Disodium wolframate

Repeated dose toxicity: oral

Administrative data

Endpoint:

sub-chronic toxicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Cross-reference

Reason / purpose for cross-reference:

reference to same study

Reference

Endpoint:

sub-chronic toxicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Reason / purpose for cross-reference:

reference to same study

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.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2021

Report date:

2021

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

EPA OPPTS 870.3100 (90-Day Oral Toxicity in Rodents)

GLP compliance:

yes

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Disodium wolframate

EC Number:

236-743-4

EC Name:

Disodium wolframate

Cas Number:

13472-45-2

Molecular formula:

Na2WO4

IUPAC Name:

disodium dioxotungstenbis(olate)

Test material form:

solid: crystalline

Details on test material:

- Name of test material (as cited in study report): Sodium tungstate dihydrate
- Source: Fisher Scientific
- Analytical purity: >98%

Test animals

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.

Administration / exposure

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

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

0 mg/L drinking water

Doses / concentrations 2

Dose / conc.:

125 mg/L drinking water

Remarks:

Approximately 11.8 mg/kg/day for males and 14.0 mg/kg/day for females.

Doses / concentrations 3

Dose / conc.:

250 mg/L drinking water

Remarks:

Approximately 24.3 mg/kg/day for males and 26.1 mg/kg/day for females.

Doses / concentrations 4

Dose / conc.:

500 mg/L drinking water

Remarks:

Approximately 48.9 mg/kg/day for males and 54.4 mg/kg/day for females.

Doses / concentrations 5

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.

Doses / concentrations 6

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

Examinations

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.

Results and discussion

Results of examinations

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.

Effect levels

1

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

2

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

Target system / organ toxicity

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

Any other information on results incl. tables

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.

Applicant's summary and conclusion

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.