Trimethoxyvinylsilane

Endpoint summary

Key value for chemical safety assessment

Effects on fertility

Description of key information

In the oral combined repeated dose toxicity study with the reproduction / developmental toxicity screening test, conducted according to OECD Test Guideline 422 and in compliance with GLP (Hashima, 2005), trimethoxy(vinyl)silane was administered by gavage at doses of 62.5, 250 or 1000 mg/kg bw/day. A low number of oestrous cases was detected in females and based on this effect, a NOAEL of 250 mg/kg bw /day was determined.

In order to investigate the reproductive effects further, there is an ongoing extended one-generation reproductive toxicity study. The substance dossier will be updated when the study results are available.

Link to relevant study records

Reference

Endpoint:

screening for reproductive / developmental 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 Combined Repeated Dose and Reproductive / Developmental Toxicity Screening Test (Precursor Protocol of GL 422)

GLP compliance:

yes

Limit test:

no

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Laboratories Japan, Inc., Yokohama, Japan
- Age at study initiation: (P) 9 wks
- Weight at study initiation: (P) males: 317 - 423 g, females: 250 - 277 g
- Fasting period before study: no fasting period
- Housing: individual in stainless steel cages
- Diet: CRF-1, pelleted, ad libitum
- Water: tap water, ad libitum
- Acclimation period: at least 17 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 - 24
- Humidity (%): 41 - 71
- Air changes (per hr): 12
- Photoperiod (hrs dark / hrs light): 12/12

Route of administration:

oral: gavage

Vehicle:

corn oil

Details on exposure:

PREPARATION OF DOSING SOLUTIONS:
Dosing solutions were prepared more than once a week. Concentration of stock solution was 200 mg/ml and sotred at 4°C in a refrigerator. The stock solution was diluted with corn oil to achieve the concentration of the dosing solutions.

VEHICLE
- Lot/batch no.: V3T0416 and V4K3008

Details on mating procedure:

- M/F ratio per cage: 1/1
- Length of cohabitation: max. 14 days
- Proof of pregnancy: vaginal plug and sperm in vaginal smear referred to as day 0 of pregnancy
- Further matings after two unsuccessful attempts: no
- After successful mating each pregnant female was caged (how): Day 18 of gestation until day 4 of lactation: individual in plastic cage with wood chips

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Concentration of dosing solution was verified by GC at the study initiation and at the end of the study. The range of concentration was acceptable because it was between 93.6 - 101.2%.

Duration of treatment / exposure:

Premating exposure period (males): 14 days prior to mating
Premating exposure period (females): 14 days prior to mating
Duration of test: males: 43 days; females: until day 6 of lactation

Frequency of treatment:

daily

Details on study schedule:

- Age at mating of the mated animals in the study: 12 weeks

Dose / conc.:

62.5 mg/kg bw/day (nominal)

Dose / conc.:

250 mg/kg bw/day (nominal)

Dose / conc.:

1 000 mg/kg bw/day (nominal)

No. of animals per sex per dose:

(Males)
6 males/dose
for satellite group: 6 males/dose

(Females for reproduction toxicity study)
12 females/dose

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale: Dose levels were based on the results of a foregoing range finding study, in which animals were orally exposed to 0, 250, 500 and 1000 mg/kg bw/day (Hashima, year not available, 401223P). No mortality was observed in all groups. Reddish urine, decrease in food consumption and occult blood was observed in administered groups. Therefore, 62.5, 250 and 1000 mg/kg bw/day were selected as the dose levels for the main study.

Post-exposure period: Yes, for a sub group of males and females for 14 days

Additional details regarding this study are provided in section 7.5.1.

Parental animals: Observations and examinations:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: Twice a day during administration period, daily during recovery period, and once before necropsy

DETAILED CLINICAL OBSERVATIONS: Yes (including FOB)
- Time schedule: once before administration, Day 7, 14, 21, 28, 35 and 41 (males)
- Time schedule: once before administration, Day 8 and 15 of administration; Day 1, 8 and 15 of gestation; Day 3 of lactation
- Time schedule: once before administration, Day 8, 15, 22, 29, 36 and 42 (females for satellite group)

BODY WEIGHT: Yes
- Time schedule for examinations: twice a week
Males and satellite females: Day 1, 4, 8, 11, 15, 18, 22, 25, 29, 32, 36, 39 and 42 during administration period, Day 1, 4, 8, 11, 14 and 15 during recovery period
Pregnant females: Day 1, 4, 8, 11, 15 and 18, Day 0, 7, 11 and 21 during gestation, Day 0, 4, 6 and 7 during lactation

FOOD CONSUMPTION:
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: Yes

HAEMATOLOGY: Yes
- Time schedule for collection of blood: on day after last administration or after recovery period
- Anaesthetic used for blood collection: Yes (Pentobarbital-Na)
- Animals fasted: Yes
- How many animals: all administered animals
- Parameters checked: RBC, Haemoglobin, Hematocrit, MCV, MCH, MCHC, Platelets, Reticulocytes, PT, APTT, Fibrinogen, WBC, Differential leukocytes: Lymphocyte, Neutrophis, Eosinophis, Basophil, Monocyte

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: on day after last administration or after recovery period
- Animals fasted: Yes
- How many animals: all administered animals
- Parameters checked: AST, ALT, ALP, gamma-GTP, T-protein, Albumin, A/G, T-bilirubin, Urea nitrogen, Creatinine, Glucose, T-cholesterol, Triglycerides, Na, K, Cl, Ca, Inorganic-P

URINALYSIS: Yes
- Time schedule for collection of urine: on Day 2 and 37 in fasted males, Day 3 and 38 in non-fasted males, Day 2 during administration period and Day 5 of lactation in fasted females, Day 3 during administration period and Day 6 of lactation in non-fasted females, after recovery period in females
- Metabolism cages used for collection of urine: Yes
- Animals fasted: Yes/No
- Parameters checked: Colour, pH, Protein, Glucose, Ketone body, Bilirubin, Occult blood, Urobilinogen, Urinary sediments, Epithelial cells, Erythrocytes, Leukocytes, Casts, Crystals

Oestrous cyclicity (parental animals):

Oestrous cycle length and normality were evaluated in females by vaginal smears prior to mating, and optionally during mating, until evidence of mating was found.

Sperm parameters (parental animals):

Parameters examined in P male parental generations:
testis weight, epididymis weight,

Litter observations:

STANDARDISATION OF LITTERS
- Performed on day 4 postpartum: no

PARAMETERS EXAMINED
The following parameters were examined in F1 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:
yes, for external and internal abnormalities; possible cause of death was determined for pups born or found dead.

Postmortem examinations (parental animals):

SACRIFICE
- Male animals: All surviving animals after administration period or recovery period
- Maternal animals: All surviving animals after day 6 of lactation

ORGAN WEIGHT: Yes: Brain, pituitary, thyroids, thymus, heart, liver, spleen, kidney, adrenals, testes, epididymides, ovaries, uterus, lung

GROSS PATHOLOGY: Yes: heart, lung, trachea, liver, pancreas, sublingual gland, submandibular gland, oesophagus, stomach, duodenum, jejunum, ileum, cecum, colon, rectum, thymus, spleen, submandibuar lymph node, mesentric lympha node, kidney, urinary bladder, testis, epididymis, seminal vesicle, prostate, ovary, uterus, pituitary, adrenal, thyroid, parathyroid, cerebrum, cerebellum, medulla oblongata, spinal code, sciatic nerve, eyeball, Harderian gland, bone (sternum or femur), and mammary gland

HISTOPATHOLOGY: Yes: heart, lung, trachea, liver, pancreas, sublingual gland, submandibular gland, oesophagus, stomach, duodenum, jejunum, ileum. cecum. colon, rectum, thymus, spleen, submandibuar lymph node, mesentric lympha node, kidney, urinary bladder, urethra, ovary, uterus, pituitary, adrenal, thyroid, parathyroid, cerebrum. cerebellum. medulla oblongata, spinal code, sciatic nerve, eyeball, Harderian gland, bone (sternum or femur), bone marrow (sternum or femur), and mammary gland

Postmortem examinations (offspring):

SACRIFICE
- All F1 offspring at 4 days of age.

GROSS NECROPSY
- Gross necropsy consisted of external and internal examinations including the cervical, thoracic, and abdominal viscera.

