Tetramethylsilane

Endpoint summary

Key value for chemical safety assessment

Effects on fertility

Description of key information

A combined repeat dose inhalation toxicity study and reproductive/developmental toxicity screening study was carried out for tetramethylsilane (CAS No. 75 -76 -3, EC No. 200-899 -1) according to OECD Test Guideline 422 and in compliance with GLP (Dow Corning Corporation, 2005, reliability score 1). There were no adverse effects on general systemic, reproductive or developmental endpoints at the highest dose tested, 5000 ppm (ca. 18,000 mg/m³). Based on this study, tetramethylsilane does not affect fertility or reproductive organs in Sprague-Dawley rats. See repeated dose endpoint summary, and the developmental toxicity discussion below.

Link to relevant study records

Reference

Endpoint:

screening for reproductive / developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Study period:

02.12.2003 to 27.05.2005

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 422 (Combined Repeated Dose Toxicity Study with the Reproduction / Developmental Toxicity Screening Test)

GLP compliance:

yes (incl. QA statement)

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, Inc.
- Age at study initiation: 9 weeks minimum
- Weight at study initiation: Males: 289.6 to 339.7 g; females: 183.3 to 244.1 g.
- Fasting period before study: No
- Housing: Individually in suspended wire-mesh cages.
- Diet (e.g. ad libitum): Ad libitum
- Water (e.g. ad libitum): Ad libitum
- Acclimation period: Six days


ENVIRONMENTAL CONDITIONS
- Temperature (°F): 64-79
- Humidity (%): 30-70
- Air changes (per hr): 10-15
- Photoperiod (hrs dark / hrs light): 12/12


IN-LIFE DATES: From: 19.04.2004 To: 09.08.2004

Route of administration:

inhalation: vapour

Type of inhalation exposure (if applicable):

whole body

Vehicle:

unchanged (no vehicle)

Details on exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: 2000 l stainless steel and glass Rochester-style inhalation chambers.
- Method of holding animals in test chamber: stainless steel exposure caging (four layers of 20 animal compartments).
- Source and rate of air: Room air
- Method of conditioning air: Air passed through HEPA and activated charcoal filters before delivery to the chamber. Moisture was added to maintain relative humidity.
- System of generating particulates/aerosols: Not applicable
- Temperature, humidity, pressure in air chamber: 22±3oC, 50±20%,
- Air flow rate: No data
- Air change rate: 10-15 air changes/hour
- Method of particle size determination: Not applicable.
- Treatment of exhaust air: No data


TEST ATMOSPHERE
- Brief description of analytical method used: gas chromatograph with flame ionisation detection
- Samples taken from breathing zone: yes

Details on mating procedure:

- M/F ratio per cage: 1/1
- Length of cohabitation: Continuous until proof of mating.
- Proof of pregnancy: vaginal plug or 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): Individually in home cage.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

The test atmosphere from each chamber was sampled by an automated sampling system. The test atmosphere was continuously pulled from the chamber and delivered to the analyser. Analysis was by gas chromatograph with flame ionisation detection (GC/FID) and each chamber was evaluated at least once per hour during the exposure period.

Duration of treatment / exposure:

6 hours/day
Males: 29 days (including 14 days premating).
Females, reproductive group: 14 days premating, through mating, to gestation day 19 (termination day four postpartum).
Females, toxicity group: 28 days

Frequency of treatment:

Daily

Details on study schedule:

Not applicable to screening study.

Dose / conc.:

200 ppm

Remarks:

target concentration

Dose / conc.:

1 000 ppm

Remarks:

target concentration

Dose / conc.:

2 000 ppm

Remarks:

target concentration

No. of animals per sex per dose:

Ten

Control animals:

yes

Details on study design:

- Dose selection rationale: Based on the results of a range-finding study.
- Rationale for animal assignment (if not random): Random

Positive control:

None

Parental animals: Observations and examinations:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: Mortality, morbidity and moribundity noted at least twice daily (all animals). Clinical observations made once per day (all animals).


DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: Once before the first exposure, and weekly thereafter (all animals).


BODY WEIGHT: Yes
- Time schedule for examinations: Individual body weights were determined before the first exposure and at least weekly thereafter, and the day of necropsy. Pregnant females were weighed on gestation days 0, 7, 14 and 20, within 24 hours after parturition, and on day 4 postpartum.


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


FOOD EFFICIENCY:
- Body weight gain in kg/food consumption in kg per unit time X 100 calculated as time-weighted averages from the consumption and body weight gain data: No


WATER CONSUMPTION: No

Oestrous cyclicity (parental animals):

Not examined.

