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Administrative data

Key value for chemical safety assessment

Effects on fertility

Description of key information

To assess the reproductive toxicity of tetraethyl orthosilicate (CAS 78-10-4, EC No. 201-083-8), the higher quality study for its condensed hydrolysis product polysilicic acid (equivalent to synthetic amorphous silica [SAS], CAS No. 12926-00-8, EC No. 231-545-4) is identified as the key source of data.

 

In the key study with SAS conducted according to OECD Test Guideline 416 and in compliance with GLP (Wolterbeek et al. 2015, reliability score 1), the NOAELs for systemic and reproductive toxicity in Wistar rats were ≥1000 mg/kg bw/day. In this two-generation reproductive study, rats were administered SAS (described as NM-200) 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.

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:
1 (reliable without restriction)
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.
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 (reliability score 1), 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. Condensed polysilicic acid (equivalent to synthetic amorphous silica) is the primary hydrolysis product of tetraethyl orthosilicate.
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 1, based on data for tetraethyl orthosilicate and its condensed hydrolysis product SAS
Effect on fertility: via inhalation route
Endpoint conclusion:
no study available
Effect on fertility: via dermal route
Endpoint conclusion:
no study available
Additional information

OVERVIEW

The reproductive toxicity data set for tetraethyl orthosilicate are comprised of the key OECD Test Guideline 416 study for its condensed hydrolysis product polysilicic acid (equivalent to SAS) (Wolterbeek et al. 2015) and the supporting OECD Test Guideline 422 study for tetraethyl orthosilicate (CIT Safety & Health Research Laboratories 2005), both by oral gavage in the rat and reliability score 1.

 

The oral reproductive toxicity data for the tetraethyl orthosilicate condensed hydrolysis product SAS is read across to tetraethyl orthosilicate. The basis for this approach is presented in detail in the repeated dose toxicity endpoint summary (under additional information, oral route, systemic effects, basis for SAS read-across). In summary, the tetraethyl orthosilicate condensed hydrolysis product polysilicic acid is equivalent to SAS. Further, following neat or aqueous-based tetraethyl orthosilicate dosing, insoluble polysilicic acid will predominate in the small intestine and the concentration of soluble monosilicic acid (expressed as ‘SiO2 equivalent’) will be comparable to the level expected after SAS administration. Thus, it is appropriate to use toxicology data on SAS to address the potential for oral reproductive toxicity of tetraethyl orthosilicate.

 

A summary for the non-silane hydrolysis product ethanol is available (OECD SIDS Document UNEP Publication; SIDS Initial Assessment Report for SIAM 19; Berlin, Germany 19-22 October 2004, www.inchem.org/). The lowest ethanol NOAELs for fertility and developmental toxicity were 2000 mg/kg bw/day and are well above any limit doses in OECD guideline tests concerning reproductive toxicity. Ethanol is not classified for developmental toxicity in Annex VI of Regulation (EC) No 1272/2008.

 

ORAL ROUTE

 

STUDY FINDINGS

The key study for reproductive toxicity is a two-generation reproductive toxicity study with SAS, conducted according to OECD Test Guideline 416 and in compliance with GLP (Wolterbeek et al., 2015, reliability score 1). Wistar rats were administered SAS (described as NM-200) (in highly deionised water containing 10% foetal bovine serum) at doses of 100, 300 and 1000 mg/kg bw/day by oral gavage. Observations and examinations included cage side observations, detailed clinical observations (no details provided), body weight, food consumption, oestrous cyclicity (parental F0 / F1 animals), sperm parameters (parental F0 / F1; testes / epididymis weight, sperm count / motility), litter observations (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, gross necropsy (parental F0 / F1; external and internal examinations). Parental F0 / F1 histopathology: 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. 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. Offspring organ weight and histopathology: Same for parental animals. Reproductive indices: Mating, fertility, fecundity, gestation. Offspring viability indices: Live birth, viability (day 4), viability (day 21). There were no adverse findings in parental animals or offspring at any dose level in any generation. Therefore, the NOAELs for systemic toxicity and reproductive (fertility and developmental) toxicity were concluded to be ≥1000 mg/kg bw/day in this study.

