Chlorodimethylsilane

Endpoint summary

Description of key information

In the key repeated 28-day oral study (Ramm & Bomhard, 1986) read-across from trimethylsilanol, adverse effects (reduced body weight gain, reduced alkaline phosphatase, reduced glucose (males), increased liver weights (females), and increased adrenal weights (males), and minor deposits in the bile ducts) were observed at the highest dose of 750 mg/kg bw/day. The NOAEL was 250 mg/kg bw/day, as effects observed at this or the lower dose of 80 mg/kg bw/day, were not dose-dependent and often values were within the normal range for historical controls.
In the key repeated inhalation study (Fleeman, 2008; an OECD 422 study) read-across from trimethylsilanol, test substance-related effects were limited to changes in hematology (lower eosinophil and lymphocyte counts for males) and serum chemistry (higher alanine aminotransferase for males and toxicity phase females) at 600 ppm trimethylsilanol. These changes occurred in the absence of correlating histologic changes and were not considered adverse. Therefore, under the conditions of this screening study, an exposure level of 600 ppm (2213.5 mg/m3) was considered to be the no-observed-adverse-effect level (NOAEL) for trimethylsilanol. Since chlorodimethylsilane is hydrolysed to dimethylsilane and hydrogen chloride, additional local irritation can be expected due to the acidic nature of the HCl. There are no data for the oral and dermal routes.

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Endpoint conclusion

Dose descriptor:

NOAEL

250 mg/kg bw/day

Repeated dose toxicity: inhalation - systemic effects

Endpoint conclusion

Dose descriptor:

NOAEC

2 213.5 mg/m³

Additional information

There are no adequate repeated dose toxicity data on chlorodimethylsilane or its hydrolysis product, dimethylsilanol, so good quality data for the related substance trimethylsilanol have been used to assess the general systemic toxicity of chloro(methyl)silane. Local effects from the other hydrolysis product, hydrogen chloride (HCl), are not addressed by these data.

In the absence of measured data for chlorodimethylsilane, it is considered appropriate to use these results in support of the repeated dose toxicity endpoint for chlorodimethylsilane as the registered 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.

Repeated dose toxicity: inhalation - systemic effects (target organ) respiratory: other

Justification for classification or non-classification

The data do not suggest that chlorodimethylsilane should be classified for adverse effects following repeated exposures. It has been proposed that it be classified for its corrosive effects in Section 7.3.