Sperm parameters (parental animals):

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

Litter observations:

STANDARDISATION OF LITTERS
- Performed on day 4 postpartum: no, study terminated on Day 4 post-partum as screening study only.


PARAMETERS EXAMINED
The following parameters were examined in F1 offspring: number and sex of pups, stillbirths, live births, runts, presence of gross anomalies, litter weights, postnatal mortality. Live pups were counted, sexed and the sex ratio calculated.


GROSS EXAMINATION OF DEAD PUPS: no, for external and internal abnormalities; possible cause of death was not determined for pups born or found dead.

Postmortem examinations (parental animals):

SACRIFICE
- Male animals: All surviving animals on Day 29 of exposure.
- Maternal animals: All surviving animals on postnatal day 4.


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


HISTOPATHOLOGY / ORGAN WEIGHTS: See Key study entry in Section 7.5.3.

Postmortem examinations (offspring):

SACRIFICE: Day 4 postpartum.


GROSS NECROPSY: Not conducted.


HISTOPATHOLOGY / ORGAN WEIGHTS: Not conducted.

Statistics:

All data analysis was conducted using SAS version 8.2. Statistically significant probabilities were reported for p-values of <0.05, 0.02 and 0.01.

Reproductive indices:

Mean gestation length, mean number of implantation sites, mean number of corpora lutea, mean mating and fertility indices.

Offspring viability indices:

Mean litter size, mean live litter size, mean litter weight, mean ratio live births/litter size.

Clinical signs:

no effects observed

Body weight and weight changes:

no effects observed

Food consumption and compound intake (if feeding study):

no effects observed

Organ weight findings including organ / body weight ratios:

no effects observed

Histopathological findings: non-neoplastic:

no effects observed

Other effects:

not examined

Reproductive function: oestrous cycle:

not examined

Reproductive function: sperm measures:

no effects observed

Reproductive performance:

no effects observed

CLINICAL SIGNS AND MORTALITY: there were no deaths or treatment-related clinical signs of toxicity.


BODY WEIGHT AND WEIGHT GAIN: statistically significant increase in body weight gains observed during week four of toxicity group females. No other significant finding.


FOOD CONSUMPTION: No significant findings.


HAEMATOLOGY: In males, slight but statistically significant decreases in percent monocytes were noted in 1000 and 5000 ppm groups. However, the decrease was not considered to be of toxicological significance because the values were within the laboratory historical controls.


CLINICAL CHEMISTRY: In females there were statistically significant decreases in chloride levels in the 1000 and 5000 ppm exposure groups. The slight decreases were not considered treatment-related because they were within the range typical of this strain and age.


REPRODUCTIVE FUNCTION: ESTROUS CYCLE (PARENTAL ANIMALS): Not examined.


REPRODUCTIVE FUNCTION: SPERM MEASURES (PARENTAL ANIMALS): No adverse findings.


REPRODUCTIVE PERFORMANCE (PARENTAL ANIMALS): No adverse findings.


ORGAN WEIGHTS (PARENTAL ANIMALS): Slight but statistically significant increase in mean spleen weights was observed in the 5000 ppm group females. There was no correlation with histopathological changes.


GROSS PATHOLOGY (PARENTAL ANIMALS): No adverse findings.


HISTOPATHOLOGY (PARENTAL ANIMALS): There were no findings clearly attributable to treatment. There were some minor, adaptive changes in the liver.

Key result

Dose descriptor:

NOAEL

Effect level:

>= 5 000 ppm

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: No adverse effects observed

Clinical signs:

no effects observed

Mortality / viability:

no mortality observed

Body weight and weight changes:

no effects observed

Sexual maturation:

not examined

Organ weight findings including organ / body weight ratios:

not examined

Gross pathological findings:

not examined

Histopathological findings:

not examined

VIABILITY (OFFSPRING): No adverse findings.


CLINICAL SIGNS (OFFSPRING): No clinical signs reported.


BODY WEIGHT (OFFSPRING): No effect on pup weights.

Key result

Dose descriptor:

NOAEL

Generation:

F1

Effect level:

>= 5 000 ppm

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: No adverse effects observed

Reproductive effects observed:

no

Conclusions:

In an inhalation OECD 422 study conducted to GLP (reliability score 1) the NOAELs for general systemic toxicity of the adult rats and reproductive toxicity were both at least 5000 ppm (the highest concentration tested) in rats.

