Dimethoxydimethylsilane

Endpoint summary

Description of key information

Oral:
WoE approach: not acutely toxic based on repeated dose toxicity studies (DRF and OECD TG 422), RA CAS 78-62-6: LD50=9775 mg/kg bw

Inhalation:
OECD TG 403: LC50 >4700 mg/m³

Dermal:

There are no data available for acute toxicity via the dermal route (data waiving according to Column 2 of REACH Annex VIII, Section 8.5.3).

Key value for chemical safety assessment

Acute toxicity: via oral route

Link to relevant study records

Reference

Reference 1

Endpoint:

acute toxicity: oral

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

other:

Reference 2

Endpoint:

acute toxicity: oral

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

weight of evidence

Justification for type of information:

Please refer to the attached justification below and the overall justification for grouping of substances attached in IUCLID Section 13.

Reason / purpose for cross-reference:

read-across source

Key result

Sex:

male

Dose descriptor:

LD50

Effect level:

11.3 mL/kg bw

Based on:

test mat.

95% CL:

8.22 - 15.6

Remarks on result:

other:

Remarks:

equivalent to LD50 = 9775 mg/kg bw (Chemical Hygiene Fellowship, 1979, CAS 78-62-6)

Interpretation of results:

other: CLP/EU GHS criteria are not met, no classification required according to Regulations (EC) No 1272/2008

Conclusions:

One study is available from structural analogue substance CAS 78-62-6. The LD50 for CAS 78-62-6 was estimated to be 9775 mg/kg bw. As explained in the analogue justification, the differences between the target and the source are unlikely to lead to differences in the oral LD50.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Quality of whole database:

The hazard assessment is based on a weight of evidence approach taking into account repeated dose toxicity studies. The database is, therefore, sufficient to fulfil the standard information requirements set out in Annex VII, Item 8.5, in accordance with Annex XI, Item 1.2, of Regulation (EC) No. 1907/2006.

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:

30-08-1988 to 12-09-1988

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: The study was conducted according to the appropriate OECD test guideline, and in compliance with GLP.

Qualifier:

according to guideline

Guideline:

OECD Guideline 403 (Acute Inhalation Toxicity)

Deviations:

yes

Remarks:

Report lacking data on whether clinical examination and physical measurements were conducted.

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: Not reported.
- Weight at study initiation: 175-200 g ( Males and Females).
- Housing: The rats were housed in stainless steel, wire mesh bottomed cages of conventional design. At the onset of experiment, the animals were moved into special stainless steel cages. These cages were designed to house the animals during the exposure periods. The animals were returned to their original housing after the exposure period.
- Diet : The animals were fed PURINA Rodent Chow ad libitum except during the exposure period.
- Water : The animals were fed water ad libitum except during the exposure period.


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 ± 3
- Humidity (%): 30 -50
- Air changes (per hr): 14 - 15 air changes per hour
- Photoperiod (hrs dark / hrs light): 12/12

IN-LIFE DATES: From: Not reported

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: Exposure was conducted in stainless steel and glass exposure chambers. The chambers were operated under dynamic conditions.
- Exposure chamber volume: 450-litre
- Method of holding animals in test chamber: Not reported.
- Source and rate of air: Airflow rates through the chambers were monitored continuously by calibrated Magnehelic gauges connected across orifices at the chamber inlets.
- Method of conditioning air: Not reported
- System of generating particulates/aerosols: Test material was introduced into the test chamber through a specially designed glass J-tube with a flow FMI Lab pump. Laboratory air filtered with a Matheson 462 cartridge filter passed through the J-tube. The air/vapour mixture entered the top of the chamber where it was diluted with room air. Heating tape was used to heat the air which passed through the J-tube, and glass beads were used to further help vaporize the test material. After the exposure period, the vapour generating equipment was turned off and the vapour concentration in the chamber was allowed to return to zero.
- Method of particle size determination: Not reported.
- Treatment of exhaust air: The exhaust air was filtered (hepa and carbon), cleaned with a water cyclone, then exhausted from the roof of the building.
- Temperature, humidity, pressure in air chamber: Chamber temperature and relative humidity were monitored with Cole-Parmer Model No.3310-40 (certified) temperature and humidity gauges.