 

In the supporting study conducted according to Test Guideline OECD 422 and in compliance with GLP (CIT Safety & Health Research Laboratories 2005, oral gavage in corn oil, reliability score 1), there were no treatment-related effects on reproduction (fertility and developmental toxicity) evident up to 100 mg/kg bw/day tetraethyl orthosilicate in Sprague-Dawley rats. Parental observations and examinations performed included cage side and detailed clinical observations, neurobehavioral / motor activity, body weight, and food consumption. Blood samples were also collected at the end of the treatment period, with haematology and biochemistry analysis performed. For all adult animals, a complete macroscopic post-mortem examination consisted of external surfaces, all orifices, cranial cavity, external surfaces of brain and spinal cord, thoracic, abdominal and pelvic cavities with their associated organs and tissues and the neck with its associated organs and tissues. Organ weights were obtained for multiple tissues. For males and the toxicity females, a microscopic examination was undertaken for multiple tissues in the control and high dose groups, for the kidney (all dose groups), and for any macroscopic lesions observed in the low- and mid-dose groups. Male reproductive parameters (testis, epididymis and prostate weight, sperm morphology and spermatogenesis) were examined. For maternal females, length of gestation and number of implantation sites were recorded and classified as scars, early resorptions, late resorptions, live and dead foetuses. In non-pregnant or un-mated females, presence of implantation scars on the uterus was checked. Reproductive indices included mating index, fertility index, and gestation index.

Pup and litter weights were recorded on days 1 and 4 post-partum. During lactation, pups were observed daily for clinical signs or abnormal behaviour. The total litter size and numbers of pups of each sex were recorded as soon as possible after birth. The litters were observed daily, with the number of live, dead and cannibalized pups and of any runts noted. Any gross malformations in pups were noted. No further pup examination performed. Offspring viability indices included live birth index and viability index.

 

The NOAEL for reproductive toxicity was ≥100 mg/kg bw/day and supports the key study finding of no reproductive effects. The NOAELs for systemic toxicity were 50 and 10 mg/kg bw/day for females and males, respectively, based primarily on effects on the kidneys. However, as discussed in the repeated dose endpoint summary, the parental renal findings are considered a consequence of the corn oil dosing in this study and the resulting delay in tetraethyl orthosilicate hydrolysis.

Effects on developmental toxicity

Description of key information

The developmental toxicity of tetraethyl orthosilicate (CAS No. 78-10-4, EC No. 201-083-8) is assessed using a weight of evidence approach, taking into account the reliable OECD Test Guideline 422 data for tetraethyl orthosilicate and the reliable OECD Test Guideline 414 data for its condensed hydrolysis product polysilicic acid (equivalent to SAS, CAS No. 112926-00-8, EC No. 231-545-4). An OECD Test Guideline 414 study is not available for tetraethyl orthosilicate. Based on the weight of evidence, the overall developmental NOAEL for tetraethyl orthosilicate is ≥1000 mg/kg bw/day.

 

In a study conducted with tetraethyl orthosilicate according to OECD Test Guideline 422 and in compliance with GLP (CIT Safety & Health Research Laboratories 2005, reliability score 1, oral gavage in corn oil), the NOAEL for developmental effects in offspring from Sprague-Dawley rats was at least 100 mg/kg bw/d, the highest dose tested. The NOAEL maternal was 50 mg/kg bw/day based primarily on renal tubular nephropathy at 100 mg/kg bw/day in toxicity group females. However, as discussed in the repeated dose endpoint summary, the maternal renal findings are considered a consequence of the corn oil dosing in this study and the resulting delay in tetraethyl orthosilicate hydrolysis.