Statistics:

Barlett test, Dunnett test, chi-square test, Cochran-Armitage test

Reproductive indices:

- Copulation index: (number of pairs with successful copulations/number of pairs)x100
- Fertility index: (number of pregnant females/number of pairs with successful copulation)x100
- Implantation index: (number of implantation scars/number of corpora lutea)x100
- Gestation index: (number of dams having live pups/number of pregnant dams)x100
- Delivery index: (number of pups born/number of implantation scars)x100
- Birth index: (number of live pups born/ number of implantation scars)x100

Offspring viability indices:

- Sex ratio at birth: (number of male pups/number of female pups
- Live birth index: (number of live pups born/number of pups born)x100
- Viability index: (number of live pups on Day 4 of lactation/number of live pups born)x100

Clinical signs:

effects observed, treatment-related

Description (incidence and severity):

Transient salivation, soiled hair, a decrease in locomotor activity, reddish urine, hypothermia, perioral smudges, perianal soiling, diarrhoea, bradypnea, and piloerection were noted in the dying animals. Transient salivation, soiled hair and reddish urine were noted in the surviving males and females of the 1000 and 250 mg/kg bw/day groups.

Mortality:

mortality observed, treatment-related

Description (incidence):

Two males and 1 female from the 1000 mg/kg bw/day group died on Day 16 and 17 (males) and Day 8 (female).

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

Low body weights were noted in males on Day 4 to 42 during administration period and Day 1 and 4 during recovery period.
Females of the 1000 mg/kg bw/day group showed also decrease in body weight.

Food consumption and compound intake (if feeding study):

no effects observed

Description (incidence and severity):

Food consumption was decreased on Day 2 in males of 62.5 and 250 mg/kg bw/day group and on Day 2, 5 and 9 of males in 1000 mg/kg bw/day. Males in 62.5 mg/kg bw/day group and 250 mg/kg bw/day group showed more food consumption on Day 9 and 5, respectively. Increased food consumption was also observed in males of 1000 mg/kg bw/day on Day 5, 9 and 12 in recovery period. These increase was not observed as a toxicity effect of the test item, since no change was observed in body weight.

Food efficiency:

not examined

Ophthalmological findings:

not examined

Haematological findings:

effects observed, treatment-related

Description (incidence and severity):

Decreased red blood cell counts, haemoglobin concentrations, hematocrit, MCV, and MCH and increased fibrinogen concentrations were noted in males of the 1000 mg/kg bw/day group after administration period. Prolonged APTT was observed in males of 62.5 mg/kg bw/day after recovery period. This change was no regarded as a tox effect of the test item due to lack of dose-responsibility. Red blood cell counts, haemoblobin, hematocrit were decreased and reticulocytes were increased in males administered with 1000 mg/kg bw/day. Besides, decreased fibrinogen were observed in 250 and 1000 mg/kg bw/day administered males. However, this change disappeared after recovery period. This change was not caused by the test item.
Lower hematocrit in females of the 1000 and 250 mg/kg bw/day groups, and decreased haemoglobin concentrations and prolonged APTT in females of the 1000 mg/kg bw/day group were also noted after administration period. Decreased MCV and MCH was detected in females of 250 mg/kg bw/day after recovery period. Decreased MCV, MCH, MCHC and RBC were also observed in females of 1000 mg/kg bw/day group.

Clinical biochemistry findings:

effects observed, treatment-related

Description (incidence and severity):

Increased CL was observed in males of 62.5 mg/kg bw/day after administration period. However, dose- responsibility was not noted. Low total protein, albumin, A/G ratios, and potassium, and high g-GTP, urea nitrogen, and creatinine were noted in males of the 1000 mg/kg bw/day group after administration period. The change of g-GTP was not caused by the test item because no changes of liver was detected by the histopathological findings. Lower AST was detected in males of 250 and 1000 mg/kg bw/day after administration period but this was not regarded as a tox effect of the test item.

Decreased total protein and increased A/G ratio was detected in males of 1000 mg/kg bw/day after recovery period. Increased chloride was noted in males of 1000 mg/kg bw/day after recovery period but this was not caused by the test item due to the range of background data (106.4 ± 1.9 mEq/l). Inorganic phosphate was increased in same group. This change was not considered as a tox effect of the test item, since this was not observed after administration period.
Low total protein and triglycerides in females of the 1000 mg/kg bw/day group were noted after administration period, and a tendency for high g-GTP in females of the 1000 and 250 mg/kg bw/day groups was observed. The decrease in t-bilirubin was not considered as a tox effect of the test item in females of 1000 mg/kg bw/day after administration period. Decreased in total protein was observed in females of 1000 mg/kg bw/day after recovery period. Increased ALP and Cl observed in females of 1000 mg/kg bw/day was not caused by the test item, since this dat was similar to the background data of this test facility (ALP: 242.7 ± 1012.4 IU/l, Cl: 107.7 ± 2.1 mEq/l).

Urinalysis findings:

effects observed, treatment-related

Description (incidence and severity):

Males on Day 2 before administration: increased volume and decreased specific gravity, occult blood positive, epithelial cells and erythrocytes were noted in 1000 mg/kg bw/day. 250 mg/kg bw/day groups showed occult blood and erythrocytes.
Females on Day 2 before administration: increased volume and decreased specific gravity, occult blood positive, erythrocytes and leukocytes were noted in 1000 mg/kg bw/day. 250 mg/kg bw/day groups showed occult blood and erythrocytes.
Males on Day 3 after administration: 250 mg/kg bw/day groups showed white turbidity, occult blood and erythrocytes. White turbidity, occult blood, erythrocytes and leukocytes were observed in 1000 mg/kg bw/day.
Females on Day 3 after administration: 250 mg/kg bw/day groups showed white turbidity, occult blood and erythrocytes. White turbidity, occult blood, erythrocytes and epithelial cells were observed in 1000 mg/kg bw/day.
Males on Day 37 before administration: Decreased specific gravity, occult blood, epithelial cells, erythrocytes and leucocytes were observed in 1000 mg/kg bw/day.
Females on last day before administration: Epithelial cells were observed in 250 mg/kg bw/day and erythrocytes and leucocytes were observed in 1000 mg/kg bw/day.
Males on Day 37 after administration: 250 mg/kg bw/day groups showed white turbidity, erythrocytes and leucocytes. White turbidity, occult blood, erythrocytes and leucocytes were observed in 1000 mg/kg bw/day.
Females on last day after administration: Leucocytes were found in 1000 mg/kg bw/day.
Males and females after recovery period: No changes were observed.

Behaviour (functional findings):

no effects observed

Description (incidence and severity):

Salivation was observed in males and females of 1000 mg/kg bw/day after administration. Ease of removal from cage was decreased in 250 mg/kg bw/day but this was observed before administration. Salivation was observed in 1000 mg/kg bw/day. No changes were noted in both sexes regarding sensory response and grip strength. Increased spontaneous motor activity was noted in males 250 mg/kg bw/day but this was not regarded as a specific toxic effect due to lack of dose response. No change of spontaneous motor activity was reported in females.

Immunological findings:

not examined

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

In dead males in 1000 mg/kg bw/day, two animals showed postmortal change in whole organs and tissues. One dead male showed vacuolization of lamina propria in jejunum, one male showed hyperplasia of transitional epithelium in kidney, two males showed slight hyperplasia of transitional epithelium in urinary bladder, two males showed hyperplasia of transitional epithelium in urethra, one animal showed atrophy of seminiferous tubule in testis and one animal showed cell debris in lumen in epididymis.

One death occured in females in 1000 mg/kg bw/day. The dead animal showed moderate postmortal change in whole organs and tissues, slight cellular infiltration of heart, slight hyperplasia of transitional epithelium in kidney and slight hyperplasia of transitional epithelium in urinary bladder. However, these observed changes in dead males and female were not marked. Death was caused by deteriorating general conditions by the test substance.

Histopathological findings after administration and recovery phase are listed in Tables.

On histopathological examination, hyperplasia of transitional epithelium in the urinary bladder was noted in males at all doses. The effect seemed to be substance-related and followed a dose-response relationship. The incidence of hyperplasia in the 250 and 1000 mg/kg bw/day groups was statistically significantly increased up to the end of the recovery period, although a slight decrease (mild to slight) in severity was observed from end of administration period to the end of the recovery period. Hyperplasia that was observed in 2/6 male rats of the 62.5 mg/kg bw/day group after the administration period seemed to be treatment-related, as there were no incidences in the control group; hyperplasia was not observed in the urinary bladder of females in the 62.5 mg/kg bw/day goup. In general, hyperplasia in the urinary tract/bladder is not a typical spontaneous lesion, but simple hyperplasia may also occur in untreated animals. Often it is a secondary effect provoked by inflammation or physical damage. The effects observed in males at 62.5 mg/kg bw/day were not evaluated as adverse, as the incidence was not increased statistically significantly and the severity of the effect was stated as "slight". In addition the effects were fully reversible within the recovery period.

