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Toxicological information

Repeated dose toxicity: oral

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Administrative data

Endpoint:
short-term repeated dose toxicity: oral
Type of information:
experimental study
Adequacy of study:
weight of evidence
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:
For justification of Weight-of-Evidence, please refer to justification documentation in IUCLID chapter 13.
Cross-referenceopen allclose all
Reason / purpose for cross-reference:
reference to same study
Reason / purpose for cross-reference:
reference to same study
Reference
Endpoint:
sub-chronic toxicity: oral
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment
Remarks:
Published literature fulfilled basic scientific principles. From existing studies of toxicokinetic profiles of Tin (IV) dioxide and Tin (II) oxide, it can be concluded that the toxicokinetic profiles of these two substances appear to be similar. Minor differences between Tin (II) and Tin (IV) in their absorption and distribution indicate that Tin (II) may be a bit more toxic than Tin (IV). Therefore Tin (II) oxide can be used as a structural surrogate for Tin (IV) dioxide in the 90 days repeated toxicity test.
Justification for type of information:
For justification of Read-across/Weight of Evidence, please refer to justification documentation in IUCLID chapter 13.
Reason / purpose for cross-reference:
reference to same study
Reason / purpose for cross-reference:
reference to same study
Reason / purpose for cross-reference:
assessment report
Remarks:
justification for Weight-of-Evidence approach
Qualifier:
no guideline followed
Principles of method if other than guideline:
In order to investigate repeated toxicity in 90 days of series of tin compounds, Two tin compounds, stannous oxide (SnO) and stannous chloride (SnCI2•2H20)examined were fed to groups of ten male and ten female rats at dietary levels of 0 (control), 0.03, 0.10, 0.30 and 1.00 % for 90 days.
GLP compliance:
not specified
Limit test:
no
Species:
rat
Strain:
Wistar
Sex:
male/female
Details on test animals or test system and environmental conditions:
Male and female weanling rats from the Institute's Wistar-derived colony were housed in groups of five in stainless steel cages with screen bottoms. The diet used for both control and treated groups was the Institute's stock diet, with the following percentage composition: soyabean-oil meal, 10; fish meal, 8; meat scraps, 4; dried whey, 2; yellow maize, 29.05; wheat, 36; grass meal, 3; brewer's yeast, 3, complete B-vitamin mixture, 0.1; vitamin-ADEK preparation, 0.6; bone meal, 0.75; trace mineral salt, 0.5; soyabean oil, 3. This diet was found to contain calcium (0.98 %), phosphorus (0.80 %), iron (205 ppm), copper (23 ppm), manganese (85 ppm) and zinc (38 ppm). Test diets were prepared by blending the stock diet and the tin compouds in a Stephan cutter. Diets and tap water were provided ad lib.
Route of administration:
oral: feed
Vehicle:
unchanged (no vehicle)
Details on oral exposure:
Two tin compounds, stannous oxide (SnO) and stannous chloride (SnCI2•2H2O) were examined in 13-wk feeding studies. Each of these compounds was fed to groups of ten male and ten female rats at dietary levels of 0.0 (control), 0.03, 0.10, 0.30 and 1.00 % for 90 days.
Analytical verification of doses or concentrations:
no
Details on analytical verification of doses or concentrations:
Due to stability of tin compounds, the analytical verification for these substances is unnecessary.
Duration of treatment / exposure:
13 weeks
Frequency of treatment:
Animals were dosed once each day at approximately the same time each day, seven days per week.
Remarks:
Doses / Concentrations:
0%
Basis:
nominal in diet
Remarks:
Doses / Concentrations:
0.03%
Basis:
nominal in diet
Remarks:
Doses / Concentrations:
0.1%
Basis:
nominal in diet
Remarks:
Doses / Concentrations:
0.3%
Basis:
nominal in diet
Remarks:
Doses / Concentrations:
1.0%
Basis:
nominal in diet
No. of animals per sex per dose:
10 males and 10 femels
Control animals:
yes, concurrent no treatment
Details on study design:
Two tin compounds, stannous oxide and stannous chloride were examined in 13-wk feeding studies. Each of these compounds was fed to groups of ten male and ten female rats at dietary levels of 0.0 (control), 0.03, 0.10, 0.30 and 1.00 % for 90 days. Individual body weights were recorded weekly. The food intake of each group was measured at weekly intervals up to wk 4 and in wk 11-12. Haematological studies were carried out at wk 12 and provided measurements of haemoglobin concentration and haematocrit value, counts of red blood cells and total and differential counts of white blood cells. Additional haematological observations were made in the study on tin chloride. These consisted of haemoglobin readings at wk 2, 4, 6 and 9, and terminal determinations of haptoglobin concentration, numbers of reticulocytes and the osmotic resistance of the erythrocytes. Serum activities of glutamic-oxalacetic and glutamic--pyruvic transaminases and of alkaline phosphatase were determined terminally in both experiments. Bilirubin concentrations were measured terminally only in the study with tin chloride.
Urine examinations, including appearance, pH, glucose, protein, occult blood, ketones and microscopy of the sediment were conducted upon pooled samples from each group in wk 13.

