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Toxicological information

Developmental toxicity / teratogenicity

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Administrative data

Endpoint:
developmental toxicity
Type of information:
read-across based on grouping of substances (category approach)
Adequacy of study:
key study
Study period:
not specified
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:
Read-across
The basis for the read-across concept for this project is the equilibrium between sulfites, hydrogensulfites, and metabisulfites in aqueous solutions depending on pH value which is clearly described in published literature and summarised in the following equations:[1],[2]
SO2 + H2O <->`H2SO3´ H2SO3<->H+ + HSO3- <-> 2H+ +SO32- 2HSO3- <->H2O +S2O52 –
As the nature of the cation should make no significant difference in this case concerning toxicity and solubility (all compounds are very soluble in water), only the chemical and biological properties of the anion are considered relevant. Based on the described equilibrium correlations, we propose unrestricted read-across between the groups of sulfites, hydrogensulfites and metabisulfites. Additionally, it is known that sodium dithionite disproportionates in water to form sodium hydrogen sulfite and sodium thiosulfate (equation II) so that this substance can also be added to the read-across concept.[2],[1]
It is expected for this case that the substance is not stable enough under physiological conditions to fulfil the requirements of study guidelines and so the products of decomposition have to be considered.
2 S2O42-+ H2O→2HSO3-+ S2O32 -

All sulfite, hydrogensulfite and metabisulfite substances are highly soluble in water, establishing upon dissolution an equilibrium that depends on solution pH as follows: ,

1. SO2 + H2O <-> H2SO3
2. H2SO3 <-> H+ + HSO3- <-> 2H+ + SO32-
3. 2 HSO3- <-> H2O + S2O52-

Under oxidising conditions, e.g., in surface waters, sulfite is oxidized to sulfate catalytically by (air) oxygen or by microbial action. A half-life of 77 hour was measured in deionized water, already suggesting substantial abiotic degradation. However, the presence of metal cations in the environment, such as copper, iron and manganese, accelerates the oxidation rate. In soils, HSO3- and SO32- ions are unstable and quickly oxidise. Further, because of the instability of SO32-, metal sulfites are generally too soluble to persist in soils. Thus, the most stable and predominant sulfur form in freshwater and in all but highly reduced environments is sulfate (SO42-). In highly reduced soils and sediments, sulfites may be reduced to sulfides (Lindsay, 1979; OECD SIDS, 2012).

Only the properties of the sulfite anion are considered relevant determinants of environmental toxicity since respective cations, i.e. ammonium, calcium, magnesium, sodium and potassium, are not assumed to contribute substantially to differences therein. Sulfite, although naturally present in the environment and also a metabolite and intermediate of sulfur-containing amino acids in organisms, may have an impact on the environment at elevated levels. Sulfites do not bioaccumulate.

In sum, unrestricted read-across between the sulfites, hydrogensulfites and metabisulfites is justified.
Cross-referenceopen allclose all
Reason / purpose:
reference to same study
Reference
Endpoint:
developmental toxicity
Type of information:
read-across based on grouping of substances (category approach)
Adequacy of study:
key study
Study period:
not specified
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:
Read-across
The basis for the read-across concept for this project is the equilibrium between sulfites, hydrogensulfites, and metabisulfites in aqueous solutions depending on pH value which is clearly described in published literature and summarised in the following equations:[1],[2]
SO2 + H2O <->`H2SO3´ H2SO3<->H+ + HSO3- <-> 2H+ +SO32- 2HSO3- <->H2O +S2O52 –
As the nature of the cation should make no significant difference in this case concerning toxicity and solubility (all compounds are very soluble in water), only the chemical and biological properties of the anion are considered relevant. Based on the described equilibrium correlations, we propose unrestricted read-across between the groups of sulfites, hydrogensulfites and metabisulfites. Additionally, it is known that sodium dithionite disproportionates in water to form sodium hydrogen sulfite and sodium thiosulfate (equation II) so that this substance can also be added to the read-across concept.[2],[1]
It is expected for this case that the substance is not stable enough under physiological conditions to fulfil the requirements of study guidelines and so the products of decomposition have to be considered.
2 S2O42-+ H2O→2HSO3-+ S2O32 -

