Registration Dossier

Diss Factsheets

Administrative data

Description of key information

In the key acute oral toxicity study (Hüls Prüfinstitut für Toxikologie, 1993a) conducted to OECD test guideline (now deleted 401) and GLP, the oral LD50 was greater than 2000 mg/kg bw in male and female rats. Within the first three hours after administration in males and the first six hours in females, there were signs of toxicity. Within three hours the signs were ruffled fur, crouching posture, mild sedation, ataxia, and swaying motion. By five to six hours there were no signs in 8/10 animals. Six hours after administration, one female had signs of severe toxicity (ruffled fur, medium to heavy sedation, ataxia, prone position, hypothermia, laboured breathing, closed eyes and chromodacryorrhea. While all other animals ate their food, after three hours this animal still refused to eat. After 24 hours there were no signs of toxicity in any of the animals. 
In the key acute inhalation study (that was comparable to OECD 403 and to GLP (DCC, 1984), the LC50 for Dow Corning X1-2204 (isobutyltrimethoxysilane) was greater than 1525 ppm (11 mg/l) (the only concentration tested) in Sprague-Dawley rats. The animals were lethargic and unresponsive during the exposure period. However, on removal from the chamber, the animals quickly recovered and did not show any stress or signs of toxicity during the 14-day observation period.
There are no dermal data for the registration substance, but the skin irritation and skin sensitisation studies did not report any systemic effects. An acute dermal toxicity study is available for a related substance (triethoxy-(2-methylpropyl)silane) in which the LD50 was >2000 mg/kg bw (Huntingdon Research Centre, 1987b), confirming the low acute toxicity of the substance; the relevance of this substance is discussed further in Section 7.5.

Key value for chemical safety assessment

Acute toxicity: via oral route

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed
Dose descriptor:
LD50
Value:
2 000 mg/kg bw

Acute toxicity: via inhalation route

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed
Dose descriptor:
LC50
Value:
11 000 mg/m³ air

Acute toxicity: via dermal route

Endpoint conclusion
Endpoint conclusion:
no study available

Additional information

Only one study was available for the oral route, which was a reliable, GLP and guideline-compliant study (Hüls Prüfinstitut für Toxikologie, 1993a). For the inhalation route there are two reliability score 2 studies. The key study was selected as the most recent of these and for which the appropriate exposure duration was used according to current guidelines.


Justification for selection of acute toxicity – oral endpoint
The selected study is the only acute oral toxicity study available for the registered substance. It was carried out in accordance with an appropriate OECD test guideline and in compliance with GLP.

Justification for selection of acute toxicity – inhalation endpoint
The selected study is the most recent and reliable acute inhalation toxicity study available for the registered substance. It was carried out in accordance with an appropriate OECD test guideline and in compliance with GLP.

Justification for classification or non-classification

The available results for the oral and inhalation routes do not trigger classification for lethality for trimethoxy(2-methylpropyl)silane according to Regulation (EC) No 1272/2008.