The rats fed the highest level of tin chloride were sacrificed after 8 wk because of poor condition and high mortality. Organs and tissues were fixed in buffered formalin. In wk 14, the remaining rats were killed by decapitation and examined for gross changes. The heart, kidneys, liver, spleen, brain, gonads, thymus, thyroid and adrenals were weighed and paraffin-wax sections of these and a wide range of other organs were stained with haematoxylin and eosin. Detailed microscopic examinations were performed on those fed the two highest levels of tin chloride and on the controls. In the rats fed the intermediate levels of tin chloride, only the liver, kidneys and stomach were examined.
Positive control:
no
Observations and examinations performed and frequency:
Individual body weights were recorded weekly. The food intake of each group was measured at weekly intervals up to wk 4 and in wk 11-12. Haematological studies were carried out at wk 12 and provided measurements of haemoglobin concentration and haematocrit value, counts of red blood cells and total and differential counts of white blood cells. Additional haematological observations were made in the study on tin chloride. These consisted of haemoglobin readings at wk 2, 4, 6 and 9, and terminal determinations of haptoglobin concentration, numbers of reticulocytes and the osmotic resistance of the erythrocytes. Serum activities of glutamic-oxalacetic and glutamic--pyruvic transaminases and of alkaline phosphatase were determined terminally in both experiments. Bilirubin concentrations were measured terminally only in the study with tin chloride.
Urine examinations, including appearance, pH, glucose, protein, occult blood, ketones and microscopy of the sediment were conducted upon pooled samples from each group in wk 13.