All sulfite, hydrogensulfite and metabisulfite substances are highly soluble in water, establishing upon dissolution an equilibrium that depends on solution pH as follows: ,

1. SO2 + H2O <-> H2SO3
2. H2SO3 <-> H+ + HSO3- <-> 2H+ + SO32-
3. 2 HSO3- <-> H2O + S2O52-

Under oxidising conditions, e.g., in surface waters, sulfite is oxidized to sulfate catalytically by (air) oxygen or by microbial action. A half-life of 77 hour was measured in deionized water, already suggesting substantial abiotic degradation. However, the presence of metal cations in the environment, such as copper, iron and manganese, accelerates the oxidation rate. In soils, HSO3- and SO32- ions are unstable and quickly oxidise. Further, because of the instability of SO32-, metal sulfites are generally too soluble to persist in soils. Thus, the most stable and predominant sulfur form in freshwater and in all but highly reduced environments is sulfate (SO42-). In highly reduced soils and sediments, sulfites may be reduced to sulfides (Lindsay, 1979; OECD SIDS, 2012).

Only the properties of the sulfite anion are considered relevant determinants of environmental toxicity since respective cations, i.e. ammonium, calcium, magnesium, sodium and potassium, are not assumed to contribute substantially to differences therein. Sulfite, although naturally present in the environment and also a metabolite and intermediate of sulfur-containing amino acids in organisms, may have an impact on the environment at elevated levels. Sulfites do not bioaccumulate.

In sum, unrestricted read-across between the sulfites, hydrogensulfites and metabisulfites is justified.
Reason / purpose:
reference to same study
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 414 (Prenatal Developmental Toxicity Study)
GLP compliance:
no
Limit test:
no
Specific details on test material used for the study:
not specified
Species:
rat
Strain:
Wistar
Details on test animals and environmental conditions:
TEST ANIMALS
- Age at study initiation: virgin adult female albino rats
- Housing: individually housed in mesh bottom cages
- Diet (ad libitum)
- Water (ad libitum): fresh tap water
Route of administration:
oral: gavage
Vehicle:
water
Details on exposure:
VEHICLE
- Amount of vehicle (if gavage): doses administered as a water solution.
Analytical verification of doses or concentrations:
not specified
Details on analytical verification of doses or concentrations:
nto specified
Details on mating procedure:
- Impregnation procedure: cohoused; females were mated with young adult males (one male was not permitted to impregnate more than one female per group)
- Proof of pregnancy: vaginal sprem plug was considered day 0 of gestation
Duration of treatment / exposure:
day 6 to 15 of gestation
Frequency of treatment:
daily
Duration of test:
until day 20 of gesation
Dose / conc.:
1.55 mg/kg bw/day (actual dose received)
Dose / conc.:
7.19 mg/kg bw/day (actual dose received)
Dose / conc.:
33.4 mg/kg bw/day (actual dose received)
Dose / conc.:
155 mg/kg bw/day (actual dose received)
No. of animals per sex per dose:
22 - 25 mated animals
Control animals:
yes, concurrent vehicle
other: positive control: 250 mg/kg body weight of Aspirin
Details on study design:
not specified
Maternal examinations:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: daily
- Cage side observations checked: mortality, appearance and behaviour

DETAILED CLINICAL OBSERVATIONS:No data

BODY WEIGHT: Yes
- Time schedule for examinations: days 0, 6, 11, 15 and 20 of gestation

FOOD CONSUMPTION: Yes
- Time schedule: daily

WATER CONSUMPTION: No data

POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on gestation day 20
- all dams were subjected to Caesaren section under surgical anesthesia.
Ovaries and uterine content:
The ovaries and uterine content was examined after termination: Yes
Examinations included:
- Gravid uterus weight: No data
- Number of corpora lutea: Yes
- Number of implantations: Yes
- Number of resorptions: Yes
- Number of live and dead foetuses: Yes

Fetal examinations:
External examinations: Yes
- All foetuses underwent a gross examination for the presence of external congenital abnormalities. .

Soft tissue examinations: Yes
- One-third of the foetuses of each litter underwent detailed visceral examinations employing the Wilson technique.

