/vPvB profile is the same, and the dose descriptors are, or are expected to be, lower for the source substance. For more details, refer to the read-across category approach included in the Category section or Annex 3 in the CSR.

Endpoint:
sub-chronic toxicity: oral
Type of information:
read-across based on grouping of substances (category approach)
Adequacy of study:
key study
Study period:
no data
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Remarks:
Well documented, scientifically sound study that was conducted according to EPA OTS 798.2650 (90-Day Oral Toxicity in Rodents)
Justification for type of information:
1. HYPOTHESIS FOR THE CATEGORY APPROACH: The hypothesis is that properties are likely to be similar or follow a similar pattern because of the presence of a common metal ion, in this case tungstate.
2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES):
Source: Sodium tungstate
Target: Tungsten Carbide
3. CATEGORY APPROACH JUSTIFICATION: See Annex 3 in CSR
4. DATA MATRIX: See Annex 3 in CSR
Reason / purpose for cross-reference:
reference to same study
Reason / purpose for cross-reference:
read-across: supporting information
Qualifier:
according to guideline
Guideline:
EPA OTS 798.2650 (90-Day Oral Toxicity in Rodents)
Qualifier:
equivalent or similar to guideline
Guideline:
OECD Guideline 408 (Repeated Dose 90-Day Oral Toxicity Study in Rodents)
GLP compliance:
yes
Limit test:
no
Species:
rat
Strain:
Sprague-Dawley
Sex:
male/female
Details on test animals or test system and environmental conditions:
TEST ANIMALS
- Source: Purchased from Charles River Laboratories, Raleigh, NC
- Age at study initiation: 5 weeks
- Weight at study initiation: about 150 grams when received 199-230 grams at the start of testing)
- Housing: individually housed in polycarbonate cages
- Diet: Harlan Teklad, 8728C Certified Rodent Diet, ad libitum
- Water: ad libitum
- Acclimation period: 1 week


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 17-26°C (64-79 °F)
- Humidity (%): 30-70
- Photoperiod (hrs dark / hrs light): The light/dark cycle was a 12-hour interval


IN-LIFE DATES: From: no data To: no data
Route of administration:
oral: gavage
Vehicle:
water
Details on oral exposure:
PREPARATION OF DOSING SOLUTIONS: Sodium tungstate dihydrate was solubilized with deionized (DI) water to produce four dosing solutions of 200, 125, 75, and 10 mg Na2WO4 /mL. This was achieved by placing 224.5, 140.35, 84.20, and 11.23 grams of sodium tungstate dihydrate into 1000 mL volumetric flasks and adding DI water to obtain 1000 mL of solution. Aliquots of test solutions were analyzed for purity and stability by the Aberdeen Test Center and found to be consistent for the purity and stable during the period of studies.

A 90-day stability study on a single suspension of sodium tungstate in DI water was initiated prior to beginning the ALD. This solution was sampled and analyzed weekly for a period of approximately 90 calendar days to ensure that the dosing solutions would remain stable throughout the 90-day study.

Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
Each batch of solutions that was mixed was sampled and analyzed to verify the concentrations prior to use.
Duration of treatment / exposure:
90 days (91 calendar days)
Frequency of treatment:
Tungstate or control solutions were administered daily (7 days per week, total of 90 doses)
Dose / conc.:
10 mg/kg bw/day (actual dose received)
Dose / conc.:
75 mg/kg bw/day (actual dose received)
Dose / conc.:
125 mg/kg bw/day (actual dose received)
Dose / conc.:
200 mg/kg bw/day (actual dose received)
No. of animals per sex per dose:
10 animals/sex/dose
Control animals:
yes, concurrent vehicle
Details on study design:
- Dose selection rationale: Based on previous studies;
- Rationale for animal assignment: Randomly distributed using the LABCAT Randomization Program into four treatment groups and one control group.
Positive control:
no
Observations and examinations performed and frequency:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule:
- Cage side observations included but were not limited to changes in skin and fur, eyes, mucous membranes, occurrence of secretions and excretions, and autonomic activity (eg lacrimation, 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 (eg excessive grooming, repetitive circling) or bizarre behavior (eg self-mutilation, walking backwards), were recorded. Records indicated time of onset, degree, and duration of all signs. A scoring system for observations explicitly defined by the USACHPPM Toxicity Evaluation Program was used.

- Animals were observed daily for toxic signs.


DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: A careful clinical examination was made for each animal prior to initiation of treatment and once weekly during treatment of animals.

BODY WEIGHT: Yes
- Time schedule for examinations: recorded on days -3, -1, 0 (first day of dosing), 7, and weekly thereafter.


FOOD CONSUMPTION AND COMPOUND INTAKE:
- Compound intake calculated as time-weighted averages from the consumption and body weight gain data: 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): No


OPHTHALMOSCOPIC EXAMINATION: Yes
- Time schedule for examinations: Ophthalmic examinations were performed prior to the scheduled start of the 90-day study and within a week of the scheduled necropsies.
- Dose groups that were examined: performed on all control and treated animals


HAEMATOLOGY: Yes
- Time schedule for collection of blood: At the end of the 90 days, before the rats were euthanized
- Anaesthetic used for blood collection: No data
- Animals fasted: No data
- How many animals: all animals
- Parameters examined include white blood cell count (WBC), WBC differential (% neutrophils (NEU %N), % lymphocytes (LYM %L), % monocytes (MONO %M), % eosinophils (EOS %E), % basophils (BASO %B), red blood cell count (RBC), hemoglobin (HGB), hematocrit (HCT), mean cell volume (MCV), mean cell hemoglobin (MCH), mean cell hemoglobin concentration (MCHC), red blood cell distribution width (RDW), platelets (PLT), and mean platelet volume (MPV). Blood Coagulation, average prothombin time (AVG PT) and average activated prothombin time (AVG APTT) were analyzed by using MCA 210 Microsample Coagulation Analyzer™ (BioData Corporation, Horsham, Pennsylvania).


CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: At the end of the 90 days, before the rats were euthanized
- Animals fasted: No data
- How many animals: all animals
- The clinical chemistry analytes included: alkaline phosphatase (ALK P), alanine aminotransferase (ALT), aspartate aminotransferase (AST), blood urea nitrogen (BUN), calcium (Ca), cholesterol (CHOL), creatinine kinase (CK), creatinine (CREA), glucose (non-fasting) (GLU), lactate dehydrogenase (LDH), total bilirubin (TBIL), total protein (TP), triglycerides (TRIG), sodium (Na), potassium (K), and chloride (Cl).


URINALYSIS: Yes
- Time schedule for collection of urine: Performed on 8 out of 10 animals from all dose groups (including negative control) within 2 weeks of the final (90-day) necropsies
- Metabolism cages used for collection of urine: No data
- Animals fasted: No data
- Urinalysis was conducted by measuring volume, color, appearance, pH, specific gravity, glucose, bilirubin, urobilinogen, ketone, blood, protein, nitrite, and leukocytes.


NEUROBEHAVIOURAL EXAMINATION: No


OTHER: The brain, heart, liver, kidneys, spleen, adrenals, thymus, epididymides/uterus, and testes/ovaries were removed and weighed for absolute organ weights, organ-to-body weight ratios, and organ-to-brain weight ratios.
Sacrifice and pathology:
GROSS PATHOLOGY: Yes
HISTOPATHOLOGY: Yes; The tissues harvested for histopathological evaluation included the brain, pituitary, thyroid w/ parathyroid, thymus, lungs, trachea, heart, bone marrow, salivary gland, liver, spleen, kidney, adrenal, pancreas, gonads, uterus, aorta, esophagus, stomach, duodenum, jejunum, ileum, caecum, colon, urinary bladder, lymph node, peripheral nerve, thigh musculature, eye, spinal cord (three levels), and exorbital lachrymal gland.