Histopathological findings: neoplastic:

no effects observed

Reproductive function: oestrous cycle:

effects observed, treatment-related

Description (incidence and severity):

The number of estrous cases before pairing in 1000 mg/kg bw/day was less than that of the control group.

Reproductive function: sperm measures:

no effects observed

Description (incidence and severity):

Moderate atrophy of seminiferous tubule, slight degeneration of semiferous tubule, slight vacuolization of Sertoli cell and slight retention of spermalid were observed in 1000 mg/kg bw/day. Slight decrease in sperm and slight or moderate cell debris in lumen in epididymis were observed in 1000 mg/kg bw/day.

Reproductive performance:

no effects observed

Description (incidence and severity):

No changes were observed in reproductive parameters.

Dose descriptor:

NOAEL

Remarks:

reproduction

Effect level:

1 000 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male

Basis for effect level:

other: No effects on reproductive performance.

Dose descriptor:

NOAEL

Remarks:

reproduction

Effect level:

250 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

female

Basis for effect level:

other: Low number of oestrous cases.

Dose descriptor:

NOAEL

Remarks:

systemic toxicity

Effect level:

62.5 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

histopathology: non-neoplastic

Critical effects observed:

yes

Lowest effective dose / conc.:

250 mg/kg bw/day (actual dose received)

System:

urinary

Organ:

bladder

Treatment related:

yes

Dose response relationship:

yes

Relevant for humans:

not specified

Clinical signs:

no effects observed

Description (incidence and severity):

No changes were observed.

Mortality / viability:

no mortality observed

Description (incidence and severity):

No changes were observed.

Body weight and weight changes:

no effects observed

Description (incidence and severity):

Litter weight on Day 4 of lactation was decreased in 1000 mg/kg bw/day. However, this change occurred accidentally since no changes were found in mean pups weight on Day 0 and 4 of lactation, male and female weight on Day 0 and 4.

Food consumption and compound intake (if feeding study):

not examined

Food efficiency:

not examined

Ophthalmological findings:

not examined

Haematological findings:

not examined

Clinical biochemistry findings:

not examined

Urinalysis findings:

not examined

Sexual maturation:

not examined

Anogenital distance (AGD):

not examined

Nipple retention in male pups:

not examined

Organ weight findings including organ / body weight ratios:

not examined

Gross pathological findings:

no effects observed

Description (incidence and severity):

One dead pup showed atrophy of lung in 250 mg/kg bw/day administered group. This change was not related to the test item since no dose-responsibility was found. One survival pup showed dilatation of pelvis in 1000 mg/kg bw/day administration group. This change was not regarded as test compound related effect but accidentally happened.

Histopathological findings:

not examined

Behaviour (functional findings):

not examined

Developmental immunotoxicity:

not examined

Dose descriptor:

NOAEL

Generation:

F1

Effect level:

1 000 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: No adverse effects observed.

Critical effects observed:

no

Reproductive effects observed:

yes

Lowest effective dose / conc.:

1 000 mg/kg bw/day (actual dose received)

Treatment related:

yes

Relation to other toxic effects:

reproductive effects occurring together with other toxic effects, but not as a secondary non-specific consequence of other toxic effects

Dose response relationship:

yes

Relevant for humans:

not specified

Table 1: Reproductive functions of male and female rats.

	F0 (mg/kg/day)
Parameter	0	62.5	250	1000
Number of females	12	12	12	11
No. of estrous cases before pairing (14 days)	3.2±0.4	3.2±0.4	3.1±0.3	2.5±0.7*
Copulation index	100	91.7	91.7	90.9
No. of conceiving days	2.8±1.4	1.8±1.3	2.8±3.8	4.7±2.4
Female fertility index	100.0	100	100.0	100.0

 

Table 2: Observation of pups (F1).

	F1 (mg/kg/day)
Parameter	0	62.5	250	1000
Length of gestation	22.2±0.4	22.5±0.7	22.5±0.5	22.6±0.5
Corpora lutea	16.7±1.8	16.3±3.5	15.8±1.5	15.6±1.3
Implantation scars	15±1.5	14.5±4.3	14.5±1.9	13.7±1.3
Implantation index (%)	90.1±6.4	87.2±17.7	91.3±7.6	88±6.8
Gestational index	100	100	100	100
Pups born	14.3±1.6	13.3±4.6	13.9±1.9	12.9±1.1
Stillbirths	0.4±0.7	0.1±0.3	0.3±0.5	0.2±0.6
Live pubs born	13.9±1.7	13.2±4.6	13.6±1.7	12.7±1.1
Sex ratio at birth	1.74±1.25	0.96±0.73	0.94±0.54	1.18±0.77
Delivery index (%)	92.9±7.7	88.7±13.5	94.7±6.3	93.1±7.3
Birth index (%)	92.8±7.7	88.6±13.5	94.6±6.3	93.0±7.3
Live birth index (%)	97.2±4.5	99.4±2.1	98.2±3.1	98.6±4.4
Live pups on day 4 of lactation	13.8±1.7	12.9±4.4	13.5±1.7	12.4±1.1
Sex ratio on day 4 of lactation	1.74±1.24	0.97±0.72	0.93±0.53	1.14±0.8
Viability index (%)	99.4±2.0	98.3±4.1	98.7±2.8	97.7±5.0
External abnormalities (%)	0	0	1.2±4.0	0
Acaudate	0	0	1.2±4.0	0

 

Table 3: General signs of pups.

	F1 (mg/kg/day)
Parameter	0	62.5	250	1000
No. of pups (normal/death)
day 0 of lactation	167/5	145/1	150/3	127/2
day 1 of lactation	166/1	145/0	149/1	125/2
day 2 of lactation	166/0	144/1	148/1	124/1
day 4 of lactation	166/0	143/1	148/0	124/0
day 4 of lactation	166/0	142/1	148/0	124/0

 

Table 4: Body weights of pups.

	F1 (mg/kg/day)
Parameter	0	62.5	250	1000
Male weight
day 0 of lactation	6.7±0.6	6.6±0.8	7.0±0.7	6.8±0.7
day 4 of lactation	10.7±1.0	10.5±1.7	10.7±1.1	10.5±0.7
Female weight
day 0 of lactation	6.3±0.4	6.3±0.6	6.8±0.6	6.5±0.5
day 4 of lactation	10.1±0.9	9.8±1.2	10.6±1.0	10.3±0.6
Mean pups weight
day 0 of lactation	6.6±0.5	6.6±0.8	6.9±0.6	6.7±0.6
day 4 of lactation	10.4±0.9	10.3±1.7	10.7±1.0	10.4±0.7
Litter weight
day 0 of lactation	91.0±9.0	83.4±25.5	93.9±14.4	84.7±7.9
day 4 of lactation	143.4±11.7	126.8±35.1	142.8±18.0	128.6±10.5*

Significantly different from control group (*: p<0.05)

 

 

Conclusions:

In a reliable study with trimethoxy(vinyl)silane, conducted according to OECD Test Guideline 422 and in compliance with GLP, NOAELs for reproductive performance of parental animals were estimated to be 1000 mg/kg bw/day for males and 250 mg/kg bw/day for females. The NOAEL for offspring was 1000 mg/kg bw/day. The NOAEL for systemic toxicity of the parents was 62.5 mg/kg bw/day.

Effect on fertility: via oral route

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEL

250 mg/kg bw/day

Study duration:

subacute

Species:

rat

Effect on fertility: via inhalation route

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEC

2 425 mg/m³

Study duration:

subchronic

Species:

rat

Effect on fertility: via dermal route

Endpoint conclusion:

no study available

Additional information

In the oral combined repeated dose toxicity study with the reproduction / developmental toxicity screening test, conducted according to OECD Test Guideline 422 and in compliance with GLP (Hashima, 2005), trimethoxy(vinyl)silane was administered by gavage at doses of 62.5, 250 or 1000 mg/kg bw/day. The NOAELs for reproductive performance of parental animals were estimated to be 1000 mg/kg bw/day for males and 250 mg/kg bw/day for females. The NOAEL for development was 1000 mg/kg bw/day. Regarding reproductive toxicity, a low number of estrous cases was noted in the 1000 mg/kg bw/day group. No changes attributable to the test article were noted for the copulation index, number of conceiving days, number of pregnant females, fertility index, gestation length, gestation index, delivery conditions, nursing conditions, number of corpora lutea, number of implantation sites, or the implantation rate. No effects were noted for the offspring.

