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Diss Factsheets

Administrative data

Key value for chemical safety assessment

Effects on fertility

Description of key information

No reproductive toxicity studies are available for silicon tetrachloride, therefore, good quality data for the condensed hydrolysis product, synthetic amorphous silica (SAS) have been used. There are no reproductive toxicity data for the other hydrolysis product, hydrogen chloride. Limited data are available regarding the reproduction and development of animals following oral, dermal or inhalation exposure to hydrogen chloride or hydrochloric acid, however, protons and chloride ions both exist as normal constituents of body fluid in animals, hence low concentrations of hydrogen chloride appear not to cause adverse effects in animals. Therefore hydrochloric acid would not contribute to any reproductive toxicity (fertility or developmental) effects at the dose levels tested.

The key study for reproductive toxicity is a two-generation reproductive toxicity study, conducted according to OECD Test Guideline 416 and in compliance with GLP. Wistar rats were administered SAS (described as NM-200 synthetic amorphous silica) (in highly deionised water containing 10% foetal bovine serum) at doses of 100, 300 and 1000 mg/kg bw/day by oral gavage. There were no adverse findings in parental animals or offspring at any dose level in any generation. Therefore, the NOAEL for general toxicity and reproductive toxicity was concluded to be ≥1000 mg/kg bw/day in this study (Wolterbeek et al.,2015).

Link to relevant study records
Reference
Endpoint:
two-generation reproductive toxicity
Type of information:
experimental study
Adequacy of study:
key study
Study period:
No data
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 416 (Two-Generation Reproduction Toxicity Study)
GLP compliance:
yes
Limit test:
no
Species:
rat
Strain:
Wistar
Sex:
male/female
Details on test animals or test system and environmental conditions:
TEST ANIMALS
- Source: Charles River Deutschland (Sulzfeld, Germany)
- Age at study initiation: (P) no data (4-5 weeks at purchase); (F1): 22 days
- Weight at study initiation: No data
- Fasting period before study: Not relevant
- Housing: Macrolon cages with a bedding of wood shavings and strips of paper as environmental enrichment. During mating a single female and male were housed together. Once mated the females were housed individually, and later they were housed individually with their litters.
- Diet: Ad libitum
- Water: Ad libitum
- Acclimation period: No data

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 ± 2°C
- Humidity (%): 45-65%
- Air changes (per hr): approximately 10 changes per hour
- Photoperiod (hrs dark / hrs light): 12 hours dark / 12 hours light

IN-LIFE DATES: No data
Route of administration:
oral: gavage
Vehicle:
other: highly deionised water containing 10% foetal bovine serum
Details on exposure:
PREPARATION OF DOSING SOLUTIONS: Once per week throughout the study, seven bottles per dosing group were prepared, each containing the relevant amount of test substance. On each day, the required amount of vehicle was added to achieve concentrations of 0, 10, 30 and 100 mg/ml test substance and stirred for at least 60 minutes.
Details on mating procedure:
- M/F ratio per cage: 1:1
- Length of cohabitation: Up to 2 weeks
- Proof of pregnancy: Sperm in vaginal smear referred to as day 0 of pregnancy
- After successful mating each pregnant female was caged (how): Individually (no further details)
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
At various weeks during the study, samples were taken from each of the dosing formulations for analytical investigation of hydrodynamic diameters of the silica particles.
Details on study schedule:
- F1 parental animals not mated until at least 10 weeks after selected from the F1 litters.
- Selection of parents from F1 generation when pups were 22 days of age.
- Age at mating of the mated animals in the study: at least 10 weeks
Dose / conc.:
100 mg/kg bw/day (actual dose received)
Dose / conc.:
300 mg/kg bw/day (actual dose received)
Dose / conc.:
1 000 mg/kg bw/day (actual dose received)
No. of animals per sex per dose:
28 (F0), 4 (F1, F2)
Control animals:
yes, concurrent vehicle
Details on study design:
- Dose selection rationale: Random
Positive control:
None
Parental animals: Observations and examinations:
CAGE SIDE OBSERVATIONS: Yes, throughout the study, all animals were checked daily for clinical signs and abnormal behaviour.

DETAILED CLINICAL OBSERVATIONS: No data
- Limited information on this.

BODY WEIGHT: Yes
- Time schedule for examinations: The body weight of all males and females was recorded weekly during premating, and for males, weekly thereafter. Mated females were weighed on gestation days 0, 4, 7, 10, 14, 17 and 21 and during lactation on post-natal days 1, 4, 7, 10, 14, 17 and 21. Animals were also weighed on their scheduled necropsy day.

FOOD CONSUMPTION: During the premating period, food consumption was measured weekly for each cage. Individual food consumption of all mated females was recorded from gestation days 0-4, 4-7, 7-10, 10-14, 14-17 and 17-21 and for all females with live pups on post-partum days 1-4, 4-7, 7-10, 10-14, 14-17 and 17-21.

WATER CONSUMPTION: No
Oestrous cyclicity (parental animals):
Three weeks prior to the end of the premating period of the F0 and F1 generation, vaginal smears were made from each female to evaluate the estrous cycle length and normality.
Sperm parameters (parental animals):
Parameters examined in F0 and F1 male parental generations: testes weight, epididymis weight, caudal epididymal sperm count, sperm motility and testicular sperm count
Litter observations:
STANDARDISATION OF LITTERS
- Performed on day 4 postpartum: yes
- Maximum of 8 pups/litter (4/sex/litter as nearly as possible); excess pups were killed and discarded.

PARAMETERS EXAMINED
The following parameters were examined in F1 / F2 offspring: number and sex of pups, stillbirths, live births, postnatal mortality, presence of gross anomalies, weight gain, physical or behavioural abnormalities

GROSS EXAMINATION OF DEAD PUPS: a necropsy was performed on stillborn pups and pups that died during lactation.
Postmortem examinations (parental animals):
SACRIFICE
It is not clear from the publication when scheduled sacrifices occurred. The study is stated to be according to OECD TG 416, so timings are assumed to follow this guideline, i.e. F0 and F1 males dosed until they are no longer needed for assessment of reproductive effects and females are sacrificed after weaning of their litter.

GROSS NECROPSY
- Gross necropsy consisted of external and internal examinations

HISTOPATHOLOGY / ORGAN WEIGHTS
The adrenals, brain, epididymides, kidneys, liver, ovaries, pituitary gland, prostate, seminal vesicles with coagulating glands, spleen, testes, thyroid, uterus with cervix (after counting of implantation sites), vagina and all gross lesions were weighed (except vagina) and preserved for microscopic examination for the control and the highest dose groups and on macroscopic abnormalities of all groups. Also, reproductive organs of F0 and F1 males who failed to sire, and of the non-mated/non-pregnant females from the low and mid dose groups were examined microscopically.
Postmortem examinations (offspring):
SACRIFICE
- The F1 offspring not selected as parental animals and all F2 offspring were sacrificed at 21 days of age.
- Of the remaining F1 pups, one male and one female from each litter were selected for a thorough necropsy, and the brain, spleen and thymus were weighed. Sexual maturation was studied by scoring the day of vaginal opening in females and testes descent and preputial separation in males from post-natal days 31, 21 and 39, respectively.

HISTOPATHOLOGY / ORGAN WEIGHTS
As for parental animals.
Statistics:
For some offspring viability data, sexual maturation, some sperm parameters and organ weights: Anova followed by Dunnett's multiple comparison test.
For some offspring data: Fisher's exact test.
For precoital time, gestation time and post-implantation loss per animal: Kruskal-Wallis + Mann-Whitney U test.
For some offspring data: Kruskal-Wallis followed by Dunnett's multiple comparison.
For some sperm parameters: Kruskal-Wallis non-parametric analysis of variance followed by Mann-Whitney U test.
Reproductive indices:
Mating, fertility, fecundity, gestation
Offspring viability indices:
Live birth, viability (day 4), viability (day 21)
Clinical signs:
no effects observed
Description (incidence and severity):
No clinical signs were observed in any dose groups throughout the study.
Mortality:
no mortality observed
Description (incidence):
No mortality occurred throughout the study.
Body weight and weight changes:
no effects observed
Description (incidence and severity):
No differences in the body weight occurred throughout the study.
Food consumption and compound intake (if feeding study):
no effects observed
Description (incidence and severity):
No differences in the food consumption occurred throughout the study.
Food efficiency:
not examined
Water consumption and compound intake (if drinking water study):
not examined
Ophthalmological findings:
not examined
Haematological findings:
not examined
Clinical biochemistry findings:
not examined
Urinalysis findings:
not examined
Behaviour (functional findings):
not examined
Immunological findings:
not examined
Organ weight findings including organ / body weight ratios:
no effects observed
Histopathological findings: non-neoplastic:
no effects observed
Description (incidence and severity):
No histopathological findings were observed at any dose.
Histopathological findings: neoplastic:
not examined
Other effects:
not examined
Reproductive function: oestrous cycle:
no effects observed
Description (incidence and severity):
The oestrous cycle length was not affected in female animals.
Reproductive function: sperm measures:
no effects observed
Description (incidence and severity):
No differences in epididymal sperm motility, epididymal sperm count, epididymal sperm morphology, testicular sperm count and daily sperm production were observed.
Reproductive performance:
no effects observed
Description (incidence and severity):
No differences in the reproductive performance occurred throughout the study. The mating index ranged from 96 to 100 %.
Post-implantation loss ranged from 8.6 to 10.5 for the F0 generation.
Key result
Dose descriptor:
NOAEL
Effect level:
>= 1 000 mg/kg bw/day (actual dose received)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: No adverse effects were observed in parental animals.
Critical effects observed:
no
Clinical signs:
no effects observed
Mortality / viability:
mortality observed, non-treatment-related
Description (incidence and severity):
One female of the low-dose group of the F0 generation delivered only dead pups. This finding was incidental and not considered as treatment-related. There were no other findings.
Body weight and weight changes:
no effects observed
Description (incidence and severity):
No differences in the body weight occurred for the pups.
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:
not examined
Clinical biochemistry findings:
not examined
Urinalysis findings:
not examined
Sexual maturation:
no effects observed
Description (incidence and severity):
No difference in the sexual maturation was found in the F1 animals among NM-200 groups and the control group.
Anogenital distance (AGD):
not specified
Nipple retention in male pups:
not specified
Organ weight findings including organ / body weight ratios:
no effects observed
Description (incidence and severity):
No effects were observed on pup body weights and on the absolute and relative weight of the brain, thymus and spleen of male and female pups. A statistically significant decreased relative weight of the thyroid of the male animals of the mid-dose group was observed. However, no statistically significant differences were observed between absolute and relative organ weights of male and female animals and there were no findings in the histopathology. Consequently, the finding was considered as not treatment-related.
Gross pathological findings:
no effects observed
Description (incidence and severity):
No treatment-related effects were observed at necropsy.
Histopathological findings:
no effects observed
Description (incidence and severity):
No histopathological findings were observed at any dose.
Other effects:
no effects observed
Behaviour (functional findings):
not examined
Developmental immunotoxicity:
not examined
The gestation index for the F1 generation was 89-98%. Post-implantation loss ranged from 8.9 to 17.7 for the F1 generation.
Key result
Dose descriptor:
NOAEL
Generation:
F1
Effect level:
>= 1 000 mg/kg bw/day (actual dose received)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: No adverse effects were observed in the F1 offspring.
Critical effects observed:
no
Dose descriptor:
NOAEL
Generation:
F2
Effect level:
>= 1 000 mg/kg bw/day (actual dose received)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: No adverse effects were observed in any of the F2 offspring.
Critical effects observed:
no
Reproductive effects observed:
no