Following fixation, complete tissues from the control, 125 and 200 mg/kg/day group males and females were trimmed, embedded in paraffin, sectioned at 5 microns, stained with hematoxylin and eosin, and examined via routine light microscopy. Additionally, kidney sections from all animals in the 10 and 75 mg/kg/day dosage groups and all gross lesions were similarly processed. The microscopic sections were of adequate size and quality to allow critical histologic evaluation.
Statistics:
Data from each treatment group were statistically compared to controls using a two-factor ANOVA with sex and dose and sex by dose interaction. When significance was observed, the data were further analyzed using a Dunnett's test to compare the doses to the 0 mg/kg dose. A one-factor ANOVA for each sex was used to see dose differences. Again, a Dunnett's test was used to compare the doses to the control. If a normality test failed, the data were subjected to a log transformation prior to performing ANOVA. If the normality test failed again after the data were transformed, ANOVA on ranks (Kruskal-Wallis test) was performed. Statistical significance was defined at the p< 0.05 level.

Food consumption, body weights, organ-to-brain weight ratios and organ-to-body weight ratios were compared among dosage groups and controls using a one-way analysis of variance (ANOVA) and, if statistical significance was found, Dunnett's post hoc test was used to compare dosage groups to the control group. The parameters were collected with the LABCAT system and statistically analyzed using Sigma-Stat (Sigma-Stat, Jandel Scientific, Corte Madera, CA). Clinical chemistry, hematology, and urinalysis data were entered into Sigma-Stat using a one- way ANOVA and Bonferroni's post hoc test to compare dosage groups to the control group. Where a normality test had failed after the data had been log transformed, an ANOVA on ranks was performed.
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:
no effects observed
Clinical biochemistry findings:
no effects observed
Urinalysis findings:
no effects observed
Behaviour (functional findings):
not examined
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
Histopathological findings: neoplastic:
not examined
Details on results:
CLINICAL SIGNS AND MORTALITY
The rats showed no overt toxic or clinical signs during the study


BODY WEIGHT AND WEIGHT GAIN
Significant differences between males and females in overall mean body weights were observed for all days except Day 0. No significant differences between treatment groups (10, 75, 125 and 200 mg/kg/day) in mean body weight were observed for females. However, significant treatment group differences in mean body weight were observed for males on Days 70, 77, 84 and 90. The cntrol group had significantly different mean body weights from the 200 mg/kg group on Days 77, 84 and 90. The 10 mg/kg group had significantly different mean body weights from the 200 mg/kg group on Days 70, 77, 84 and 90. The 75 mg/kg group had significantly different mean body weight from the 200 mg/kg group on Day 77.

The decrease seen was primarily due to significant decreases in liver, heart, testes and epididymis weights of male animals given 200 mg/kg sodium tungstate. This was strongly correlated with a decrease in food consumption in these animals.


FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study)
The decrease in body weight was strongly correlated with a decrease in food consumption in these animals.

OPHTHALMOSCOPIC EXAMINATION
All observations prior to study initiation were within normal limits. Observations taken within a week of the scheduled necropsies revealed no abnormalities.


HAEMATOLOGY
No significant dose related adverse alterations were observed for hematological parameters for any treatment group.

Significant differences between sexes were observed for WBC, basophils, RBC, MCV, MCH, and RDW. For MCV, MCH and RDW, the females had greater values than the males and for WBC, basophils and RBC the males had greater values than the female. No significant sex by dose interactions or dose group differences were observed.


CLINICAL CHEMISTRY
Since the males and females showed some significant differences in clinical chemistries and there were also significant sex by dose interactions, comparison of dose groups was conducted for males and females separately. For males only, a significant difference between dose groups was observed for creatinine, the 75 mg/kg dose group (0.32±0.02 mg/dL) was significantly less than the 200 mg/kg dose group (0.40±0.02 mg/dL). For females only, significant differences between dose groups were observed for glucose, sodium and chloride. The mean glucose for the 75 mg/kg group (188.8±5.09 mg/dL) was significantly greater than the control group (161.3±6.58 mg/dL). This was also greater than the biological range of 120-186 mg/dL. The mean sodium for the 10 mg/kg group (148±0.27 mmol/L) was significantly greater than the 200 mg/kg group (146±0.38 mmol/L). The mean chloride for the 125 mg/kg group (107±0.47 mmol/L) was significantly greater than the 200 mg/kg group (106±0.37 mmol/L). Sodium and chloride values for all groups, however were within the biological range of 141-148 mmol/l and 101-108 mmol/L, respectively, for Sprague-Dawley rats.

URINALYSIS
Examination of urine samples taken approximately 1 week prior to necropsy revealed no significant changes in volume, specific gravity or pH. No distinct dose-related trends were observed in glucose, bilirubin, ketone, blood, protein, urobilinogen, nitrite, or leukocytes.

ORGAN WEIGHTS
Females given 200 mg/kg had increases in kidney and spleen weight. Histopathology indicated an increase in renal tubular regeneration at this dosage level which may have been responsible for the increase in kidney weight. Most metals were excreted through renal clearance and gastrointestinal excretion. Renal effects are common with heavy metals and this finding was not unexpected.

GROSS PATHOLOGY
Individual animal necropsy observations were reviewed at the time of histologic examination. All macroscopic changes were considered to be spontaneous and/or incidental in nature and unrelated to test article exposure. All tissues evaluated showed no treatment related effects.

HISTOPATHOLOGY: NON-NEOPLASTIC
Individual animal necropsy observations were reviewed at the time of histologic examination. All macroscopic changes were considered to be spontaneous and/or incidental in nature and unrelated to test article exposure.

Following fixation, complete tissues (brain, pituitary, thyroid w/parathyroid, thymus, lungs, trachea, heart, bone marrow, salivary gland, liver, spleen, kidney, adrenal, pancreas, gonads, uterus, aorta, esophagus, stomach, duodenum, jejunum, ileum, caecum, colon, urinary bladder, lymph node, peripheral nerve, thigh musculature, eye, spinal cord (three levels), and exorbital lachrymal gland) from the control, and two high dose groups (125 and 200 mg/kg/day) males and females were trimmed, embedded in paraffin, sectioned at 5 microns, stained with hematoxylin and eosin, and examined via routine light microscopy. Additionally, kidney sections and target tissues (stomach and epididymides) from all animals in the 10 and 75 mg/kg/day dosage groups and all gross lesions were similarly processed. The microscopic sections were of adequate size and quality to allow critical histologic evaluation.

Rats dosed with sodium tungstate showed considerable histopathological changes in the kidneys of male and female rats. Mild to severe regeneration of renal cortical tubules was noted in 1/9 and 10/10 males and 1/10 and 8/10 females in the 125 and 200 mg/kg/day dosage groups, respectively. For clarity, basophilic tubular profiles bearing thickened basement membranes were diagnosed as chronic progressive nephropathy, and in all affected animals, this lesion was minimal and widely scattered throughout the cortex; incidence was similar between control and test article-treated groups, with males more commonly affected than females.

Some histologic findings were noted in the glandular stomach of males and females in all dosage groups. Subacute inflammation consisting primarily of eosinophils admixed with fewer mononuclear cells was observed throughout the submucosa of 2/10, 1/10, 5/9, 4/10 males and 0/10, 1/10, 8/10, 9/10 females in the 10, 75, 125 and 200 mg/kg/day dosage groups, respectively. Goblet cell metaplasia was also observed throughout the mucosa of the glandular stomach in 1/10, 4/10, 8/9, 8/10 males and 0/10, 4/10, 8/10, 10/10 females in the 10, 75, 125 and 200 mg/kg/day dosage groups, respectively.

Histopathologial analysis of epidydimis of male rats dosed with sodium tungstate showed considerable effects at high dose group. Cellular debris within the lumen with and without hypospermia was noted in the epididymides of 3/10 males in the 200 mg/kg/day dosage group. A single male in the 10 mg/kg/day group exhibited a similar lesion; however, the finding in this individual was minimal and unilateral, likely a spontaneous occurrence, and was considered to be unrelated to test article exposure. The lesion was not observed in 75 and 125 mg/kg/day group males.

Although tubular regeneration could be identified within the kidneys of control group animals as well as rats in the 10 and 75 mg/kg/day dosage groups, affected tubules were rare to few and minimally affected; this was considered to be consistent with spontaneous nephropathy syndrome.