Skeletal examinations: Yes
- Two-third of the foetuses were cleared in potassium hydroxide, stained with alizarin red S dye and examined for skeletal defects (sternebrae, ribs, vertebrae, skull, extremities and miscellaneous)

Head examinations: No data

- Body weights of the live pups were recoded.
- Sex of the foetuses was recorded
Statistics:
not specified
Indices:
not specified
Historical control data:
not specified
Clinical signs:
not specified
Dermal irritation (if dermal study):
not specified
Mortality:
no mortality observed
Body weight and weight changes:
no effects observed
Food consumption and compound intake (if feeding study):
not specified
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
Neuropathological findings:
not specified
Histopathological findings: non-neoplastic:
not specified
Histopathological findings: neoplastic:
not specified
Other effects:
not specified
Details on results:
- The survival of pregnant females was not affected by treatment with potassium metabisulfite.
- Maternal body weights and weight gains were comparable among groups.
Number of abortions:
no effects observed
Pre- and post-implantation loss:
no effects observed
Total litter losses by resorption:
no effects observed
Early or late resorptions:
no effects observed
Dead fetuses:
no effects observed
Changes in pregnancy duration:
not specified
Description (incidence and severity):
Migrated Data from removed field(s)
Field "Effects on pregnancy duration" (Path: ENDPOINT_STUDY_RECORD.DevelopmentalToxicityTeratogenicity.ResultsAndDiscussion.ResultsMaternalAnimals.MaternalDevelopmentalToxicity.EffectsOnPregnancyDuration): not specified
Changes in number of pregnant:
no effects observed
Other effects:
not specified
Details on maternal toxic effects:
- The pregnancy rates was comparable among groups (control group: 23 pregnant rats; 1.55 mg/kg bw/d: 20 pregnant rats; 7.19 mg/kg bw/d: 20 pregnant rats; 33.4 mg/kg bw/d: 20 pregnant rats; 155.0 mg/kg bw/d: 20 pregnant rats).
- There were no treatment-related effects on the number of abortions, corpora lutea, implantation sites, live litters and resorptions.
Key result
Remarks on result:
not determinable due to absence of adverse toxic effects
Abnormalities:
not specified
Fetal body weight changes:
no effects observed
Description (incidence and severity):
Migrated Data from removed field(s)
Field "Fetal/pup body weight changes" (Path: ENDPOINT_STUDY_RECORD.DevelopmentalToxicityTeratogenicity.ResultsAndDiscussion.ResultsFetuses.FetalPupBodyWeightChanges): not specified
Reduction in number of live offspring:
no effects observed
Changes in sex ratio:
no effects observed
Changes in litter size and weights:
not specified
Changes in postnatal survival:
not specified
External malformations:
not specified
Skeletal malformations:
no effects observed
Visceral malformations:
no effects observed
Other effects:
not specified
Details on embryotoxic / teratogenic effects:
- The number of live and dead foetuses, sex ratio and average foetal weight was not affected by treatment of dams with potassium metabisulfite.
- The number of abnormalities seen in either soft or skeletal tissues of the test groups did not differ from the number occurring spontaneously in the sham-treated controls.
Key result
Dose descriptor:
NOAEL
Remarks:
teratogenicity
Remarks on result:
not determinable due to absence of adverse toxic effects
Key result
Dose descriptor:
NOAEL
Remarks:
developmental toxicity
Remarks on result:
not determinable due to absence of adverse toxic effects
Abnormalities:
not specified
Developmental effects observed:
not specified
Conclusions:
The administration of up to 155 mg/kg bw/d of potassium metabisulfite to pregnant rats for 10 consecutive days had no clearly discernible effect on nidation or on maternal or foetal survival. The number of abnormalities seen in either soft or skeletal tissues of the test groups did not differ from the number occurring spontaneously in the sham-treated controls. Thus, the NOAEL for maternal and developmental toxicity can be expected above the highest dose of 155 mg/kg body weight potassium metabisulfite in this rat study.
Reason / purpose:
reference to same study
Reference
Endpoint:
developmental toxicity
Type of information:
read-across based on grouping of substances (category approach)
Adequacy of study:
key study
Study period:
not specified
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:
Read-across
The basis for the read-across concept for this project is the equilibrium between sulfites, hydrogensulfites, and metabisulfites in aqueous solutions depending on pH value which is clearly described in published literature and summarised in the following equations:[1],[2]
SO2 + H2O <->`H2SO3´ H2SO3<->H+ + HSO3- <-> 2H+ +SO32- 2HSO3- <->H2O +S2O52 –
As the nature of the cation should make no significant difference in this case concerning toxicity and solubility (all compounds are very soluble in water), only the chemical and biological properties of the anion are considered relevant. Based on the described equilibrium correlations, we propose unrestricted read-across between the groups of sulfites, hydrogensulfites and metabisulfites. Additionally, it is known that sodium dithionite disproportionates in water to form sodium hydrogen sulfite and sodium thiosulfate (equation II) so that this substance can also be added to the read-across concept.[2],[1]
It is expected for this case that the substance is not stable enough under physiological conditions to fulfil the requirements of study guidelines and so the products of decomposition have to be considered.
2 S2O42-+ H2O→2HSO3-+ S2O32 -