 

In the 14-week repeated dose vapour inhalation toxicity study in rats which was conducted according to current guideline and in compliance with GLP (Bushy Run Research Center, 1990), rats were repeatedly exposed to nominal concentrations of  10, 100 or 400 ppm of the registered substance for 6 hours per day over 14 weeks. The reproductive organs of male and female animals were examined microscopically in response to treatment with test article. In the 400 ppm group after 14 weeks exposure the absolute testes weight was statistically significantly lower when compared to control mean values. When expressed as a percentage of body weight, the testes weights were equivalent to control values. There was no effect on absolute testes weight in the 400 ppm recovery group animals. There were no histopathological lesions reported for any of the reproductive organs examined in any group. No effect was noted on male reproductive organs in the study.

Effects on developmental toxicity

Description of key information

In the prenatal developmental toxicity study, conducted according to EPA OTS 798.4350 (Inhalation Developmental Toxicity Screen) and in compliance with GLP, pregnant female rats were exposed to the test concentrations of 25, 100 or 250 ppm via whole body inhalation during gestation days 6 to 15. Exposure of pregnant rats during organogenesis to trimethoxy(vinyl)silane by inhalation resulted in slight maternal toxicity at 100 and 300 ppm as evidenced by concentration-dependent reductions in gestational body weight gain (gestation days 6-9). There was evidence of slightly delayed development in fetuses from the 300 ppm group as indicated by delayed ossification in several skeletal districts. No exposure-related embryotoxicity or teratogenicity was observed in this study (Bushy Run Research Center, 1993). The observed variations are not considered toxicologically relevant, particularly in the presence of maternal toxicity, and therefore the NOAEC is greater than or equal to 300 ppm (approximately 1730 mg/m³).

In the prenatal developmental toxicity study in rabbits, conducted according to OECD Test Guideline 414 and in compliance with GLP, the LOAEL for maternal toxicity was concluded to be 7.5 mg/kg bw/day based on degenerative changes characterized by tubular dilatation and tubular basophilia in all dose groups; the NOAEL for developmental toxicity was concluded to be equal to or greater than 75 mg/kg bw/day (the highest dose tested) based on no observed adverse effects in any of the foetuses (BSL Bioservice, 2020).

Link to relevant study records

Reference

Reference 1

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Study period:

25th of October 2019 to 9th of June 2020

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 414 (Prenatal Developmental Toxicity Study)

Version / remarks:

Adopted 25 June 2018

Deviations:

yes

Remarks:

General clinical observation were not recorded for several animals on one weekend

GLP compliance:

yes (incl. QA statement)

Limit test:

no

Species:

rabbit

Strain:

New Zealand White

Remarks:

Crl: KBL

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River, 97633 Sulzfeld, Germany
- Age at study initiation: Approximately 19-25 weeks
- Weight at study initiation: males: 4060 – 3377 g (mean: 3681 g ± 20 % = 2945 – 4418 g)
females: 4190 - 2519 g (mean: 3472 g ± 20 % = 2777 – 4166 g)
- Fasting period before study: no
- Housing: Housed in ABS-plastic or Noryl rabbit cages, floor 4200 cm2, semi barrier housing in an air-conditioned room.
- Diet: Altromin 2123 (manufactured by Altromin Spezialfutter GmbH & Co.KG, Im Seelenkamp 20, D-32791 Lage) maintenance diet for rabbits, rich in crude fibre, ad libitum
- Water: tap water (with municipal residue and microbiological controls at regular intervals), ad libitum
- Acclimation period: At least 5 days.

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 18 ± 3 °C
- Humidity (%): 55 ± 10 %
- Air changes (per hr): 10 x / hour
- Photoperiod (hrs dark / hrs light): 12 hours light, 12 hours dark

IN-LIFE DATES: Not specified

Route of administration:

oral: gavage

Vehicle:

corn oil

Details on exposure:

PREPARATION OF DOSING SOLUTIONS: The test substance was weighted and the vehicle was added to the appropriate final concentrations. The formulation was vortexed and/or stirred until visual homogeneity was achieved. After homogenisation, the formulation was overlaid with argon to prevent instability caused by repeated contact of the test substance formulation with air. The test substance formulations were prepared once every 9 days (within the stability time frame). Formulates were kept under magnetic stirring during the daily administration. The prepared formulation was stored protected from light and at room temperature.

VEHICLE
- Justification for use and choice of vehicle: The vehicle has been selected in consultation with the sponsor based on the test item’s characteristics. The test item was dissolved in dried and de-acidified corn oil.
- Concentration in vehicle: 0, 7.5, 25, 75 mg/mL
- Amount of vehicle: 1 mL/kg bw
- Lot/batch no.: Sigma-MKCH1635, MKCK6411, Caelo-19112904
- Purity: not specified

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Before beginning of the treatment period, formulation samples were prepared and analysed in order to obtain knowledge about stability and homogeneity of the test item in the selected vehicle. The test item was shown to be homogenous and samples were not collected during the main study for the investigation of homogeneity. Samples were taken in duplicate during the main study only for substance concentration analysis in the first, third, fifth and last weeks of the study for all doses including the vehicle control.

Details on mating procedure:

- Impregnation procedure: Cohoused
- If cohoused: A female was taken to a male’s cage
- M/F ratio per cage: 1:1 ratio (male to female)
- Length of cohabitation: Until mating was confirmed
- In case of unsuccessful mating, the female was taken back to its original cage and mating of the female with another male or at another time was considered.
- Further matings after two unsuccessful attempts: Not specified
- Verification of same strain and source of both sexes: Yes
- Proof of pregnancy: Visual inspection and based on the falling of male on its back or side and emittance of a typical cry. The day on which a confirmed mating was observed is referred to as day 0 of pregnancy
- Any other deviations from standard protocol: No

Duration of treatment / exposure:

Between GD 6 to GD 27

Frequency of treatment:

Daily

Duration of test:

28 days

Dose / conc.:

0 mg/kg bw/day

Remarks:

Control

Dose / conc.:

7.5 mg/kg bw/day

Remarks:

Low Dose, LD

Dose / conc.:

25 mg/kg bw/day

Remarks:

Middle Dose, MD

Dose / conc.:

75 mg/kg bw/day

Remarks:

High Dose, HD

No. of animals per sex per dose:

20 pregnant females per group.
16 males for mating only
100 females in total
In total 116 animals

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale: A previous dose range finding study examined the developmental effects at doses of 0, 100, 250 and 400 mg/kg bw/day. Test item-related maternal toxicological effects in terms of reduced body weight gain, food consumption and gravid uterine weight were observed at 100, 250 and 400 mg/kg bw/day; slightly lower carcass weight was observed at the 400 mg/kg bw/day dose group; reduced male and female foetal weight was seen in all the dose groups and inflammatory, degenerative and hyperplastic lesions in the urinary tract organs were reported in all dose groups. Based on these results and and in consultation with the sponsor, the following doses were selected for the 3 dose groups: 0 mg/kg bw/day for the control (C) group, treated with the vehicle corn oil, 7.5 mg/kg bw/day for the low dose (LD), 25 mg/kg bw/day for the middle dose (MD) and 75 mg/kg bw/day for the high dose (HD).
- Rationale for animal assignment: randomised

Maternal examinations:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: All animals were observed for morbidity and mortality twice daily except on weekends and public holidays when observations were made once daily. However, one deviation from the protocol was that clinical signs were not recorded for some animals for 2 days, on a weekend.

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: General clinical observations were made at least once per day. Clinical observations included spontaneous activity, lethargy, recumbent position, convulsions, tremors, apnoea, asphyxia, vocalisation, diarrhoea, changes in the skin and fur, eyes and mucous membranes (salivation, discharge), piloerection and pupil size. Changes in gait, posture, response to handling, as well as the presence of colonic or tonic movements, stereotypes or bizarre behaviour were also recorded.