Table 1 Reproductive Performance of female rats receiving NM-200

              NM-200 dose (mg/kg bw/day)
 Parameter of reproductive performance  Generation  0  100  300  1000
 Mating index (%)  F0  96  100  100  100
   F1  100  100  100  100
 Fertility index (%)  F0  96  100  96  96
   F1  98  93  93  89
 Fecundity index (%) F0   100  100  96  96
   F1  89  93  93  89
 Gestation index (%)  F0  100  96  100  100
   F1  100  100  96  96
 Precoital time (days)  F0  2.7±0.21  2.8±0.25  2.3±0.19  2.5±0.21
   F1  2.8±0.27  2.5±0.2  2.4±0.2  2.4±0.26
 Gestation time (days)  F0  21.7±0.09  21.6±0.11  21.6±0.1  21.6±0.1
   F1  21.3±0.09  21.2±0.08  21.4±0.12  21.3±0.09
 Postimplantation loss per animal (%)  F0  8.6±2.66  10.5±3.72  9.5±2.54  10.1±2.52
   F1  8.9±1.48  13.6±3.68  17.6±5.47  14.8±4.91

Table 2 - Offspring data from rats receiving NM-200

                NM-200 dose (mg/kg bw/day)
   Generation  0  100  300  1000
 Pups delivered (total)  F0  10.3±2.9  10.7±2.3 11.3± 2.0  11.0±1.5
   F1 11.5 ±1.6 10.7±2.8   10.4±2.8 11.0± 2.6
 Live birth index (%)  F0  97.3±9.9 94.8± 19.1  96.5±12.7 98.7± 4.9
   F1  96.2±6.1 90.7± 17.3  94.2±12.7 93.5± 16.1
 Pup mortality day 1 (%)  F0  2.7±9.9 5.2± 19.1  3.5±12.7 1.3± 4.9
   F1  3.8±6.1 9.3± 17.3 5.8 ±19.0 6.5± 16.1
 Viability index day 4 (%)  F0  99.3±2.5 99.6± 2.0  98.9±4.2 98.8± 3.5
  F1   84.7±28.0 83.8± 34.6 95.3 ± 20.0  73.8±42.3
 Viability index day 21 (%)  F0  100±0  100±0  100±0  100±0 
   F1  100±0  99.5 ±2.6  98.6 ±6.8  100±0
 Whole litter losses (litters lost/total number of litters)  F0  2/27  2/28  2/27  0/27
   F1  1/25  3/26  1/25  4/24
 Sex ratio day 1 (% males)  F0  51.9±17.6  43.9± 12.2  50.8 ±15.6  51.1± 10.9
   F1  47.4± 16.2   52.6±21.4  45.3± 19.6  42.3± 15.4
Conclusions:
In a two-generation reproductive toxicity study, conducted according to OECD Test Guideline 416 and in compliance with GLP, the NOAEL for systemic and reproductive toxicity of synthetic amorphous silica was concluded to be ≥1000 mg/kg bw/day in Wistar rats based on no adverse effects up to the highest dose tested, 1000 mg/kg bw/day.
Effect on fertility: via oral route
Endpoint conclusion:
no adverse effect observed
Dose descriptor:
NOAEL
1 000 mg/kg bw/day
Study duration:
chronic
Species:
rat
Quality of whole database:
Klimisch score of 2
Effect on fertility: via inhalation route
Endpoint conclusion:
no study available
Effect on fertility: via dermal route
Endpoint conclusion:
no study available
Additional information

There are no adequate reproductive toxicity data on silicon tetrachloride so good quality data for the hydrolysis product polysilicic acid (equivalent to synthetic amorphous silica (SAS)) have been used to assess the potential for adverse effects on fertility following exposure to silicon tetrachloride.

Overview:

It is considered not to be ethical to perform repeated dose toxicity testing with silicon tetrachloride by any route of exposure due to its known corrosive properties. Following repeated oral dosing, the corrosive nature of the product could affect the lining of the stomach, giving rise to hyperplasia and a subsequent reduced food intake. This would confound the interpretation of any systemically driven effects. A guideline-compliant repeated-dose inhalation study should elicit systemic toxicity at the highest test concentration. Since the local corrosive effects of silicon tetrachloride would be significant a valid inhalation study according to the relevant guidelines is technically not feasible to do. It is also unlikely that any systemic effects would be seen at dose levels made sufficiently low (<10 ppm) to prevent the known corrosive effects and/or distress in the test species. This has been confirmed in a 28-day inhalation study with another chlorosilane, dichloro(dimethyl)silane (WIL, 2014) in which there were no effects of treatment on clinical signs, body weight or food consumption that would indicate a systemic effect. Furthermore, the histopathology in the study indicated that the effects in the upper respiratory tract were similar to HCl. It is therefore concluded that HCl will dominate the inhalation toxicity profile of silicon tetrachloride.

With regard to the dermal and inhalation routes, due to the known corrosive effects of silicon tetrachloride, appropriate H-phrases and P-statements are included in the labelling, meaning that repeated skin and inhalation exposure is not expected. Any accidental skin contact or inhalation exposure could cause severe local effects but would be unlikely to cause any systemic effects.

ORAL ROUTE

SYSTEMIC EFFECTS

There are no adequate reproductive toxicity data on silicon tetrachloride so good quality data for synthetic amorphous silica (CAS 112926-00-8) have been used to assess the reproductive toxicity of silicon tetrachloride. Local effects from the hydrolysis product, hydrogen chloride (HCl) are not addressed by these data.

Silicon tetrachloride, like all inorganic chlorosilanes, is a severely corrosive substance that is decomposed by water, producing silicic acid and HCl. The reaction is highly exothermic (Merck, 2013). Hydrolysis half-life is less than 0.3 min at 25°C and pH 4, 7 and 9. The initial products of hydrolysis are hydrogen chloride (HCl) and monosilicic acid (soluble silica). It has not been possible to isolate monosilicic acid (Jones et al., 2000).

 

Monosilicic acid condenses to insoluble polysilicic acid [equivalent to synthetic amorphous silica (SAS)] at concentrations higher than 120 mg/l ‘SiO2equivalent’ in water (Holleman-Wiberg, 2001). At very high concentration, polysilicic acid can condense to silicon dioxide (SiO2). The hydrolysis products of hydrochloric acid and (poly)silicic acid are significant for the chemical safety assessment (CSR).

 

Monosilicic acid and polysilicic acid are naturally occurring substances which are ubiquitous in the environment. Soluble monosilicic acid is the major bioavailable form of silicon and plays an important role in the biogeochemical cycle of silicon (ECETOC, 2006). Typical background concentrations of monosilicic acid in the environment are up to 75 mg/l ‘SiO2equivalent’ in river water and up to 14 mg/l ‘SiO2equivalent’ in seawater (Iler, 1979).

 

The literature gives various values for the solubility of silicic acid, determined indirectly as ‘SiO2 equivalent’ because the soluble species cannot be directly measured:

The solubility of monosilicic acid according to Alexander et al. (1954) at 25 °C:

  • 150 mg/l ‘SiO2 equivalent’ at pH 2.0 and pH 3.0
  • 130 mg/l ‘SiO2equivalent’ at pH 4.2
  • 110 mg/l ‘SiO2equivalent’ at pH 5.7
  • 100 mg/l ‘SiO2equivalent’ at pH 7.7
  • 490 mg/l ‘SiO2equivalent’ at pH 10.3
  • 1120 mg/l ‘SiO2equivalent’ at pH 10.6

 The solubility of monosilicic acid according to Goto and Okura (1953) at 25 °C:

  • 120 mg/l ‘SiO2equivalent’ at pH 2.0 150 mg/l ‘SiO2equivalent’ at pH 7.
  • 150 mg/l ‘SiO2equivalent’ at pH 7.0

The solubility of monosilicic acid according to Elmer and Nordberg (1958) at neutral pH:

  • 170 mg/l ‘SiO2equivalent’ at 35°C 270 mg/l ‘SiO2equivalent’ at 65°C
  • 270 mg/l ‘SiO2equivalent’ at 65°C 465 mg/l ‘SiO2equivalent’ at 95°
  • 465 mg/l ‘SiO2equivalent’ at 95°C

 

With the described properties of silicon tetrachloride in mind, it is not possible to conduct reproductive toxicity studies in experimental animals due to the corrosive nature of this substance. Nor can the hydrolysis product, monosilicic acid, be tested as it is not possible to isolate this substance. However, we know from physicochemical properties that following ingestion of silicon tetrachloride, the conditions in the stomach are such that following an initial rapid hydrolysis to soluble monosilicic acid, this monomer will start to condense to form insoluble polysilicic acid (equivalent to SAS). This condensation will start to occur once the concentration of monosilicic acid reaches approximately 150 mg/l in the gastric juices.

Monosilicic acid (soluble silica) undergoes condensation reactions in solution at about 120 mg/l ‘SiO2 equivalent’. The solubility of monosilicic acid in water is 150 mg/l ‘SiO2equivalent'.

Following dosing by oral gavage, partitioning will occur between the dose vehicle and the aqueous environment in the stomach.

Mass dosed (in mg/day) = Body weight (in kg) x dose level (in mg/kg bw/day)

 

Dose concentration (in mg/l) = mass dosed (in mg/day)÷volume (in l)

So, the dose level (mg/kg bw/day) required to reach the dose concentration of 150 mg/l 'SiO2 equivalent', the estimated (conservative) maximum concentration of silicic acid that can occur in the stomach before condensation to insoluble polysilicic acid (equivalent to SAS) begins is calculated as follows:

Body weight of rat = 0.3kg

Dose level = X                                                        

Estimated aqueous volume = 0.0015 l                                                                      

Dose concentration = 150 mg/l

150 mg/l = 0.3 kg x dose level (mg/kg bw/day)÷0.0015l

Dose level = 0.75 mg/kg bw/day 'SiO2equivalent'

Therefore, based on a condensation limit of 150 mg/l, the maximum dose level that could be used in practice to ensure exposure mainly to monosilicic acid in the stomach of experimental animals is approximately 0.75 mg/kg bw/day or less of 'SiO2 equivalent'.