All sulfite, hydrogensulfite and metabisulfite substances are highly soluble in water, establishing upon dissolution an equilibrium that depends on solution pH as follows: ,

1. SO2 + H2O <-> H2SO3
2. H2SO3 <-> H+ + HSO3- <-> 2H+ + SO32-
3. 2 HSO3- <-> H2O + S2O52-

Under oxidising conditions, e.g., in surface waters, sulfite is oxidized to sulfate catalytically by (air) oxygen or by microbial action. A half-life of 77 hour was measured in deionized water, already suggesting substantial abiotic degradation. However, the presence of metal cations in the environment, such as copper, iron and manganese, accelerates the oxidation rate. In soils, HSO3- and SO32- ions are unstable and quickly oxidise. Further, because of the instability of SO32-, metal sulfites are generally too soluble to persist in soils. Thus, the most stable and predominant sulfur form in freshwater and in all but highly reduced environments is sulfate (SO42-). In highly reduced soils and sediments, sulfites may be reduced to sulfides (Lindsay, 1979; OECD SIDS, 2012).

Only the properties of the sulfite anion are considered relevant determinants of environmental toxicity since respective cations, i.e. ammonium, calcium, magnesium, sodium and potassium, are not assumed to contribute substantially to differences therein. Sulfite, although naturally present in the environment and also a metabolite and intermediate of sulfur-containing amino acids in organisms, may have an impact on the environment at elevated levels. Sulfites do not bioaccumulate.

In sum, unrestricted read-across between the sulfites, hydrogensulfites and metabisulfites is justified.
Reason / purpose:
reference to same study
Reason / purpose:
reference to same study
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 414 (Prenatal Developmental Toxicity Study)
GLP compliance:
no
Limit test:
no
Specific details on test material used for the study:
not specified
Species:
mouse
Strain:
CD-1
Details on test animals and environmental conditions:
TEST ANIMALS
- Age at study initiation: virgin adult female albino mice
- Housing: individually housed in disposable plastic cages
- Diet (ad libitum)
- Water (ad libitum): fresh tap water
Route of administration:
oral: gavage
Vehicle:
water
Details on exposure:
VEHICLE
- Amount of vehicle (if gavage): test item was administered as a water solution (1.0 mL/kg of body weight).
Analytical verification of doses or concentrations:
not specified
Details on analytical verification of doses or concentrations:
not specified
Details on mating procedure:
- Impregnation procedure: cohoused; females were mated with young adult males.
- Proof of pregnancy: vaginal plug considered as day 0 of gestation
Duration of treatment / exposure:
day 6 to 15 of gestation
Frequency of treatment:
daily
Duration of test:
until day 17 of gestation
Dose / conc.:
5.5 mg/kg bw/day (actual dose received)
Dose / conc.:
25.5 mg/kg bw/day (actual dose received)
Dose / conc.:
118 mg/kg bw/day (actual dose received)
Dose / conc.:
550 mg/kg bw/day (actual dose received)
No. of animals per sex per dose:
24 - 29 mated animals
Control animals:
yes, sham-exposed
other: positive control: 150 mg/kg body weight of Aspirin
Details on study design:
not specified
Maternal examinations:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: daily
- Cage side observations checked: mortality, appearance and behaviour

DETAILED CLINICAL OBSERVATIONS: No data

BODY WEIGHT: Yes
- Time schedule for examinations: days 0, 6, 11, 15 and 17 of gestation.