Sacrifice and pathology:
The rats fed the highest level of tin chloride were sacrificed after 8 wk because of poor condition and high mortality. Organs and tissues were fixed in buffered formalin. In wk 14, the remaining rats were killed by decapitation and examined for gross changes. The heart, kidneys, liver, spleen, brain, gonads, thymus, thyroid and adrenals were weighed and paraffin-wax sections of these and a wide range of other organs were stained with haematoxylin and eosin. Detailed microscopic examinations were performed on those fed the two highest levels of tin chloride and on the controls. In the rats fed the intermediate levels of tin chloride, only the liver, kidneys and stomach were examined.
Other examinations:
no data
Statistics:
no data
Clinical signs:
effects observed, treatment-related
Description (incidence and severity):
The rats fed the diet containing 1 % stannous chloride already showed abdominal distension during wk 1, abdominal distension were observed also at the 0·3 % feeding level during the first 2 wk.
Mortality:
mortality observed, treatment-related
Description (incidence):
High dose group: At wk 8, one male died. At wk 9, another three males died. Since several other males were moribund it was decided to discontinue this group and autopsy was performed.
Mid dose group: One female died in week 11
Body weight and weight changes:
effects observed, treatment-related
Description (incidence and severity):
The rats fed the diet containing 1 % stannous chloride ate little food and already showed abdominal distension during wk 1. Growth was slow in the first few weeks and stopped completely in males after 4 wk and in females after 6 wk. At wk 8, loss
of body weight occurred in seven males and four females. The group was terminated in week 9.
Poor appetite and abdominal distension were observed also at the 0·3 % feeding level during the first 2 wk. However, all rats kept growing, except for one female which lost weight in wk 10 and died in wk 11.
Food consumption and compound intake (if feeding study):
effects observed, treatment-related
Description (incidence and severity):
Food consumption was reduced in two highest dose levels.
Food efficiency:
effects observed, treatment-related
Description (incidence and severity):
Food efficiency was determined in the high dose in weeks 1-4 and was slightly reduced, but not statistically significant. The group was terminated in week 9.
Water consumption and compound intake (if drinking water study):
no effects observed
Ophthalmological findings:
not examined
Haematological findings:
effects observed, treatment-related
Description (incidence and severity):
The haemoglobin values determined at various stages showed decreased levels in the 1.0 and 0.3 % groups in both sexes from wk 4 onwards. At 1.0% there was a gradual decrease in haemoglobin content, and at 0·3 %, although a gradual rise did occur, it was distinctly slower in the initial stages than that in the controls. The mean values of haemoglobin content and cell volume were decreased in both sexes in the group given the 0.3 % diet but the differences from the controls were statistically significant only in males.
The calculated MCV and MCH of males and females in the 0.3 % group were only slightly lower than those of the other groups. The feeding of tin had no noticeable effect on the osmotic resistance of erythrocytes or on the numbers of reticulocytes.
Clinical biochemistry findings:
effects observed, treatment-related
Description (incidence and severity):
The biochemical studies of terminal blood samples showed a tendency of the alkaline-phosphatase activities to decrease with increasing levels of the tin compound but the difference from the controls was statistically signifi.cant (P < 0.05) only at the 0.3 %
feeding level in both sexes. The activities of glutamic-oxalacetic transaminase and glutamicpyruvic transaminase were comparable in all groups. Terminal blood samples from the 0.3 % group and the controls did not differ significantly in bilirubin or in haptoglobin content.
Urinalysis findings:
no effects observed
Behaviour (functional findings):
not examined
Organ weight findings including organ / body weight ratios:
effects observed, non-treatment-related
Description (incidence and severity):
The relative heart weights of males on the tin diets were higher than those in controls but showed no tendency to increase with increasing dietary levels ofthe tin compound. The relative thymus weight was significantly increased at 0.3 % only in females. None of the other organ weights showed statistically significant differences between groups.
Gross pathological findings:
effects observed, treatment-related
Description (incidence and severity):
At autopsy, the rats of the 1 % group, in which treatment had to be terminated prematurely, showed distended intestines, slight ascites, small oedematous pancreases and greyish-brown livers.
Terminal gross autopsy findings in other dose groups were essentially negative.
Histopathological findings: non-neoplastic:
effects observed, treatment-related
Description (incidence and severity):
Histopathological study of the animals in the 1% group revealed moderate testicular degeneration, severe pancreatic atrophy, a spongy state of the white matter of the brain, acute bronchopneumonia, enteritis and distinct liver changes, mainly characterized by a homogeneous appearance of the liver cell cytoplasm and a mild proliferation (oval cell type) of the bile-duct epithelium.
In animals of the other dose groups, minor histopathological alterations that could be related to treatment were noticed only in the livers of a few males and females of the 0.3 % group, in which the cytoplasm of the hepatocytes was homogeneous and the bile-duct epithelium proliferated. Additional randomly distributed microscopic pathology unrelated to treatment included early signs of chronic respiratory disease, slight focal myocarditis, foci of reticulo-endothelial cells in the liver, "morphological activation" of the thyroid, Trichosomoides parasites in the urinary tract and !arge proteinaceous droplets within the cytoplasm of renal tubular epithelial cells. Calcareous deposits in the intercorticomedullary area of the kidneys were not found at all in females at dietary levels of 0.1 % and above.
Histopathological findings: neoplastic:
no effects observed
Dose descriptor:
NOAEL
Effect level:
1 000 mg/kg diet
Based on:
test mat.
Sex:
male/female
Basis for effect level:
clinical biochemistry
haematology
Dose descriptor:
NOAEL
Effect level:
54 mg/kg bw/day (nominal)
Based on:
test mat.
Sex:
male
Basis for effect level:
clinical biochemistry
haematology
Remarks on result:
other: calculated
Dose descriptor:
NOAEL
Effect level:
62.3 mg/kg bw/day (nominal)
Based on:
test mat.
Sex:
female
Basis for effect level:
clinical biochemistry
haematology
Remarks on result:
other: calculated
Critical effects observed:
not specified

Calculation (estimation) of daily compound intake based on control animals:

food consumption week 12 males: 16.4 g/rat/day

body weight week 12 males: 301 g

==> food intake: 54.5 g diet/kg bw/d

compound content: 0.1%

==> compound intake: 54500 mg x 0.1% = 54.5 mg/kg bw/d

food consumption week 12 females: 11.6 g/rat/day

body weight week 12 females: 186 g

==> food intake: 62.3 g diet/kg bw/d

==> compound intake: 62300 mg x 0.1% = 62.3 mg/kg bw/d

Conclusions:
It suggested that insoluble tin compounds (stannic oxide and stannous oxide) are relatively harmless at dietary levels of 1%, whereas cationic tin compounds soluble in water or dilute acid may be toxic at dietary levels above 0.1%.
Executive summary:

In the test, groups of rats (Wistar; n=10/sex/group) were fed diets containing Tin (II) oxide and stannous chloride at dose of 0, 0.03, 0.10, 0.30, or 1.00% for periods of 13 weeks. Effects on behaviour, mortality, body weights, food consumption, blood, urine, biochemical parameters, and organ weights were examined; and gross microscopic examinations were performed. No adverse effects were noted at any dose of tin oxide. However, severe growth retardation, decreased food efficiency, slight anaemia, and slight histological changes in the liver were observed with 0.3% or more of stannous chloride.