A correction for molecular weight gives a maximum dose level for silicon tetrachloride:

Mr [silicon tetrachloride]                =             169.90 g/mol

Mr [silicon dioxide]                         =             60.08 g/mol

Dose level [Silicon tetrachloride]        =          [Dose level [silicon dioxide]  x  Mr [silicon tetrachloride]]

                                                                                                   Mr [silicon dioxide]

 

                                                            =       (0.75 mg/kg bw/day) x (169.90 g/mol)

                                                                                        (60.08 g/mol)

 

                                                            =        2.12 mg/kg bw/day

Therefore, based on a condensation limit of 150 mg/l the maximum dose level of silicon tetrachloride that can be dosed to ensure exposure mainly to monosilicic acid is approximately 2 mg/kg bw/day.

For comparison purposes, using the above calculation, the following shows the dose concentrations for the dose levels typically used in experimental animal studies (100, 300 and 1000 mg/kg bw/day).

Body weight                                = 0.3 kg

Total amount dosed                     = 30 mg

Estimated aqueous volume           = 1.5 ml

Dose concentration                      = 20,000 mg/l

Body weight                                = 0.3 kg

Total amount dosed                     = 90 mg

Estimated aqueous volume           = 1.5 ml

Dose concentration                     =  60,000 mg/l

Body weight                                 = 0.3 kg

Total amount dosed                      = 300 mg

Estimated aqueous volume           = 1.5 ml

Dose concentration                       = 200,000 mg/l

Therefore, dosing at these levels clearly gives a dose concentration in the stomach that far exceeds the dose at which condensation to polysilicic acid (equivalent to SAS) starts to occur. Consequently, the majority of the dose in the stomach will be present as insoluble polysilicic acid (equivalent to SAS). In all cases only approximately 150 mg/l will be present as soluble monosilicic acid.

Overall, it can be concluded that gavaging silicon tetrachloride at doses unlikely to cause local corrosive effects and at doses that give mainly soluble monosilicic acid (2 mg/kg bw/day or less) would be unethical based on animal usage. However, because the vast majority of a gavaged dose will rapidly condense to insoluble polysilicic acid (equivalent to SAS) it is appropriate to use toxicology data on SAS to address the potential for oral reproductive toxicity of silicon tetrachloride.

The key study for reproductive toxicity is a two-generation reproductive toxicity study, conducted according to OECD Test Guideline 416 and in compliance with GLP. Wistar rats were administered SAS (described as NM-200 synthetic amorphous silica) (in highly deionised water containing 10% foetal bovine serum) at doses of 100, 300 and 1000 mg/kg bw/day by oral gavage. There were no adverse findings in parental animals or offspring at any dose level in any generation. Therefore, the NOAEL for general toxicity and reproductive toxicity was concluded to be ≥1000 mg/kg bw/day in this study (Wolterbeek et al., 2015).

Limited data are available regarding the reproductive toxicity in animals following oral, dermal or inhalation exposure to hydrogen chloride. However, protons and chloride ions exist as normal constituents of body fluid in animals, hence low concentrations of hydrogen chloride appear not to cause adverse effects in animals. Therefore, the hydrolysis product of silicon tetrachloride, HCl, would not be expected to cause reproductive toxicity in experimental animals or humans following initial exposure to silicon tetrachloride.

References

Alexander G.B., Heston W.M. and Iler R.K. (1954) J. Phys. Chem., 58, 453.

Cotton F.A. and Wilkinson G. (1999) Advanced Inorganic Chemistry, 6th Edition, p. 271

ECETOC (2006) Synthetic Amorphous Silica (CAS No. 7631-86-9), JACC REPORT No. 51

Elmer and Nordberg (1958) J. Am.Chem. Soc., 41, 517

Goto K. and Okura T. (1953) Kagaku, 23, 426.

Holleman-Wiberg, (2001) Inorganic Chemistry, Academic Press, p. 865

Iler, Ralph K. (1979) The Chemistry of Silica: Solubility, Polymerization, Colloid and Surface Properties and Biochemistry of Silica, Wiley, p. 13.

Jones, R. G., Wataru, A., and Chojnowski, J. (2000) Silicon-Containing Polymers: The Science and Technology of Their Synthesis, Kluwer Academic Press pp168-169

Merck Index (2013) Monograph Number. 8639 (15th Ed)

Effects on developmental toxicity

Description of key information

No developmental toxicity studies are available for silicon tetrachloride, therefore good quality data for the condensed hydrolysis product, synthetic amorphous silica (SAS) have been used. There are no reproductive toxicity data for the other hydrolysis product, hydrogen chloride. Limited data are available regarding the reproduction and development of animals following oral, dermal or inhalation exposure to hydrogen chloride or hydrochloric acid, however, protons and chloride ions both exist as normal constituents of body fluid in animals, hence low concentrations of hydrogen chloride appear not to cause adverse effects in animals. Therefore hydrochloric acid would not contribute to any reproductive toxicity (fertility or developmental) effects at the dose levels tested.

In a prenatal developmental study (Hofmann et al., 2015) conducted according to OECD Test Guideline 414 and in compliance with GLP, pregnant Wistar rats were administered SAS (described as NM-200 synthetic amorphous silica) (in highly deionised water containing 10% foetal bovine serum) at doses of 100, 300 and 1000 mg/kg bw/day by oral gavage on gestation days 6-19. The dosing schedule and investigations were conducted according to the OECD Test Guideline. There were no adverse, treatment-related findings in parental animals or offspring. There were a number of incidental foetal malformations and variations, which all occurred at a rate no larger than that of the control/historical controls, without statistical significance and without a dose-response relationship. Therefore, the NOAEL for general toxicity and developmental (including teratogenicity) toxicity was ≥1000 mg/kg bw/day.

In a prenatal developmental toxicity study, conducted prior to OECD Test Guidelines or GLP, the teratogenic effect of silica gel was investigated in pregnant mice, rats, hamsters and rabbits (Food and Drug Research Laboratories, 1973).

The test material was administered at doses of up to 1340 mg/kg (body weight) to pregnant mice for 10 consecutive days, during gestation days 6 to 15; up to 1350 mg/kg (body weight) to pregnant rats for 10 consecutive days, during gestation days 6 to 15; up to 1600 mg/kg (body weight) to pregnant hamsters for 5 consecutive days, during gestation days 6 to 10; or up to 1600 mg/kg (body weight) to pregnant rabbits for 13 consecutive days, during gestation days 6 to 18. There were no clearly discernible effects on implantation or on maternal or foetal survival in mice, rats, hamsters or rabbits.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. There were no effects on neonatal survival in rabbits. Neonatal survival was not examined for the other test species.

Link to relevant study records

Referenceopen allclose all

Endpoint:
developmental toxicity
Type of information:
experimental study
Adequacy of study:
weight of evidence
Study period:
No data
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 414 (Prenatal Developmental Toxicity Study)
Qualifier:
according to guideline
Guideline:
EPA OPPTS 870.3700 (Prenatal Developmental Toxicity Study)
GLP compliance:
yes
Limit test:
no
Species:
rat
Strain:
Wistar
Details on test animals or test system and environmental conditions:
TEST ANIMALS
- Source: Charles River Laboratories, Germany GmbH
- Age at study initiation: 12-15 weeks
- Weight at study initiation: 195.3- 271g
- Fasting period before study: Not relevant
- Housing: Individually in Macrolon type III cages, with a bedding of dust-free wood shavings and wooden gnawing blocks as environmental enrichment.
- Diet (e.g. ad libitum): Ad libitum
- Water (e.g. ad libitum): Ad libitum
- Acclimation period: 5 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 ± 2°C
- Humidity (%): 30-70%
- Air changes (per hr): approximately 15 changes per hour
- Photoperiod (hrs dark / hrs light): 12/12

IN-LIFE DATES: No data
Route of administration:
oral: gavage
Vehicle:
other: highly deionised water containing 10% foetal bovine serum
Details on exposure:
PREPARATION OF DOSING SOLUTIONS: Dosing formulations of synthetic amorphous silica were pre-pared with highly deionized water containing 10% foetal bovine serum in order to avoid agglomeration.
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
The formulations were analysed by scanning electron microscopy after shock freezing and in situ analytical ultracentrifugation.
Details on mating procedure:
- Impregnation procedure: cohoused
- If cohoused:
- M/F ratio per cage: 1-2 untreated females with 1 untreated male
- Length of cohabitation: Not stated but mating occurred between 15:30 and 7.30 on the day after cohousing started.
- Verification of same strain and source of both sexes: yes
- Proof of pregnancy: sperm in vaginal smear referred to as day 0 of pregnancy
Duration of treatment / exposure:
Gestation day 6-19
Frequency of treatment:
One dose per day
Duration of test:
Approximately 21 days
Dose / conc.:
100 mg/kg bw/day
Dose / conc.:
300 mg/kg bw/day
Dose / conc.:
1 000 mg/kg bw/day
No. of animals per sex per dose:
25 females per dose
Control animals:
yes, concurrent vehicle
Details on study design:
- Dose selection rationale: Highest dose was chosen as the limit dose according to the test guideline.
Maternal examinations:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: described as 'regular'

DETAILED CLINICAL OBSERVATIONS: No data

BODY WEIGHT: Yes
- Time schedule for examinations: described as 'regular'

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study): Yes (described as 'regular')