BODY WEIGHT: Yes
- Time schedule for examinations: All animals were weighed once before initiation of pairing to ensure that the body weights were within ±20 % variation.
The mated females were weighed on GDs 0, 3, 6, 9, 12, 15, 18, 21, 24, 27 and 28.
Males were not weighed in this study except once before initiation of pairing

FOOD CONSUMPTION AND COMPOUND INTAKE: Yes
Food consumption of pregnant females were measured for the following intervals: GD 0-3, 3-6, 6-9, 9-12, 12-15, 15-18, 18-21, 21-24, 24-27 and 28.
Food consumption was not measured for males during the entire study or for females before confirmation of mating.

WATER CONSUMPTION AND COMPOUND INTAKE: No

POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on gestation day # 28
- Organs examined: The urinary tract (kidneys, ureter and urinary bladder) and liver were examined histopathologically.

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: [all per litter]
- Skeletal examinations: Yes: [all per litter]
- Head examinations: Yes: [half per litter]
- Other: Once the soft tissue evaluation of all foetuses was completed, half of the foetuses were decapitated. Foetuses with intact heads and without heads were then processed for skeletal and cartilaginous double staining by Alcian blue and Alizarin red and evaluated for skeletal anomalies.

Statistics:

Toxicology and pathology data were captured either on paper according to appropriate SOPs or using the validated computerised system Ascentos® System (version 1.3.4, Pathology Data Systems Ltd.).
A statistical assessment of the results of the body weight and food consumption was performed by comparing values of dosed animals with control animals using a one-way ANOVA and a post-hoc Dunnett Test. Results of absolute and relative organ weights, thyroid hormones and foetal evaluation parameters like external, visceral, craniofacial and skeletal parameters were statistically analysed by comparing values of dosed with control animals using either a parametric one-way ANOVA and a post-hoc Dunnett Test or a non-parametric Kruskal-Wallis Test and a post-hoc Dunn’s Test, based on the results of homogeneity and normality tests. The statistics were performed with GraphPad Prism V.6.01 software or Ascentos 1.3.4 software (p<0.05 is considered as statistically significant).

Clinical signs:

effects observed, non-treatment-related

Description (incidence and severity):

There were no treatment-related clinical signs observed in the females of any of the treatment group.

Clinical signs observed on a few days during the treatment period of the study. LD group: skin and fur, hairless area (right hind paw) in one animal on GDs 26-27; in one animal on the right or left hind paw on GDs 20-28; skin and fur, hairless area (left forelimb and hind limb) in one animal on GDs 25-28 and skin and fur, hairless area (left hind limb) in one animal on GDs 19-22 and GDs 25-28.
MD group: skin and fur, scratch/cut (neck) was observed in one animal on GD 0. Skin and fur, hairless area (left fore and hind paw, right forepaw) was observed in one animal on GDs 7-28 and 8-17.
HD group: skin and fur, hairless area (left and right hind paw) was observed in one animal on GD 25-28; in one animal on the left and right hind limb on GDs 24-28 and 26-28 and in one animal on the left and right hind paw on GDs 21-25 and GDs 21-28, respectively.
These clinical signs are considered to be incidental findings and not related to treatment with test item.

Dermal irritation (if dermal study):

not examined

Mortality:

no mortality observed

Description (incidence):

No test item-related mortality was observed during the treatment period and all animals survived until the end of the study.

One control group rabbit was found dead immediately after dosing on GD 7. It showed clinical signs of cough/sneezing at the post dose observation. Macroscopic observation revealed dark and abnormal red colour lungs. The cause of the death is assumed to be a gavage error during administration.

Body weight and weight changes:

no effects observed

Description (incidence and severity):

The mean body weight remained unaffected by the treatment with the test item and slightly increased with the progress of the study in all groups throughout the study period. No statistical significance was achieved in any treatment groups on any day or interval of body weight measurement and all values in the treatment groups were comparable to the controls. The inconsistent and statistically non-significant decreases or increases observed on different days of body weights measurement in the treatment groups between GD 3 and GD 27 are considered to be incidental and not test item-related.

Food consumption and compound intake (if feeding study):

no effects observed

Description (incidence and severity):

Food consumption in the LD, MD and HD groups was comparable to the control. Slightly lower food consumption was observed on GDs 9-12 and 21-24 in the LD group (9.31% and 16.38 % respectively, below control). Other slight differences in food consumption did not follow any dose-dependency in the treated groups and thus were not considered toxicologically relevant.

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:

no effects observed

Description (incidence and severity):

No test item-related effects of statistical or toxicological relevance were noted for the uterine weight

Gross pathological findings:

effects observed, non-treatment-related

Description (incidence and severity):

No test item-related gross pathological changes of toxicological significance were observed during the macroscopic examination of the terminally sacrificed females of the control, LD, MD and HD groups.
A few specific macroscopic changes recorded in the female animals during the macroscopic examination at terminal sacrifice were dark/dark red colour lungs (1/25 in each control, LD and MD groups; abnormal coloured liver (1/25 in control), enlarged liver (1/25 in each control and MD group), red/white gallbladder (1/25 in control), small gallbladder (2/25 in LD group), enlarged gallbladder (1/25 in control, 2/25 in LD female, 2/25 in MD and 1/25 in HD), abnormal shape kidneys in one control, oviduct cyst (1/25 in control female and 2/25 in LD), abnormal shape uterus right horn in LD group (1/25 in LD group) and cyst in the uterus horns (2/25 in control, 1/25 in LD, 2/25 in MD group and 2/25 in HD group) and right uterus horn absent in LD female.

Neuropathological findings:

not examined

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

Microscopic changes that could be attributed to treatment with the test item were observed in the kidneys, urinary bladder and ureters of all groups treated with the test item.
In kidneys, diffuse transitional cell hyperplasia (urothelial hyperplasia) was observed in 5/25 and 4/25 animals from the MD and HD groups, respectively. Further, degenerative changes characterized by tubular dilatation (2/25, 10/25 and 8/25 in LD, MD and HD groups, respectively) and tubular basophilia (5/25, 8/25 and 1/25 in LD, MD and HD groups, respectively) were noted in animals from all dose groups.
In the urinary bladder, diffuse transitional cell hyperplasia (urothelial hyperplasia) was observed in 9/25, 12/25 and 17/25 animals from the LD, MD and HD treatment groups, respectively. The transitional cell hyperplasia was accompanied by submucosal oedema (2/25, 5/25 and 13/25 in LD, MD and HD groups, respectively) and congestion (5/25, 6/25 and 13/25 in LD, MD and HD groups, respectively) and in one MD group animal and one HD group animal, by accumulation of mixed cell infiltrates in the submucosa.
In ureters, diffuse transitional cell hyperplasia (urothelial hyperplasia) was noted in 10/25, 12/25 and 13/25 animals from the LD, MD and HD treatment groups, respectively.
Overall, the incidence and/or severity of the transitional cell hyperplasia increased in a dose-dependent manner, whereas for all the other changes described above, no clear dose-dependency was observed.
All the above-mentioned findings observed in the urinary tract were deemed to be adverse changes.
In the liver, no test item-related changes were observed. All observed hepatic changes were within the range of normal background lesions which may be observed in animals of this strain and age or were considered incidental lesions.
The remainder of microscopic findings recorded were within the range of normal background lesions which may be observed in animals of this strain and age or were incidental lesions that were not related to treatment with the test item.

Histopathological findings: neoplastic:

not examined

Other effects:

no effects observed

Number of abortions:

no effects observed

Description (incidence and severity):

None of the females showed signs of abortion or premature delivery prior to the scheduled sacrifice, except one LD female on GD 28.

Pre- and post-implantation loss:

no effects observed

Description (incidence and severity):

Mean preimplantation loss was 0.27, 0.09 and 0.26 in the LD, MD and HD groups, respectively, when compared to control (0.04). Mean post implantation loss was 0.91, 0.23 and 0.30 in the LD, MD and HD groups, respectively, when compared to control (1.50). These findings were observed without dose dependency and were considered to be a biological variation in this species.

Total litter losses by resorption:

not specified

Early or late resorptions:

no effects observed

Description (incidence and severity):

Mean early resorption was 0.27, 0.14 and 0.09 in the LD, MD and HD groups, respectively, when compared to control (0.79). Mean late resorption was 0.18, 0.09 and 0.22 in the LD, MD and HD groups, respectively, when compared to control (0.25). These findings were observed without dose dependency and were considered to be a biological variation in this species.

