Trichloro(methyl)silane

Endpoint summary

Additional information

Introduction

 

There are no in vivo data on the toxicokinetics of trichloro(methyl)silane. The following summary has therefore been prepared based on validated predictions of the physicochemical properties of the substance itself and its hydrolysis products. Trichloro(methyl)silane is a moisture-sensitive, volatile liquid. Rapid hydrolysis occurs (t_1/2 < 1.5 min at 1.5 °C, OECD 111), producing methylsilanetriol. 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.

Absorption

Oral

Significant oral exposure is not expected for this corrosive substance.

 

Dermal

The high volatility of trichloro(methyl)silane means that it is likely to evaporate off the skin. It is also rapidly hydrolysed to methylsilanetriol and hydrogen chloride (HCl) in contact with moist skin. The physicochemical properties (water solubility = 1E+06 mg/l; log K_ow= -2.4) of the hydrolysis product methylsilanetriol show that it is possibly too hydrophilic to cross the lipid rich environment of the stratum corneum. Therefore dermal absorption is likely to be low for this hydrolysis product. The available acute dermal and dermal irritation studies do not show any evidence of systemic effects. However, since the hydrolysis product, HCl, is corrosive to the skin, damage to the skin might increase penetration.

 

Inhalation

Trichloro(methyl)silane is expected to be rapidly hydrolysed in the lungs. The hydrophilic nature of the hydrolysis product, methylsilanetriol, suggests that absorption following inhalation will be limited as it is likely to be retained with the mucous (Csanady & Filser, 2001). However, as for the dermal route, absorption might be increased following corrosion of the respiratory tract lining. However, there were no signs of systemic absorption in available inhalation studies.

 

Distribution

The distribution of the very hydrophilic hydrolysis product, methylsilanetriol might be expected to be limited by its hydrophilicity, and therefore slow diffusion across membranes. However, repeated dose studies on the read-across substance, trimethoxy(methyl)silane (also hydrolysed to methylsilanetriol), in which clear toxicity was observed, do suggest that distribution occurs in particular to the liver, kidney and adrenal glands.

 

Metabolism

Apart from the initial hydrolysis to methylsilanetriol and HCl, most of which will occur before entry into the body, there are no data on the metabolism of trichloro(methyl)silane. Genetic toxicity tests in vitro showed no consistent observable differences in effects with and without metabolic activation.

 

Excretion

The molecular weight and hydrophilicity of methylsilanetriol suggest that it will be primarily excreted in urine. The high volatility suggests that some will also be excreted in exhaled air. There is no potential for accumulation of trichloro(methyl)silane, or methylsilanetriol in the body based on their physicochemical properties.

Csanady G.A. and Filser J.G. (2001) The relevance of physical activity for the kinetics of inhaled gaseous substances. Arch Toxicol, 74, 663-672.