WATER CONSUMPTION: No

POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on gestation day 20
- Organs examined: uterus and ovaries
Ovaries and uterine content:
The ovaries and uterine content were examined after termination: Yes
Examinations included:
- Gravid uterus weight: Yes
- Number of corpora lutea: Yes
- Number of implantations: Yes
- Number of early resorptions: Yes
- Number of late resorptions: Yes
Fetal examinations:
- External examinations: Yes: all per litter
- Soft tissue examinations: Yes: half per litter
- Skeletal examinations: Yes: half per litter
- Head examinations: Yes, but no data on number examined
Statistics:
The data for food consumption, maternal, litter weight and body weight change, carcass and gravid uterus weight, number of corpora lutea and implantations, number of resorptions, number of live foetuses, percent pre- and post- implantation loss, percent live foetuses per litter, number of pups per litter, post- implantation loss, and mean placental weights were analysed by the two-sided Dunnett’s test for the hypothesis of equal means. The female mortality, number of pregnant females, and number of litters with foetal proportions. Proportions of foetuses per litter with findings were analysed by pairwise comparison of each dose group with the control group by a one-sided Wilcoxon test for the hypothesis of equal medians.
Clinical signs:
no effects observed
Description (incidence and severity):
No treatment-related clinical signs occurred throughout the study.
Dermal irritation (if dermal study):
not examined
Mortality:
no mortality observed
Description (incidence):
No treatment-related mortality occurred throughout the study.
Body weight and weight changes:
no effects observed
Description (incidence and severity):
No difference in the body weight or body weight gain occurred throughout the study.
Food consumption and compound intake (if feeding study):
no effects observed
Description (incidence and severity):
No difference in the food consumption occurred throughout the study.
Food efficiency:
not examined
Water consumption and compound intake (if drinking water study):
not examined
Ophthalmological findings:
not examined
Haematological findings:
not examined
Clinical biochemistry findings:
not examined
Urinalysis findings:
not examined
Behaviour (functional findings):
not examined
Immunological findings:
not examined
Organ weight findings including organ / body weight ratios:
no effects observed
Description (incidence and severity):
The average carcass weight was not affected by the treatment throughout the study.
Gross pathological findings:
no effects observed
Description (incidence and severity):
No treatment-related findings were observed at necropsy.
Neuropathological findings:
not examined
Histopathological findings: non-neoplastic:
not specified
Histopathological findings: neoplastic:
not examined
Other effects:
no effects observed
Number of abortions:
not specified
Pre- and post-implantation loss:
no effects observed
Description (incidence and severity):
A slightly higher pre-implantation loss occurred in the groups treated with SAS when compared to the control group. However, this was not considered as treatment-related as treatment started after implantation. No other differences occurred throughout the study.
Total litter losses by resorption:
not specified
Early or late resorptions:
not examined
Dead fetuses:
no effects observed
Changes in pregnancy duration:
not examined
Changes in number of pregnant:
effects observed, non-treatment-related
Description (incidence and severity):
Three rats of the control group, four rats of the low dose group and two animals of the high dose group were not pregnant. Since there was no dose-relationship occurring, the findings were not considered as treatment-related.
Other effects:
effects observed, non-treatment-related
Description (incidence and severity):
The mean number of corpora lutea was not affected.
The blood coagulum around the placenta or fused placenta were observed for 1-2 littermates of the control, the mid and the high dose group. This was considered as spontaneous and therefore, not considered as treatment-related.

Some isolated cartilage findings without impact on the respective bony structures occurred in all groups including the controls. The observed cartilage findings were related to the skull and the sternum. Although, the incidence of notched manubrium was statistically significantly higher in the high-dose group which was within the historical control range. Therefore, these changes were not considered as treatment-related.
Key result
Dose descriptor:
NOAEL
Remarks:
Maternal
Effect level:
>= 1 000 mg/kg bw/day (actual dose received)
Based on:
test mat.
Basis for effect level:
other: No adverse effects observed in maternal animals.
Abnormalities:
no effects observed
Fetal body weight changes:
no effects observed
Description (incidence and severity):
The mean foetal weights did not show any biologically relevant differences between the test substance-treated groups and the control.
Reduction in number of live offspring:
not specified
Changes in sex ratio:
no effects observed
Description (incidence and severity):
No differences in the sex distribution occurred throughout the study.
Changes in litter size and weights:
not specified
Changes in postnatal survival:
not examined
External malformations:
effects observed, non-treatment-related
Description (incidence and severity):
One foetus in the low and one in the high dose group had multiple malformations. Mandibular micrognathia mirrored the severely malformed skull bones found during skeletal examination in one foetus. The changes were considered to be related to each other. The cleft palate observed in the other foetus is present in the historical control data at a comparable incidence. Both findings were considered to be spontaneous in nature and without a relation to dosing. The total incidence of external malformations in treated animals did not differ significantly from that of the control group.
Skeletal malformations:
effects observed, non-treatment-related
Description (incidence and severity):
Skeletal malformations were noted in single foetuses at dose levels of 0, 100 and 1000 mg/kg bw/day which affected individual foetuses. However, there were no statistically significant differences between the test groups and not a dose-response relationship. Additionally, the overall incidences of skeletal malformations were comparable to those found in the historical control data.
Skeletal variations of different bone structures were observed with or without effects on corresponding cartilage. The observed skeletal variations were related to several parts of foetal skeletons and appeared without a relation to dosing. The overall incidences of skeletal variations were comparable to the historic control data. There were no dosing-related statistical significance and the incidences were within historical control ranges and consequently, not considered as treatment-related.
Visceral malformations:
effects observed, non-treatment-related
Description (incidence and severity):
In the control group, one soft tissue malformation, supernumerary unilateral liver lobes were observed in the control group. Three soft tissue variations i.e. short innominate, enlarged atrial chamber of the heart and uni- or bilateral dilation of renal pelvis were detected. However, no dose response occurred. The observable differences between the groups reflect the usual fluctuation for this parameter and were clearly withing the range of the historical control data.
Other effects:
no effects observed
Key result
Dose descriptor:
NOAEL
Effect level:
>= 1 000 mg/kg bw/day (actual dose received)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: There were no adverse effects on developmental parameters.
Abnormalities:
no effects observed
Developmental effects observed:
no

Table 1- Summary of reproductive and developmental results

 Dose (mg/kg bw/d)    0 (vehicle control)  100  300  1000
 Females mated  N 25 25 25 25
  Pregnant  N 22 21 25  23 
  Conception rate  % 88  84  100  92 
  Aborted  N 0 0 0 0
  Premature births  N 0  0  0  0 
  Dams with viable foetuses  N 22 21  25  23 
  Dams with total litter loss  N 0  0  0  0 
Female mortality N 0 0  0  0 
Pregnant at terminal sacrifice  N 22  21  25  23 
   % 88 84  100  92 
Corpora luteaD mean ± SD  14.2 ± 2.4  13.9 ± 2.08  14.0 ± 1.99  14.7 ± 2.03
Implantation sitesD mean ± SD  13.5 ± 2.56  12.5 ± 2.8  12.8 ± 1.62  13.4 ± 2.27
Pre-implantation loss (%)D mean ± SD  4.9 ± 7.31  9.4 ± 17.69 7.7 ± 11.81  8.4 ± 12.31 
Post-implantation loss (%)D mean ± SD  8.3 ± 9.96 5.2 ± 5.22  9.9 ± 16.2  6.0 ± 3.56 
  Early resorptions (%)D    7.6 ± 9.27 5.2 ± 5.22  9.9 ± 16.2  5.6 ± 3.75 
  Late resorptions (%)D    0.7 ± 2.26 0  0  0.3 ± 1.49 
  Dead foetuses    0 0  0 0
 Dams with viable foetuses  N 22 21 25  23 
  Live foetusesD  mean ± SD  12.4 ± 2.59 11.8 ± 2.71  11.5 ± 2.47  12.7 ± 2.23 
  Live foetuses (% implantation)D  mean ± SD  91.7 ± 9.96 94.8 ± 5.22  90.1 ± 16.2  94.0 ± 3.56 
  MalesD  mean ± SD  5.9 ± 1.7 5.5 ± 1.91  6.5 ± 1.85  5.7 ± 1.79 
  Males (%)D  mean ± SD  43.7 ± 10.64 46.5 ± 18.79  50.9 ± 14.23  43.2 ± 13.09 
  FemalesD  mean ± SD  6.5 ± 1.95 6.3 ± 2.76  5.0 ± 2.34  6.9 ± 2.21 
  Females (%)D  mean ± SD  48.0 ± 11.17 48.3 ± 18.55 39.2 ± 15.98  50.9 ± 11.85 
 Sex ratio (% males)    47.4 46.8  56.3  45.4 
 Placental weightsD  mean ± SD  0.47 ± 0.040 0.47 ± 0.042  0.46 ± 0.038  0.47 ± 0.038 
   N 22  21  25  23 
  Of male foetusesD  mean ± SD 0.49 ± 0.038  0.48 ± 0.036  0.47 ± 0.043  0.48 ± 0.037 
   N 22 21  25  23 
  Of female foetusesD  mean ± SD 0.46 ± 0.042  0.46 ± 0.052  0.46 ± 0.044  0.46 ± 0.041 
   N 22 20  25  23 
 Foetal weightsD  mean SD 3.4 ± 0.26  3.4 ± 0.15  3.4 ± 0.24  3.4 ± 0.14 
   N 22  21  25  23 
  MalesD  mean SD 3.5 ± 0.27  3.4 ± 0.18  3.5 ± 0.24  3.5 ± 0.14 
   N 22  21  25  23 
  FemalesD  mean SD 3.3 ± 0.25 3.3 ± 0.17  3.4 ± 0.28  3.3 ± 0.15 
   N 22  20  25  23 

*p<0.05; **p<0.01 (D, two-sided Dunnett's test)

Table 2 - Summary of foetal malformations

 Dose (mg/kg bw/d)   0 (vehicle control)  100  300  1000
Litters evaluated  N 22 21  25  23 
Foetuses evaluated  N 272  248  288  291 
                
Total Malformations               
Foetal incidence  N 3 1 0  1 
 % 1.1  0.4  0.0  0.3 
 Litter incidenceF  N 2  1  0  1 
   % 9.1 4.8  0.0  4.3 
 Affected foetuses per litterW  mean% ± SD 1.3 ± 4.07  0.4 ± 1.98  0.0 ± 0.00  0.3 ± 1.60 

*<0.05; **p<0.01 (F, one-sided Fisher's exact test; W, one-sided Wilcoxon)

Conclusions:
In a developmental toxicity study, conducted according to OECD Test Guideline 414 and in compliance with GLP, the NOAEL for general systemic and developmental toxicity was concluded to be ≥1000 mg/kg bw/day based on no adverse effects observed.
Endpoint:
developmental toxicity
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
Qualifier:
no guideline followed
Principles of method if other than guideline:
The study was conducted prior to implementation of OECD Test Guidelines. The study follows a protocol similar to OECD Test Guideline 414 with some deviations.
GLP compliance:
no
Remarks:
The study was conducted prior to GLP compliance
Limit test:
no
Species:
hamster
Strain:
other: Virgin adult female golden hamsters
Details on test animals or test system and environmental conditions:
TEST ANIMALS
- Source: not specified
- Age at study initiation: not specified
- Weight at study initiation: not specified
- Fasting period before study: not specified
- Housing: individually housed in mesh bottom cages
- Diet (e.g. ad libitum): food was freely available, ad libitum
- Water (e.g. ad libitum): fresh tap water was freely available, ad libitum
- Acclimation period: not specified

ENVIRONMENTAL CONDITIONS
- Temperature (°C): temperature and humidity-controlled quarters
- Humidity (%): temperature and humidity-controlled quarters
- Air changes (per hr): not specified
- Photoperiod (hrs dark / hrs light): not specified

Route of administration:
oral: gavage
Vehicle:
not specified
Details on exposure:
PREPARATION OF DOSING SOLUTIONS: The test material was prepared and doses calculated according to Table 1.