FOOD CONSUMPTION: Yes
- Time schedule: daily

WATER CONSUMPTION: No data

POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on gestation day 17
- all dams were subjected to Caesaren section under surgical anesthesia.
Ovaries and uterine content:
The ovaries and uterine content was examined after termination: Yes
Examinations included:
- Gravid uterus weight: No data
- Number of corpora lutea: Yes
- Number of implantations: Yes
- Number of resorptions: Yes
- Number of live and dead foetuses: Yes
Fetal examinations:
External examinations: Yes
- All foetuses underwent a gross examination for the presence of external congenital abnormalities. .

Soft tissue examinations: Yes
- one-third of the foetuses of each litter underwent detailed visceral examinations employing 10x magnification.

Skeletal examinations: Yes
- Two-third of the foetuses were cleared in potassium hydroxide, stained with alizarin red S dye and examined for skeletal defects (sternebrae, ribs,vertebrae, skull, extremities and miscellaneous)

Head examinations: No data

- Body weights of the live pups were recoded.
- Sex of the foetuses was recorded
Statistics:
not specified
Indices:
not specified
Historical control data:
not specified
Clinical signs:
not specified
Dermal irritation (if dermal study):
not specified
Mortality:
mortality observed, non-treatment-related
Body weight and weight changes:
no effects observed
Food consumption and compound intake (if feeding study):
not specified
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
Neuropathological findings:
not specified
Histopathological findings: non-neoplastic:
not specified
Histopathological findings: neoplastic:
not specified
Other effects:
not specified
Details on results:
- The survival of pregnant females was not affected by treatment with sodium thiosulfate.
- Maternal body weights and weight gains were comparable among groups.
Number of abortions:
no effects observed
Pre- and post-implantation loss:
no effects observed
Total litter losses by resorption:
no effects observed
Early or late resorptions:
no effects observed
Dead fetuses:
no effects observed
Changes in pregnancy duration:
not specified
Description (incidence and severity):
Migrated Data from removed field(s)
Field "Effects on pregnancy duration" (Path: ENDPOINT_STUDY_RECORD.DevelopmentalToxicityTeratogenicity.ResultsAndDiscussion.ResultsMaternalAnimals.MaternalDevelopmentalToxicity.EffectsOnPregnancyDuration): not specified
Changes in number of pregnant:
no effects observed
Other effects:
not specified
Details on maternal toxic effects:
- The pregnancy rates was comparable among groups (control group: 21 pregnant mice; 5.5 mg/kg bw/d : 20 pregnant mice; 25.5 mg/kg bw/d: 22 pregnant mice; 118 mg/kg bw/d: 21 pregnant mice; 550 mg/kg bw/d: 21 pregnant mice)
- There were no treatment-related effects on the number of abortions, corpora lutea, implantation sites, live litters and resorptions.

