2,4,6,8,10-pentamethylcyclopentasiloxane

Acute Toxicity: inhalation

Administrative data

Endpoint:

acute toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2001-2002

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2002

Report date:

2001

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 403 (Acute Inhalation Toxicity)

Version / remarks:

modified: whole-body, 5M/5F, one dose of 5 mg/l (vapour)

Deviations:

yes

Remarks:

but not considered to have impacted the study outcome. (page containing Table with deviations missing)

GLP compliance:

yes

Remarks:

US-EPA TSCA GLP 40 CRF part 792

Test type:

standard acute method

Limit test:

yes

Test material

Test material information

Constituent 1

Reference substance name:

2370-99-0

IUPAC Name:

2370-99-0

Constituent 2

Reference substance name:

2,4,6,8,10-pentamethylcyclopentasiloxane

EC Number:

228-204-7

EC Name:

2,4,6,8,10-pentamethylcyclopentasiloxane

Cas Number:

6166-86-5

Molecular formula:

C5H20O5Si5

IUPAC Name:

2,4,6,8,10-pentamethyl-1,3,5,7,9,2,4,6,8,10-pentaoxapentasilecane

Constituent 3

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

Specific details on test material used for the study:

Test substance identified as mixture of 2,4,6,8,10-pentamethylcyclopentasiloxane (CAS 6166-86-5) (45%) and 2,4,6,8-tetramethylcyclotetrasiloxane (CAS 2370-88-9) (54%) and the impurity 0.9% hexamethylcyclohexasiloxane.

Test animals

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Details on test animals or test system and environmental conditions:

5 male, 5 female rats, strain Sprague-Dawley, Crl:CD(SD)IGS
At start of study: age 9 weeks.
body weights females 201.8 - 227.7 grams
body weights males 298.1-334.5 grams
one group only
indentification by eartags and indivudual cage labels
individually housed in wire-meshe cages elevated above absorbent material. regularly cleaned in accordance with good animal husbandry.
environmentally controlled animal rooms
artificial lighting, light/dark 12/12
temperature 22+-3 degr.C , 30-70% relative humidity, 10-15 air changes /hr
certified rodent diet ad lib except during exposure. reverse-osmosis purified tap water at lib.

Administration / exposure

Route of administration:

inhalation: vapour

Type of inhalation exposure:

whole body

Vehicle:

clean air

Remarks:

source: Nash air compressor AL-574; serial filters Matheson 460/461 and Balston 100-118-DX and 100-8-BX.Dilutuion air stream: HEPA-filtered, activated carbon filtered, warmed and humidified room air.

Details on inhalation exposure:

whole- body exposure
limit test
target concentration 450 ppm = 5 mg/l
measured concentrations 445 ppm= 4.9 mg/l
GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: Rochester-type, Stainless steel and glass whole-body exposure chamber.
- Exposure chamber volume: 450 liters
- Method of holding animals in test chamber: stainless steel mesh caging
- Source and rate of air: Room air, mean chamber airflow rate 105 +- 0.8 L/min. (14 air changes /hr) dilution air stream:
- method of conditioning; HEPA-filtered, activated carbon filtered, warmed and humidified room air.
- Temperature: 24.1 _-1.2 degr C
- humidity: 49.7 +- 3% RH
- pressure in air chamber:
- oxygen content: 20.9 degr. C
TEST ATMOSPHERE
- Brief description of analytical method used: Varian Gas chromatograph 3400 with GC/IFD; one sample /30 minutes. Calibrated using 5 levels of bag standards in the range of 250-650 pppm
- Samples taken from breathing zone: No.

VEHICLE
- Composition of vehicle: compressed, filtered air:

Analytical verification of test atmosphere concentrations:

yes

Remarks:

See above for analytical method details. measured concentration showed good correlation with calculated nominal concentrations (4.3% difference)

Duration of exposure:

ca. 240 min

Remarks on duration:

20 minutes lead time to build up to min. 99% of target concentration; 240 minutes at target concentration; 20 minutes end lag time to reduce concentrations to max 1% of target concentrations.

Concentrations:

mean measured chamber concentration: 4.9 +- 0.2 mg/l (445 +- 16.6 ppm)
See table in "any other observations on results"

No. of animals per sex per dose:

5 males, 5 females

Control animals:

no

Details on study design:

- Duration of observation period following administration: 14 days
- Frequency of observations:Mortality twice daily, once during weekends. Clinical signs: once daily
- Frequency of weighing: day1, prior to exposure; day 8; day 15 (prior to sacrifice)
- Necropsy of survivors performed: yes (complete gross pathology examination)

Statistics:

not applicable: no mortality

Results and discussion

Preliminary study:

not performed.

Effect levels

Effect levels 1

Key result

Sex:

female

Dose descriptor:

LC50

Effect level:

> 4.9 mg/L air (analytical)

Based on:

test mat.

Exp. duration:

4 h

Effect levels 2

Key result

Sex:

male

Dose descriptor:

LC50

Effect level:

> 4.9 mg/L air (analytical)

Based on:

test mat.

Exp. duration:

4 h

Mortality:

None

Clinical signs:

other: None

Body weight:

Body weight ranges and body weight gains were within acceptable ranges thoughout duration of the study (barring one deviation) (Table individual body weight gains missing)

Gross pathology:

No gross pathology findings

Other findings:

none reported

Any other information on results incl. tables

Conditions during exposure.
Time point (30 min. intervals)	Measured conc. (ppm)	Measured conc. (mg/l)	Tempera-ture (°C)	Humidity (%RH)	Air flow (L/min)
1	N.A.	N.A.	21.6	53.1	106
2	414	4.5	22.7	53.2	106
3	425	4.7	23.3	51.5	105
4	444	4.9	23.9	47.4	105
5	446	4.9	24.7	44.8	105
6	446	4.9	25.0	48.4	105
7	460	5.0	25.0	53.7	105
8	444	4.9	24.8	48.8	105
9	456	5.0	24.9	48.2	105
10	467	5.1	24.8	48.0	103
Mean	445	4.9	24.1	49.7	105
SD	16.6	0.2	1.2	3.0	0.8

Applicant's summary and conclusion

Interpretation of results:

GHS criteria not met

Remarks:

The concluded LC50 value corresponds to Category 3 for acute inhalation toxicity according to Regulation (EC) No. 1272/2008. However, since this was the only dose tested and there were no deaths, clinical signs of toxicity or macroscopic changes at necropsy it is concluded that the test substance does not require any classification for acute inhalation toxicity.

Conclusions:

In the acute inhalation toxicity study, conducted according to OECD 403 and in compliance with GLP, the concluded LC50 value was 4.9 mg/l. No mortality, clinical signs of toxicity or macroscopic changes were observed at the end of the treatment period.

Executive summary:

An acute inhalation study was performed with a mixture of 2,4,6,8,10-pentamethylcyclopentasiloxane (CAS 6166-86-5) and 2,4,6,8-tetramethylcyclotetrasiloxane (CAS 2370-88-9). 5 male and 5 female animals were exposed in a whole-body exposure chamber for 4 hours and subseqently observed for 1 days. Only one dose was tested: nominal 5 mg/l, measured 4.9 mg/l. No mortalitiy or any clinical signs were observed. The LC50 of the mixture is > 4.9 mg/l.