Chloro(methyl)silane

Endpoint summary

Key value for chemical safety assessment

Effects on fertility

Effect on fertility: via inhalation route

Dose descriptor:

NOAEC

2 213.5 mg/m³

Additional information

In the absence of measured data for chloro(methyl)silane, it is considered appropriate to use the result for trimethylsilanol in support of the repeated dose toxicity endpoint for chloro(methyl)silane as the registered substance is hydrolysed very rapidly in the presence of moisture to dimethylsilanol and hydrogen chloride. The tested substance, trimethylsilanol is closely related to methylsilanol (replacement of two -H with two -CH₃) and both substances have similar physicochemical properties (high water solubility and low log K_ow), therefore the toxicological properties are expected to be similar.

Data for analternative read-across substance, methyltrimethoxysilane, is also available. This substance hydrolyses rapidly to methylsilanetriol, which is the substance that is expected to form after hydrolysis of both the Si-Cl and Si-H bonds in methylchlorosilane. However, in the absence of conclusive evidence that the Si-H bond would hydrolyse under relevant conditions, the best read-across for the initial hydrolysis product methylsilanol was sought. The number of -OH groups at Si, rather than the number of -Me groups, is considered the key determinant of the toxicology of the substance. Therefore, the data for trimethylsilanol are selected as key.

Short description of key information:
In the key repeated inhalation study (Fleeman, 2008; an OECD 422 study) read across from trimethylsilanol, there were no adverse effects on reproduction parameters. Therefore, under the conditions of this screening study, an exposure level of 600 ppm (2213.5 mg/m3) was considered to be the NOAEC for trimethylsilanol.
Oral exposure to methyltrimethoxysilane was also not associated with reproductive toxicity.

Effects on developmental toxicity

Description of key information

In the key repeated inhalation study (Fleeman, 2008; an OECD 422 study) read across from trimethylsilanol, there were no adverse effects on developmental parameters. Therefore, under the conditions of this screening study, an exposure level of 600 ppm (2213.5 mg/m3) was considered to be the NOAEC for trimethylsilanol. 
Oral exposure to methyltrimethoxysilane was also not associated with reproductive toxicity. 

Effect on developmental toxicity: via inhalation route

Dose descriptor:

NOAEC

2 213.5 mg/m³

Additional information

It is considered appropriate to use this result in support of the developmental toxicity endpoint for chloro(methyl)silane as this substance is hydrolysed very rapidly in the presence of moisture to methylsilanol and hydrogen chloride. The tested substance, trimethylsilanol is closely related to methylsilanol (replacement of 2 x-H with 2 x -CH₃) and both substances have similar physicochemical properties (high water solubility and low log K_ow), therefore the toxicological properties are expected to be similar.

Data for analternative read-across substance, methyltrimethoxysilane, is also available. This substance hydrolyses rapidly to methylsilanetriol, which is the substance that is expected to form after hydrolysis of both the Si-Cl and Si-H bonds in methylchlorosilane. However, in the absence of conclusive evidence that the Si-H bond would hydrolyse under relevant conditions, the best read-across for the initial hydrolysis product methylsilanol was sought. The number of -OH groups at Si, rather than the number of -Me groups, is considered the key determinant of the toxicology of the substance. Therefore, the data for trimethylsilanol are selected as key.

Justification for classification or non-classification

There are no data to suggest that chloro(methyl)silane should be classified for adverse effects on reproduction and development.