 

In a prenatal developmental study conducted with the tetraethyl orthosilicate condensed hydrolysis product polysilicic acid (equivalent to SAS) according to OECD Test Guideline 414 and in compliance with GLP (Hofmann et al. 2015, reliability score 1), the NOAEL for maternal and developmental toxicity (including teratogenicity) was ≥1000 mg/kg bw/day. Pregnant Wistar rats were administered SAS (described as NM-200) at doses of 100, 300 and 1000 mg/kg bw/day by oral gavage on gestation days 6-19. There were no adverse treatment-related findings in parental animals or offspring.

 

In a pre-OECD / pre-GLP prenatal developmental toxicity study conducted with SAS (Food and Drug Research Laboratories 1973a through d, reliability score 2, oral gavage in corn oil), the maternal and developmental NOAELs for four species (mice, rats, hamsters, rabbits) ranged from ≥ 1340 to ≥1600 mg/kg bw/day of SAS. SAS was administered at doses from 13.4 to 1600 mg/kg bw/day, during gestation day 6 up to day 18 (overall ranges across 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:
2002/09/27 - 2005/04/29
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
other: OECD Guideline 422 (Combined Repeated Dose Toxicity Study with the Reproduction / Developmental Toxicity Screening Test)
GLP compliance:
yes
Limit test:
no
Species:
rat
Strain:
Sprague-Dawley
Remarks:
Crl CD (SD) IGS BR
Details on test animals or test system and environmental conditions:
TEST ANIMALS
- Source: Charles River Laboratories, France.
- Age at study initiation: Males: 8 weeks, females: 10 weeks, for principal, toxicity, and complementary
groups
- Weight at study initiation: Males: 283-339 g, females: 213-285 g, for principal, toxicity, and
complementary groups
- Fasting period before study: None
- Housing: Individually in suspended wire-mesh cages. From day 14 post-coitum, females housed
individually in polycarbonate cages
- Diet (e.g. ad libitum): A04 C pelleted maintenance diet, ab libitum
- Water (e.g. ad libitum): Tap water, ab libitum
- Acclimation period: 9 days for principal and toxicity groups, 11 days for complementary

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 ±2
- Humidity (%): 50 ±20
- Air changes (per hr): 12
- Photoperiod (hrs dark / hrs light): 12/12

IN-LIFE DATES: From: 2002/03/09 - 2002/11/21 for principal and toxicity groups. From: 2004/03/23 -
2004/04/30 for complementary groups.
Route of administration:
oral: gavage
Vehicle:
corn oil
Details on exposure:
Details on exposure
PREPARATION OF DOSING SOLUTIONS: Doses selected based on a 7-day range-finding study. The test substance was mixed with the required quantity of vehicle at concentrations of 3.33, 16.66 and 33.33 mg/mL. The dosage forms were performed as follows: the required quantity of test substance was weighed into an appropriate container; 75% of the final volume of the vehicle was added and the preparation was homogenised with a magnetic stirrer. Sufficient vehicle was thereafter added to make the solutions up to the required volume. The vehicle for the control group was measured first, followed by preparation of the low and intermediate, then the high dose forms to avoid contamination. Solutions were kept for up to 9 days.