Key result
Remarks on result:
not determinable due to absence of adverse toxic effects
Abnormalities:
not specified
Fetal body weight changes:
no effects observed
Description (incidence and severity):
Migrated Data from removed field(s)
Field "Fetal/pup body weight changes" (Path: ENDPOINT_STUDY_RECORD.DevelopmentalToxicityTeratogenicity.ResultsAndDiscussion.ResultsFetuses.FetalPupBodyWeightChanges): not specified
Reduction in number of live offspring:
no effects observed
Changes in sex ratio:
no effects observed
Changes in litter size and weights:
not specified
Changes in postnatal survival:
not specified
External malformations:
not specified
Skeletal malformations:
no effects observed
Visceral malformations:
no effects observed
Other effects:
not specified
Details on embryotoxic / teratogenic effects:
- The number of live and dead foetuses, sex ratio and average foetal weight was not affected by treatment of dams with sodium thiosulfate.
- The number of abnormalities seen in either soft or skeletal tissues of the test groups did not differ from the number occurring spontaneously in the sham-treated controls.
Key result
Dose descriptor:
NOAEL
Remarks:
teratogenicity
Remarks on result:
not determinable due to absence of adverse toxic effects
Key result
Dose descriptor:
NOAEL
Remarks:
developmental toxicity
Remarks on result:
not determinable due to absence of adverse toxic effects
Abnormalities:
not specified
Developmental effects observed:
not specified
Conclusions:
The administration of up to 550 mg/kg bw/d of sodium thiosulfate to pregnant mice for 10 consecutive days had no clearly discernible effect on nidation or on maternal or foetal survival. The number of abnormalities seen in either soft or skeletal tissues of the test groups did not differ from the number occurring spontaneously in the sham-treated controls. Thus, the NOAEL for maternal and developmental toxicity can be expected above the highest dose of 550 mg/kg body weight sodium thiosulfate in this mice study.

Data source

Reference
Reference Type:
publication
Title:
Unnamed
Year:
1972

Materials and methods

Test guideline
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 414 (Prenatal Developmental Toxicity Study)
GLP compliance:
no
Limit test:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
solid: crystalline
Details on test material:
- Name of test material (as cited in study report): Sodium thiosulfate (FDA 71-35)
- Physical state: solid, fine white crystalline material
Specific details on test material used for the study:
not specified

Test animals

Species:
hamster
Strain:
other: Golden
Details on test animals and environmental conditions:
TEST ANIMALS
- Age at study initiation: virgin adult female hamsters
- Housing: individually housed in mesh bottom cages
- Diet (ad libitum)
- Water (ad libitum): fresh tap water

Administration / exposure

Route of administration:
oral: gavage
Vehicle:
water
Details on exposure:
VEHICLE
- Amount of vehicle (if gavage): test item was administered as a water solution (1 or 2 mL/kg of body weight)
Analytical verification of doses or concentrations:
not specified
Details on analytical verification of doses or concentrations:
not specified
Details on mating procedure:
- Impregnation procedure: cohoused
- M/F ratio per cage: females were mated (1 to 1) with mature males.
- Proof of pregnancy: motile sperm in vaginal smear was considered Day 0 of gestation.
Duration of treatment / exposure:
day 6 to 10 of gestation
Frequency of treatment:
daily
Duration of test:
until day 14 of gestation
Doses / concentrationsopen allclose all
Dose / conc.:
4 mg/kg bw/day (actual dose received)
Dose / conc.:
19 mg/kg bw/day (actual dose received)
Dose / conc.:
86 mg/kg bw/day (actual dose received)
Dose / conc.:
400 mg/kg bw/day (actual dose received)
No. of animals per sex per dose:
22 mated animals
Control animals:
yes, sham-exposed
other: positive control: 250 mg/kg body weight of Aspirin
Details on study design:
not specified

Examinations

Maternal examinations:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: daily
- Cage side observations checked: mortality, appearance and behaviour

DETAILED CLINICAL OBSERVATIONS: No data

BODY WEIGHT: Yes
- Time schedule for examinations: days 0, 8, 10 and 14 of gestation.

FOOD CONSUMPTION: Yes
- Time schedule: daily

WATER CONSUMPTION: No data

POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on gestation day 14
- all animals were subjected to Caesaren section under surgical anesthesia.
Ovaries and uterine content:
The ovaries and uterine content was examined after termination: Yes
Examinations included:
- Gravid uterus weight: No data
- Number of corpora lutea: Yes
- Number of implantations: Yes
- Number of resorptions: Yes
- Number of live and dead foetuses: Yes
Fetal examinations:
External examinations: Yes
- All foetuses underwent a gross examination for the presence of external congenital abnormalities. .

Soft tissue examinations: Yes
- One-third of the foetuses of each litter underwent detailed visceral examinations employing 10x magnification.

