Trisiloxane, 3-ethyl-1,1,1,3,5,5,5-heptamethyl-

Acute Toxicity: inhalation

Administrative data

Endpoint:

acute toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2003-07-21

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2003

Report date:

2003

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 403 (Acute Inhalation Toxicity)

Test guideline 2

Qualifier:

according to guideline

Guideline:

EU Method B.2 (Acute Toxicity (Inhalation))

GLP compliance:

yes

Limit test:

yes

Test material

Test material information

Constituent 1

Reference substance name:

-

EC Number:

469-070-1

EC Name:

-

Cas Number:

17861-60-8

Molecular formula:

C9H26O2Si3

IUPAC Name:

4-ethyl-2,2,4,6,6-pentamethyl-3,5-dioxa-2,4,6-trisilaheptane

Test material form:

liquid

Remarks:

Clear colourless liquid

Specific details on test material used for the study:

Batch/lot number:Taf 002
Purity >95%
Density 828 g/L

Test animals

Species:

rat

Strain:

Wistar

Remarks:

Crl:(WI) WU BR

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Age at study initiation: 5 - 6 weeks
- Mean weight at study initiation: male: 215 g female: 160 g
- Housing: individually during exposure, 5 per cage during 14 days observation (divided by sex)
- Diet (e.g. ad libitum): ad libitum, except during exposure
- Water (e.g. ad libitum): ad libitum, except during exposure
- Acclimation period: 13 days

ENVIRONMENTAL CONDITIONS
- Temperature: 21,6 +/- 0.2°C
- Humidity: 64 +/- 1%
- Air changes (per hr): 10
- Photoperiod (dark/light): 12 h/12 h

Administration / exposure

Route of administration:

inhalation: vapour

Type of inhalation exposure:

nose only

Vehicle:

other: humidified air

Remark on MMAD/GSD:

N/A test substance tested as vapour

Details on inhalation exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: nose only inhalation chamber
- Exposure chamber volume: ca 50 L
- Method of holding animals in test chamber: Battelle plastic animal holders
- Source and rate of air: compressed dry air and 16.6 L/min
- Method of conditioning air: humidifier
- System of generating particulates/aerosols: N/A test substance tested as vapour
- Method of particle size determination: N/A test substance tested as vapour
- Treatment of exhaust air: filter
- Temperature, humidity, pressure in air chamber: 21.6 +/-0.1°C, 55 +/-1%, not reported except that positive pressure was maintained in chamber

TEST ATMOSPHERE
- Brief description of analytical method used: test atmosphere was sampled by passing metered amounts of test atmosphere through a cascade of a primary and secondary impinger filled with methanol. Samples were analysed after dilution with water. The concentration of test material in the impinger solution was determined by measuring the concentration of elemental Si using ICP-AES
- Samples taken from breathing zone: no

VEHICLE
- Composition of vehicle (if applicable): N/A
- Concentration of test material in vehicle (if applicable): N/A
- Justification of choice of vehicle: N/A
- Lot/batch no. (if required): N/A
- Purity: N/A

TEST ATMOSPHERE (if not tabulated)
- Particle size distribution: N/A
- MMAD (Mass median aerodynamic diameter) / GSD (Geometric st. dev.): N/A

CLASS METHOD (if applicable)
- Rationale for the selection of the starting concentration: N/A

Analytical verification of test atmosphere concentrations:

yes

Duration of exposure:

4 h

Concentrations:

10.0 +/- 0.4 g/m3 (highest attainable concentration)

No. of animals per sex per dose:

5

Control animals:

no

Results and discussion

Effect levels

Sex:

male/female

Dose descriptor:

LC50

Effect level:

> 10 mg/L air

Exp. duration:

4 h

Mortality:

Male: 10 mg/L; Number of animals: 5; Number of deaths: 0
Female: 10 mg/L; Number of animals: 5; Number of deaths: 0

Clinical signs:

other: Signs of toxicity related to dose levels: Although observation of the rats was limited during exposure due to the stay in restraining tubes, a slightly decreased breathing rate was observed in all animals at all four (approximately hourly) observation

Body weight:

Although body weight gain in male animals was slightly lower in the first than in the second week, overall, body weight gain was as expected for animals of this strain and age.

Gross pathology:

At necropsy, macroscopic abnormalities consisted of petechiae on the lobes of the lungs in three male animals. In one male animal petechiae were seen on one lobe and in two male animals these petechiae were seen on all lobes.

Applicant's summary and conclusion

Interpretation of results:

GHS criteria not met

Conclusions:

There were no mortalities in male and female rats following a 4-hour nose-only exposure to heptamethylethyltrisiloxane at the maximum attainable concentration of 10 g/m3. Therefore the LC50 of vapour of heptamethylethyltrisiloxane >10 g/m3 for both sexes

Executive summary:

In an acute inhalation study, groups of Wistar derived rats (5/sex) were exposed by the inhalation route (nose-only) for a single 4-hour period to the maximium attainable concentration of 10 g/m3 heptamethylethyltrisiloxane vapour. Following exposure, animals were observed for 14 days. No mortalities occurred. Shortly after exposure cinical signs consisted of red/brown discolouration of the head in all female animals. No other treatment related clinical signs of toxicity were observed. Body weight gain was within limits of that expectd for animals of this age and strain. At necropsy, macroscopic changes were limited to petechiae seen on one or more lobes of the lungs in three male animals. Under the conditions of this study the rat acute inhalation 4 hour nose-only body LC₅₀was >10 g/m3 in males and females.