VEHICLE
- Justification for use and choice of vehicle (if other than water): Not specified
- Concentration in vehicle: 3.33, 16.66 and 33.33 mg/mL
- Amount of vehicle (if gavage): Various depending on concentration
- Lot/batch no. (if required): 81K2204 and 062K0006
- Purity: Not specified.
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
Verification of dosing solutions:
- Principal and toxicity groups: Concentration from one sample (1 mL) from each control and test item dosage forms prepared for use in weeks 1, 2, 3, 4, 5, 6, 7 and 8 was determined
- Complementary group: Concentration of samples taken from each control and test item dosage forms prepared for the complementary groups in weeks 1 and 4 was determined.
Details on mating procedure:
- M/F ratio per cage: 1:1
- Length of cohabitation: Overnight
- Proof of pregnancy: Vaginal plug / sperm in vaginal smear referred to as day 0 of pregnancy
- Further matings after two unsuccessful attempts: Each female was placed with the same male until mating occurred or 14 days elapsed
- After successful mating each pregnant female was caged (how): From day 14 post-coitum, females housed individually in polycarbonate cages
Duration of treatment / exposure:
28 days up to 53 days:
- Principal males: Pre-mating period (15 days), during the mating and post-mating periods until
final sacrifice for the males (at least 4 weeks in total)
- Principle (maternal) females: Pre-mating (15 days) and mating period, during pregnancy and
lactation, until day 4 post-partum inclusive (or until sacrifice for un-mated females) for the females
- Toxicity females: Same as principal males
- Complementary animals: Same as principal males
Frequency of treatment:
daily
Duration of test:
28 days up to 53 days
Dose / conc.:
10 mg/kg bw/day
Dose / conc.:
50 mg/kg bw/day
Dose / conc.:
100 mg/kg bw/day
No. of animals per sex per dose:
10M, 10F
Control animals:
yes, concurrent vehicle
Details on study design:
- Rationale for animal assignment (if not random): Random
Maternal examinations:
Examinations in parental animals and/or toxicity females:
- Clinical signs: All animals were examined for mortality and clinical signs twice a day.
- Neurobehavioral: In all males of the principal group and in all females of the toxicity groups, landing footsplay, forelimb grip strength, and rectal temperature were measured before the first day of treatment and shortly before terminal sacrifice. In all males and females of the complementary groups, touch response, pupil reflex, visual stimulus, auditory startle reflex, tail pinch response, landing footsplay, forelimb grip strength, rectal temperature, righting reflex were assessed before the first day of treatment and shortly before terminal sacrifice.
- Motor activity: Measured in all males in the principal group, all females in the toxicity group, and all animals in complementary group, before the first day of treatment and shortly before terminal sacrifice, over 10 minutes for principal / toxicity groups, 60 minutes for complementary.
- Body weight: The body weight of each male in the principal, each female in the toxicity and each animal in the complementary groups, was recorded on treatment day 1, then once a week until sacrifice. The body weight of each female from the principal groups was recorded treatment day 1, then once a week until mated (or until sacrifice) and on days 0, 7, 14 and 20 post-coitum and days 1 and 4 post-partum.
- Food consumption: The quantity of food consumed by each animal of all groups was recorded once a week, over a 7-day period (except during the mating period) until sacrifice. The quantity of food consumed by each female of the principal group was recorded once a week during the pre-mating period and then on days 0-7, 7-14, 14-20 post-coitum and days 1-4 post-partum.
- Parturition: From day 20 post-coitum, the females were observed at least three times per day (twice a day during weekends and public holidays). Females were allowed to litter normally and rear their progeny until day 4 post-partum. Any sign of a difficult or prolonged parturition was recorded. The day of completed parturition was designated day 1 post-partum. The length of gestation was calculated.
- Blood samples: Collected from all males of the principal groups and from all females of the toxicity groups at the end of the treatment period, with hematology and biochemistry analysis.
Ovaries and uterine content:
The ovaries were weighed and subjected to gross and microscopic exam after termination. The uterine content was examined.

Uterine examinations included:
- Gravid uterus weight: Not specified
- Number of corpora lutea: Not for maternal animals, but recorded for 2 non-pregnant / non-mated females
- Number of implantations: Yes
- Number of early resorptions: Not specified
- Number of late resorptions: Yes
Fetal examinations:
PARAMETERS EXAMINED
Pup and litter weight was recorded on days 1 and 4 post-partum. During lactation, pups were observed daily for clinical signs or abnormal behavior. The total litter size and numbers of pups of each sex were recorded as soon as possible after birth. The litters were observed daily, with number of live, dead and cannibalized pups and of any runts noted.