Luminal cellular debris was observed in the epididymis of three rats from the 200 mg/kg group. Epididymal changes of this type are commonly encountered as rats reach sexual maturity, and were presumed to represent degenerative cells that were released from the testis. However, rats in the present study should have reached sexual maturity before the time of necropsy. It was interesting to note that two of the rats with the most pronounced epididymal luminal cell debris were found dead or moribund sacrifice rats that died on days 55 and 56, respectively, rather than the scheduled terminal necropsy on study days 90-91. The epididymis of one animal had luminal cell debris that was limited to the tail region, suggesting some transient event that resulted in release of degenerative cells from the testis or epididymis for a defined period of time. There were no identifiable testicular lesions that would explain the presence of degenerated cells in the lumen of the epididymis.
Key result
Dose descriptor:
BMDL10
Effect level:
102 mg/kg bw/day (actual dose received)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
histopathology: non-neoplastic
Key result
Dose descriptor:
NOAEL
Effect level:
75 mg/kg bw/day (actual dose received)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
histopathology: non-neoplastic
Key result
Dose descriptor:
LOAEL
Effect level:
125 mg/kg bw/day (actual dose received)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
histopathology: non-neoplastic
Key result
Critical effects observed:
yes
Lowest effective dose / conc.:
125 mg/kg bw/day (actual dose received)
System:
urinary
Organ:
kidney
Treatment related:
yes
Dose response relationship:
yes
Relevant for humans:
yes
Conclusions:
Sodium tungstate administered orally to male and female Sprague-Dawley rats by gavage for 90 consecutive days induced a number of statistically significant alterations in weights at 200 mg/kg. The administration of sodium tungstate at 125 and 200 mg/kg to male and female Sprague-Dawley rats via oral gavage for 90 consecutive days resulted in pronounced renal changes, specifically mild to severe regeneration of renal cortical tubules. The LOAEL in male and female rats = 125 mg/kg and the NOAEL in male and female rats = 75 mg/kg.
Executive summary:

No oral repeated dose toxicity data of sufficient quality are available for tungsten carbide (target substance). However, oral repeated dose toxicity data are available for sodium tungstate (source substance), which are used for read-across. Due to lower water solubility and lower toxicity for the target substance compared to the source substance, the resulting read-across from the source substance to the target substance is appropriate as a conservative estimate of potential toxicity for this endpoint. In addition, read-across is appropriate because the classification and labelling is more protective for the source substance than the target substance, the PBT/vPvB profile is the same, and the dose descriptors are, or are expected to be, lower for the source substance. For more details, refer to the tungstate read-across category approach in the Category section or Annex 3 in the CSR.

Endpoint conclusion
Endpoint conclusion:
adverse effect observed
Dose descriptor:
BMDL10
102 mg/kg bw/day
Study duration:
subchronic
Species:
rat
Quality of whole database:
The reliability of this study for the substance tested is a K1
System:
urinary
Organ:
kidney

Repeated dose toxicity: inhalation - systemic effects

Link to relevant study records

Referenceopen allclose all

Endpoint:
short-term repeated dose toxicity: inhalation
Type of information:
read-across based on grouping of substances (category approach)
Adequacy of study:
key study
Study period:
2010-08-31 to 2010-01-29
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Remarks:
The reliability of this study for the substance tested is a K1, but in application of read-across to a different substance ECHA’s guidance specifies that the score can be a maximum of K2. Due to higher water solubility and greater in vitro bioaccessibility in synthetic alveolar, lysosomal, and interstitial fluids simulating inhalation exposure for the source substance (TBO) as compared to the target substance (tungsten carbide) and lack of toxicity from acute toxicity studies for the target and source substances, toxicity data on the source substance is expected to represent a worse case, so read-across is appropriate between these substances. In addition, read-across is appropriate for this endpoint because the classification and labelling for human health toxicity endpoints is the same for the source and target substances, the PBT/vPvB profile is the same, and the dose descriptors are, or are expected to be, sufficiently similar or lower for the source substance. For more details, refer to the attached description of the read-across approach.
Justification for type of information:
1. HYPOTHESIS FOR THE CATEGORY APPROACH: The hypothesis is that properties are likely to be similar or follow a similar pattern because of the presence of a common metal ion, in this case tungstate.
2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES):
Source: Tungsten Oxide
Target: Tungsten Carbide
3. CATEGORY APPROACH JUSTIFICATION: See Annex 3 in CSR
4. DATA MATRIX: See Annex 3 in CSR
Reason / purpose for cross-reference:
reference to same study
Reason / purpose for cross-reference:
read-across: supporting information
Qualifier:
according to guideline
Guideline:
OECD Guideline 412 (Subacute Inhalation Toxicity: 28-Day Study)
GLP compliance:
yes
Limit test:
no
Species:
rat
Strain:
Sprague-Dawley
Sex:
male/female
Details on test animals or test system and environmental conditions:
TEST ANIMALS
- Source: Charles River Laboratories, (St. Constant, Canada)
- Age at study initiation: approximately 8 weeks
- Weight at study initiation: One day following receipt, body weight ranges of the first shipment of rats 226 to 279 g (males) and 146 to 173 g (females). One day following receipt, body weight range of the second shipment of male rats was 207 to 234 g.
- Fasting period before study: no food or water was provided during exposures.
- Housing: At the start of food consumption measurements, the rats were individually housed in clear polycarbonate rodent cages (Allentown Caging Equipment Co., Allentown, NJ).
-Diet: Certified Rodent Chow 5002 meal (PMI Nutrition International, Inc., Brentwood, MO) was provided ad libitum, except during inhalation exposures and scheduled fasting periods. Diet analysis reports received from the supplier are maintained with facility records. The diet contained no known contaminants at levels that would be expected to interfere with the test substance or the animals or confound interpretation of the study.
- Water (eg ad libitum): Each rodent cage was provided with an automatic watering system (Edstrom Industries, Inc., Waterford, WI) supplying fresh city of Chicago water without additional treatment ad libitum, except during inhalation exposures.
- Acclimation period: The animals were quarantined for 2 weeks; To condition the animals for placement and restraint in the nose-only exposure tubes, and reduce stress during the exposure phase, the animals were acclimated to the restraining tubes during a three-day acclimation period. Animals were restrained for 1/4 (1.5 hours), 1/2 (3 hours), and 3/4 (4.5 hours) of the daily exposure duration (6 hours) on three non-holiday weekdays before the animals were exposed.


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 18.6 to 23.0 °C
- Humidity (%): 25.1-64.6%
- Air changes (per hr): no data
- Photoperiod (hrs dark / hrs light): automatic 12-hour light/dark cycle was maintained in the exposure and housing chamber laboratories.



IN-LIFE DATES: From: 2010-09-09 To: 2010-10-21
Route of administration:
inhalation: dust
Type of inhalation exposure:
nose only
Vehicle:
other: unchanged (no vehicle)
Remarks on MMAD:
MMAD / GSD: The mean MMADs of the test atmosphere were 2.63, 2.87 and 2.74 um with GSDs of 1.89, 1.94 and 1.92 for Groups 2 through 4, respectively.