Dead fetuses:

no effects observed

Description (incidence and severity):

One pup in the control group and one pup in the LD group were dead at scheduled sacrifice. These findings were observed without dose dependency and were considered to be a biological variation in this species.

Changes in pregnancy duration:

no effects observed

Description (incidence and severity):

None of the females showed signs of premature delivery prior to the scheduled sacrifice.

Changes in number of pregnant:

no effects observed

Description (incidence and severity):

Three LD, three MD, and two HD females were confirmed to be non-pregnant at scheduled sacrifice.

Other effects:

no effects observed

Description (incidence and severity):

Number of corpora lutea was not affected by the treatment.

Key result

Dose descriptor:

LOAEL

Effect level:

ca. 7.5 mg/kg bw/day (actual dose received)

Based on:

test mat.

Basis for effect level:

histopathology: non-neoplastic

Key result

Abnormalities:

effects observed, treatment-related

Localisation:

other: Urinary tract

Fetal body weight changes:

no effects observed

Description (incidence and severity):

There were no test item-related effects of toxicological relevance observed for the mean foetus weight, male and female foetus weight on a per litter basis (group mean of individual litter mean) in any of the treatment groups when compared to control.

Reduction in number of live offspring:

no effects observed

Description (incidence and severity):

There were no test item-related effects of toxicological relevance observed for the number of live offspring.

Changes in sex ratio:

no effects observed

Description (incidence and severity):

The number of the difference in the sex ratio was unaffected by the test substance.

Changes in postnatal survival:

not examined

External malformations:

no effects observed

Description (incidence and severity):

Foetal external examination on the day of terminal sacrifice revealed no test item-related external findings in foetuses of any of the treated groups.
Statistical analysis of data revealed no significant differences compared to the control group. One incidence of cleft palate was observed in one male pup no. 4 from animal no. 2 and considered to be incidental in nature.

Skeletal malformations:

effects observed, non-treatment-related

Description (incidence and severity):

Skeletal examination of the foetuses observed for skeletal and cartilaginous findings revealed a range of findings that were of a type or occurred at an incidence generally comparable to or slightly lower/higher in the treatment groups when compared to the control group.

A statistically significant lower foetal incidence of pelvic girdle, caudal shift was observed in the MD and HD groups (0%) when compared to control (13%). A statistically significant higher litter incidence of vertebra thoracic centrum/centra was observed in the MD group (81.8%) when compared to control (30.4%) and higher foetal incidences in the MD group (21.3) when compared to control (8.3%). A statistically significant higher litter incidence of dumbbell ossification in vertebra thoracic centrum was observed in the MD group (50%) when compared to control (13%). A statistically significant higher foetal incidence of bipartite ossification in vertebra thoracic centrum was observed in the MD group (14.4%) when compared to control (4.2%). A statistically significant higher foetal incidence of misaligned ossification of hind limb proximal phalanx was observed in the HD group (3.2%) when compared to control (0%). A statistically significant lower foetal incidence of unossified forelimb medial phalanx was observed in the LD group (27.1%) when compared to control (52.4%). A statistically significant higher litter incidence of unossified 6th sternebra was observed in the MD group (54.5%) when compared to control (13%). A statistically significant lower foetal incidence of long costal cartilage was observed in the HD group (32.7%) when compared to control (59%). A statistically significant lower foetal incidence of interrupted costal cartilage was observed in the LD, MD and HD groups (0% in each) when compared to control (4.6%). All these statistically significant findings were observed without any dose dependency, hence they are not considered to be test item-related, but rather spontaneous in nature.
Higher or lower litter incidences, but without achieving statistical significance were observed as mentioned below. Higher litter incidences of hole in the xiphoid (LD, MD and HD groups (19%, 22.7% and 34.8%, respectively) were observed compared to 26.1 % in control. Higher litter incidences of unossified forelimb proximal phalanx (LD, MD and HD groups (14.3%, 18.2% and 30.4%, respectively) were observed compared to 8.7% in control. Higher or lower litter incidence of skull hyoid body (incomplete ossification, unossified) was observed in treated groups (76.2 %, 81.8 % and 91.3 % in the LD, MD and HD groups, respectively) and control group (91.3 %). Higher or lower litter incidence of hind limb talus (incomplete ossification, unossified) was observed in treated groups (19 %, 18.2 % and 30.4 % in the LD, MD and HD groups, respectively) and control group (21.7 %).
Higher or comparable litter incidence of pelvic girdle, caudal shift was observed in the treated groups 52.4 %, 50 % and 52.2 % in the LD, MD and HD groups, respectively) and control group (52.2 %). Higher or lower litter incidence of unossified 5th sternebra was observed in treated groups (42.9 %, 54.5 % and 73.9 % in the LD, MD and HD groups, respectively) and control group (69.6 %). Higher or lower litter incidence of incomplete ossification of 5th sternebra was observed in treated groups (76.2 %, 77.3 % and 91.3 % in the LD, MD and HD groups, respectively) and control group (87 %). Lower litter incidence of interrupted vertebra cervical cartilaginous ventral plate was observed in treated groups (42.9 %, 40.9 % and 43.5 % in the LD, MD and HD groups, respectively) and control group (52.2 %). Higher litter incidence of rudimentary ribs was observed in treated groups (76.2 %, 95.5 % and 78.3 % in the LD, MD and HD groups, respectively) and control group (65.2 %). Higher or lower litter incidence of unossified hind limb medial phalanx was observed in treated groups (23.8 %, 27.3 % and 60.9 % in the LD, MD and HD groups, respectively) and control group (30.4 %).
Higher or lower litter incidence of unossified and incomplete ossification of pelvic girdle pubis was observed in treated groups (28.6 %, 22.7 % and 52.2 % in the LD, MD and HD groups, respectively) and control group (30.4 %). Higher litter incidence of incomplete ossification of 6th sternebra was observed in treated groups (42.9 %, 68.2 % and 52.2 % in the LD, MD and HD groups, respectively) and control group (39.1 %). Higher litter incidence of misaligned costal cartilage was observed in treated groups (28.6 %, 27.3 % and 39.1 % in the LD, MD and HD groups, respectively) and control group (8.7 %). Higher litter incidence of nodulated costal cartilage was observed in treated groups (0 %, 18.2 % and 30.4 % in the LD, MD and HD groups, respectively) and control group (4.3 %). Higher or lower litter incidence of short costal cartilage was observed in treated groups (14.3 %, 45.5 % and 56.5 % in the LD, MD and HD groups, respectively) and control group (21.7 %).
The observed incomplete ossification of a few bones and other skeletal findings in the treatment groups were either marginally lower or higher and were not considered to be adverse. Generally delayed ossification is not regarded to persist postnatally as it is not associated with long-term consequences on survival, general growth and development. There was no indication of a test item-related trend in the type and/or incidences of other skeletal findings, therefore they were considered to be spontaneous in nature.

All the above findings are considered to be incidental and without dose dependency, as frequencies were even less in number compared to controls. Therefore, these findings are not considered to be treatment-related, but rather spontaneous in nature.
There were further non-statistically significant findings that were considered to be spontaneous in nature and not related to the treatment with the test item.

Visceral malformations:

effects observed, non-treatment-related

Description (incidence and severity):

Internal observation of the foetal viscera revealed a range of visceral findings in all groups including control.

Higher litter incidence of dilated aortic arch - was observed in the MD group (9.1%) when compared to control (4.3%). Higher litter incidence of enlarged liver was observed in the HD group (8.7%) when compared to control (0%). Higher litter incidence of supernumerary liver lobe was observed in the MD and HD groups (36.4% and 30.4%, respectively) when compared to control (26.1%). Higher litter incidence of cleft at liver lobe was observed in the LD, MD and HD groups (23.8%, 50% and 34.8%, respectively) when compared to control (60.9%). Higher litter incidence of heart with large ventricle, thin ventricular wall and dilated ductus arteriosus was observed in the MD group (9.1% for each finding) when compared to control (0%). Higher litter incidences of small lung were observed in the MD group (9.1%) when compared to control (0%). Higher litter incidences of fluid-filled abdomen was observed in MD group (9.1%) when compared to control (4.3%). Higher litter incidences of discoloured kidney were observed in the MD group (9.1%) and dilated pelvis (13%) in the HD group when compared to control (0% for each observation). Higher litter incidences of large gall bladder were observed in the LD, MD and MD groups (14.3%, 13.6%, and 17.4%, respectively) when compared to control (0%).