GROSS EXAMINATION
Any gross malformations in pups were noted. No further examination performed.
- Soft tissue examinations: No
- Skeletal examinations: No
- Head examinations: No
Statistics:
These statistical methods were used to assess the results: Kolmogorov-Lilliefors, Bartlett, Fisher, Dunn, Mann-Whitney / Wilcoxon, Student, Dunnett, one-way analysis of variances, Fischer exact probability (proportions). The specific method(s) applied varied by endpoint, number of groups, nature of the data.
Indices:
Live birth index: No. live born pups / No. of pups delivered x 100
Viability index (on day 4 post-partum): No. surviving pups on day 4 post-partum / No. live born pups x 100
Historical control data:
Discussed in context of male / female hematology and blood biochemistry, and for number of pups per litter
Details on results:
See 7.5.184 for maternal related findings, primary result was slight treatment-related degenerative/necrotic nephropathy in 3/10 toxicity females at 100 mg/kg bw/day.
Pre- and post-implantation loss:
no effects observed
Description (incidence and severity):
No significant changes in the number of implantation sites in the control and the treated groups. Slightly lower number of implantation sites at 100 mg/kg bw/day, not considered treatment related, see litter size below.
Dead fetuses:
no effects observed
Description (incidence and severity):
No stillborn pups.
Details on maternal toxic effects:
No substance-related effects on the maternal animals. However, the finding of slight degenerative/necrotic nephropathy in 3/10 toxicity group females at 100 mg/kg bw/day is considered relevant to the parent females.
Dose descriptor:
NOAEL
Effect level:
50 mg/kg bw/day
Based on:
test mat.
Basis for effect level:
other: maternal toxicity
Fetal body weight changes:
no effects observed
Description (incidence and severity):
All groups were similar.
Reduction in number of live offspring:
effects observed, non-treatment-related
Description (incidence and severity):
No stillborn pups. Number of liveborn pups was similar in the 10 and 50 mg/kg/day groups when compared to the controls, while it was slightly lower at 100 mg/kg/day. This lower value was the contribution of one female in this group with five implantation sites and a low litter size of three liveborn fetuses. Finding considered to be incidental.
Changes in sex ratio:
no effects observed
Description (incidence and severity):
Similar in the control and the treated groups, and close to a theoretical value of 50%.
Changes in litter size and weights:
effects observed, non-treatment-related
Description (incidence and severity):
Slightly low mean number of pups delivered per litter at 100 mg/kg bw/day was linked to the slightly lower number of implantation sites and mainly due to one female. Not considered treatment related since the change was slight, not statistically significant and within the range of historical control data.
Changes in postnatal survival:
no effects observed
Description (incidence and severity):
Post-natal mortality was similar between groups.
External malformations:
no effects observed
Description (incidence and severity):
No gross external treatment-related abnormalities.
Skeletal malformations:
not examined
Visceral malformations:
not examined
Other effects:
no effects observed
Description (incidence and severity):
No notable clinical signs in the pups.
Dose descriptor:
NOAEL
Effect level:
>= 100 mg/kg bw/day
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: teratogenicity
Abnormalities:
no effects observed
Developmental effects observed:
no
Conclusions:
In study conducted according to OECD Test Guideline 422 and in compliance with GLP (reliability score 1), the NOAEL for developmental effects in offspring from rats treated with tetraethyl orthosilicate was at least 100 mg/kg bw/d, the highest dose tested. The NOAEL for the dams was 50 mg/kg bw/day based on renal tubular nephropathy at 100 mg/kg bw/day in toxicity group females. The developmental toxicity finding contributes to the overall weight of evidence for this endpoint.
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:
In a pre-OECD guideline / pre-GLP study (reliability score 2), the administration of up to 1600 mg/kg (body weight) of synthetic amorphous silica 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. The maternal and developmental NOAELs were >= 1600 mg/kg bw/day. The developmental toxicity finding contributes to the overall weight of evidence for this endpoint. Condensed polysilicic acid (equivalent to synthetic amorphous silica) is the primary hydrolysis product of tetraethyl orthosilicate.
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:
In a pre-OECD guideline / pre-GLP study (reliability score 2), the administration of up to 1340 mg/kg bw/d of synthetic amorphous silica 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. The maternal and developmental NOAELs were >= 1340 mg/kg bw/day. The developmental toxicity finding contributes to the overall weight of evidence for this endpoint. Condensed polysilicic acid (equivalent to synthetic amorphous silica) is the primary hydrolysis product of tetraethyl orthosilicate.
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:
In a pre-OECD guideline / pre-GLP study (reliability score 2), the administration of up to 1600 mg/kg bw/day of synthetic amorphous silica 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. The maternal and developmental NOAELs were >= 1600 mg/kg bw/day. The developmental toxicity finding contributes to the overall weight of evidence for this endpoint. Condensed polysilicic acid (equivalent to synthetic amorphous silica) is the primary hydrolysis product of tetraethyl orthosilicate.
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:
In a pre-OECD guideline / pre-GLP study (reliability score 2), the administration of up to 1350 mg/kg (body weight) of the synthetic amorphous silica 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. The maternal and developmental NOAELs were >= 1350 mg/kg bw/day. The developmental toxicity finding contributes to the overall weight of evidence for this endpoint. Condensed polysilicic acid (equivalent to synthetic amorphous silica) is the primary hydrolysis product of tetraethyl orthosilicate.
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 (reliability score 1), the NOAEL for maternal and developmental toxicity was concluded to be ≥1000 mg/kg bw/day based on no adverse effects observed. The developmental toxicity finding contributes to the overall weight of evidence for this endpoint. Condensed polysilicic acid (equivalent to synthetic amorphous silica) is the primary hydrolysis product of tetraethyl orthosilicate.
Effect on developmental toxicity: via oral route
Endpoint conclusion:
no adverse effect observed
Dose descriptor:
NOAEL
1 000 mg/kg bw/day
Study duration:
subacute
Species:
rat
Quality of whole database:
Klimisch score 1, based on strength of the weight of evidence for tetraethyl orthosilicate and its condensed hydrolysis product SAS
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