Details on inhalation exposure:
GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: The nose-only chamber employed for test substance exposure was contained in an acrylic enclosure to isolate the exposure chamber and protect laboratory personnel. The dilution air to the atmosphere generator was of breathable quality and was filtered with a compressed air filter and a carbon absorber. The exhaust from the exposure chamber was moved through a particulate filter by a ring compressor and exhausted outside the building. Inlet and exhaust flows to and from the chamber were continuously monitored by rotameters.
- Method of holding animals in test chamber: During the inhalation exposures, the rats were restrained in nose-only exposure animal holding tubes (CH Technologies, Westwood, NJ). Animal tube loading and unloading, and tube insertion and removal from the exposure chamber were performed
according to standard procedures designed to minimize stress to study rats. At all times that rats were restrained in holders, they were observed
frequently and when necessary, action was taken to avoid injury, death, or improper exposure. Prior to the start of the exposure, rats were transferred from their housing cages to the nose-only holding tubes. Following confirmation of correct animal number, the animals in the holders were inserted into the ports of the exposure chambers. Following the exposure, the holders were removed. The rats were removed from the holders and returned to their home cages. Chamber port rotation occurred weekly.
- System of generating particulates/aerosols: Test atmospheres in the exposure chambers were generated by aerosolizing the test substance using a compressed air-operated Wright Dust Aerosol Generation System positioned over the chamber. Each inhalation exposure system was equipped with a separate aerosol generation system. The test substance was weighed out and packed into a dust reservoir daily. A constant speed rotating scraper separated a thin film of the test substance at the surface of the cake and delivered it into a dispersing unit, drawn in by aspiration and dispersed by a high velocity air jet. The resulting test atmosphere entered a mixing plenum where it was diluted with breathable quality compressed air to the target concentration prior to introduction to the nose-only inhalation exposure chamber.
- Air flow rate: The total airflow was set to produce an airflow range of approximately 0.5 to 1.0 L/min/exposure port.
- Method of particle size determination: The aerosol particle size distribution was monitored twice per week during the exposure phase of the study by an Aerodynamic Particle Sizer (APS) 3321 with Aerosol Diluter 3302A (both manufactured by TSI Inc., Shoreview, MN). The APS sizes particles in the range from 0.5 to 20 um using a time-of-flight technique that measures aerodynamic diameter in real time.


TEST ATMOSPHERE
- Brief description of analytical method used: The test atmosphere mass concentration was monitored gravimetrically by collecting gravimetric samples on pre-weighed glass fiber filters placed in closed-face filter holders. Samples were collected at a constant flow rate equal to the port flow of the delivery tube, and the total volume of air sampled was measured by a dry gas meter. Test atmosphere samples were collected at least three times during the exposure (generally, once during the first two hours, once during the middle two hours and once during the last two hours). The filter-collected samples were weighed and one filter per group per day (including the control to confirm the absence of test substance in the test atmosphere) was analyzed chemically to confirm the mass of TBO collected; percent recovery (chemical analysis concentration vs gravimetric concentration) was calculated for each filter analyzed. Chemical analysis was conducted by means of ICP-mass spectrometry. In addition, the test atmosphere aerosol concentration in each chamber was monitored with a real-time aerosol sensor (model # pDR-1000AN, MIE, Inc. Bedford, MA). The sensors were employed only as a real-time indicator of short-term changes in aerosol concentration and were used in guiding laboratory personnel if concentration excursions were encountered.
- Samples taken from breathing zone: yes
Analytical verification of doses or concentrations:
yes
Duration of treatment / exposure:
6 hours/day, 7 days/week for 28 days (14-day recovery period)
Frequency of treatment:
daily
Remarks:
Doses / Concentrations:
0.08, 0.325 and 0.65 mg/L Air
Basis:
other: Target TBO Concentration
Remarks:
Doses / Concentrations:
15.2, 61.8, 123.6 mg/kg/day
Basis:
other: Target Inhaled Concentration (calculated)
Remarks:
Doses / Concentrations:
0.081, 0.331, and 0.652 mg/L
Basis:
other: mean concentrations determined gravimetrically
Remarks:
Doses / Concentrations:
14.8, 60.2, and 118.8 mg/kg/day
Basis:
other: mean inhaled concentrations (calculated)
No. of animals per sex per dose:
5 animals/sex/group
Control animals:
yes, sham-exposed
Details on study design:
- Dose selection rationale:
- Rationale for animal assignment: Rats were assigned to groups using a computerized randomization procedure based on body weights using a "measure random" method that will produce similar group mean values.
- Group 1: Control
- Group 2: Low dose group
- Group 3: Mid dose group
- Group 4: High dose group
- Rationale for selecting satellite groups: Designated Subgroup
- Post-exposure recovery period in satellite groups: 14 days
Positive control:
no
Observations and examinations performed and frequency:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: The toxicology animals were observed for mortality and moribundity once daily during quarantine, twice daily during the exposure period (once in the morning and once in the afternoon) and once daily during the recovery period.


DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: All animal groups (core and recovery) received a thorough clinical examination daily during the study. Clinical observations during the exposure period were recorded before the exposure and within one hour after exposure termination following removal from the exposure chamber and holding tube. All clinical signs of altered behavior, changes in coat condition, unusual discharge of body fluid, abnormal respirations, lesions or other relevant findings were recorded. Clinical observations were recorded using ToxData© System, version 2.1.E.5 (Pathology Data Systems, Basel, Switzerland).


BODY WEIGHT: Yes
- Time schedule for examinations: Body weights of all animals were determined one day after receipt and on the day of randomization to facilitate test subject selection. Body weights were measured for core and recovery animals on study days 1, 8, 15, 22, 28 (body weights for recovery animals were measured on study Day 29); fasted body weight measured on Day 29 (core animals only). During the recovery period, body weights were measured on study Days 36, 42 and a fasted body weight on study Day 43. Body weight measurements were collected using ToxData© System, version 2.1.E.5.


FOOD CONSUMPTION:
- Food consumption for each animal was determined and mean daily diet consumption calculated as g food/kg body weight/day: Yes; Food consumption for the core and recovery animals was measured five days prior to the first exposure (included in the study data but not reported), and daily on study Days 1, 8, 15, 22 and 29. During the recovery period, food consumption was measured on study Days 36 and 42. Food consumption was collected using ToxData© System, version 2.1.E.5.


HAEMATOLOGY: Yes
- Time schedule for collection of blood: Performed on all core animals on study Day 29 and all recovery animals on study Day 43.
- Anaesthetic used for blood collection: Yes; 70% CO2/30% O2
- Animals fasted: Yes
- How many animals: All animals
- Parameters examined: Red blood cell count and morphology, hematocrit, hemoglobin concentration, mean corpuscular volume, mean corpuscular hemoglobin, mean corpuscular hemoglobin concentration, total and differential leukocyte count (absolute and relative), reticulocyte count (absolute
and relative) and platelet count. The following coagulation parameters were evaluated: fibrinogen, prothrombin time and activated partial thromboplastin time. The data was evaluated using a Diagnostica Stago STA Compact CT Coagulation Analyzer (DIAGNOSTICA STAGO, Inc., Parsippany, NJ), the Coagulation data were transferred from the Coagulation Analyzer to ToxData System, version 2.1.E.5.


CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: Performed on all core animals on study Day 29 and all recovery animals on study Day 43.
- Animals fasted: Yes
- How many animals: All animals
- Parameter examined: alanine aminotransferase, albumin, alkaline phosphatase, aspartate aminotransferase, total bilirubin, blood urea nitrogen, calcium, chloride, cholesterol, creatinine, gamma-glutamyl transpeptidase, glucose, lactate dehydrogenase, phosphorus, potassium, sodium, total protein and triglycerides.


URINALYSIS: Yes
- Time schedule for collection of urine: Performed on all core animals on study Day 29 and all recovery animals on study Day 43.
- Metabolism cages used for collection of urine: No data
- Animals fasted: No data
- Parameters examined: pH, protein, glucose, ketones, occult blood, bilirubin, urobilinogen, nitrite and leukocytes. Refractive index was measured with a refractometer, and a species-specific urine solids table was used to convert the refractive index to specific gravity. Urine was evaluated macroscopically for color, clarity and volume, and the sediment was analyzed microscopically.


OTHER:
ORGAN WEIGHTS: At the terminal and recovery necropsies, the adrenal glands, brain, epididymides, paired kidneys, liver, lungs, spleen, uterus, thymus and paired gonads (testes or ovaries) were removed, trimmed, and weighed. Organ weight/body weight ratios (relative organ weights) were calculated using the fasted body weights obtained prior to necropsy.

Sacrifice and pathology:
GROSS PATHOLOGY: Yes; complete necropsies were conducted on all animals at terminal and recovery sacrifice. The necropsy included examination of the external surface and all orifices; all body cavities including the cranial cavity; and collection and fixation of the following tissues and organs: adrenal glands, brain, epididymides, heart (with aorta), kidneys, liver (two sections including left lateral and median lobes), lungs (with mainstem bronchi), ovaries, pancreas, seminal vesicles, spleen, sternum (bone marrow), testes, thymus and uterus. Gross lesions were also collected and preserved from all animals. In addition, the section of the tail bearing the animal identification number was also collected and preserved from all animals, and two bone marrow smears were collected from the femur of each animal.

