Hydroxytrimethylsilane

Endpoint summary

Description of key information

There are no skin sensitisation studies available for trimethylsilanol, so a weight of evidence approach has been used, which uses studies conducted on other alkyl alkoxysilanes and silanols. There are ten skin sensitisation studies available for ten related substances in the group of alkyl alkoxysilanes and silanols, encompassing linear, branched and cyclic structures. None of these reliable results showed sensitisation in guinea pig tests (Hazelton france, 1992; Hüls Prüfinstitut für Toxikologie, 1993; Hüls AG, 1997; Pharmatox, 1994, Albrecht, 2001; Safepharm Laboratories Ltd., 1996; Huntingdon Research Centre Ltd., 1989; Research Toxicology Centre, 2004; WIL, 2000 and Hill Top Biolab Inc., 1988).

Key value for chemical safety assessment

Skin sensitisation

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not sensitising)

Additional information:

There are no skin sensitisation studies available for trimethylsilanol, so a weight of evidence approach has been used, which uses studies conducted on other alkyl alkoxysilanes and silanols (PFA, 2015t).

The alkyl alkoxysilanes and silanols analogue group, which includes trimethylsilanol, applies to substances with the general formula R(_4-x)-Si(OR’)_x and R(_4-x)-Si(OH)_x(x = 1-3), where R can be one of more of:

 

-H

-alkyl group (linear, branched or cyclic; saturated or unsaturated)

 

and R’ can be one or more of:

 

-CH₃(methoxy)

-CH₂CH₃(ethoxy)

 

but excludes substances containing only –H and –OR’ groups i.e. those that produce inorganic Si-containing hydrolysis products.

All ten of the read-across studies gave negative results. For one additional substance, trimethoxy(methyl)silane, a positive result was reported for sensitisation in a study (Harlan, 2009). There are no functional groups present in the substance (or any of the identified impurities of the substance) that indicate sensitising potential. There were, however, some methodological issues with the study itself relating to ambiguous skin reactions in test and control groups, and it was concluded by the reviewer that the result was ambiguous. One more recent study on trimethoxy(methyl)silane concluded that the substance is not sensitising, and the weight of evidence for the substance is that it is not sensitising (Toxikon, 2013).

Furthermore, two producers of trimethoxy(methyl)silane have provided statements which confirm that there have been no cases of skin sensitisation amongst workers during more than 20 years of manufacture (Wacker, 2017; Momentive, 2017).

These data included internal information from: relevant plants, number of employees, exposure description; medical surveillance, regular health checks (especially concerning skin status) already performed on employees of the relevant plants, information from the Network of Departments of Dermatology for the surveillance and scientific evaluation of contact allergies, information from Employer's liability insurance association (BG Bau), information from customer and a comprehensive literature search there have been no cases of skin sensitisation during more than 20 years of production, handling and use of trimethoxy(methyl)silane.

There is therefore no evidence that this substance causes skin sensitisation under relevant exposures in workers.

This conclusion is in agreement with evidence for other substances in this group which indicates that they are not skin sensitisers.

PFA, 2015t, Peter Fisk Associates, Analogue report - mammalian toxicity of alkyl alkoxysilanes, PFA.404.002.002

Respiratory sensitisation

Endpoint conclusion

Endpoint conclusion:

no study available

Justification for classification or non-classification

Based on the read-across studies trimethylsilanol does not require classification for skin sensitisation according to Regulation (EC) No 1272/2008.