2,4,6,8-tetramethylcyclotetrasiloxane

Acute Toxicity: oral

Administrative data

Endpoint:

acute toxicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2010-05-04 to 2010-07-22

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2010

Report date:

2010

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 420 (Acute Oral Toxicity - Fixed Dose Method)

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

EU Method B.1 bis (Acute Oral Toxicity - Fixed Dose Procedure)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Test type:

fixed dose procedure

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

2,4,6,8-tetramethylcyclotetrasiloxane

EC Number:

219-137-4

EC Name:

2,4,6,8-tetramethylcyclotetrasiloxane

Cas Number:

2370-88-9

Molecular formula:

C4H16O4Si4

IUPAC Name:

2,4,6,8-tetramethyl-1,3,5,7,2,4,6,8-tetroxatetrasilocane

Constituent 2

Reference substance name:

2,4,6,8-Tetramethylcyclotetrasiloxane (supplied as Dow Corning® ZTOMCATSTM CVD Precursor)

IUPAC Name:

2,4,6,8-Tetramethylcyclotetrasiloxane (supplied as Dow Corning® ZTOMCATSTM CVD Precursor)

Test animals

Species:

rat

Strain:

Wistar

Sex:

female

Details on test animals or test system and environmental conditions:

Test animals:
Animals: Rat, RccHan: WIST(SPF)
Rationale: Recognized by international guidelines as a recommended test system.
Breeder: Harlan Laboratories B.V., Kreuzelweg 53, 5961 NM Horst / The Netherlands
Number of Animals: 6 females (nulliparous and non-pregnant)
Age (when treated): 10 - 11 weeks
Body Weight Range (when treated): 163.4 g – 194.6 g
Identification: Unique cage number and corresponding color-coded spots on the tail. The animals were marked at acclimatization start.
Randomization: Selected by hand at time of delivery. No computer generated randomization program.
Acclimatization: At least 7 days under laboratory conditions, after health examination. Under laboratory conditions, after health examination. Only animals without any visible signs of illness were used for the study.

Environmental conditions:
Conditions: Standard Laboratory Conditions. Air-conditioned with 10-15 air changes per hour, and continuously monitored environment with a room temperature of 22 ± 3 °C and a relative humidity between 30-70% (excepted once with a value of 72.7% during approximately 1 hour), automatically controlled light cycle of 12 hours light and 12 hours dark and music played during the daytime light period.

Accommodation: In groups of up to five by sex in Makrolon type-3 (if one animal/cage) to type-4 (if more than one animal/cage) cages with wire mesh tops and standard softwood bedding (‘Lignocel’ J. Rettenmaier&Söhne GmbH&CoKG, 73494 Rosenberg / Germany, imported by Provimi Kliba AG, 4303 Kaiseraugst / Switzerland) including paper enrichment (Enviro-dri from Lillico, Biotechnology, Surrey, UK).

Diet: Pelleted standard Provimi Kliba 3433 rat/mouse maintenance diet, batch no. 83/09 (Provimi Kliba AG, 4303 Kaiseraugst / Switzerland) ad libitum (except for the overnight fasting period prior to intubation and approximately 3-4 hours post dose). Results of analyses for contaminants are archived at Harlan Laboratories Ltd.

Water: Community tap water from Füllinsdorf ad libitum. Results of bacteriological, chemical and contaminant analyses are archived at Harlan Laboratories Ltd.

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

unchanged (no vehicle)

Details on oral exposure:

The dose solutions were prepared shortly before each application occasion using a magnetic stirrer as homogenizer.

The test item was weighed into a tared glass beaker on a suitable precision balance. Homogeneity of the neat test item was maintained during administration using a magnetic stirrer.

The test item was administered neat as delivered by the Sponsor at a variable dose concentration: 300 mg/kg or 2000 mg/kg.

The animals received a single dose of the test item by oral gavage administration after being fasted for approximately 17 to 20 hours, but with free access to water. Food was presented approximately 3 to 4 hours after administration of neat test item.

Sighting Study: A single animal was used for each dose level investigated. The following initial dose levels were used: 300 and 2000 mg/kg. The dose level chosen was that which was expected to produce evident toxicity. In the absence of any relevant toxicity data, 300 mg/kg was used in the first instance. As no signs of toxicity were seen at the initial dose, then the next higher dose level was investigated. Since no mortality occurred at 2000 mg/kg the sighting test was complete and the main study was conducted at this dose level. Dosing was sequential, allowing approximately 72 hours before investigation of the next dose level. The animals were observed for fourteen days.

The dosing volume was 0.31 mL/kg (300 mg/kg) or 2.06 mL/kg (2000 mg/kg).