HISTOPATHOLOGY: Yes; The adrenal glands, kidneys, liver (two sections including left lateral and median lobes), lungs (with mainstem bronchi), spleen and any gross lesions for the control and high dose groups were processed for microscopic evaluation for all core and recovery animals at necropsy (except as noted in Protocol Deviation No. 1). Tissues from other dose group animals were saved for future evaluations. Lungs (with mainstem bronchi) for the low and mid dose groups were processed for microscopic evaluation for all core toxicology animals at terminal necropsy.
Statistics:
Clinical observations were tabulated, but not statistically analyzed.

Body weight, body weight gain, food consumption and clinical pathology (haematology, coagulation and clinical chemistry) were analyzed for normality and equal variance. If the data set was normally distributed and of equal variance, statistical comparisons were conducted using a one-way analysis of variance (ANOVA), with post-hoc comparisons made using Dunnett's test. If normality and/or equal variance failed for a data set, statistical comparisons were conducted using the nonparametric Kruskal-Wallis ANOVA, with post-hoc comparisons made using Dunn's test. These parameters were compared using the statistical software provided by ToxData System, version 2.1.E.5. Urinalysis and organ weight data were compared using SYSTAT Software, version 10.2 (Systat Software Inc, Chicago, IL). Each sex was analyzed separately. Probability values of p < 0.05 (ToxData) or p 0.05 (SYSTAT) were considered significant.


Urinalysis (refractive index, specific gravity and pH only) and organ weight data were compared using ANOVA, with post-hoc comparisons made using Dunnett's test.

The Filtered Air Control group (Group 1) served as the control group for all comparisons.
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
Clinical biochemistry findings:
effects observed, treatment-related
Urinalysis findings:
effects observed, treatment-related
Behaviour (functional findings):
not examined
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:
not examined
Details on results:
CLINICAL SIGNS AND MORTALITY
- No exposure-related deaths occurred during the study.
- The following clinical observations were observed during the pre- and post-exposure periods: skin/fur discoloration (blue), discoloration around the mouth, redness around nose fur, redness around the eyes, salivation, scab, injury, wet inguinal fur and limping. These observations (with the exception of skin/fur discoloration, discoloration around the mouth, scab, injury, and limping) are typical in nose-only exposure studies and were regarded as consequential to the rigors of nose-only exposure tube confinement.


BODY WEIGHT AND WEIGHT GAIN
- There were no statistically significant differences in group mean body weights for the male or female animals. Mean body weight gain was statistically significantly increased in High group females for Day 22-28, but the increase was not considered biologically relevant. No dose-related pattern was observed in either sex during the study.


FOOD CONSUMPTION
- There were no statistically significant differences in food consumption measurements, and no dose-related trend was observed in either sex.


HAEMATOLOGY
- At the end of the exposure period, white blood cells (WBC) and absolute eosinophils were statistically significantly increased in males in the Mid group, and absolute neutrophils, monocytes and eosinophils were statistically significantly increased in males in the High group, when compared to the Filtered Air Control. In females, relative reticulocytes were statistically significantly increased in the Mid group compared to the Filtered Air Control group. At the end of the recovery period, hemoglobin, hematocrit, MCV and absolute large unstained cells were statistically significantly increased in the High group males, when compared to the Filtered Air Control. At the end of the recovery period, absolute and relative reticulocytes were statistically significantly increased in the High group females, when compared to the Filtered Air Control. All red blood cell morphology observations were normal at the end of the exposure and recovery periods.
- Coagulation: At the end of the exposure period, no statistically significant differences were seen in males or females. No statistically significant differences were seen in males or females at the end of the recovery period.



CLINICAL CHEMISTRY
- At the end of the exposure period, calcium and glucose were statistically significantly increased in males in the Mid group and phosphorus was statistically significantly increased in Mid and High group males compared to the Filtered Air Control group. In females, gamma-glutamyl transpeptidase was significantly decreased in the Low group, calcium was statistically significantly increased in the Mid group, and chloride, phosphorus and albumin/globulin ratio levels were statistically significantly increased and globulin levels were statistically significantly decreased in the High group, compared to the Filtered Air Control group. At the end of the recovery period, cholesterol was statistically significantly increased in High group males, when compared to the Filtered Air Control. No statistically significant differences were seen in females at the end of the recovery period.


URINALYSIS
- Prior to terminal necropsy, urine refractive index and specific gravity were statistically significantly decreased for males in the low and High groups. At the end of the recovery period, no statistically significantly differences were observed between the groups.


ORGAN WEIGHTS
- At terminal necropsy, mean absolute and relative lung weights were statistically significantly increased in the Low, Mid and High groups for males, and in the Mid and High groups for females, compared to the Filtered Air Control group. At the recovery necropsy, mean absolute and relative lung weights were statistically significantly increased in males and females in the High group, mean relative testes weights were statistically significantly increased in males in the High group, and mean absolute and relative adrenal weights were statistically significantly decreased in males in the High group.


GROSS PATHOLOGY
- At Day 29, animals exposed to 0.65 mg/L air TBO had an increased incidence of pigmentation of the lungs which was correlated with the microscopic finding of alveolar foreign material and alveolar pigmented macrophages. Some animals exposed to 0.08 or 0.325 mg/L air levels also had pigmentation of the lungs with similar microscopic findings. In addition, the skin over the nasal bone was pigmented blue in all groups exposed to TBO. At Day 43, animals exposed to 0.65 mg/L air TBO had an increased incidence of pigmentation of the lungs which was correlated with the microscopic finding of alveolar foreign material and/or alveolar pigmented macrophages.


HISTOPATHOLOGY: NON-NEOPLASTIC
- At terminal sacrifice, there was an increase in the severity of alveolar pigmented macrophages, alveolar foreign material and individual alveolar foamy macrophages in animals exposed to all target concentrations of TBO. These three findings were considered related to exposure to TBO at all dose levels. In addition, at the 0.325 mg/L air and 0.65 mg/L air dose males there was an increase in the incidence of aggregates of foamy macrophages in the alveoli; this finding was also in the females exposed to 0.65 mg/L air concentration. There is a clear exposure response relationship in males for aggregates of macrophages in alveoli; this relationship is present, but less clear in the females. The finding of aggregated foamy macrophages was considered related to exposure of test substance at the 0.325 and 0.65 mg/L air concentrations in males and at the 0.65 mg/L air in females.

- After 14 days without exposure, there was the same incidence of animals with alveolar pigmented macrophages; however, the severity was slightly
decreased. There was a decrease in the severity of animals in Group 4 (0.65 mg/L air TBO) which had alveolar foreign material and individual alveolar foamy macrophages. There was a very small decrease in severity of foamy macrophage aggregates after 14 days without exposure. There was limited recovery of findings when compared to the terminal sacrifice animals.
Dose descriptor:
NOAEL
Effect level:
> 0.65 other: mg/L air (target)
Sex:
male/female
Basis for effect level:
other: No significant effects were observed at any dose
Dose descriptor:
NOAEL
Effect level:
> 0.652 mg/L air (analytical)
Sex:
male/female
Basis for effect level:
other: no significant effects were observed at any dose
Critical effects observed:
not specified

Overall means for tungsten oxide (aka tungsten blue oxide or TBO) concentrations were determined gravimetrically to be 0.081, 0.331 and 0.652 mg/L for Groups 2 through 4, respectively. The TBO % recovery ranged from 100.83-102.38%.. Small amounts of TBO in the chemically-analyzed filters for the Filtered Air Control group were attributed to contamination during the filter analysis processing and/or the calibration curve. The Filtered Air Control group filter-collected mean gravimetric value was 0.000 mg/L. The particle size distribution of the test atmosphere was within the respirable range. The overall mean TBO inhaled dose levels were 14.8, 60.2 and 118.8 mg/kg/day for Groups 2 through 4, respectively. The overall mean male TBO inhaled dose levels were 13.7, 55.7 and 110.2 mg/kg/day for Groups 2 through 4, respectively. The overall mean female TBO inhaled dose levels were 15.8, 64.7 and 127.3 mg/kg/day for Groups 2 through 4, respectively. The male inhaled dose levels were 10-11% below the target levels for all groups, while the female inhaled dose levels were 3-5% above the target levels for all groups. Prior to exposure initiation, the homogeneity of the test atmosphere in each TBO exposure chamber was confirmed.