OVERVIEW

The developmental toxicity data set for tetraethyl orthosilicate is assessed on a weight of evidence basis and comprises these reliable studies:

- OECD Test Guideline 422 study with tetraethyl orthosilicate in the rat (CIT Safety & Health Research Laboratories 2005, reliability score 1, oral gavage in corn oil)

- OECD Test Guideline 414 with the condensed hydrolysis product polysilicic acid (equivalent to SAS) in the rat (Wolterbeek et al. 2015, reliability score 1, oral gavage in highly deionised water containing 10% foetal bovine serum)

- Pre-OECD / pre-GLP study with SAS in mice, rats, hamsters, and rabbits (Food and Drug Research Laboratories 1973, reliability score 2, oral gavage in corn oil). Study was similar to OECD Test Guideline 414 with some deviations.

 

The oral developmental toxicity data for the tetraethyl orthosilicate condensed hydrolysis product SAS is read across to tetraethyl orthosilicate. The basis for this approach is presented in detail for the repeated dose toxicity endpoint summary (under additional information, oral route, systemic effects, basis for SAS read-across). In summary, the tetraethyl orthosilicate condensed hydrolysis product polysilicic acid is nearly identical to SAS. Further, following neat or aqueous-based tetraethyl orthosilicate dosing, insoluble polysilicic acid will predominate in the small intestine and the concentration of soluble monosilicic acid (expressed as ‘SiO2 equivalent’) will be comparable to the level expected after SAS administration. Thus, it is appropriate to use toxicology data on SAS as part of the weight of evidence of the potential for oral developmental toxicity of tetraethyl orthosilicate.

