Registration Dossier

Administrative data

Link to relevant study record(s)

Description of key information

Key value for chemical safety assessment

Additional information

Introduction

There are no in vivo data on the toxicokinetics of trichloro(ethyl)silane. The following summary has therefore been prepared based on the physicochemical properties of the substance itself and its hydrolysis products. Trichloro(ethyl)silane is a moisture-sensitive, volatile liquid. Rapid hydrolysis occurs, producing ethylsilanetriol and hydrogen chloride. Exposure may occur via the inhalation or dermal routes. Relevant inhalation exposure would be to the hydrolysis products (hydrolysis would occur rapidly when inhaled, even if a mixture of parent and hydrolysis products were present in air). The substance would also hydrolyse rapidly in contact with moist skin. The resulting HCl hydrolysis product would be severely irritating or corrosive. At sufficiently high concentrations, subsequent condensation of the silanol hydrolysis product can occur, resulting in formation of siloxanes.

Absorption

Oral

Significant oral exposure is not expected for this corrosive substance.

Dermal

The molecular weights of the parent and hydrolysis products favour absorption across the skin. However, the very high water solubility (1E+06 mg/l) and low predicted log Kow(-1.9) of the hydrolysis product, ethylsilanetriol, suggest that it is too hydrophilic to cross the lipid rich stratum corneum. Therefore dermal uptake is likely to be low. Since the other hydrolysis product, HCl, is corrosive to the skin, damage to the skin might increase penetration. There are no reliable studies to check for signs of dermal toxicity as evidence of dermal absorption.

Inhalation

The partition coefficient and high water solubility suggest that this substance is likely to be retained in the mucous of the lungs, and absorption limited. As with dermal exposure, damage to membranes caused by the corrosive nature of the other hydrolysis product, HCl, might enhance the uptake. Acute inhalation studies showed local signs but no definite systemic effects.

Distribution

All absorbed material is likely to be in the form of the hydrolysis products, ethylsilanetriol and hydrogen chloride. Ethylsilanetriol is a small molecule, and is likely to be widely distributed, but its hydrophilic nature will limit its diffusion across membranes (including the blood-brain and blood-testes barriers) and its accumulation in fatty tissues. Hydrogen and chloride ions will enter the body’s natural homeostatic processes.

Metabolism

Trichloroethylsilane is rapidly hydrolysed to ethylsilanetriol and hydrogen chloride in the presence of moisture. Most if not all of this will have occurred before absorption into the body. There is no data regarding the metabolism of ethylsilanetriol. Genetic toxicity tests in vitro using either trichloro(ethyl)silane or the related substance trichloro(methyl)silane showed no clear, observable differences in effects with and without metabolic activation.

Excretion

The low molecular weight and high water solubility of ethylsilanetriol suggest that it is likely to be rapidly eliminated via the kidneys in urine. There is therefore no evidence to suggest that this substance will accumulate in the body.