Conclusions:
The NOAEL was determined to be > 0.65 mg/L exposed by nose-only TBO inhalation for 6 hours per day, 7 days per week for 28 consecutive days.
Executive summary:

No inhalation repated dose toxicity data of sufficient quality are available for tungsten carbide (target substance). However, inhalation repeated dose toxicity data are available for tungsten oxide (source substance), which are used for read-across. Due to lower water solubility and similar toxicity for the target substance compared to the source substance, the resulting read-across from the source substance to the target substance is appropriate. In addition, read-across is appropriate because the classification and labelling is similar for the source substance than the target substance, the PBT/vPvB profile is the same, and the dose descriptors are, or are expected to be, lower for the target substance. For more details, refer to the read-across category approach in the Category section or Annex 3 in the CSR.

Endpoint:
sub-chronic toxicity: inhalation
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1983-05-05 to 1986-02-01
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Remarks:
Similar to OECD Guideline 413 with the following deviations: (1) Only one concentration was tested rather than 3: (2) 8 animals/sex/dose were evaluated rather than 10/sex/dose; (3) ophthalmological and clinical chemistry evaluations were not conducted; (4) histopathology did not include bone marrow evaluation.
Qualifier:
equivalent or similar to guideline
Guideline:
OECD Guideline 413 (Subchronic Inhalation Toxicity: 90-Day Study)
Deviations:
yes
Remarks:
(1) Only one concentration was tested rather than 3: (2) 8 animals/sex/dose were evaluated rather than 10(3) ophthalmological and clinical chemistry evaluations were not conducted; (4) histopathology did not include bone marrow evaluation.
GLP compliance:
not specified
Limit test:
no
Species:
mouse
Strain:
B6C3F1
Sex:
male/female
Details on test animals or test system and environmental conditions:
TEST ANIMALS
- Source: Simonsen Laboratories (Gilroy, CA)
- Age at study initiation: 9-11 weeks
- Housing: individually in stainless steel, wire-mesh cages
- Diet: ad libitum (except during exposure periods)
- Water: ad libitum

ENVIRONMENTAL CONDITIONS
- Photoperiod (hrs dark / hrs light): 12/12

IN-LIFE DATES: From: 1983-05-09 to 1983-06-09 To: 1983-08-02 to 1983-09-02
Route of administration:
inhalation: dust
Type of inhalation exposure:
whole body
Vehicle:
other: unchanged (no vehicle)
Remarks on MMAD:
MMAD / GSD: MMAD = 4.2 um with a GSD = 1.86
Details on inhalation exposure:
- The tungsten particles were aerosolized using model 9310 generators. The automatic feed systems of the generators were not employed because the physical consistency of these powders rendered the feed mechanisms ineffective. Instead, each powder was mixed with bronze beads from the respective generator by vigorously shaking in a plastic container. During the mixing process, the bronze beads were coated with dust particles. To disperse the particles, dry, filtered air was introduced through the microporous stainless steel support screen at the bottom of the bed. he air caused the beads to Collide with one another, striping the particles from the beads and carrying the resultant aerosol to the outlet of the generator. The delivery line from each generator leading to the air intake line of the exposure chambers was equipped with a 60 mCi 85Kr neutralizing source to bring the electrical charge of the particles to Boltzman equilibrium.
- Separate generators were used to aerosolize the WC dust in each chamber.
- Exposures were carried out in 5.0 m Hinners type chambers constructed of stainless steel and Lucite. Airflow through the chambers was 11 chamber volumes per hour. Exhaust air from the chambers was passed through electrostatic precipitators, a prefilter and a HEPA filter before being discharged. Temperature in each chamber was monitored continuously by computer and the average temperature during each 0 .5 hr interval recorded. The average temperature during the exposure of these animals was 20 .5 °C . The mean average daily temperature ranged from 19 .2 to 22 .7 °C and the minimum and maximum 0 .5 hr averages were 18 .6 and 23 .9 °C, respectively .
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
On-line monitoring of the aerosol mass in the exposure chambers was accomplished using RAM-1 mass monitors and strip chart recorders. During each daily exposure period, at least one but more frequently 2, filter samples were drawn from each exposure chamber. The total dust concentrationsin the tungsten carbide (WC) chambers were determined gravimetrically. The concentration of WC was determined by difference .
Duration of treatment / exposure:
13 weeks
Frequency of treatment:
6 hours/day, 5 days/week
Remarks:
Doses / Concentrations:
15 mg/m3
Basis:
nominal conc.
Remarks:
Doses / Concentrations:
14.97 mg/m3
Basis:
analytical conc.
No. of animals per sex per dose:
8 mice/sex were designated for observation of body weight changes, organ weights, hematology, and pathology. Another 10 male mice were designated for cytogenetic and sperm abnormality studies.
Control animals:
yes, sham-exposed
Details on study design:
Post-exposure period: 6 days
Positive control:
none
Observations and examinations performed and frequency:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: daily prior to exposure, when the food troughs were removed and clean catch pans were provided, and again following the exposure period when the food troughs were replaced.

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: On the days that the animals were weighed.

BODY WEIGHT: Yes
- Time schedule for examinations: Each animal was weighed in the morning of its initial exposure and then weekly on Mondays and Wednesdays and on the morning following their final exposure and on the day of the endpoint assessment.

OPHTHALMOSCOPIC EXAMINATION: No

HAEMATOLOGY: Yes
- Time schedule for collection of blood: At sacrifice
- Anaesthetic used for blood collection: Yes
- Animals fasted: No data
- How many animals: No data
- Parameters that were examined: white and red blood cell counts, hemoglobin, hematocrits, mean corpuscular volume, mean corpuscular hemoglobin, and mean corpuscular hemoglobin concentration.

CLINICAL CHEMISTRY: No

URINALYSIS: No

NEUROBEHAVIOURAL EXAMINATION: No
Sacrifice and pathology:
GROSS PATHOLOGY: Yes, 8 animals/sex/dose
HISTOPATHOLOGY: Yes, Brain, pituitary, adrenals, trachea, esophagus, thyroid, parathyroids, thymus, heart, pancreas, spleen, kidneys, liver, preputial glands, gall bladder, larynx, peribronchial lymph node, lungs, uterus, testis, prostate, epididymis, urinary bladder, stomach, duodenum, jejunum, ileum cecum, colon, salivary gland, skin, mammary gland, mesenteric lymph node, nasal turbinate, sternum, rib junction, skeletal muscle, peripheral nerve, eyes, diaphragm and penis
Other examinations:
Cytogenetic and sperm abnormality studies.
Statistics:
Growth of male and female exposure groups were analyzed separately. Variation in body weights was examined by analysis of covariance with repeated measures, in which the exposure groups represented the treatment factors, weekly weights were the repeated measures, and initial weights were considered the covariants. Differences in growth rates among the exposure groups were investigated by finding least squares linear regression equations that expressed the mean weekly adjusted weight for each group as a function of exposure time. To statistically assess the differences of means of a single variable between any 2 groups the Student's-t test was employed. However, one way analysis of variance (ANOVA) was used to compare the means of single variables across exposure groups. When ANOVA indicated a significant difference among group means, Duncan's multiple range method of multiple comparisons was used to investigate the source of the differences (p = 0 .05). In addition to ANOVA, quasi-static compliance data and flow-volume data were each analyzed as sets of variables. These sets were compared among exposure groups by a multi-variate analysis of variance (MANOVA). To investigate differences among exposure groups based on histopathologic data, the values were non-parametrically ranked and were then analyzed by the Kruskal-Wallis non-parametric test. When a significant difference was indicated among the groups, non-parametric multiple comparisons were performed according to the Mann-Whitney Simultaneous Test Procedure to identify the source of the differences.
Clinical signs:
effects observed, treatment-related
Mortality:
mortality observed, treatment-related
Body weight and weight changes:
not specified
Food consumption and compound intake (if feeding study):
not examined
Food efficiency:
not examined
Water consumption and compound intake (if drinking water study):
not examined
Ophthalmological findings:
not examined
Haematological findings:
no effects observed
Clinical biochemistry findings:
not examined
Urinalysis findings:
not examined
Behaviour (functional findings):
not examined
Organ weight findings including organ / body weight ratios:
not examined
Gross pathological findings:
no effects observed
Histopathological findings: non-neoplastic:
no effects observed
Histopathological findings: neoplastic:
not examined
Details on results:
The incidence of chronic runny nose (rhinitis) in female mice was 0/8 controls and 4/8 of the tungsten carbide group. Other changes in the tissues of the female exposure groups appeared to be incidental. No significant effects on hematological parameters were reported.