 

The authors concluded that the differences in response to different tin compounds suggested that insoluble tin compounds are relatively harmless whereas cationic tin compounds soluble in water or dilute acid may be toxic at dietary levels above 0.1%. From these studies, it is concluded that dietary exposure to levels of Tin (II) oxide up to 1% for 13 weeks, did not induce any effect in rats.

Reason / purpose for cross-reference:
assessment report
Remarks:
Justification for Weight-of-Evidence approach

Data source

Reference
Reference Type:
publication
Title:
Unnamed
Year:
1973

Materials and methods

Test guideline
Qualifier:
no guideline followed
Principles of method if other than guideline:
In order to investigate repeated toxicity in 28 days of series of tin compounds, Rats were fed on diets containing 0 (control), 0.03, 0.10, 0.30 or 1.00 % of tin dioxide, stannous orthophosphate, oxalate and sulphide, stannous sulphate, stannous oleate, or stannous tartrate for periods of 4 weeks.
GLP compliance:
no
Limit test:
no

Test material

Constituent 1
Chemical structure
Reference substance name:
Tin dioxide
EC Number:
242-159-0
EC Name:
Tin dioxide
Cas Number:
18282-10-5
Molecular formula:
O2 Sn
IUPAC Name:
Tin dioxide
Details on test material:
Stannic oxide (pure, E. Merk AG, Darmastad, Germany)

Test animals

Species:
rat
Strain:
other: weanling rats from the Institutes Wistar-derived colony
Sex:
male/female
Details on test animals or test system and environmental conditions:
Male and female weanling rats from the Institute's Wistar-derived colony were housed in groups of five in stainless steel cages with screen bottoms. The diet used for both control and treated groups was the Institute's stock diet, with the following percentage composition: soyabean-oil meal, 10; fish meal, 8; meat scraps, 4; dried whey, 2; yellow maize, 29.05; wheat, 36; grass meal, 3; brewer's yeast, 3, complete B-vitamin mixture, 0.1; vitamin-ADEK preparation, 0.6; bone meal, 0.75; trace mineral salt, 0.5; soyabean oil, 3. This diet was found to contain calcium (0.98 %), phosphorus (0.80 %), iron (205 ppm), copper (23 ppm), manganese (85 ppm) and zinc (38 ppm). Test diets were prepared by blending the stock diet and the tin compouds in a Stephan cutter. Diets and tap water were provided ad lib.

Administration / exposure

Route of administration:
oral: feed
Vehicle:
unchanged (no vehicle)
Details on oral exposure:
The various tin compounds examined were fed to groups of ten male and ten female rats at dietary levels of 0-0 (control), 0.03, 0.10, 0.30 and 1.00 % for 28 days.
Analytical verification of doses or concentrations:
no
Details on analytical verification of doses or concentrations:
Due to stability of these tin compounds, the analytical verification for these substances is unnecessary.
Duration of treatment / exposure:
4 weeks
Frequency of treatment:
Diet containing test substances were provided continuously ad libitum throughout the course of the study.
Doses / concentrationsopen allclose all
Remarks:
Doses / Concentrations:
0%
Basis:
nominal in diet
Remarks:
Doses / Concentrations:
0.03%
Basis:
nominal in diet
Remarks:
Doses / Concentrations:
0.1%
Basis:
nominal in diet
Remarks:
Doses / Concentrations:
0.3%
Basis:
nominal in diet
Remarks:
Doses / Concentrations:
1.0%
Basis:
nominal in diet
No. of animals per sex per dose:
10 males and 10 famels
Control animals:
yes, concurrent no treatment
Details on study design:
The various tin compounds examined were fed to groups of ten male and ten female rats at dietary levels of 0-0 (control), 0.03, 0.10, 0.30 and 1.00 % for 28 days. Body weight and food intake were recorded weekly. Haematological examinations were made on all rats on day 27 using blood from the tip of the tail. Measurements were made of haemoglobin concentration, packed cell volume and counts of erythrocytes and leucocytes. At autopsy the liver, kidneys, heart and spleen were weighed and samples of these organs were processed in the usual way for histological examination.
Positive control:
not required

Examinations

Observations and examinations performed and frequency:
Body weight and food intake were recorded weekly. Haematological examinations were made on all rats on day 27 using blood from the tip of the tail. Measurements were made of haemoglobin concentration, packed cell volume and counts of erythrocytes and leucocytes. At autopsy the liver, kidneys, heart and spleen were weighed and samples of these organs were processed in the usual way for histological examination.
Sacrifice and pathology:
At autopsy the liver, kidneys, heart and spleen were weighed and samples of these organs were processed in the usual way for histological examination.
Other examinations:
no data
Statistics:
Wilcoxon's test

