Trichloroisobutylsilane

Endpoint summary

Description of key information

No repeat-dose toxicity data are available for trichloroisobutylsilane, therefore good quality data have been read across from the related substance triethoxyisobutylsilane. The key repeated dose toxicity study was a 90-day nose-only inhalation study conducted in male and female rats, according to OECD 413. The study identified a NOAEC value of at least 2.54 mg/l (measured concentration), which was the highest dose tested. There were no significant treatment-related effects.

Key value for chemical safety assessment

Repeated dose toxicity: inhalation - systemic effects

Endpoint conclusion

Dose descriptor:

NOAEC

2 540 mg/m³

Additional information

The key study for repeated dose toxicity is the only reliable study for this endpoint, based on read-across from the related substance triethoxyisobutylsilane(CAS 17980 -47 -1). The registered substance, trichloroisobutylsilane, and the surrogate substance both hydrolyse in contact with water to produce the common hydrolysis product isobutylsilanetriol, with the other hydrolysis products being hydrogen chloride and ethanol respectively. Although at pH 7, the triethoxy analogue hydrolyses more slowly than the trichloro (half-life 22 hours compared to <1 minute), under acidic conditions such as in the stomach following oral ingestion, the triethoxy substance is expected to hydrolyse rapidly, based on experience with other ethoxy silanes.

Since both substances generate a common hydrolysis product, in the absence of other data it is considered appropriate to read-across the result of the reliable OECD 413 test for the inhalation route. However, uptake in the lungs is likely to be significantly greater for the triethoxy analogue (log K_ow 3.6) than for the trichlorosilane or silanetriol. The NOAEC for the triethoxy analogue is therefore likely to be conservative for the inhalation route. At the dose levels relevant for testing and human exposure, ethanol generated in vivo would not contribute any systemic toxicity effects.

Hydrogen chloride, generated by hydrolysis of trichloroisobutylsilane can be expected to cause local irritant or corrosive effects at sufficiently high concentrations. These effects are not addressed by the read-across data.

Justification for classification or non-classification

The available data do not support classification under Regulation (EC) No 1272/2008 or Directive 67/548/EEC.