No effects were seen in males.

Bone marrow was not evaluated as part of the general histopathology evaluation, but subsets of rats were exposed and bone marrow was removed from the femurs and slides were prepared for a genetic toxicity evaluation. However, the slides prepared were not reviewed.

Dose descriptor:
LOEL
Effect level:
15 mg/m³ air (nominal)
Sex:
female
Basis for effect level:
other: Chronic rhinitis in females
Dose descriptor:
NOAEL
Effect level:
>= 15 mg/m³ air (nominal)
Sex:
male
Basis for effect level:
other: no apparent effects
Critical effects observed:
not specified
Conclusions:
The LOAEL for females was 15 mg/m3 based on chronic rhinitis. No effects were seen in males exposed at this dose level therefore the NOAEL for males was determined to be >=15 mg/m3.
Endpoint:
sub-chronic toxicity: inhalation
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Remarks:
Similar to OECD Guideline 413 with the following deviations: (1) Only one concentration tested rather than 3: (2) 8 animals/sex/dose were evaluated rather than 10/sex/dose; (3) ophthalmological and clinical chemistry evaluations were not conducted; (4) histopathology did not include bone marrow evaluation.
Qualifier:
equivalent or similar to guideline
Guideline:
OECD Guideline 413 (Subchronic Inhalation Toxicity: 90-Day Study)
Deviations:
yes
Remarks:
See rationale for reliability above
GLP compliance:
not specified
Limit test:
no
Species:
rat
Strain:
Fischer 344
Sex:
male/female
Details on test animals or test system and environmental conditions:
TEST ANIMALS
- Source: Simonsen Laboratories (Gilroy, CA)
- Age at study initiation: 9-11 weeks
- Housing: individually in stainless steel, wire-mesh cages
- Diet: ad libitum (except during exposure periods)
- Water: ad libitum

ENVIRONMENTAL CONDITIONS
- Photoperiod (hrs dark / hrs light): 12/12
Route of administration:
inhalation: dust
Type of inhalation exposure:
whole body
Vehicle:
other: unchanged (no vehicle)
Remarks on MMAD:
MMAD / GSD: MMAD = 4.2 um (SW = 0.2 um) with a GSD = 1.86 (SE = 0.10)
Details on inhalation exposure:
- The tungsten particles were aerosolized using model 9310 generators. The automatic feed systems of the generators were not employed because the physical consistency of these powders rendered the feed mechanisms ineffective. Instead, each powder was mixed with bronze beads from the respective generator by vigorously shaking in a plastic container. During the mixing process, the bronze beads were coated with dust particles. To disperse the particles, dry, filtered air was introduced through the microporous stainless steel support screen at the bottom of the bed. he air caused the beads to Collide with one another, striping the particles from the beads and carrying the resultant aerosol to the outlet of the generator. The delivery line from each generator leading to the air intake line of the exposure chambers was equipped with a 60 mCi 85Kr neutralizing source to bring the electrical charge of the particles to Boltzman equilibrium.
- Separate generators were used to aerosolize the WC dust in each chamber.
- Exposures were carried out in 5.0 m Hinners type chambers constructed of stainless steel and Lucite. Airflow through the chambers was 11 chamber volumes per hour. Exhaust air from the chambers was passed through electrostatic precipitators, a prefilter and a HEPA filter before being discharged. Temperature in each chamber was monitored continuously by computer and the average temperature during each 0 .5 hr interval recorded. The average temperature during the exposure of these animals was 20 .5 °C . The mean average daily temperature ranged from 19 .2 to 22 .7 °C and the minimum and maximum 0 .5 hr averages were 18 .6 and 23 .9 °C, respectively .
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
On-line monitoring of the aerosol mass in the exposure chambers was accomplished using RAM-1 mass monitors and strip chart recorders. During each daily exposure period, at least one but more frequently 2, filter samples were drawn from each exposure chamber. The total dust concentrations in the tungsten carbide chambers were determined gravimetrically.
Duration of treatment / exposure:
13 weeks
Frequency of treatment:
6 hours/day, 5 days/week
Remarks:
Doses / Concentrations:
15 mg/m3
Basis:
nominal conc.
Remarks:
Doses / Concentrations:
14.97 mg/m3
Basis:
analytical conc.
No. of animals per sex per dose:
24 male rats were designated for respiratory physiology studies. After pulmonary testing these animals were sacrificed and the left lung was processed for pathological examination while the right lung was submitted for biochemical analysis.

8 rats/sex were designated for observation of body weight changes, organ weights, hematology and pathology.

10 male rats were designated for cytogenetic and sperm abnormality studies (these endpoints were not reported).
Control animals:
yes
Details on study design:
Post-exposure period: 6 days
Positive control:
none
Observations and examinations performed and frequency:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: daily prior to exposure, when the food troughs were removed and clean catch pans were provided, and again following the exposure period when the food troughs were replaced.

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: On the days that the animals were weighed.

BODY WEIGHT: Yes
- Time schedule for examinations: Each animal was weighed in the morning of its initial exposure and then weekly on Mondays and Wednesdays and then on the morning following their final exposure and on the day of the endpoint assessment.

OPHTHALMOSCOPIC EXAMINATION: No

HAEMATOLOGY: Yes
- Time schedule for collection of blood: At sacrifice
- Anaesthetic used for blood collection: Yes
- Animals fasted: No data
- How many animals: No data
- Parameters that were examined: white and red blood cell counts, hemoglobin, hematocrits, mean corpuscular volume, mean corpuscular hemoglobin, and mean corpuscular hemoglobin concentration

CLINICAL CHEMISTRY: No

URINALYSIS: No

NEUROBEHAVIOURAL EXAMINATION: No

OTHER: Pulmonary function tests
- Number of animals: 8 male rats/dose
- Parameters: tidal breathing, heart rate, lung volumes, pressure volume characteristics, diffusion capacity, multi-breath nitrogen washout, maximumexpiratory flow volume, vital capacity. Following pulmonary function tests, animals were sacrificed and the right lung was evaluated for biochemical parameters and the left lung was evaluated pathologically.
Sacrifice and pathology:
GROSS PATHOLOGY: Yes, 8 animals/sex/dose
HISTOPATHOLOGY: Yes, Brain, pituitary, adrenals, trachea, esophagus, thyroid, parathyroids, thymus, heart, pancreas, spleen, kidneys, liver, clitorial glands, larynx, peribronchial lymph node, lungs, uterus, ovaries, testis, prostate, epididymis, urinary bladder, stomach, duodenum, jejunum, ileum cecum, colon, salivary gland, skin, mammary gland, mesenteric lymph node, nasal turbinate, sternum, rib junction, diaphragm and penis.
Other examinations:
Animals undergoing pulmonary testing were sacrificed and the left lung was processed for pathological examination while the right lung was submitted for biochemical analysis (weight, water content, protein, DNA, elastin, collagen).