Main Study: A group of five animals was used for the highest dose level investigated (2000 mg/kg). The five animals included one animal tested at the selected dose level in the sighting study and an additional four animals in the main study. The dosing volume was 2.06 mL/kg body weight.

Rationale: Oral administration was considered to be an appropriate application method as it is a possible route of human exposure during manufacture, handling and use of the test item.

Doses:

300 mg /kg body weight (sighting study)
2000 mg/kg body weight (sighting study and main study)

No. of animals per sex per dose:

1 female at 300 mg/kg;
5 females at 2000 mg/kg

Control animals:

no

Details on study design:

Observations:
Viability / Mortality: Daily during the acclimatization. Once before the treatment and within the first 30 minutes and at approximately 1, 2, 3 and 5 hours after administration on test day 1 (in common with the clinical signs) and twice daily during days 2 – 15.

Clinical Signs: Daily during the acclimatization and treatment period. Additionally, within the first 30 minutes and at approximately 1, 2, 3 and 5 hours after administration on test day 1. Once daily during days 2-15. Observations included changes in the skin and fur, eyes and mucous membranes, and respiratory, circulatory, autonomic and central nervous system, and somatomotor activity and behaviour pattern. Particular attention was directed to observation of tremors, convulsions, salivation, diarrhoea, lethargy, sleep and coma.

Body Weights: On test days 1 (prior to administration), 8 and 15.

Necropsy:
All animals were killed at the end of the observation period by carbon dioxide asphyxiation and discarded after macroscopic examinations were performed. An external examination and opening of the abdominal and thoracic cavities for examinations of major organs were performed. The appearance of any macroscopic abnormalities was recorded. No organs or tissues were retained.

Statistics:

No statistical analysis was performed.

Results and discussion

Preliminary study:

The animal of the first sighting study dosed at 300 mg/kg bw survived. as did the second animal dosed at 2000 mg/kg bw

Effect levels

Sex:

female

Dose descriptor:

LD50

Effect level:

> 2 000 mg/kg bw

Based on:

test mat.

Mortality:

No intercurrent deaths occurred during the course of the study.

Clinical signs:

other: Slightly ruffled fur was observed in the animal dosed at 300 mg/kg bw from test day 3 to day 5, and in one animal dosed at 2000 mg/kg bw from 2 hours after administration to test day 3. No clinical signs were observed in the four additional animals dosed

Gross pathology:

No macroscopic findings were recorded at necropsy.

Applicant's summary and conclusion

Interpretation of results:

GHS criteria not met

Conclusions:

2,4,6,8-Tetramethylcyclotetrasiloxane did not show any evidence of toxicity at the dose level of 2000 mg/kg bw after single oral administration to five female rats, observed over a period of 14 days. The study concluded a LD50 value greater than 2000 mg/kg bw.

Executive summary:

The acute toxicity of 2,4,6,8 -tetramethylcyclotetrasiloxane when administered by a single oral gavage to rats was investigated according to OECD test guideline No. 420 and Commission Regulation (EC) No. 440/2008, B.1.

To determine the dose level investigated in the main study, a sighting study was conducted with two animals (female RccHan:WIST (SPF) rat). The test item was administered neat as delivered by the Sponsor. The two animals were separately treated with the test item at the initial dose level of 300 or 2000 mg/kg bw by single oral gavage administration. The dosing volumes were 0.31 mL/kg (300 mg/kg) or 2.06 mL/kg (2000 mg/kg), respectively. In the main study, an additional four female animals were treated with the test item at the dose level of 2000 mg/kg bw.

The animals were examined daily during the acclimatization period and mortality, viability and clinical signs were recorded. All animals were examined for clinical signs within the first 30 minutes and approximately 1, 2, 3 and 5 hours after treatment on day 1 and once daily during test days 2-15. Mortality/viability was recorded within the first 30 minutes and approximately 1, 2, 3 and 5 hours after administration on test day 1 (with the clinical signs) and twice daily during days 2-15. Body weights were recorded on day 1 (prior to administration) and on days 8 and 15. All animals were necropsied and examined macroscopically.

All animals survived until the end of the study period.

In the sighting study, slightly ruffled fur was observed in the animal dosed at 300 mg/kg from test day 3 to day 5, and in the animal dosed at 2000 mg/kg bw from 2 hours after administration to test day 3. No clinical signs were observed in the four additional animals dosed at 2000 mg/kg bw throughout the entire observation period of the main study. The body weight of the animals was within the range commonly recorded for this strain and age. No macroscopic findings were recorded at necropsy.

2,4,6,8-Tetramethylcyclotetrasiloxane did not show any evidence of toxicity at the dose level of 2000 mg/kg bw after single oral administration to five female rats, observed over a period of 14 days.

LD50 (female rat): greater than 2000 mg/kg bw.