Chlorotrimethylsilane

Endpoint summary

Additional information

Introduction

There are no in vivo data on the toxicokinetics of chlorotrimethylsilane. The following summary has therefore been prepared based on validated predictions of the physicochemical properties of the substance itself and its hydrolysis products.Chlorotrimethylsilane is a moisture-sensitive, volatile liquid. Rapid hydrolysis occurs, producing trimethylsilanol (TMS; CAS 1066-40-6) and hydrogen chloride (HCl). 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

No measured dermal penetration data are available for the substance itself. However, in a well conducted guideline study conducted to OECD 428 and GLP (reliability score 1), the total percentage of the dose of the hydrolysis product, 14C-TMS, absorbed was estimated to be <0.08% of the applied dose. Almost all (99.9%) of the recovered 14C-TMS volatilised from the skin surface and was captured in the charcoal baskets placed above the exposure sites. The majority of the absorbed dose penetrated through the skin to the receptor fluid. Therefore once hydrolysis has occurred, absorption of trimethylsilanol is poor. Since the other hydrolysis product, HCl is corrosive to the skin, damage to the skin might increase penetration. Deaths, and lung and liver pathology in the key acute dermal study provide evidence that chlorotrimethylsilane is absorbed in vivo following exposure to high doses (in the presence of severe dermal irritation). 

 

Inhalation

The moderate partition coefficient of 1.19 and small molecular weight of the hydrolysis products are favourable for absorption directly across the respiratory tract epithelium by passive diffusion. As with dermal exposure, damage to membranes caused by the corrosive nature of the HCl hydrolysis product might enhance the uptake. Acute inhalation studies showed local signs of corrosion, but no definite systemic effects.

 

Distribution

All absorbed material is likely to be in the form of the hydrolysis products, trimethylsilanol and hydrogen chloride. Trimethylsilanol is a small molecule, and is likely to be widely distributed. The log K_ow of this hydrolysis product means that it is likely to distribute widely into cells, and intracellular concentrations might be higher than the extracellular concentration, particularly in fatty tissues. Hydrogen and chloride ions will enter the body’s natural homeostatic processes.

 

Metabolism

Chlorotrimethylsilane is rapidly hydrolysed to trimethylsilanol and hydrogen chloride in the presence of moisture. It is likely to occur before absorption into the body. There is no data regarding the metabolism of DMSD. Genetic toxicity tests in vitro showed no observable differences in effects with and without metabolic activation.

 

Excretion

The molecular weight of TMS suggests that it will be excreted in urine.