Skeletal examinations: Yes
- Two-third of the foetuses were cleared in potassium hydroxide, stained with alizarin red S dye and examined for skeletal defects (sternebrae, ribs, vertebrae, skull, extremities and miscellaneous)

Head examinations: No data

- Body weights of the live pups were recoded.
- Sex of the foetuses was recorded
Statistics:
not specified
Indices:
not specified
Historical control data:
not specified

Results and discussion

Results: maternal animals

General toxicity (maternal animals)

Clinical signs:
not specified
Dermal irritation (if dermal study):
not specified
Mortality:
mortality observed, non-treatment-related
Body weight and weight changes:
no effects observed
Food consumption and compound intake (if feeding study):
not specified
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
Neuropathological findings:
not specified
Histopathological findings: non-neoplastic:
not specified
Histopathological findings: neoplastic:
not specified
Other effects:
not specified
Details on results:
- The survival of pregnant females was not affected by treatment with sodium thiosulfate.
- Maternal body weights and weight gains were comparable among groups.

Maternal developmental toxicity

Number of abortions:
no effects observed
Pre- and post-implantation loss:
no effects observed
Total litter losses by resorption:
no effects observed
Early or late resorptions:
no effects observed
Dead fetuses:
no effects observed
Changes in pregnancy duration:
not specified
Description (incidence and severity):
Migrated Data from removed field(s)
Field "Effects on pregnancy duration" (Path: ENDPOINT_STUDY_RECORD.DevelopmentalToxicityTeratogenicity.ResultsAndDiscussion.ResultsMaternalAnimals.MaternalDevelopmentalToxicity.EffectsOnPregnancyDuration): not specified
Changes in number of pregnant:
no effects observed
Other effects:
not specified
Details on maternal toxic effects:
- The pregnancy rates was comparable among groups (control group: 21 pregnant hamsters; 4.0 mg/kg bw/d: 20 pregnant hamsters; 19.0 mg/kg bw/d: 21 pregnant hamsters; 86 mg/kg bw/d: 22 pregnant hamsters; 400 mg/kg bw/d: 20 pregnant hamsters).
- There were no treatment-related effects on the number of abortions, corpora lutea, implantation sites, live litters and resorptions.

Effect levels (maternal animals)

Key result
Remarks on result:
not determinable due to absence of adverse toxic effects

Maternal abnormalities

Abnormalities:
not specified

Results (fetuses)

Fetal body weight changes:
no effects observed
Description (incidence and severity):
Migrated Data from removed field(s)
Field "Fetal/pup body weight changes" (Path: ENDPOINT_STUDY_RECORD.DevelopmentalToxicityTeratogenicity.ResultsAndDiscussion.ResultsFetuses.FetalPupBodyWeightChanges): not specified
Reduction in number of live offspring:
no effects observed
Changes in sex ratio:
no effects observed
Changes in litter size and weights:
not specified
Changes in postnatal survival:
not specified
External malformations:
not specified
Skeletal malformations:
no effects observed
Visceral malformations:
no effects observed
Other effects:
not specified
Details on embryotoxic / teratogenic effects:
- The number of live and dead foetuses, sex ratio and average foetal weight was not affected by treatment of dams with sodium thiosulfate.
- The number of abnormalities seen in either soft or skeletal tissues of the test groups did not differ from the number occurring spontaneously in the sham-treated controls.

Effect levels (fetuses)

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Key result
Dose descriptor:
NOAEL
Remarks:
teratogenicity
Remarks on result:
not determinable due to absence of adverse toxic effects
Key result
Dose descriptor:
NOAEL
Remarks:
developmental toxicity
Remarks on result:
not determinable due to absence of adverse toxic effects

Fetal abnormalities

Abnormalities:
not specified

Overall developmental toxicity

Developmental effects observed:
not specified

Applicant's summary and conclusion

Conclusions:
The administration of up to 400 mg/kg bw/d of sodium thiosulfate to pregnant hamsters for 5 consecutive days had no clearly discernible effect on nidation or on maternal or foetal survival. The number of abnormalities seen in either soft or skeletal tissues of the test groups did not differ from the number occurring spontaneously in the sham-treated controls. Thus, the NOAEL for maternal and developmental toxicity can be expected above the highest dose of 400 mg/kg body weight sodium thiosulfate in this hamster study.