Higher or lower litter incidences of small gall bladder were observed in LD, MD and MD groups (33.3%, 18.2%, and 17.4%, respectively) when compared to control (34.8%). Higher or lower litter incidences of discoloured gallbladder contents were observed in all treated groups (81%, 95.5%, and 87% in LD, MD and HD groups, respectively) when compared to control (87%).

Higher litter incidences of discoloured spleen were observed in the MD and HD groups (18.2%, and 8.7%, respectively) and small spleen in HD group (13%) when compared to control (4.3% for both observations). Higher litter incidences of discoloured thymus were observed in the LD, MD and HD groups (28.6%, 27.3%, and 30.4%, respectively) when compared to control (26.1%) and long thymus in the MD and HD groups (40.9% and 43.5%, respectively) when compared to control (39.1%).

Visceral findings observed in the dose groups were at frequencies generally comparable to or in some cases slightly higher or lower in frequency compared to controls. As observed findings were either minor variation and/or showed a lack of dose dependency and consistency, no serious toxicological significance can be attributed to these findings and they were considered to be spontaneous in nature.

There was no statistical significance observed in litter incidences of findings in treatment groups when compared with the control and no indication of a test item-related trend in the type and incidences of visceral findings.

Other effects:

effects observed, non-treatment-related

Description (incidence and severity):

Craniofacial examination by razor blade serial sectioning technique revealed no treatment-related findings in the dose groups when compared to the control group. However, a few findings were observed as described below;
A statistically non-significant lower or higher litter incidence of haemorrhages in the nasal cavity was observed in the LD, MD and HD groups (19%, 22.7% and 52.2%, respectively) when compared to control (30.4%). Though the findings for the HD group were slightly higher when compared to control, these findings are not considered to be treatment-related, but rather spontaneous in nature.
Single incidences of hematoma in the subdural region and subcutaneous hematoma in the head in the LD group (4.8 % above control for each observation) and subcutaneous hematoma in the head in the HD group (4.3%) were observed, when compared to control. These findings are not considered to be test item-related, but rather spontaneous in nature.

Statistical analysis of the data revealed no statistical significance for any of these findings.

Key result

Dose descriptor:

NOAEL

Remarks:

foetal

Effect level:

>= 75 mg/kg bw/day

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: No adverse effects observed

Key result

Abnormalities:

no effects observed

Key result

Developmental effects observed:

no

Conclusions:

In a prenatal developmental toxicity study in rabbits, conducted according to OECD Test Guideline 414 and in compliance with GLP, the LOAEL for maternal toxicity was concluded to be 7.5 mg/kg bw/day based on degenerative changes characterized by tubular dilatation and tubular basophilia in all dose groups; the NOAEL for developmental toxicity was concluded to be equal to or greater than 75 mg/kg bw/day based on no observed adverse effects in any of the foetuses.

Reference 2

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1993

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EPA OTS 798.4350 (Inhalation Developmental Toxicity Screen)

GLP compliance:

yes

Limit test:

no

Species:

rat

Strain:

other: CD(R)

Route of administration:

inhalation

Type of inhalation exposure (if applicable):

whole body

Vehicle:

unchanged (no vehicle)

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

The analytically determined concentrations of test item vapour were 24.6, 96.7 and 312.0 ppm for target concentrations of 25, 100 and 300 ppm, respectively.

Details on mating procedure:

Mating not performed; timed-pregnant CD® rats were exposed during gestation

Duration of treatment / exposure:

gestation days 6-15

Frequency of treatment:

6 hours/day

Duration of test:

Up to gestation day 21

Dose / conc.:

25 ppm

Dose / conc.:

100 ppm

Dose / conc.:

300 ppm

No. of animals per sex per dose:

25 timed-pregnant CD® rats/dose level

Control animals:

yes

Details on study design:

Four groups, each consisting of 25 timed-pregnant CD® rats, were exposed to vinyltrimethoxysilane; CAS No. 2768-02-7 vapour or filtered air for 6 hours/day on gestational days (gd) 6 through 15. Target concentrations of test item were 0 (control), 25, 100, and 300 ppm. The dams were sacrificed on gestation day 21.

Maternal examinations:

Clinical observations were made daily. In addition, each group of dams was observed from outside their respective exposure chambers for overt clinical signs during the actual exposures. Body weights were measured on gd 0, 6, 9, 12, 15, 18 and 21. Maternal food consumption was measured at
3-day intervals throughout gestation. At scheduled sacrifice on gd 21, the dams were evaluated for body weight, liver and kidney weights, and gravid uterine weight, . Maternal liver, kidneys, and the upper and lower respiratory tract were retained in 10% neutral buffered formalin.

Ovaries and uterine content:

The number of corpora lutea, and number and status of implantation sites (including early and late resorptions, dead fetuses, and live fetuses) were avaluated.

Fetal examinations:

All live and dead foetuses were dissected from the uterus, weighed and examined externally for malformations, variations, and gender determinations.
Approximately one-half of the live foetuses in each litter were examined for visceral and craniofacial malformations and variations. The remaining one-half of the foetuses were stained with alizarin red S and were examined for skeletal malformations and variations.

Clinical signs:

no effects observed

Description (incidence and severity):

One dam from the 300 ppm group was removed from the study on gd 14 due to trauma unrelated to exposure. There were no treatment-related effects clinical signs.

Mortality:

no mortality observed

Description (incidence):

No treatment-related mortality occurred during the study.

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

There were no treatment-related effects on gestational body weight. However, on gd 6 to 9 body weight gain was decreased by 28 and 34% in the 100 and 300 ppm groups, respectively.

Food consumption and compound intake (if feeding study):

no effects observed

Description (incidence and severity):

There were no treatment-related effects on food consumption.

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:

no effects observed

Description (incidence and severity):

Macroscopic assessment of the dams and organ weights measured at necropsy did not reveal any treatment-related effects.

Gross pathological findings:

no effects observed

Description (incidence and severity):

Macroscopic assessment of the dams and organ weights measured at necropsy did not reveal any treatment-related effects.

Neuropathological findings:

not examined

Histopathological findings: non-neoplastic:

not examined

Histopathological findings: neoplastic:

not examined

Number of abortions:

not specified

Pre- and post-implantation loss:

not specified

Total litter losses by resorption:

not specified

Early or late resorptions:

not specified

Dead fetuses:

not specified

Changes in pregnancy duration:

effects observed, treatment-related

Description (incidence and severity):

A 300 ppm female delivered early on gd 21, and therefore, was removed from the study and all data summaries with the exception of pregnancy calculations.

Changes in number of pregnant:

no effects observed

Description (incidence and severity):

The pregnancy rate was equivalent for all groups and ranged from 96 to 100%. Two females, one each from the 25 and 300 ppm groups, had only non-viable implants and one female each from the 25 and 100 ppm groups were not pregnant.

Other effects:

no effects observed

Description (incidence and severity):

Assessment of the various reproductive endpoints did not reveal any differences among the groups.

Dose descriptor:

NOAEL

Effect level:

25 ppm

Based on:

test mat.

Basis for effect level:

body weight and weight gain

Abnormalities:

effects observed, treatment-related

Localisation:

other: body weight gain

Fetal body weight changes:

no effects observed

Description (incidence and severity):

Mean fetal body weight/litter were not different among control and treated groups.

Reduction in number of live offspring:

not examined

Changes in sex ratio:

not specified

Changes in litter size and weights:

no effects observed

Changes in postnatal survival:

not examined

External malformations:

no effects observed

Description (incidence and severity):

Fetal examinations indicated no evidence of treatment-related embryolethality or teratogenicity.

Skeletal malformations:

effects observed, treatment-related

Description (incidence and severity):

Developmental delay in the 300 ppm group was indicated by an increase in the incidence of delayed skeletal ossification of the anterior arch of the atlas, thoracic centra, interparietal, matatarsals, and phalanges. A statistical increase in the number of litters at 100 ppm with unossified anterior arch of the atlas was not considered to be biologically significant because no other endpoints were similarly affected and the incidence (79.2%) was close to that observed in historical controls (29.2-73.9%).

Visceral malformations:

no effects observed

Dose descriptor:

NOAEC

Effect level:

100 ppm

Based on:

test mat.