TEST ATMOSPHERE
- Brief description of analytical method used: Not reported

Analytical verification of test atmosphere concentrations:

not specified

Duration of exposure:

4 h

Concentrations:

The test material target concentration was 5.0 mg/l. The actual nominal chamber concentration was 4.7 mg/l (calculation by weight).

No. of animals per sex per dose:

5 males and 5 females.

Control animals:

yes

Details on study design:

- Duration of observation period following administration: 14 days
- Frequency of observations and weighing: Gauge readings were recorded hourly during the chamber period. Animals were observed once a day during weekdays. Individual animal body weights were taken prior to exposure and on days 7 and 14 after exposure.
- Necropsy of survivors performed: Not reported
- Other examinations performed: body weight

Sex:

male/female

Dose descriptor:

LC50

Effect level:

> 4 700 mg/m³ air

Based on:

test mat.

Exp. duration:

4 h

Mortality:

No mortalities were observed in either groups during the exposure or post-exposure periods.

Clinical signs:

other: Not reported.

Body weight:

No apparent test material related effect on body weights.

Gross pathology:

Not reported.

 Table 2. Mortality Data.

Test Material Concentration (mg/l)	Number of Dead/Number exposed
	Males	Females
0	0/5	0/5
4.7	0/5	0/5

 

Table 3. Mean Body Weight Data (g).

Days After Exposure	Group I, Control		Test Group II
	Males	Females	Males	Females
0	189 ± 5	183 ± 10	188 ± 5	183 ± 12
7	242 ± 8	214 ± 15	248 ± 9	205 ± 15
14	295 ± 13	233 ± 21	305 ± 15	230 ± 20

Interpretation of results:

other: CLP/EU GHS criteria are not met, no classification required according to Regulation (EC) No 1272/2008

Conclusions:

In an acute inhalation (vapour) study conducted in compliance with OECD 403 and GLP, in which rats were exposed to to >4700 mg/m³ dimethoxydimethylsilane for four hours resulted in no mortality. Therefore, LC50 was determined to be >4700 mg/m³.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

LC50

Value:

> 4 700 mg/m³ air

Quality of whole database:

The available information comprises an adequate and reliable study, and is thus sufficient to fulfil the standard information requirements set out in Annex VIII, 8.5, of Regulation (EC) No 1907/2006.

Acute toxicity: via dermal route

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

No studies were identified to assess the acute oral toxicity potential of dimethoxy(dimethyl)silane (CAS 1112-39-6). Based on a weight-of-evidence based adaptation according to REACH Annex XI, section 1.2 considering the results of a 7-day dose-range finding study (Dow Corning Corporation, 2008) and a combined repeated dose and reproduction / developmental screening study (Dow Corning Corporation, 2010), dimethoxy(dimethyl)silane is not expected to be acutely toxic. In addition, reliable data on acute oral toxicity for the structural analogue substance diethoxy(dimethyl)silane (CAS 78-62-6, LD50 = 9775 mg/kg bw) strengthen the conclusion, that dimethoxy(dimethyl)silane does not warrant classicification for acute oral toxicity according to Regulation (EC) No. 1272/2008.

 

The key acute inhalation study was the only study available. The study was conducted in compliance with GLP and according to OECD TG 403. Exposure of rats to dimethoxy(dimethyl)silane (CAS 1112-39-6) vapour at a concentration of 4.7 mg/L (4700 mg/m³) for four hours resulted in no mortality. Therefore LC50 was determined to be >4700 mg/m³ (Dow Corning Corporation, 1989).

 

No studies were available to assess the acute dermal toxicity potential of dimethoxy(dimethyl)silane (CAS 1112-39-6). However, in accordance with Column 2 of REACH Annex VIII, the acute toxicity study via the dermal route (required in Section 8.5.3) does not need to be conducted as reliable data via the oral and inhalation routes are available. 

Justification for classification or non-classification

The available data on acute toxicity by the oral and inhalation route do not meet the criteria for classification according to Regulation (EC) 1272/2008, and are therefore conclusive but not sufficient for classification of the registered substance.