VEHICLE
- Justification for use and choice of vehicle (if other than water): The controls were sham treated with the vehicle at a level equivalent to the group receiving the highest test dose.
- Concentration in vehicle: See Table 1
- Amount of vehicle (if gavage): See Table 1
Analytical verification of doses or concentrations:
not specified
Details on mating procedure:
The female animals were mated with mature adult males (1:1), and the appearance of motile sperm in the vaginal smear was considered day 0 of gestation.
Duration of treatment / exposure:
In the study pregnant female animals were given orally the test substance via intubation from gestation day 6 to 10.
Frequency of treatment:
daily
Duration of test:
10 days
Dose / conc.:
0 mg/kg bw/day (actual dose received)
Remarks:
sham control
Dose / conc.:
250 mg/kg bw/day (actual dose received)
Remarks:
Aspirin - positive control
Dose / conc.:
16 mg/kg bw/day (actual dose received)
Remarks:
test item
Dose / conc.:
74.3 mg/kg bw/day (actual dose received)
Remarks:
test item
Dose / conc.:
345 mg/kg bw/day (actual dose received)
Remarks:
test item
Dose / conc.:
1 600 mg/kg bw/day (actual dose received)
Remarks:
test item
No. of animals per sex per dose:
Number of female animals per group before mating:
Sham control: 23 females
Positive control: 24 females
16 mg/kg bw/day test substance: 23 females
74.3 mg/kg bw/day test substance: 23 females
345 mg/kg bw/day test substance: 23 females
1600 mg/kg bw/day test substance: 24 females

Number of pregnant female animals per group on gestation day 0:
Sham control: 22 females
Positive control: 20 females
16 mg/kg bw/day test substance: 22 females
74.3 mg/kg bw/day test substance: 22 females
345 mg/kg bw/day test substance: 21 females
1600 mg/kg bw/day test substance: 21 females
Control animals:
yes
Maternal examinations:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: All animals were observed daily for appearance and behaviour.

DETAILED CLINICAL OBSERVATIONS: No data


BODY WEIGHT: Yes
- Time schedule for examinations: Body weights were recorded on days 0, 8, 10, and 14 of gestation.

FOOD CONSUMPTION: Yes
- Particular attention was given to food consumption and weight, in order to rule out any abnormalities which may have occurred as a result of anorexic effects in the pregnant female animal.

POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on gestation day # 14
- Organs examined: genital tract

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: No data
- Number of implantations: Yes
- Number of resorptions: Yes
- The urogenital tract of each dam was examined in detail for anatomical normality
- Live and dead foetuses: Yes
Fetal examinations:
- External examinations: Yes: [all per litter]
- Soft tissue examinations: Yes: [one-third of the foetuses of each litter]
- Skeletal examinations: Yes: [two-thirds of the foetuses of each]
- Head examinations: Yes: No data
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
Ophthalmological findings:
not examined
Haematological findings:
not examined
Clinical biochemistry findings:
not examined
Urinalysis findings:
not examined
Behaviour (functional findings):
not examined
Immunological findings:
not examined
Organ weight findings including organ / body weight ratios:
not examined
Gross pathological findings:
not examined
Neuropathological findings:
not examined
Histopathological findings: non-neoplastic:
not examined
Histopathological findings: neoplastic:
not examined
Number of abortions:
effects observed, non-treatment-related
Description (incidence and severity):
Only one abortion occurred for one female at 74.3 mg/kg bw/day. No other effects were seen in any of the groups. This abortion was not considered to be test substance-related, but a biological variation.
Pre- and post-implantation loss:
no effects observed
Description (incidence and severity):
There were no effects on the number of implantation sites in test substance-treated groups compared to the sham control animals.
Total litter losses by resorption:
effects observed, non-treatment-related
Description (incidence and severity):
Higher number of resorptions was seen in test item-treated groups 74.3 and 345 mg/kg bw/day than the control. There was no dose response relationship and this finding was not considered to be test item-related but a biological variation.
Early or late resorptions:
not examined
Dead fetuses:
effects observed, non-treatment-related
Description (incidence and severity):
There were 3 dead foetuses in 1600 mg/kg bw/day and 1 dead foetus in the sham and positive control groups. There was no dose response relationship and this effects was not considered to be test item-related but a biological variation.
Changes in pregnancy duration:
no effects observed
Description (incidence and severity):
No effects observed.
Changes in number of pregnant:
no effects observed
Description (incidence and severity):
Only one abortion occurred for one female at 74.3 mg/kg bw/day. No other effects were seen in any of the groups. This abortion was not considered to be test substance-related, but a biological variation. There were no other changes in the number of pregnant animals in any of the test substance-treated groups throughout the study period.
Key result
Dose descriptor:
NOAEL
Effect level:
>= 1 600 mg/kg bw/day (actual dose received)
Based on:
test mat.
Basis for effect level:
other: No adverse effects observed.
Abnormalities:
no effects observed
Fetal body weight changes:
no effects observed
Description (incidence and severity):
The average foetus weight was comparable among all groups.
Reduction in number of live offspring:
no effects observed
Description (incidence and severity):
The number of live foetuses was comparable among all groups.
Changes in sex ratio:
no effects observed
Changes in litter size and weights:
no effects observed
Changes in postnatal survival:
not examined
External malformations:
no effects observed
Description (incidence and severity):
The number of abnormalities seen did not differ from the number occurring spontaneously in the sham-treated controls.
Skeletal malformations:
effects observed, non-treatment-related
Description (incidence and severity):
The number of abnormalities seen in skeletal tissues of the test groups did not differ from the number occurring spontaneously in the sham-treated controls.
Visceral malformations:
no effects observed
Description (incidence and severity):
No soft tissue abnormalities were observed.
Key result
Dose descriptor:
NOAEL
Effect level:
>= 1 600 mg/kg bw/day (actual dose received)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: No adverse effects observed.
Abnormalities:
no effects observed
Developmental effects observed:
no

See attachments for result tables.

Conclusions:
The administration of up to 1600 mg/kg (body weight) of the test material to pregnant hamster for 5 consecutive days, during gestation days 6 to 10, had no clearly discernible effect on implantation 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.
Endpoint:
developmental toxicity
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
Qualifier:
no guideline followed
Principles of method if other than guideline:
The study was conducted prior to implementation of OECD Test Guidelines. The study follows a protocol similar to OECD Test Guideline 414 with some deviations.
GLP compliance:
no
Remarks:
The study was conducted prior to GLP compliance
Limit test:
no
Species:
mouse
Strain:
CD-1
Details on test animals or test system and environmental conditions:
TEST ANIMALS
- Source: not specified
- Age at study initiation: not specified
- Weight at study initiation: not specified
- Fasting period before study: not specified
- Housing: ganghoused in disposable plastic cages
- Diet (e.g. ad libitum): food was freely available, ad libitum
- Water (e.g. ad libitum): fresh tap water was freely available, ad libitum
- Acclimation period: not specified

ENVIRONMENTAL CONDITIONS
- Temperature (°C): temperature and humidity-controlled quarters
- Humidity (%): temperature and humidity-controlled quarters
- Air changes (per hr): not specified
- Photoperiod (hrs dark / hrs light): not specified

Route of administration:
oral: gavage
Vehicle:
water
Details on exposure:
PREPARATION OF DOSING SOLUTIONS: The doses were administered as a water solution (10 ml/kg of body weight)

VEHICLE
- Justification for use and choice of vehicle (if other than water): water
- Concentration in vehicle: not specified
- Amount of vehicle (if gavage): 10 ml/kg of body weight
Analytical verification of doses or concentrations:
not specified
Details on mating procedure:
The female animals were mated with young adult males, and observation of the vaginal sperm plug was considered day 0 of gestation.
Duration of treatment / exposure:
In the study pregnant female mice were given orally the test substance via intubation from gestation day 6 to 15.
Frequency of treatment:
daily
Duration of test:
10 days
Dose / conc.:
0 mg/kg bw/day (actual dose received)
Remarks:
sham control
Dose / conc.:
150 mg/kg bw/day (actual dose received)
Remarks:
Aspirin - positive control
Dose / conc.:
13.4 mg/kg bw/day (actual dose received)
Remarks:
test item
Dose / conc.:
62.3 mg/kg bw/day (actual dose received)
Remarks:
test item
Dose / conc.:
289 mg/kg bw/day (actual dose received)
Remarks:
test item
Dose / conc.:
1 340 mg/kg bw/day (actual dose received)
Remarks:
test item
No. of animals per sex per dose:
Number of female animals per group before mating:
Sham control: 24 females
Positive control: 25 females
13.4 mg/kg bw/day test substance: 27 females
62.3 mg/kg bw/day test substance: 24 females
289 mg/kg bw/day test substance: 25 females
1340 mg/kg bw/day test substance: 40 females

Number of pregnant female animals per group on gestation day 0:
Sham control: 22 females
Positive control: 20 females
13.4 mg/kg bw/day test substance: 21 females
62.3 mg/kg bw/day test substance: 22 females
289 mg/kg bw/day test substance: 22 females
1340 mg/kg bw/day test substance: 26 females
Control animals:
yes
Maternal examinations:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: All animals were observed daily for appearance and behaviour.

DETAILED CLINICAL OBSERVATIONS: No data

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

FOOD CONSUMPTION: Yes
- Particular attention was given to food consumption and weight, in order to rule out any abnormalities which may have occurred as a result of anorexic effects in the pregnant female animal.

POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on gestation day # 17
- Organs examined: urogenital tract and uterine content

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: No data
- Number of implantations: Yes
- Number of resorptions: Yes
- The urogenital tract of each dam was examined in detail for anatomical normality
- Live and dead foetuses: Yes
Fetal examinations:
- External examinations: Yes: [all per litter]
- Soft tissue examinations: Yes: [one-third of the foetuses of each litter]
- Skeletal examinations: Yes: [two-thirds of the foetuses of each]
- Head examinations: Yes: No data
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
Ophthalmological findings:
not examined
Haematological findings:
not examined
Clinical biochemistry findings:
not examined
Urinalysis findings:
not examined
Behaviour (functional findings):
not examined
Immunological findings:
not examined
Organ weight findings including organ / body weight ratios:
not examined
Gross pathological findings:
not examined
Neuropathological findings:
not examined
Histopathological findings: non-neoplastic:
not examined
Histopathological findings: neoplastic:
not examined
Number of abortions:
no effects observed
Description (incidence and severity):
No abortions occurred in any of the test substance-treated groups. One abortion occurred in the positive control group.
Pre- and post-implantation loss:
no effects observed
Description (incidence and severity):
There were no effects on the number of implantation sites in test substance-treated groups compared to the sham control animals.
Total litter losses by resorption:
effects observed, non-treatment-related
Description (incidence and severity):
Higher number of resorptions was seen for dams in the 13.4 and 1340 mg/kg bw/day groups. However, no such effects were seen in the other treatment groups and since no dose-response relationship was noted, this effect was considered non-test substance related, but a biological variation.
Early or late resorptions:
not examined
Dead fetuses:
effects observed, non-treatment-related
Description (incidence and severity):
The total number of dead foetuses in the test item-treated groups was comparable to the sham control group animals.
There were total deaths of 4 foetuses in the sham control animals with 3 dams which had 1 or more dead foetuses. There were total deaths of 3 foetuses in the 13.4 and 62.3 mg/kg bw/day test animals with 3 dams per group which had 1 or more dead foetuses. There were total deaths of 7 foetuses in the 1340 mg/kg bw/day animals with 6 dams which had 1 or more dead foetuses.
There were no control or test item-treated animals that had all foetuses dead.
Changes in pregnancy duration:
no effects observed
Description (incidence and severity):
No effects observed.
Changes in number of pregnant:
no effects observed
Description (incidence and severity):
There were no changes in the number of pregnant animals in any of the test substance-treated groups throughout the study period. One positive control animal had an abortion before gestation day 17.
Key result
Dose descriptor:
NOAEL
Effect level:
>= 1 340 mg/kg bw/day (actual dose received)
Based on:
test mat.
Basis for effect level:
other: No adverse effects observed.
Abnormalities:
no effects observed
Fetal body weight changes:
no effects observed
Description (incidence and severity):
The average foetus weight was comparable among all groups.
Reduction in number of live offspring:
no effects observed
Description (incidence and severity):
The number of live foetuses was comparable among all groups.
Changes in sex ratio:
no effects observed
Changes in litter size and weights:
no effects observed
Changes in postnatal survival:
not examined
External malformations:
effects observed, non-treatment-related
Description (incidence and severity):
The number of abnormalities seen did not differ from the number occurring spontaneously in the sham-treated controls.
Skeletal malformations:
effects observed, non-treatment-related
Description (incidence and severity):
The number of abnormalities seen in skeletal tissues of the test groups did not differ from the number occurring spontaneously in the sham-treated controls.
Visceral malformations:
effects observed, non-treatment-related
Description (incidence and severity):
One foetus from 1340 mg/kg bw/day group has a short tail and one other foetus from 1340 mg/kg bw/day group had meningoencephalocele. The number of abnormalities seen in soft tissues of the test groups did not differ from the number occurring spontaneously in the sham-treated controls.
Key result
Dose descriptor:
NOAEL
Effect level:
>= 1 340 mg/kg bw/day (actual dose received)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: No adverse effects observed.
Abnormalities:
no effects observed
Developmental effects observed:
no

See attachments for result tables.

Conclusions:
The administration of up to 1340 mg/kg (body weight) of the test material to pregnant mice for 10 consecutive days, during gestation days 6 to 15, had no clearly discernible effect on implantation 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.
Endpoint:
developmental toxicity
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
Qualifier:
no guideline followed
Principles of method if other than guideline:
The study was conducted prior to implementation of OECD Test Guidelines. The study follows a protocol similar to OECD Test Guideline 414 with some deviations.
GLP compliance:
no
Remarks:
The study was conducted prior to GLP compliance
Limit test:
no
Species:
rabbit
Strain:
Dutch
Details on test animals or test system and environmental conditions:
TEST ANIMALS
- Source: not specified
- Age at study initiation: not specified
- Weight at study initiation: not specified
- Fasting period before study: not specified
- Housing: individually housed in mesh bottom cages
- Diet (e.g. ad libitum): food was freely available, ad libitum
- Water (e.g. ad libitum): fresh tap water was freely available, ad libitum
- Acclimation period: not specified

ENVIRONMENTAL CONDITIONS
- Temperature (°C): temperature and humidity-controlled quarters
- Humidity (%): temperature and humidity-controlled quarters
- Air changes (per hr): not specified
- Photoperiod (hrs dark / hrs light): not specified

Route of administration:
oral: gavage
Vehicle:
not specified
Details on exposure:
PREPARATION OF DOSING SOLUTIONS: The test material was prepared and doses calculated according to Table 1.

VEHICLE
- Justification for use and choice of vehicle (if other than water): The controls were sham treated with the vehicle at a level equivalent to the group receiving the highest test dose.
- Concentration in vehicle: See Table 1
- Amount of vehicle (if gavage): See Table 1
Analytical verification of doses or concentrations:
not specified
Details on mating procedure:
On day 0, each doe was given an injection of 0.4ml of human chorionic gonadotropin (400 IU) via the marginal ear vein. Three hours later, each doe was inseminated artificially with 0.3 ml of diluted semen from a proven donor.
Duration of treatment / exposure:
In the study pregnant female animals were given orally the test substance via intubation from gestation day 6 to 18.
Frequency of treatment:
daily
Duration of test:
13 days
Dose / conc.:
0 mg/kg bw/day (actual dose received)
Remarks:
sham control
Dose / conc.:
2.5 mg/kg bw/day (actual dose received)
Remarks:
6-aminonicotinamide - positive control
Dose / conc.:
16 mg/kg bw/day (actual dose received)
Remarks:
test item
Dose / conc.:
74.3 mg/kg bw/day (actual dose received)
Remarks:
test item
Dose / conc.:
345 mg/kg bw/day (actual dose received)
Remarks:
test item
Dose / conc.:
1 600 mg/kg bw/day (actual dose received)
Remarks:
test item
No. of animals per sex per dose:
Number of female animals per group before mating:
Sham control: 11 females
Positive control: 18 females
16 mg/kg bw/day test substance: 21 females
74.3 mg/kg bw/day test substance: 13 females
345 mg/kg bw/day test substance: 17 females
1600 mg/kg bw/day test substance: 24 females

Number of pregnant female animals per group on gestation day 0:
Sham control: 10 females
Positive control: 12 females
16 mg/kg bw/day test substance: 15 females
74.3 mg/kg bw/day test substance: 11 females
345 mg/kg bw/day test substance: 14 females
1600 mg/kg bw/day test substance: 13 females
Control animals:
yes
Maternal examinations:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: All animals were observed daily for appearance and behaviour.

DETAILED CLINICAL OBSERVATIONS: No data


BODY WEIGHT: Yes
- Time schedule for examinations: Body weights were recorded on days 0, 6, 12, 18 and 29 of gestation.

FOOD CONSUMPTION: Yes
- Particular attention was given to food consumption and weight, in order to rule out any abnormalities which may have occurred as a result of anorexic effects in the pregnant female animal.

POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on gestation day # 29
- Organs examined: urogenital tract

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
- The urogenital tract of each dam was examined in detail for anatomical normality
- Live and dead foetuses: Yes
Fetal examinations:
- The live foetuses of each litter were placed in an incubator for 24 hours for the evaluation of neonatal survival.
- External examinations: Yes: [all per litter]
- Soft tissue examinations: Yes: [all of the foetuses of each litter]
- Skeletal examinations: Yes: [all of the foetuses of each]
- Head examinations: Yes: No data
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
Ophthalmological findings:
not examined
Haematological findings:
not examined
Clinical biochemistry findings:
not examined
Urinalysis findings:
not examined
Behaviour (functional findings):
not examined
Immunological findings:
not examined
Organ weight findings including organ / body weight ratios:
not examined
Gross pathological findings:
not examined
Neuropathological findings:
not examined
Histopathological findings: non-neoplastic:
not examined
Histopathological findings: neoplastic:
not examined
Number of abortions:
effects observed, non-treatment-related
Description (incidence and severity):
Two, one and three abortions were seen in 16, 74.3 and 345 mg/kg bw/day groups, respectively. Two abortions were seen in the positive control group. No abortions were seen for the sham-treated group. These abortions were not considered to be test substance-related, but a biological variation.
Pre- and post-implantation loss:
no effects observed
Description (incidence and severity):
There were no effects on the number of implantation sites in test substance-treated groups compared to the sham control animals.
Total litter losses by resorption:
effects observed, non-treatment-related
Description (incidence and severity):
There was no dose response relationship in the observed resorptions and the effects were not considered to be test item-related but a biological variation.
Early or late resorptions:
not examined
Dead fetuses:
effects observed, non-treatment-related
Description (incidence and severity):
One dam from 16 mg/kg bw/day treatment group had all foetuses dead. Dead foetuses were also seen in all other treatment groups, but there was no dose response relationship and this effect was not considered to be test item-related but a biological variation.
Changes in pregnancy duration:
no effects observed
Description (incidence and severity):
No effects observed.
Changes in number of pregnant:
effects observed, non-treatment-related
Description (incidence and severity):
The observed abortions were not considered to be test substance-related, but a biological variation.
Other effects:
no effects observed
Description (incidence and severity):
The number of corpora lutea was unaffected by the treatment.
Key result
Dose descriptor:
NOAEL
Effect level:
>= 1 600 mg/kg bw/day (actual dose received)
Based on:
test mat.
Basis for effect level:
other: No adverse effects observed.
Abnormalities:
no effects observed
Fetal body weight changes:
no effects observed
Description (incidence and severity):
The average foetus weight was comparable among all groups.
Reduction in number of live offspring:
no effects observed
Description (incidence and severity):
The number of live foetuses was comparable among all groups.
Changes in sex ratio:
no effects observed
Changes in litter size and weights:
no effects observed
Changes in postnatal survival:
effects observed, non-treatment-related
Description (incidence and severity):
Neonatal deaths were seen in all groups and the deaths were considered to be biological variation, rather than a treatment-related effects.
External malformations:
no effects observed
Description (incidence and severity):
The number of abnormalities seen did not differ from the number occurring spontaneously in the sham-treated controls.
Skeletal malformations:
effects observed, non-treatment-related
Description (incidence and severity):
The number of abnormalities seen in skeletal tissues of the test groups did not differ from the number occurring spontaneously in the sham-treated controls.
Visceral malformations:
effects observed, non-treatment-related
Description (incidence and severity):
Soft tissue abnormalities were mainly observed for the positive control group. One pup from 345 mg/kg bw/day group had meningoencephalocele, anopia; medial rotation, of hind limbs, umbilical hernia and another pup from 1600 mg/kg bw/day had a club foot. These effects were considered to be a biological variation as they were only single instances and no dose response relationship was observed.
Key result
Dose descriptor:
NOAEL
Effect level:
>= 1 600 mg/kg bw/day (actual dose received)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: No adverse effects observed.
Abnormalities:
no effects observed
Developmental effects observed:
no

See attachments for result tables.

