Dichlorosilane

Endpoint summary

Description of key information

The requirement for acute oral and dermal studies is waived on the basis that dichlorosilane is classified as corrosive. In an inhalation whole body exposure acute study with dichlorosilane, the LC50 after a 1-hour exposure period was calculated to be 314 ppm (1297 mg/m3), which equates to a 4-hour LC50 of 157 ppm (649 mg/m3).

Key value for chemical safety assessment

Acute toxicity: via oral route

Endpoint conclusion

Endpoint conclusion:

no study available

Acute toxicity: via inhalation route

Link to relevant study records

Reference

Endpoint:

acute toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

key study

Study period:

17 June to 7 July 1986

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 403 (Acute Inhalation Toxicity)

Deviations:

yes

Remarks:

1 hour exposure period

GLP compliance:

yes

Test type:

standard acute method

Limit test:

yes

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Harlan Inc., USA
- Age at study initiation: 63 to 77 days
- Weight at study initiation: 234-298 g (male), 200-243 g (female)
- Fasting period before study: no
- Housing: stainless steel wire mesh cages
- Diet (ad libitum): pelleted feed (Purina Co., USA)
- Water (ad libitum): tap water
- Acclimation period: at least 5 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20 - 24
- Humidity (%): 42 - 69
- Air changes (per hr): not stated
- Photoperiod (hrs dark / hrs light): 12/12

IN-LIFE DATES: From: 27 May 1986 To: 7 July 1986

Route of administration:

inhalation: vapour

Type of inhalation exposure:

whole body

Vehicle:

air

Details on inhalation exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: cuboidal stainless-steel and Plexiglass chamber
- Exposure chamber volume: 120 L
- Method of holding animals in test chamber: wire mesh cage
- Source and rate of air: 30 or 50 L/min
- Method of conditioning air: not stated
- System of generating test atmosphere: dichlorosilane contained in a gas cylinder, metered through a flow meter and diluted with dry or humidified air
- Treatment of exhaust air: not stated
- Temperature, humidity, pressure in air chamber: see tables

TEST ATMOSPHERE
- Brief description of analytical method used: gas chromatograph with hot wire detector
- Samples taken from breathing zone: yes

Analytical verification of test atmosphere concentrations:

yes

Duration of exposure:

1 h

Concentrations:

257, 493, 1000 ppm

No. of animals per sex per dose:

5

Control animals:

no

Details on study design:

- Duration of observation period following administration: 14 days
- Frequency of weighing: prior to exposure, Days 7 and 14
- Necropsy of survivors performed: yes

Statistics:

The means and standard deviations of the body weights, body weight changes and exposure concentrations were calculated. No statistical comparisons were made. The LC50 was determined by a modified method of Pinney's (1954) probit analysis.

Key result

Sex:

male/female

Dose descriptor:

LC50

Effect level:

314 ppm

Based on:

other: nominal concentration

95% CL:

211 - 466

Exp. duration:

1 h

Mortality:

Mortalities were recorded in all exposure groups except for 257 ppm females (see table).

Clinical signs:

other: Clinical signs observed on the day of exposure included lacrimation, perioral and perinasal wetness, mouth breathing, audible respiration and cloudy eyes. During the post-exposure period decreased motor activity, audible respiration, unkempt fur and perio

Body weight:

A loss of body weight was recorded for all survivors on Day 7, body weight gain was recorded during the second post-exposure week (Days 7 to 14).

Gross pathology:

Gross lesions considered to be exposure-related were noted in animals which died and included red or dark discolouration of the lungs, fluid-filled pleural cavities and trachea, periocular and perinasal encrustation and cloudy eyes. There were no remarkable findings in animals that survived the 14-day observation period.

No dichlorosilane vapour was found in any of the four exposure chamber atmospheres. Water vapour reacted with dichlorosilane quickly and completely in both the low and high relative humidity experiments. The metered (nominal) dichlorosilane concentrations (% relative humidity values) for the four exposures were 1000 ppm (41%), 493 ppm (25%), 493 ppm (80%) and 257 ppm (12%).

Table 1 - Summary of Mortality

Nominal Dichlorosilane Exposure Concentration (ppm)	Exposure Chamber Relative Humidity (%)	Sex	Time of death								Total Incidence
			During exposure	Post exposure day
				1	2	3	4	8	9	12
1000	41	M F	0 0	5 5	- -	- -	- -	- -	- -	- -	5/5 5/5
493	25	M F	0 0	0 0	2 3	2 0	0 1	0 0	0 0	1 0	5/5 4/5
493	80	M F	0 0	5 4	0 1	- -	- -	- -	- -	- -	5/5 5/5
257	12	M F	0 0	0 0	0 0	0 0	0 0	2 0	1 0	0 0	3/5 0/5

Table 2 - Chamber atmosphere conditions

Nominal Dichlorosilane Exposure Concentration (ppm)	Temperature (^oC) (Mean ± SD)	Relative Humidity (%) (Mean ± SD)
1000 493 493 257	25 ± 1 23 ± 0 23 ± 0 23 ± 1	41 ± 15 25 ±11 80 ± 1 12 ± 9

Table 3 - Nominal Exposure Concentrations

Nominal Dichlorosilane Exposure Concentration (ppm)	Relative Humidity (%)	Exposure Duration (min)	Chamber Airflow Rate (L/min)	Dichlorosilane Flow Rate (mL/min)	Actual Dichlorosilane Exposure Concentration (ppm)
1000 493 493 257	41 25 80 12	60 60 60 60	30 50 50 50	30.0 24.7 24.7 12.9	0 0 0 0

Table 4 - Hydrogen Chloride Exposure Concentrations

Nominal Dichlorosilane Exposure Concentration (ppm)	Relative Humidity (%)	Mean (±SD) Exposure Conc of Hydrogen Chloride (ppm)
		GC Method	Detector Tube Method
1000 493 493 257	41 25 80 12	1050 (± 237) 1880 (± 77) < 250 320 (± 191)	2300 (± 260) 1870 (± 153) 770 (± 231) 850 (± 71)

Interpretation of results:

Category 2 based on GHS criteria

Conclusions:

One hour inhalation whole body exposure to dichlorosilane at nominal concentrations of 257, 493 or 1000 ppm resulted in mortalities at all concentrations and clinical signs consistent with exposure to hydrogen chloride. The LC50 for dichlorosilane was calculated to be 314 ppm (95% confidence limits 211 - 466 ppm). This equates to a 4-hour LC50 of 157 ppm.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

LC50

Value:

649 mg/m³ air

Quality of whole database:

Study was conducted according to a design comparable with an appropriate guideline and in compliance with GLP.

Acute toxicity: via dermal route

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

In the key whole-body inhalation study with dichlorosilane (BRRC, 1986) the LC₅₀ after a 1-hour exposure period was calculated to be 314 ppm (1297 mg/m³), which equates to a 4 -hour LC50 of 157 ppm (649 mg/m³). However, no dichlorosilane was found in any of the exposure chamber atmospheres at relative humidities of 12%, 25%, 25% or 80% indicating that it had reacted with water vapour quickly and completely. Mortality, body weight loss and clinical signs consistent with local irritancy were recorded at all exposure concentrations. A supporting whole-body inhalation study with dichlorosilane in male mice (Nakashima, 1996) calculated the LC₅₀ to be 144 ppm (595 mg/m³) and noted histological changes in the nasal cavity consistent with local irritancy.

Justification for classification or non-classification

Based on the available inhalation information, dichlorosilane requires classification as Acute Toxicity Inhalation Category 2, H330: Fatal if inhaled, according to Regulation (EC) No 1272/2008.