Sex:

male/female

Basis for effect level:

skeletal malformations

Abnormalities:

effects observed, treatment-related

Developmental effects observed:

yes

Lowest effective dose / conc.:

300 ppm

Treatment related:

yes

Relation to maternal toxicity:

developmental effects as a secondary non-specific consequence of maternal toxicity effects

Dose response relationship:

yes

Relevant for humans:

no

Conclusions:

Exposure of pregnant CD® rats during organogenesis to the test substance by inhalation resulted in slight maternal toxicity at 100 and 300 ppm as evidenced by concentration-dependent reductions in gestational body weight gain (gd 6-9). There was evidence of slightly delayed development in foetuses from the 300 ppm group as indicated by delayed ossification in several skeletal districts in the presence of maternal toxicity only. No exposure-related embryotoxicity or teratogenicity was observed in this study.

Effect on developmental toxicity: via oral route

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEL

75 mg/kg bw/day

Study duration:

subacute

Species:

rabbit

Effect on developmental toxicity: via inhalation route

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEC

1 730 mg/m³

Study duration:

subacute

Species:

rat

Effect on developmental toxicity: via dermal route

Endpoint conclusion:

no study available

Additional information

In the key prenatal developmental toxicity study, conducted according to EPA OTS 798.4350 (Inhalation Developmental Toxicity Screen) and in compliance with GLP, pregnant female rats were exposed to the test concentrations of 25, 100 or 250 ppm via whole body inhalation during gestation days 6 to 15 (Bushy Run Research Center, 1993). The pregnancy rate was equivalent for all groups and ranged from 96 to 100%. No treatment-related mortality occurred during the study. One dam from the 300 ppm group was removed from the study on gestation day 14 due to trauma unrelated to exposure. Another 300 ppm female delivered early on gestation day 21, and was therefore removed from the study and all data summaries with the exception of pregnancy calculations. Two females, one each from the 25 and 300 ppm groups, had only non-viable implants and one female each from the 25 and 100 ppm groups were not pregnant. Assessment of the various reproductive endpoints did not reveal any differences among the groups. Foetal examinations indicated no evidence of treatment-related embryolethality or teratogenicity. Developmental delay in the 300 ppm group was indicated by an increase in the incidence of delayed skeletal ossification of the anterior arch of the atlas, thoracic centra, interparietal, metatarsals, and phalanges. A statistical increase in the number of litters at 100 ppm with unossified anterior arch of the atlas was not considered to be biologically significant because no other endpoints were similarly affected and the incidence (79.2%) was close to that observed in historical controls (29.2-73.9%). Mean foetal body weight/litter were not different among control and treated groups. The NOAEC for maternal toxicity was concluded to be 25 ppm based on concentration-dependent reductions in gestational body weight gain and the NOAEC delayed development is greater than or equal to 300 ppm based on evidence of slightly delayed development in foetuses from the 300 ppm group as indicated by delayed ossification in several skeletal districts, but only in the presence of maternal toxicity.

 

In the key prenatal developmental toxicity study, conducted according to OECD Test Guideline 414 and in compliance with GLP, pregnant female rabbits were exposed to the test item, trimethoxy(vinyl)silane, at doses of 0, 7.5, 25 or 75 mg/kg bw/day in corn oil via oral gavage during gestation days (GDs) 6 to 27. During the period of administration, the animals were observed each day for signs of toxicity and mortality. Animals that died during the study were examined macroscopically. All surviving animals were sacrificed on their respective GD 28 Following the gross necropsy, the uteri and ovaries were removed, weighed and examined for number of implantations, resorptions (early and late), and live and dead foetuses. Foetuses were identified by colour strings, sexed and weighed. The foetuses were observed for external abnormalities, visceral, craniofacial abnormalities and skeletal abnormalities. Body weight and food consumption were measured on GDs 0, 3, 6, 9, 12, 15, 18, 21, 24, 27 and 28. The uteri of the non-pregnant females were processed and checked for the early embryonic deaths.

No test item-related mortality was observed in any of the treated groups during the treatment period of this study. Moribund sacrifice of one control female on GD 7 was attributed to a gavaging error. No treatment-related clinical signs and changes in body weight and food consumptions were observed in any the treated groups when compared to control.

No treatment-related effect on prenatal and litter data parameters and gross pathology of terminally sacrificed females was observed at any dose tested.

Furthermore, no treatment-related and toxicologically relevant external, visceral, craniofacial and skeletal findings were observed in the treatment groups when compared with the controls.

In the urinary tract, diffuse transitional cell hyperplasia was observed in kidneys, ureters and urinary bladder of several animals from all groups treated with the test item. In the urinary bladder, the hyperplastic change was accompanied by submucosal congestion, oedema and in two animals by mixed cell infiltration. There were degenerative changes in the kidneys of the affected animals, which included tubular dilatation and slightly increased tubular basophilia. The LOAEL for maternal toxicity was concluded to be 7.5 mg/kg bw/day based on the degenerative changes characterized by tubular dilatation and tubular basophilia in all dose groups; the NOAEL for developmental toxicity was concluded to be equal to or greater than 75 mg/kg bw/day based on no observed adverse effects in any of the foetuses (BSL Bioservice, 2020).

In a dose range finding study in rabbits, conducted according to a guideline similar to OECD Test Guideline 414 but not in compliance with GLP, pregnant female rabbits were exposed to the test item, trimethoxy(vinyl)silane, at doses of 0, 100, 250 or 400 mg/kg bw/day in corn oil via oral gavage during gestation days 6 to 27 (BSL Bioservice, 2019). During the period of administration, the animals were observed each day for signs of toxicity and mortality. Animals that died during the study or were euthanised in moribund condition for animal welfare reasons were examined macroscopically. All surviving female animals were sacrificed on their respective GD 28. Following the gross necropsy, the uteri and cervix were removed, weighed and examined for number of corpora lutea, implantations, resorptions (early and late) live and dead foetuses. Foetuses were identified using numbered plates with strings tied around the neck or the abdomen, sexed and weighed. All foetuses were observed for external abnormalities. Body weight was measured on GD 0, 6, 9, 12, 15, 18, 21, 24, 27 and 28. Food consumption was measured on GD 6, 9, 12, 15, 18, 21, 24 and 27. The uteri of the non-pregnant females were processed and checked for early embryonic deaths. Tissues collected (urinary tract and liver) were processed and evaluated for histopathological changes.

Test item-related maternal toxicological effects in terms of reduced body weight gain, food consumption and gravid uterine weight were observed at 100, 250 and 400 mg/kg bw/day when compared to the control group. The carcass weight was slightly lower in the HD group when compared to the control.

No pre-implantation loss was found in any of the treated groups and control group. The post-implantation loss was slightly higher in the LD, MD and HD groups when compared to the controls. This was likely related to a slightly higher rate of early resorptions in the HD group and there were no findings of early resorptions at MD and LD groups. These findings were not dose-dependent and are considered to be incidental findings and not toxicologically relevant.

The male and female foetal weight was found to be reduced in the LD, MD and HD groups when compared to the control. This reduction in mean body weight is considered to be toxicologically significant. No external foetal abnormalities were noted in this study.

Under the conditions of this study, test item at doses of 100, 250 or 400 mg/kg bw/day, produced treatment-related lesions (inflammatory, degenerative and hyperplastic lesions)in the urinary tract organs even in the low dose animals, so a no-observed-adverse-effect-level (NOAEL) could not be established.

 

In a combined repeated dose toxicity study with the reproduction/developmental toxicity screening test via the oral route, conducted according to OECD Test Guideline 422 and in compliance with GLP (Hashima, 2005), a low number of estrous cases was noted in the 1000 mg/kg bw/day group. No changes attributable to the chemical were noted in the copulation index, number of conceiving days, number of pregnant females, fertility index, gestation length, gestation index, delivery conditions, nursing conditions, number of corpora lutea, number of implantation sites, or implantation rate. The NOAELs for reproductive performance of parental animals were estimated to be 1000 mg/kg bw/day for males and 250 mg/kg bw/day for females. No changes attributable to treatment were noted in the number of pups, number of stillbirths, number of pups born, sex ratio, delivery index, birth index, live birth index, general signs, and number of live pups on Day 4 of lactation, viability index of pups on Day 4 of lactation, appearance, body weight, or necropsy findings. The NOAEL for pups was estimated to be 1000 mg/ kg bw/day.

Justification for classification or non-classification

Based on the available data, trimethoxy(vinyl)silane does not require classification for reproductive or developmental toxicity according to Regulation (EC) No 1272/2008.