10 male rats were designated for cytogenetic and sperm abnormality studies (these endpoints have not been evaluated).
Statistics:
Growth of male and female exposure groups were analyzed separately. Variation in body weights was examined by analysis of covariance with repeated measures, in which the exposure groups represented the treatment factors, weekly weights were the repeated measures, and initial weights were considered the covariants. Differences in growth rates among the exposure groups were investigated by finding least squares linear regression equations that expressed the mean weekly adjusted weight for each group as a function of exposure time. To statistically assess the differences of means of a single variable between any 2 groups the Student's-t test was employed. However, one way analysis of variance (ANOVA) was used to compare the means of single variables across exposure groups. When ANOVA indicated a significant difference among group means, Duncan's multiple range method of multiple comparisons was used to investigate the source of the differences (p = 0 .05). In addition to ANOVA, quasi-static compliance data and flow-volume data were each analyzed as sets of variables. These sets were compared among exposure groups by a multi-variate analysis of variance (MANOVA). To investigate differences among exposure groups based on histopathologic data, the values were non-parametrically ranked and were then analyzed by the Kruska-Wallis non-parametric test. When a significant difference was indicated among the groups, non-parametric multiple comparisons were performed according to the Mann-Whitney Simultaneous Test Procedure to identify the source of the differences.
Clinical signs:
effects observed, treatment-related
Mortality:
mortality observed, treatment-related
Body weight and weight changes:
no effects observed
Food consumption and compound intake (if feeding study):
not examined
Food efficiency:
not examined
Water consumption and compound intake (if drinking water study):
not examined
Ophthalmological findings:
not examined
Haematological findings:
no effects observed
Clinical biochemistry findings:
not examined
Urinalysis findings:
not examined
Behaviour (functional findings):
not examined
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
Histopathological findings: neoplastic:
not examined
Details on results:
No effects on the pulmonary function tests were reported in any exposure group. No significant effects on hematological parameters were reported. During the 13 week exposure period the control and all of the dust exposed rats gained weight at the same rate. There were no significant changes in fresh organ weights among any of the male Fischer-344 rat exposure groups. The mean lung weight of the tungsten carbide (WC) subgroup was identical to that of the controls. Also in females it appeared that WC alone had no effect on this index of pulmonary toxicity. All the lung composition variables measured were similar between control and WC treated animals.

Lesions observed in rats exposed to WC consisted of focal reactions around the end airways of the lung. These were characterized by alveolar wall thickening with an increase in the number (hyperplasia) of type II cells. Pigmented and/or foamy macrophages accompanied this end airway change. Although chronic rhinitis was not detected in any of the female rat exposure groups, the incidence in male rats appeared to be related to exposure with 0/8 of the controls and 6/7 of the WC group showing lesions. This change was characterized by submucosal infiltration of mononuclear cells in the nasal cavity. Changes in the lungs of the multiple endpoint rat exposure groups were similar to those of the rats designated for pathology evaluation. Changes observed in the non-respiratory tissues of the rats in the pathology evaluation appeared to be spontaneous lesions and/or incidental findings.
Dose descriptor:
LOEL
Effect level:
15 mg/m³ air (nominal)
Sex:
male
Basis for effect level:
other: Mild histopathological alterations in the lungs (focal reactions around the end airways) and chronic rhinitis.
Dose descriptor:
NOAEL
Effect level:
>= 15 mg/m³ air (nominal)
Sex:
female
Basis for effect level:
other: No apparent effects
Critical effects observed:
not specified

Bone marrow was not evaluated as part of the general histopathology evaluation, but subsets of rats were exposed and bone marrow was removed from the femurs and slides were prepared for a genetic toxicity evaluation. However, the slides prepared were not reviewed.

Conclusions:
The LOAEL for male rats was determined to be 15 mg/m3 based on mild histopathological alterations in the lung (focal reactions at the end airways) and chronic rhinitis, while an NOAEL for females was determined to be >=15 mg/m3.
Endpoint:
sub-chronic toxicity: inhalation
Type of information:
experimental study
Adequacy of study:
supporting study
Reliability:
4 (not assignable)
Rationale for reliability incl. deficiencies:
documentation insufficient for assessment
Remarks:
No further study details reported. No information on purity of test substance. Reliability assigned by secondary source. Only secondary source reviewed.
Qualifier:
no guideline followed
Principles of method if other than guideline:
Lung effects of a 5 month inhalation exposure to tungsten carbide were evaluated.
GLP compliance:
no
Limit test:
no
Species:
rat
Strain:
other: white
Sex:
not specified
Route of administration:
inhalation
Type of inhalation exposure:
whole body
Duration of treatment / exposure:
5 months
Frequency of treatment:
daily for one hour
Remarks:
Doses / Concentrations:
0.6 mg/L
Basis:

No. of animals per sex per dose:
no data
Control animals:
yes
Details on study design:
Post-exposure period: none
Observations and examinations performed and frequency:
Body weight
Sacrifice and pathology:
GROSS PATHOLOGY: Yes
HISTOPATHOLOGY: Yes
Body weight and weight changes:
no effects observed
Gross pathological findings:
no effects observed
Histopathological findings: non-neoplastic:
effects observed, treatment-related
Details on results:
Animals remained healthy and gained body weight well.

No macroscopic changes were detected.

On microscopic examination no changes were found in any organ except for the lungs, where perivascular and peribronchial infiltration were observed. The walls of some of the small vessels were thickened, with loose fibers and a swollen endothelium. The interalveolar septa were thickened, due to the proliferation of lymphoid-histiocytic elements. Dust particles, mainly located intracellularly, surrounded the vessels and were also found in the interalveolar septa.
Dose descriptor:
LOAEL
Effect level:
0.6 other: mg/L
Sex:
not specified
Critical effects observed:
not specified
Endpoint conclusion
Endpoint conclusion:
no adverse effect observed
Dose descriptor:
NOAEC
650 mg/m³
Study duration:
subchronic
Species:
rat
Quality of whole database:
The reliability of this study for the substance tested is a K1, but in application of read-across to a different substance ECHA’s guidance specifies that the score can be a maximum of K2. Due to higher water solubility and greater in vitro bioaccessibility in synthetic alveolar, lysosomal, and interstitial fluids simulating inhalation exposure for the source substance, tungsten oxide (aka tungsten blue oxide, or TBO) as compared to the target substance (tungsten metal) and lack of toxicity from acute toxicity studies for the target and source substances, toxicity data on the target substance is expected to represent a worse case, so read-across is appropriate between these substances. In addition, read-across is appropriate for this endpoint because the classification and labelling for human health toxicity endpoints is the same for the source and target substances, the PBT/vPvB profile is the same, and the dose descriptors are, or are expected to be, sufficiently similar or more conservative for the target substance. For more details, refer to the attached description of the read-across category approach.

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

On a rabbit 7-day maximum tolerable dose (MTD) study death was observed at 300 mg/kg/day and progressive weight loss at 200 mg/kg/day were reported suggesting that the oral MTD oral dose of sodium tungstate in the non-pregnant rabbit was less than 200 mg/kg/day.  Doses of 100 or 50 mg/kg/day were generally well tolerated with only small fluctuations in body weight. A high dose level between 100 and 200 mg/kg/day is concluded to be appropriate for the subsequent rabbit studies.

Justification for classification or non-classification

Repeated Dose Toxicity - Oral Route:

Based on bioaccessibility studies of tungsten carbide that reported a 0.04% bioelution of tungsten after 5-hrs. incubation in gastric fluid, the amount of tungsten carbide needed to reach the dose to cause adverse effects is substantially higher than 1,000 mg/kg/day (limit dose). Therefore, no hazard classification is needed for tungsten carbide.

Repeated Dose Toxicity - Inhalation Route:

No effects were reported in the 90-day inhalation toxicity study on tungsten carbide on which a classification could be based and the only dose tested was well below the classification criteria. The dose from the 90-day inhalation toxicity study was insufficient for determining classification. Therefore, the 28-day inhalation toxicity study on tungstn oxide was used for read-across. The cutoff range for a category 2 classification under CLP for a 28-day inhalation toxicity study is between 0.06 and 0.6 mg/L. The NOAEL from the 28-day inhalation toxicity study on tungsten oxide was > 0.65 mg/L. Because the NOAEL from the 28-day study was greater than the 0.6 mg/L category 2 cutoff level, classification is not warranted.