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Diss Factsheets

Toxicological information

Repeated dose toxicity: inhalation

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Administrative data

Endpoint:
short-term repeated dose toxicity: inhalation
Remarks:
combined repeated dose and reproduction / developmental screening
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

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2005
Report date:
2005

Materials and methods

Test guideline
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

Test material

Constituent 1
Chemical structure
Reference substance name:
Tetramethylsilane
EC Number:
200-899-1
EC Name:
Tetramethylsilane
Cas Number:
75-76-3
Molecular formula:
C4H12Si
IUPAC Name:
tetramethylsilane

Test animals

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

Administration / exposure

Route of administration:
inhalation: vapour
Type of inhalation exposure:
whole body
Vehicle:
other: unchanged (no vehicle)
Details on inhalation 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.
Duration of treatment / exposure:
6 hours/day 7 days/week
Males: 29 days (including 14 days premating).
Females, reproductive group: 14 days premating, through mating, to gestation day 19 (terminated day four postpartum).
Females, toxicity group: 28 days (termination day 29)
Frequency of treatment:
Daily
Doses / concentrationsopen allclose all
Dose / conc.:
200 ppm
Remarks:
target concentration
Dose / conc.:
1 000 ppm
Remarks:
target concentration
Dose / conc.:
5 000 ppm
Remarks:
target concentration
No. of animals per sex per dose:
10
Control animals:
yes
Details on study design:
- Dose selection rationale: Based on results of a dose range finding study.
- Rationale for animal assignment (if not random): Random
- Rationale for selecting satellite groups: Toxicity group females to assess toxicity without pregnancy.
- Post-exposure recovery period in satellite groups: None
Positive control:
None

Examinations

Observations and examinations performed and frequency:
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


OPHTHALMOSCOPIC EXAMINATION: No


HAEMATOLOGY: Yes
- Time schedule for collection of blood: On the day of sacrifice.
- Anaesthetic used for blood collection: Yes (isoflurane)
- Animals fasted: Yes, overnight
- How many animals: All males and toxicity group females.
- Parameters checked in table No.1 were examined.


CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: On the day of sacrifice.
- Animals fasted: Yes
- How many animals: All males and toxicity group females.
- Parameters checked in table No.1 were examined.


URINALYSIS: No


NEUROBEHAVIOURAL EXAMINATION: Yes
- Time schedule for examinations: Prior to the start of exposure and during the fourth week of exposure.
- Dose groups that were examined: all males and toxicity phase females.
- Battery of functions tested: cageside observations, hand-held observations, open field observations, categorical observations, measurements/counts, motor activity.
Sacrifice and pathology:
GROSS PATHOLOGY: Yes (see table 2)
HISTOPATHOLOGY: Yes (see table 2) for 10 animals/sex from the toxicity groups.
Other examinations:
None
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.

Results and discussion

Results of examinations

Clinical signs:
no effects observed
Description (incidence and severity):
There were no treatment-related clinical signs of toxicity.
Mortality:
no mortality observed
Description (incidence):
There were no deaths.
Body weight and weight changes:
effects observed, treatment-related
Description (incidence and severity):
Statistically significant increase in body weight gains were observed during week four of toxicity group females. No other significant finding.
Food consumption and compound intake (if feeding study):
no effects observed
Description (incidence and severity):
No significant findings.
Food efficiency:
not examined
Water consumption and compound intake (if drinking water study):
not examined
Ophthalmological findings:
not examined
Haematological findings:
effects observed, non-treatment-related
Description (incidence and severity):
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 biochemistry findings:
effects observed, non-treatment-related
Description (incidence and severity):
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.
Urinalysis findings:
not examined
Behaviour (functional findings):
effects observed, treatment-related
Description (incidence and severity):
No adverse effects in males. A slight but statistically significant (p<0.02), decrease was noted in the female 200 and 1000 ppm exposure groups compared to the control group, in which a slight increase was noted. There were no other findings.
Organ weight findings including organ / body weight ratios:
effects observed, treatment-related
Description (incidence and severity):
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 pathological findings:
no effects observed
Description (incidence and severity):
No adverse findings
Neuropathological findings:
effects observed, treatment-related
Description (incidence and severity):
No adverse effects in males. A slight but statistically significant (p<0.02) decrease in neurobehaviour was noted in the female 200 and 1000 ppm exposure groups compared to the control group, in which a slight increase was noted. There were no other findings.
Histopathological findings: non-neoplastic:
no effects observed
Histopathological findings: neoplastic:
not examined
Description (incidence and severity):
There were no findings clearly attributable to treatment. There were some minor, adaptive changes in the liver.

Effect levels

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

Target system / organ toxicity

Critical effects observed:
no

Applicant's summary and conclusion

Conclusions:
In an inhalation OECD 422 study conducted to GLP (reliability score 1) the NOAEL for systemic toxicity of the adult rats was at least 5000 ppm (the highest concentration tested).
Executive summary:

In an inhalation OECD 422 study conducted to GLP (reliability score 1) the NOAEL for systemic toxicity of the adult rats was at least 5000 ppm (the highest concentration tested).