Conclusions:
The administration of up to 1600 mg/kg bw/day of the test material to pregnant rabbits for 13 consecutive days, during gestation days 6 to 18, had no clearly discernible effect on implantation 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. There were no effects on neonatal survival.
Endpoint:
developmental toxicity
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
Qualifier:
no guideline followed
Principles of method if other than guideline:
The study was conducted prior to implementation of OECD Test Guidelines. The study follows a protocol similar to OECD Test Guideline 414 with some deviations.
GLP compliance:
no
Remarks:
The study was conducted prior to GLP compliance
Limit test:
no
Species:
rat
Strain:
Wistar
Details on test animals or test system and environmental conditions:
TEST ANIMALS
- Source: not specified
- Age at study initiation: not specified
- Weight at study initiation: not specified
- Fasting period before study: not specified
- Housing: individually housed in mesh bottom cages
- Diet (e.g. ad libitum): food was freely available, ad libitum
- Water (e.g. ad libitum): fresh tap water was freely available, ad libitum
- Acclimation period: not specified

ENVIRONMENTAL CONDITIONS
- Temperature (°C): temperature and humidity-controlled quarters
- Humidity (%): temperature and humidity-controlled quarters
- Air changes (per hr): not specified
- Photoperiod (hrs dark / hrs light): not specified

Route of administration:
oral: gavage
Vehicle:
not specified
Details on exposure:
PREPARATION OF DOSING SOLUTIONS: The test material was prepared and doses calculated according to Table 1.

VEHICLE
- Justification for use and choice of vehicle (if other than water): The controls were sham treated with the vehicle at a level equivalent to the group receiving the highest test dose.
- Concentration in vehicle: See Table 1
- Amount of vehicle (if gavage): See Table 1
Analytical verification of doses or concentrations:
not specified
Details on mating procedure:
The female animals were mated with young adult males, and observation of the vaginal sperm plug was considered day 0 of gestation.
Duration of treatment / exposure:
In the study pregnant female animals were given orally the test substance via intubation from gestation day 6 to 15.
Frequency of treatment:
daily
Duration of test:
10 days
Dose / conc.:
0 mg/kg bw/day (actual dose received)
Remarks:
sham control
Dose / conc.:
250 mg/kg bw/day (actual dose received)
Remarks:
Aspirin - positive control
Dose / conc.:
13.5 mg/kg bw/day (actual dose received)
Remarks:
test item
Dose / conc.:
62.7 mg/kg bw/day (actual dose received)
Remarks:
test item
Dose / conc.:
292 mg/kg bw/day (actual dose received)
Remarks:
test item
Dose / conc.:
1 350 mg/kg bw/day (actual dose received)
Remarks:
test item
No. of animals per sex per dose:
Number of female animals per group before mating:
Sham control: 24 females
Positive control: 25 females
13.5 mg/kg bw/day test substance: 25 females
62.7 mg/kg bw/day test substance: 25 females
292 mg/kg bw/day test substance: 25 females
1350 mg/kg bw/day test substance: 25 females

Number of pregnant female animals per group on gestation day 0:
Sham control: 23 females
Positive control: 24 females
13.5 mg/kg bw/day test substance: 25 females
62.7 mg/kg bw/day test substance: 22 females
292 mg/kg bw/day test substance: 20 females
1350 mg/kg bw/day test substance: 22 females
Control animals:
yes
Maternal examinations:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: All animals were observed daily for appearance and behaviour.

DETAILED CLINICAL OBSERVATIONS: No data


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

FOOD CONSUMPTION: Yes
- Particular attention was given to food consumption and weight, in order to rule out any abnormalities which may have occurred as a result of anorexic effects in the pregnant female animal.

POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on gestation day # 20
- Organs examined: urogenital tract and uterine content

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: No data
- Number of implantations: Yes
- Number of resorptions: Yes
- The urogenital tract of each dam was examined in detail for anatomical normality
- Live and dead foetuses: Yes
Fetal examinations:
- External examinations: Yes: [all per litter]
- Soft tissue examinations: Yes: [one-third of the foetuses of each litter]
- Skeletal examinations: Yes: [two-thirds of the foetuses of each]
- Head examinations: Yes: No data
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
Ophthalmological findings:
not examined
Haematological findings:
not examined
Clinical biochemistry findings:
not examined
Urinalysis findings:
not examined
Behaviour (functional findings):
not examined
Immunological findings:
not examined
Organ weight findings including organ / body weight ratios:
not examined
Gross pathological findings:
not examined
Neuropathological findings:
not examined
Histopathological findings: non-neoplastic:
not examined
Histopathological findings: neoplastic:
not examined
Number of abortions:
no effects observed
Description (incidence and severity):
No abortions occurred in any of the test substance-treated groups.
Pre- and post-implantation loss:
no effects observed
Description (incidence and severity):
There were no effects on the number of implantation sites in test substance-treated groups compared to the sham control animals.
Total litter losses by resorption:
effects observed, non-treatment-related
Description (incidence and severity):
Lower number of resorptions was seen in test item-treated groups than the control. This finding was not considered to be test item-related but a biological variation.
Early or late resorptions:
not examined
Dead fetuses:
no effects observed
Description (incidence and severity):
There were no dead foetuses in test item-treated animals. There were 1 dead foetus and 2 dead foetuses in the sham control and positive control groups, respectively.
Changes in pregnancy duration:
no effects observed
Description (incidence and severity):
No effects observed.
Changes in number of pregnant:
no effects observed
Description (incidence and severity):
There were no changes in the number of pregnant animals in any of the test substance-treated groups throughout the study period.
Key result
Dose descriptor:
NOAEL
Effect level:
>= 1 350 mg/kg bw/day (actual dose received)
Based on:
test mat.
Basis for effect level:
other: No adverse effects observed.
Abnormalities:
no effects observed
Fetal body weight changes:
no effects observed
Description (incidence and severity):
The average foetus weight was comparable among all groups.
Reduction in number of live offspring:
no effects observed
Description (incidence and severity):
The number of live foetuses was comparable among all groups.
Changes in sex ratio:
no effects observed
Changes in litter size and weights:
no effects observed
Changes in postnatal survival:
not examined
External malformations:
effects observed, non-treatment-related
Description (incidence and severity):
The number of abnormalities seen did not differ from the number occurring spontaneously in the sham-treated controls.
Skeletal malformations:
effects observed, non-treatment-related
Description (incidence and severity):
The number of abnormalities seen in skeletal tissues of the test groups did not differ from the number occurring spontaneously in the sham-treated controls.
Visceral malformations:
no effects observed
Description (incidence and severity):
Soft tissue abnormalities were observed in the positive control group only.
Key result
Dose descriptor:
NOAEL
Effect level:
>= 1 350 mg/kg bw/day (actual dose received)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: No adverse effects observed.
Abnormalities:
no effects observed
Developmental effects observed:
no

See attachments for result tables.

Conclusions:
The administration of up to 1350 mg/kg (body weight) of the test material to pregnant rats for 10 consecutive days, during gestation days 6 to 15, had no clearly discernible effect on implantation 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.
Effect on developmental toxicity: via oral route
Endpoint conclusion:
no adverse effect observed
Effect on developmental toxicity: via inhalation route
Endpoint conclusion:
no study available
Effect on developmental toxicity: via dermal route
Endpoint conclusion:
no study available
Additional information

There are no adequate developmental toxicity data on silicon tetrachloride so good quality data for the hydrolysis product polysilicic acid (equivalent to synthetic amorphous silica) have been used to assess the potential for adverse effects on development following exposure to silicon tetrachloride.

Overview:

It is considered not to be ethical to perform repeated dose toxicity testing with silicon tetrachloride by any route of exposure due to its known corrosive properties. Following repeated oral dosing, the corrosive nature of the product could affect the lining of the stomach, giving rise to hyperplasia and a subsequent reduced food intake. This would confound the interpretation of any systemically driven effects. A guideline-compliant repeated-dose inhalation study should elicit systemic toxicity at the highest test concentration. Since the local corrosive effects of silicon tetrachloride would be significant a valid inhalation study according to the relevant guidelines is technically not feasible to do. It is also unlikely that any systemic effects would be seen at dose levels made sufficiently low (< 10 ppm) to prevent the known corrosive effects and/or distress in the test species. This has been confirmed in a 28-day inhalation study with another chlorosilane, dichloro(dimethyl)silane (WIL, 2014) in which there were no effects of treatment on clinical signs, body weight or food consumption that would indicate a systemic effect. Furthermore, the histopathology in the study indicated that the effects in the upper respiratory tract were similar to HCl. It is therefore concluded that HCl will dominate the inhalation toxicity profile of silicon tetrachloride.

With regard to the dermal and inhalation routes, due to the known corrosive effects of silicon tetrachloride, appropriate H-phrases and P-statements are included in the labelling, meaning that repeated skin and inhalation exposure is not expected. Any accidental skin contact or inhalation exposure could cause severe local effects but would be unlikely to cause any systemic effects.

ORAL ROUTE

SYSTEMIC EFFECTS

There are no adequate developmental toxicity data on silicon tetrachloride so good quality data for synthetic amorphous silica (CAS 112926-00-8) have been used to assess the developmental toxicity of silicon tetrachloride. Local effects from the hydrolysis product, hydrogen chloride (HCl) are not addressed by these data.

Silicon tetrachloride, like all inorganic chlorosilanes, is a severely corrosive substance that is decomposed by water, producing silicic acid and HCl. The reaction is highly exothermic (Merck, 2013). Hydrolysis half-life is less than 0.3 min at 25°C and pH 4, 7 and 9. The initial products of hydrolysis are hydrogen chloride (HCl) and monosilicic acid (soluble silica). It has not been possible to isolate monosilicic acid (Jones et al., 2000).

 

Monosilicic acid condenses to insoluble polysilicic acid [equivalent to synthetic amorphous silica (SAS)] at concentrations higher than 120 mg/l ‘SiO2equivalent’ in water (Holleman-Wiberg, 2001). At very high concentration, polysilicic acid can condense to silicon dioxide (SiO2). The hydrolysis products of hydrochloric acid and (poly)silicic acid are significant for the chemical safety assessment (CSR).