Executive summary:

In an inhalation OECD 422 study conducted to GLP (reliability score 1) the NOAELs for general systemic toxicity of the adult rats and reproductive toxicity were both at least 5000 ppm (the highest concentration tested) in rats.

Effect on fertility: via oral route

Endpoint conclusion:

no study available

Effect on fertility: via inhalation route

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEC

18 000 mg/m³

Study duration:

subacute

Species:

rat

Effect on fertility: via dermal route

Endpoint conclusion:

no study available

Additional information

The key study for reproductive toxicity is the only available study for this endpoint. The study was conducted in accordance with an appropriate OECD test guideline and in compliance with GLP, and was therefore assigned Reliability 1. A range-finding study is also available.

Effects on developmental toxicity

Description of key information

A combined repeat dose inhalation toxicity study and reproductive/developmental toxicity screening study was carried out for tetramethylsilane according to OECD 422 and in compliance with GLP (Dow Corning Corporation, 2005, reliability score 1). There were no adverse effects on general systemic, reproductive or developmental endpoints at the highest dose tested, 5000 ppm (ca. 18000 mg/m³).

Link to relevant study records

Reference

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Study period:

02.12.2003 to 27.05.2005

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

other: OECD guideline 422

GLP compliance:

yes (incl. QA statement)

Limit test:

no

Species:

rat

Strain:

Sprague-Dawley

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Laboratories, Inc.
- Age at study initiation: 9 weeks minimum
- Weight at study initiation: Males: 289.6 to 339.7 g; females: 183.3 to 244.1 g.
- Fasting period before study: No
- Housing: Individually in suspended wire-mesh cages.
- Diet (e.g. ad libitum): Ad libitum
- Water (e.g. ad libitum): Ad libitum
- Acclimation period: Six days


ENVIRONMENTAL CONDITIONS
- Temperature (°F): 64-79
- Humidity (%): 30-70
- Air changes (per hr): 10-15
- Photoperiod (hrs dark / hrs light): 12/12


IN-LIFE DATES: From: 19.04.2004 To: 09.08.2004

Route of administration:

inhalation: vapour

Type of inhalation exposure (if applicable):

whole body

Vehicle:

unchanged (no vehicle)

Details on exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: 2000 l stainless steel and glass Rochester-style inhalation chambers.
- Method of holding animals in test chamber: stainless steel exposure caging (four layers of 20 animal compartments).
- Source and rate of air: Room air
- Method of conditioning air: Air passed through HEPA and activated charcoal filters before delivery to the chamber. Moisture was added to maintain relative humidity.
- System of generating particulates/aerosols: Not applicable
- Temperature, humidity, pressure in air chamber: 22±3oC, 50±20%,
- Air flow rate: No data
- Air change rate: 10-15 air changes/hour
- Method of particle size determination: Not applicable.
- Treatment of exhaust air: No data


TEST ATMOSPHERE
- Brief description of analytical method used: gas chromatograph with flame ionisation detection
- Samples taken from breathing zone: yes

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

The test atmosphere from each chamber was sampled by an automated sampling system. The test atmosphere was continuously pulled from the chamber and delivered to the analyser. Analysis was by gas chromatograph with flame ionisation detection (GC/FID) and each chamber was evaluated at least once per hour during the exposure period.

Details on mating procedure:

- M/F ratio per cage: 1/1
- Length of cohabitation: Continuous until proof of mating.
- Proof of pregnancy: vaginal plug or 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): Individually in home cage.

Duration of treatment / exposure:

6 hours/day
Males: 29 days (including 14 days premating).
Females, reproductive group: 14 days premating, through mating, to gestation day 19 (termination day four postpartum).
Females, toxicity group: 28 days

Frequency of treatment:

Daily

Duration of test:

approximately 46 days

Dose / conc.:

200 ppm

Remarks:

target concentration

Dose / conc.:

1 000 ppm

Remarks:

target concentration

Dose / conc.:

2 000 ppm

Remarks:

target concentration

No. of animals per sex per dose:

10

Control animals:

yes

Details on study design:

- Dose selection rationale: Based on the results of a range-finding study.
- Rationale for animal assignment (if not random): Random

Maternal examinations:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: Mortality, morbidity and moribundity noted at least twice daily (all animals). Clinical observations made once per day (all animals).


DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: Once before the first exposure, and weekly thereafter (all animals).


