Dimethoxymethylsilane

Endpoint summary

Description of key information

Oral (OECD TG 423), rat (female): LD50 > 2000 mg/kg bw (RA CAS 2031-62-1)
Inhalation (OECD TG 403), rat: LC50 > 4600 mg/m³ air (limit test)

Key value for chemical safety assessment

Acute toxicity: via oral route

Link to relevant study records

Reference

Endpoint:

acute toxicity: oral

Type of information:

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

Adequacy of study:

key study

Justification for type of information:

Please refer to the attached read-across justification.

Reason / purpose for cross-reference:

read-across source

Sex:

female

Dose descriptor:

LD50

Effect level:

> 2 000 mg/kg bw

Based on:

test mat.

Remarks on result:

other: no mortalities or clinical signs of toxicity observed

Interpretation of results:

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

Conclusions:

In conclusion, under the conditions of the present study, according to OECD 423 and GLP, at the limit concentration of 2000 mg/kg bw no mortalities or clinical signs of toxicity were observed. The source test substance and thus the target substance does not need to be classified for oral toxicity. As explained in the analogue justification, it is considered that the target and the source substances are unlikely to lead to differences in acute oral toxicity potential.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

LD50

Value:

> 2 000 mg/kg bw

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 VII, 8.5.1, 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:

11 Aug - 30 Dec 1988

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 403 (Acute Inhalation Toxicity)

Version / remarks:

(1981)

Deviations:

yes

Remarks:

(no gross necropsy was done at the end of the observation period, no justification for the use of a whole-body inhalation system is given)

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: Charles River Breeding Laboratories
- Weight at study initiation: 175 - 200 g
- Housing: in stainless steel wire mesh bottomed cages
- Diet: Purina rodent chow, ad libitum, except during exposure
- Water: ad libitum

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 ± 3
- Humidity (%): 30 - 50
- Photoperiod (hrs dark / hrs light): 12/12

Route of administration:

inhalation: vapour

Type of inhalation exposure:

whole body

Vehicle:

clean air

Details on inhalation exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: stainless steel and glass exposure chamber under dynamic conditions. Airflow rates through the chambers were monitored continously by calibrated Magnehelic gauges connected across orifices at the chamber inlets. Chamber temperature and relative humidity were monitored with cole-Parmer Model No. 3310-40 (certified) temperature and humidity gauges. Gauge readings were recorded hourly during the exposure period.
- Exposure chamber volume: 450 L
- Source and rate of air: laboratory air
- Method of conditioning air: the test material was introduced into the test chamber through a specially designed glass J-tube with a flow FMI Lab pump. Laboratory air filtered and dried with Matheson #462 cartridge filter passed through the J-tube. The air/vapor 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.
- Treatment of exhaust air: the exhaust air was filtered (hepa and carbon) cleaned with water cyclone and then exhausted from the roof of the building.

TEST ATMOSPHERE
- Brief description of analytical method used: airflow rates through the chambers were monitored continuously by calibrated Magnehelic gauges connected across orifices at the chamber inlets. Gauge readings were recorded hourly during the exposure period. Chamber temperature and relative humidity were monitored with Cole-Parmer Model No. 3310-40 (certified) temperature and humidity gauges. Gauge readings were recorded hourly during the exposure period.

Analytical verification of test atmosphere concentrations:

yes

Remarks:

calculated by weight

Duration of exposure:

4 h

Concentrations:

5000 mg/m³ (nominal), 4600 mg/m³ (analytical)

No. of animals per sex per dose:

5 males and females

Control animals:

yes

Details on study design:

- Duration of observation period following administration: 14 days
- Frequency of observations and weighing: animals observed daily on weekdays, body weight was determined prior to exposure and on Day 7 and 14 post exposure
- Necropsy of survivors performed: no
- Other examinations performed: clinical signs, body weight

Sex:

male/female

Dose descriptor:

LC50

Effect level:

> 4 600 mg/m³ air (analytical)

Based on:

test mat.

Remarks:

calculated by weight

Exp. duration:

4 h

Remarks on result:

other: no adverse effects or mortalities were observed

Mortality:

No mortalities were observed during the study period.

Clinical signs:

other: No other clinical signs were observed during the study period.

Body weight:

No effects on body weight were observed during the study period.

Interpretation of results:

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

Conclusions:

In conclusion, under the conditions chosen for this experiment (according to OECD 403), the test substance was found not to be toxic by inhalation, since no mortalities or clinical signs of toxicity were observed at the maximum attainable concentration.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

LC50

Value:

> 4 600 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, 8.5.2, of Regulation (EC) No 1907/2006.

Acute toxicity: via dermal route

Link to relevant study records

Reference

Endpoint:

acute toxicity: dermal

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

the study does not need to be conducted because inhalation of the substance is likely

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

No measured acute oral toxicity data are available for the registered substance, dimethoxy(methyl)silane (CAS 16881-77-9), however, data are available for the structural analogue substance diethoxy(methyl)silane (CAS 2031-62-1). Both substances hydrolyse in contact with water to produce the common silanol hydrolysis products, methylsilanediol and methylsilanetriol. Therefore, it is considered that read-across between the substances is appropriate.

 

The key acute oral toxicity study on the structural analogue substance diethoxy(methyl)silane (CAS 2031-62-1) was conducted in compliance with GLP and according to OECD TG 423 (BSL BIOSERVICE, 2007a) and reports an LD50 value of > 2000 mg/kg bw for female rats. All 3 animals dosed with 2000 mg/kg bw showed no clinical signs of toxicity and no mortality were observed.

 

The key acute inhalation toxicity study on dimethoxy(methyl)silane (CAS 16881-77-9) was conducted similar to OECD TG 403 (limit test) (Dow Corning Corporation, 1988) with minor deviations (no gross necropsy was done at the end of the experiment). No mortality or clinical signs of adverse effects were observed during the 14 day post exposure period following a 4 hour exposure with the highest attainable concentration of 4.6 mg/L. The LC50 value was determined to be > 4600 mg/m³ air.

 

No studies are available to assess the acute dermal toxicity potential of dimethoxy(methyl)silane (CAS 16881-77-9). 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. The inhalation route is considered more relevant due to the high vapour pressure of the registered substance (7.1E+03 Pa at 25°C), meaning exposure via the inhalation route is likely. Furthermore, the registered substance is not classified for acute toxicity or as STOT SE by the oral route. Nor have any signs of systemic toxicity been observed in the available in vivo dermal studies on the registered substance (OECD 429, CRL 2022 and sub-acute dermal study in rabbits, Losco 1996). Therefore, the registered substance is not expected to be acutely toxic via the dermal route and testing by the dermal route is not appropriate.

Justification for classification or non-classification

The available data on acute oral toxicity for the structural analogue substance diethoxy(methyl)silane and on inhalation toxicity for the registered substance do not meet the criteria for classification according to Regulation (EC) No. 1272/2008, and are therefore conclusive but not sufficient for classification.