 

Monosilicic acid and polysilicic acid are naturally occurring substances which are ubiquitous in the environment. Soluble monosilicic acid is the major bioavailable form of silicon and plays an important role in the biogeochemical cycle of silicon (ECETOC, 2006). Typical background concentrations of monosilicic acid in the environment are up to 75 mg/l ‘SiO2equivalent’ in river water and up to 14 mg/l ‘SiO2equivalent’ in seawater (Iler, 1979).

 

The literature gives various values for the solubility of silicic acid, determined indirectly as ‘SiO2equivalent’ because the soluble species cannot be directly measured:

The solubility of monosilicic acid according to Alexander et al. (1954) at 25°C:

  • 150 mg/l ‘SiO2equivalent’ at pH 2.0 and pH 3.0 130 mg/l ‘SiO2equivalent’ at pH 4.
  • 130 mg/l ‘SiO2equivalent’ at pH 4.2 110 mg/l ‘SiO2equivalent’ at pH 5.
  • 110 mg/l ‘SiO2equivalent’ at pH 5.7 100 mg/l ‘SiO2equivalent’ at pH 7.
  • 100 mg/l ‘SiO2equivalent’ at pH 7.7 490 mg/l ‘SiO2equivalent’ at pH 10.
  • 490 mg/l ‘SiO2equivalent’ at pH 10.3 1120 mg/l ‘SiO2equivalent’ at pH 10.
  • 1120 mg/l ‘SiO2equivalent’ at pH 10.6

The solubility of monosilicic acid according to Goto and Okura (1953) at 25°C:

  • 120 mg/l ‘SiO2equivalent’ at pH 2.0 150 mg/l ‘SiO2equivalent’ at pH 7.
  • 150 mg/l ‘SiO2equivalent’ at pH 7.0

 

The solubility of monosilicic acid according to Elmer and Nordberg (1958) at neutral pH:

  • 170 mg/l ‘SiO2equivalent’ at 35°C 270 mg/l ‘SiO2equivalent’ at 65°C
  • 270 mg/l ‘SiO2equivalent’ at 65°C 465 mg/l ‘SiO2equivalent’ at 95°C
  • 465 mg/l ‘SiO2equivalent’ at 95°C  

With the described properties of silicon tetrachloride in mind it is not possible to conduct developmental toxicity studies in experimental animals due to the corrosive nature of this substance. Nor can the hydrolysis product, monosilicic acid, be tested as it is not possible to isolate this substance. However, we know from physicochemical properties that following ingestion of silicon tetrachloride, the conditions in the stomach are such that following an initial rapid hydrolysis to soluble monosilicic acid, this monomer will start to condense to form insoluble synthetic amorphous silica (equivalent to SAS). This condensation will start to occur once the concentration of monosilicic acid reaches approximately 150 mg/L in the gastric juices.

Monosilicic acid (soluble silica) undergoes condensation reactions in solution at about 120 mg/l ‘SiO2 equivalent’. The solubility of monosilicic acid in water is 150 mg/l ‘SiO2 equivalent'.

Following dosing by oral gavage, partitioning will occur between the dose vehicle and the aqueous environment in the stomach.

Mass dosed (in mg/day) = Body weight (in kg) x dose level (in mg/kg bw/day)

 

Dose concentration (in mg/l) = mass dosed (in mg/day)÷volume (in l)

So, the dose level (mg/kg bw/day) required to reach the dose concentration of 150 mg/l 'SiO2 equivalent', the estimated (conservative) maximum concentration of silicic acid that can occur in the stomach before condensation to insoluble polysilicic acid (equivalent to SAS) begins is calculated as follows:

Body weight of rat = 0.3kg

Dose level = X                                                        

Estimated aqueous volume = 0.0015 l                                                                      

Dose concentration = 150 mg/l

150 mg/l = 0.3 kg x dose level (mg/kg bw/day)÷0.0015l

Dose level = 0.75 mg/kg bw/day 'SiO2 equivalent'

Therefore, based on a condensation limit of 150 mg/l, the maximum dose level that could be used in practice to ensure exposure mainly to monosilicic acid in the stomach of experimental animals is approximately 0.75 mg/kg bw/day or less of 'SiO2 equivalent'.

A correction for molecular weight gives a maximum dose level for silicon tetrachloride:

Mr [silicon tetrachloride]                =             169.90 g/mol

Mr [silicon dioxide]                         =             60.08 g/mol

Dose level [Silicon tetrachloride]     =            [Dose level [silicon dioxide]  x  Mr [silicon tetrachloride]]

                                                                                                Mr [silicon dioxide]

 

                                                            =            (0.75 mg/kg bw/day) x (169.90 g/mol)

                                                                                                   (60.08 g/mol)

 

                                                            =             2.12 mg/kg bw/day

Therefore, based on a condensation limit of 150 mg/l the maximum dose level of silicon tetrachloride that can be dosed to ensure exposure mainly to monosilicic acid is approximately 2 mg/kg bw/day.

For comparison purposes, using the above calculation, the following shows the dose concentrations for the dose levels typically used in experimental animal studies (100, 300 and 1000 mg/kg bw/day).

Body weight                                = 0.3 kg

Total amount dosed                     = 30 mg

Estimated aqueous volume           = 1.5 ml

Dose concentration                      = 20,000 mg/l

Body weight                                = 0.3 kg

Total amount dosed                     = 90 mg

Estimated aqueous volume           = 1.5 ml

Dose concentration                     =  60,000 mg/l

Body weight                                 = 0.3 kg

Total amount dosed                      = 300 mg

Estimated aqueous volume           = 1.5 ml

Dose concentration                       = 200,000 mg/l

Therefore, dosing at these dose levels clearly gives a dose concentration in the stomach that far exceeds the dose at which condensation to polysilicic acid (equivalent to SAS) starts to occur. Consequently, the majority of the dose in the stomach will be present as insoluble polysilicic acid (equivalent to SAS). In all cases only approximately 150 mg/l will be present as soluble monosilicic acid.

Overall, it can be concluded that silicon tetrachloride at gavage doses unlikely to cause local corrosive effects and at doses that give mainly soluble monosilicic acid (2 mg/kg bw/day or less) would be unethical based on animal usage. However, because the vast majority of a gavage dose will rapidly condense to insoluble polysilicic acid (equivalent to SAS) it is appropriate to use toxicology data on SAS to address the potential for oral toxicity of silicon tetrachloride.

 

In a prenatal developmental study (Hofmann et al., 2015) conducted according to OECD Test Guideline 414 and in compliance with GLP, pregnant Wistar rats were administered SAS (described as NM-200 synthetic amorphous silica) (in highly deionised water containing 10% foetal bovine serum) at doses of 100, 300 and 1000 mg/kg bw/day by oral gavage on gestation days 6-19. The dosing schedule and investigations were conducted according to the OECD Test Guideline. There were no adverse, treatment-related findings in parental animals or offspring. There were a number of incidental foetal malformations and variations, which all occurred at a rate no larger than that of the control/historical controls, without statistical significance and without a dose-response relationship. Therefore, the NOAEL for general toxicity and developmental (including teratogenicity) toxicity was ≥1000 mg/kg bw/day.

In a prenatal developmental toxicity study, conducted prior to OECD Test Guidelines or GLP, the teratogenic effect of silica gel was investigated in pregnant mice, rats, hamsters and rabbits (Food and Drug Research Laboratories, 1973).

The test material was administered at doses of up to 1340 mg/kg (body weight) to pregnant mice for 10 consecutive days, during gestation days 6 to 15; up to 1350 mg/kg (body weight) to pregnant rats for 10 consecutive days, during gestation days 6 to 15; up to 1600 mg/kg (body weight) to pregnant hamsters for 5 consecutive days, during gestation days 6 to 10; or up to 1600 mg/kg (body weight) to pregnant rabbits for 13 consecutive days, during gestation days 6 to 18. Body weights were recorded on a regular basis throughout gestation. All animals were observed daily for appearance and behaviour with particular attention given to food consumption and weight, in order to rule out any abnormalities which may have occurred as a result of anorexic effects in the pregnant female animal. Towards the end of gestation all pregnant female animals were subjected to Caesarean section under surgical anaesthesia, and the numbers of implantation sites, resorption sites, and live and dead foetuses were recorded. The body weights of the live pups were also recorded. The urogenital tract of each female animal was examined in detail for anatomical normality. The foetuses were subject to detailed examination for external congenital abnormalities, detailed visceral examination and skeletal defects examination. Neonatal survival of live rabbit foetuses was also investigated by placing the foetuses in an incubator for 24 hours.

There were no clearly discernible effects on implantation or on maternal or foetal survival in mice, rats, hamsters or rabbits. 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. There were no effects on neonatal survival in rabbits.

Limited data are available regarding the developmental toxicity in animals following oral, dermal or inhalation exposure to hydrogen chloride. However, protons and chloride ions exist as normal constituents of body fluid in animals, hence low concentrations of hydrogen chloride appear not to cause adverse effects in animals. Therefore, the hydrolysis product of silicon tetrachloride, HCl, would not be expected to cause developmental toxicity in experimental animals or humans following initial exposure to silicon tetrachloride.

References

Alexander G.B., Heston W.M. and Iler R.K. (1954) J. Phys. Chem., 58, 453.

Cotton F.A. and Wilkinson G. (1999) Advanced Inorganic Chemistry, 6th Edition, p271

ECETOC (2006) Synthetic Amorphous Silica (CAS No. 7631-86-9), JACC REPORT No. 51

Elmer and Nordberg (1958) J. Am.Chem. Soc., 41, 517

Goto K. and Okura T. (1953) Kagaku, 23, 426.

Holleman-Wiberg, (2001) Inorganic Chemistry, Academic Press, p. 865

Iler, Ralph K. (1979) The Chemistry of Silica: Solubility, Polymerization, Colloid and Surface Properties and Biochemistry of Silica, Wiley, p. 13.

Jones, R. G., Wataru, A., and Chojnowski, J. (2000) Silicon-Containing Polymers: The Science and Technology of Their Synthesis, Kluwer Academic Press pp 168-169

Merck Index (2013) Monograph Number. 8639 (15th Ed)

Justification for classification or non-classification

Based on the available read-across data from the hydrolysis product amorphous polysilicic acid [equivalent to synthetic amorphous silica – SAS], silicon tetrachloride does not require classification for reproductive and developmental toxicity according to Regulation (EC) No 1272/2008.

Additional information