BODY WEIGHT: Yes
- Time schedule for examinations: Individual body weights were determined before the first exposure and at least weekly thereafter, and the day of necropsy. Pregnant females were weighed on gestation days 0, 7, 14 and 20, within 24 hours after parturition, and on day 4 postpartum.


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


FOOD EFFICIENCY:
- Body weight gain in kg/food consumption in kg per unit time X 100 calculated as time-weighted averages from the consumption and body weight gain data: No


WATER CONSUMPTION: No

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 early resorptions: No data
- Number of late resorptions: No data

Fetal examinations:

- External examinations: Yes, all per litter
- Soft tissue examinations: No
- Skeletal examinations: No
- Head examinations: No

Statistics:

All data analysis was conducted using SAS version 8.2. Statistically significant probabilities were reported for p-values of <0.05, 0.02 and 0.01.

Indices:

Mean gestation length, mean number of implantation sites, mean number of corpora lutea, mean mating and fertility indices. Mean litter size, mean live litter size, mean litter weight, mean ratio live births/litter size.

Historical control data:

No data

Details on maternal toxic effects:

Maternal toxic effects:no effects

Details on maternal toxic effects:
There was no significant toxicity in dams.

Key result

Dose descriptor:

NOAEL

Effect level:

>= 5 000 ppm

Basis for effect level:

other: maternal toxicity

Key result

Dose descriptor:

NOAEL

Effect level:

>= 5 000 ppm

Basis for effect level:

other: developmental toxicity

Details on embryotoxic / teratogenic effects:

Embryotoxic / teratogenic effects:no effects

Details on embryotoxic / teratogenic effects:
There were no adverse effects on the offspring.

Dose descriptor:

NOAEL

Effect level:

>= 5 000 ppm

Basis for effect level:

other: teratogenicity

Abnormalities:

not specified

Developmental effects observed:

not specified

Conclusions:

In an inhalation OECD 422 study conducted to GLP (reliability score 1) the NOAELs for general systemic toxicity of the dams and developmental toxicity were both at least 5000 ppm (the highest concentration tested) in rats.

Executive summary:

In an inhalation OECD 422 study conducted to GLP (reliability score 1) the NOAELs for general systemic toxicity of the dams and developmental toxicity were both at least 5000 ppm (the highest concentration tested) in rats.

Effect on developmental toxicity: via oral route

Endpoint conclusion:

no study available

Effect on developmental toxicity: via inhalation route

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEC

18 000 mg/m³

Study duration:

subacute

Species:

rat

Effect on developmental toxicity: via dermal route

Endpoint conclusion:

no adverse effect observed

Additional information

Tetramethylsilane has been evaluated for reproductive and developmental toxicity in the only available study for this endpoint, which was conducted in accordance with OECD Test Guideline 422 and in compliance with GLP (Dow Corning Corporation, 2005, Reliability Score 1). Inhalation exposure of the test substance to male and female Sprague-Dawley rats at concentrations of up to 5000 ppm for 28-46 consecutive days was generally well tolerated. There were no clinical signs or effects on body weights and food consumption. No treatment-related changes were observed in any functional observational battery or motor activity parameters. There were no treatment-related alterations in haematology, serum chemistry, organ weights, organ-to-body weight ratios or microscopic examination of organs/tissues among the groups. Histopathological examination of tissues for control and high exposure animals demonstrated no significant findings. No effects were observed in any of the reproductive parameters evaluated. Based on the results of this study, the NOAEL for tetramethylsilane was 5000 ppm for systemic toxicology, reproductive performance and developmental endpoints in rats via whole-body vapour inhalation.

In accordance with Section 3 of REACH Annex XI, the extended one-generation reproductive toxicity study does not need to be conducted on the grounds that there is no significant exposure to humans. Tetramethylsilane is a highly volatile, extremely flammable liquid which forms explosive mixtures with air. Handling of the material is therefore carried out under rigorous containment, as described in Section 9. The recommended uses of the substance are limited to processes in closed systems in the chemical industry and semiconductor manufacturing sector. Very small quantities (typically <25 ml containers) may be supplied for laboratory use by trained workers. Due to the physicochemical properties, such handling is recommended to be performed only in fume cupboards or glove boxes under nitrogen. There are no wide-dispersive uses of the substance. Using a conservative approach to exposure estimation, and semi-quantitative risk characterisation based on the maximum dose tested in an OECD 422 study, all risk characterisation ratios are below 1. Further testing is therefore not required.

Justification for classification or non-classification

There are no data to suggest that tetramethylsilane should be classified for reproductive or developmental toxicity according to Regulation (EC) No 1272/2008.