Results and discussion

Results of examinations

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:
no effects observed
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:
no effects observed
Histopathological findings: neoplastic:
no effects observed
Details on results:
Rats fed stannic oxide, stannous sulphide and stannous oleate at dietary levels up to 1.0 % gained weight at a normal rate and showed no abnormalities in the haematological data examined.
The absolute and relative weights and the gross and microscopic appearance of the liver, kidneys, heart and spleen were not altered.

Effect levels

open allclose all
Dose descriptor:
NOAEL
Effect level:
789 mg/kg bw/day (nominal)
Based on:
test mat.
Sex:
female
Remarks on result:
not determinable due to absence of adverse toxic effects
Dose descriptor:
NOAEL
Effect level:
683 mg/kg bw/day (nominal)
Based on:
test mat.
Sex:
male
Remarks on result:
not determinable due to absence of adverse toxic effects
Dose descriptor:
NOAEL
Effect level:
10 000 mg/kg diet
Based on:
test mat.
Sex:
male/female
Remarks on result:
not determinable due to absence of adverse toxic effects

Target system / organ toxicity

Critical effects observed:
no

Any other information on results incl. tables

Feeding on tin dioxide to rats for 28 days did not result in any changes regarding body weight gains, hematology or absolute and relative weight of liver, kidneys, heart and spleen. 

The feeding of tin as chloride, orthophosphate, sulphate, oxalate and tartrate, however, resulted in considerable growth retardation and distinct indications of anaemia at dietary levels of 0.3 and 1.0 % in both sexes. The reduced gain in body weight was accompanied by a decrease in food intake, but food efficiency was also decreased, at least at the 1.0 % feeding level. The signs of anaemia included decreased haemoglobin levels, haematocrit values and erythrocyte counts. The mean corpuscular volume (MCV), mean corpuscular haemoglobin (MCH) and mean corpuscular haemoglobin concentration (MCHC)of the rats fed the highest level of the active tin compounds were generally slightly lower than in the corresponding controls. Although the differences were not considerable (less than 12 %) most of them were statistically significant (P< 0.05). The white blood cell counts showed the usual wide variation, both among individual rats and among the various groups, but there was no evidence that tin compounds affected the number of leucocytes.

 

None of the organs weighed (liver, kidneys, heart and spleen) was distinctly enlarged, except the livers of females ingesting tin orthophosphate, the relative weights of which showed a dose-related increase at 0.1% and above. Slightly decreased liver-to-body weight ratios occurred in groups exhibiting growth retardation.

 

At autopsy, signs of anaemia (pale eyes and viscera) were observed in animals fed the 1% dose level of tin chloride, tin oxalate or tin sulphate. In addition, rats fed on diets containing 1% tin chloride or 1% tin orthophosphate showed slightly distended small and large intestines.

Microscopic examination revealed distinct changes in the livers of males and females fed 1% of each of the various tin compounds found to be capable of inducing anaemia and growth retardation. The changes consisted of clearly homogeneous liver cell cytoplasm and a slight but definite oval cell type hyperplasia of bile ducts. Similar hepatic alterations, though of a lesser degree and frequency, were found in rats fed 0-3 % dietary levels of tin chloride, tin oxalate or tin orthophosphate. The histological appearance of the kidneys, heart and spleen was unremarkable in all cases.

 

Calculation of NOAELs for 28d stannic oxide: 

total food intake stannic oxide:

  • males: 362 g/rat in high dose = 12.9 g/rat/day for 28 day study
  • Females: 286 g/rat in high dose = 10.2 g/rat/day for 28 day study

==> comparable to food intakes of control group in 90d study at weeks 1-4

 

Estimated body weights (based on body weights of control group in 90d study at week 4 - table 2 in the publication:

  • Males 189 g
  • Females 131 g

 

Food intake per kg body weight:

  • Males: 12.9 g/0.189 kg bw = 68.25 g/kg bw/d total food intake
  • Females: 10.2 g/0.131 kg bw = 77.86 g/kg bw/d total food intake

 

Substance intake:

  • Males: 68250 mg/kg bw/d x 1% compound content = 682.5 mg/kg bw/d
  • Females: 77860 mg/kg bw/d x 1% compound content = 778.6 mg/kg bw/d

 

Applicant's summary and conclusion

Conclusions:
There was no evidence of any deleterious effects of tin dioxide at the maximum dose tested.