Hexamethyldisiloxane

Acute Toxicity: inhalation

Administrative data

Endpoint:

acute toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1997

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1997

Report date:

1997

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 403 (Acute Inhalation Toxicity)

Principles of method if other than guideline:

The mean actual exposure concentrations were significantly higher than OECD limit test guideline of 5 mg/l.

GLP compliance:

yes

Test type:

standard acute method

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Hexamethyldisiloxane

EC Number:

203-492-7

EC Name:

Hexamethyldisiloxane

Cas Number:

107-46-0

Molecular formula:

C6H18OSi2

IUPAC Name:

trimethyl[(trimethylsilyl)oxy]silane

Test animals

Species:

rat

Strain:

Fischer 344

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS

- Source: Charles River Laboratories, Raleigh, NC

- Age at study initiation:Males approximately 8 weeks and females approximately 10 weeks old when exposed.

- Weight at study initiation: 126 - 150 g

- Housing: Individually in stainless steel, wire mesh-bottom cages

- Diet: Purina rodent chow ad libitum except during exposure

- Water: Ad libitum

- Acclimation period: One week

ENVIRONMENTAL CONDITIONS

- Temperature (°C): 22 ± 2

- Humidity (%): 30 - 70

- Air changes (per hr): Not stated

- Photoperiod (12 hrs dark /12 hrs light):

IN-LIFE DATES: From: 15th February 1994 To: 3rd March 1994

Administration / exposure

Route of administration:

inhalation

Type of inhalation exposure:

whole body

Vehicle:

other: unchanged (no vehicle)

Details on inhalation exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION

- Exposure apparatus: Stainless steel and glass exposure chambers

- Exposure chamber volume: 120 litre

- Method of holding animals in test chamber:

- Source and rate of air: Ambient air; 10-15 air changes per hour (20.4 - 20.5 litres per minute)

- Method of conditioning air: HEPA and charcoal filters

- System of generating particulates/aerosols: Not applicable

- Method of particle size determination: Not applicable

- Treatment of exhaust air: HEPA and charcoal filters then passed through water scrubber

- Temperature, humidity in chamber: 22.9 - 23.9 °C; 52.0 - 61.2% humidity

TEST ATMOSPHERE

- Brief description of analytical method used: Gas chromatography

- Samples taken from breathing zone: Yes

VEHICLE

Not applicable

TEST ATMOSPHERE
- Particle size distribution: Not applicable

- MMAD (Mass median aerodynamic diameter) / GSD (Geometric st. dev.): Not applicable

Analytical verification of test atmosphere concentrations:

yes

Remarks:

GC

Duration of exposure:

4 h

Concentrations:

11,000; 14,000 and 18,000 (nominal); 10,067; 14,050 and 16,659 ppm (as measured by gas chromatography)

No. of animals per sex per dose:

5/sex/dose

Control animals:

not specified

Details on study design:

- Duration of observation period following administration: 14 days

- Necropsy of survivors performed: yes

- Other examinations performed: clinical signs, body weight, organ weights, gross pathology

Statistics:

No statistical analysis included.

Results and discussion

Effect levels

Effect levels 1

Key result

Sex:

male/female

Dose descriptor:

LC50

Effect level:

15 956 ppm

Based on:

test mat.

Exp. duration:

4 h

Remarks on result:

other: 95% CL = 14,024-34,045

Effect levels 2

Sex:

male/female

Dose descriptor:

other: NOEL

Effect level:

10 067 ppm

Based on:

test mat.

Exp. duration:

4 h

Mortality:

See Table 1.

One animal in the mid-dose group was sacrificed for human reasons on Day 2. This was not included in the statistical analysis.

Clinical signs:

other: During the 4-hour exposure, some of the animals exposed to concentrations of 14,050 and 16,659 ppm test material experienced prostration and convulsions. Ataxia was also observed in the high exposure group. The primary clinical sign after the exposure was

Body weight:

No apparent effects on body weight gains were observed.

Gross pathology:

In animals that died, congestion and/or haemorrhage of various lobes of the lung were observed in males and females. Congestion of the lungs was also noted in one female from each of the two higher exposure groups at the final sacrifice of the animals that survived exposure.

Other findings:

- Potential target organs: Lung

- Other observations: Response was generally consistent between males and females.

Any other information on results incl. tables

Table 1: Concentrations, exposure conditions and number of evident toxicity per animals treated

Nominal Conc. (ppm)	Analytical Conc. (ppm)	Number dead/Number exposed
		Males	Females	Combined
11000	10067	0/5	0/5	0/10
14000	14050	1/5	1/5	2/10
18000	16659	3/5	3/5	6/10

 

Applicant's summary and conclusion

Interpretation of results:

GHS criteria not met

Conclusions:

An acute inhalation LC50 of 15,956 ppm with (95% confidence limits of 14,024-34,045) was determined for male and female rats in an reliable study conducted according to an appropriate test protocol, and in compliance with GLP. This is equivalent to ca. 106 mg/l.