 

A summary for the non-silane hydrolysis product ethanol is available (OECD SIDS Document UNEP Publication; SIDS Initial Assessment Report for SIAM 19; Berlin, Germany 19-22 October 2004, www.inchem.org/). The lowest ethanol NOAELs for fertility and developmental toxicity were 2000 mg/kg bw/day and are well above any limit doses in OECD guideline tests concerning reproductive toxicity. Ethanol is not classified for developmental toxicity in Annex VI of Regulation (EC) No 1272/2008.

 

ORAL ROUTE

 

STUDY FINDINGS

Based on a weight of evidence approach, the overall developmental NOAEL for tetraethyl orthosilicate is ≥1000 mg/kg bw/day, based on the studies for tetraethyl orthosilicate and its condensed hydrolysis product polysilicic acid (equivalent to SAS). 

 

In a study conducted with tetraethyl orthosilicate according to OECD Test Guideline 422 and in compliance with GLP (CIT Safety & Health Research Laboratories 2005, reliability score 1, oral gavage in corn oil), the NOAEL for developmental effects in offspring from Sprague-Dawley rats was at least 100 mg/kg bw/d, the highest dose tested. The observations and examinations were conducted according to the test guideline, with further details provided in the additional information for fertility. The developmental toxicity finding contributes to the overall weight of evidence for this endpoint. The maternal NOAEL was 50 mg/kg bw/day based primarily on renal tubular nephropathy at 100 mg/kg bw/day in the females toxicity group. However, as discussed in the repeated dose endpoint summary, the maternal renal findings are considered a consequence of the corn oil dosing in this study and the resulting delay in tetraethyl orthosilicate hydrolysis.

 

In a prenatal developmental study conducted with the tetraethyl orthosilicate condensed hydrolysis product polysilicic acid (equivalent to SAS) according to OECD Test Guideline 414 and in compliance with GLP (Hofmann et al. 2015, reliability score 1), pregnant Wistar rats were administered SAS (described as NM-200) (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 examinations were conducted according to the test guideline. There were no adverse, treatment-related findings in parental animals or offspring. There were several incidental foetal malformations and variations, which all occurred at a rate no higher than that of the study and historical controls, without statistical significance and without a dose-response relationship. Therefore, the NOAELs for maternal and developmental toxicity (including teratogenicity) were ≥1000 mg/kg bw/day. The developmental toxicity finding contributes to the overall weight of evidence for this endpoint and provides the highest reliable NOAEL in the rat.

 

In a prenatal developmental toxicity study conducted with SAS prior to OECD test guidelines or GLP (Food and Drug Research Laboratories 1973a through d, reliability score 2, oral gavage in corn oil), the teratogenic effect of SAS was investigated in pregnant mice, rats, hamsters, and rabbits. SAS was administered:

- at doses of up to 1340 mg/kg bw/day to pregnant mice for 10 consecutive days, during gestation days 6 to 15

- up to 1350 mg/kg bw/day to pregnant rats for 10 consecutive days, during gestation days 6 to 15

- up to 1600 mg/kg bw/day to pregnant hamsters for 5 consecutive days, during gestation days 6 to 10

- up to 1600 mg/kg bw/day 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 to assess possible anorexic effects in the pregnant female animal. Towards the end of gestation, all pregnant females 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. Neonatal survival was not examined for the other test species.

 

The maternal and developmental NOAELs for SAS were:

- ≥ 1340 mg/kg bw/day in mice

- ≥ 1350 mg/kg bw/day in rats

- ≥ 1600 mg/kg bw/day in hamsters and in rabbits.

 

The developmental toxicity findings contributes to the overall weight of evidence for this endpoint.

Justification for classification or non-classification

Based on the available data for tetraethyl orthosilicate and its condensed hydrolysis product polysilicic acid (equivalent to SAS), tetraethyl orthosilicate does not require classification for reproductive or developmental toxicity according to Regulation (EC) No. 1272/2008.

Additional information