Registration Dossier

Administrative data

Description of key information

The skin and eye irritation studies were read across from 3-trimethoxysilylpropane-1-thiol (CAS 4420-74-0).  The reliability 2 study which was not compliant with GLP reports the test substance not irritating to skin or eyes (BRRC 1990).

Key value for chemical safety assessment

Skin irritation / corrosion

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed (not irritating)

Eye irritation

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed (not irritating)

Respiratory irritation

Endpoint conclusion
Endpoint conclusion:
no study available

Additional information

No reliable skin or eye irritation data are available for the registered substance. Data are therefore read-across from the structural analogue 3-(trimethoxysilyl)propanethiol (CAS 4420-74-0).

In a reliable skin irritation study not conducted to GLP, gamma-mercaptopropyltrimethoxysilane (3-(trimethoxysilyl)propanethiol)was not irritating to the skin of New Zealand white rabbits (BRRC 1990). The undiluted test substance was applied to the intact (shaved) skin of six New Zealand white rabbits for four hours under an occlusive dressing. The dressings were then removed, the skin washed and the skin reactions observed for up to 14 days. None of the rabbits had any signs of skin irritation, and no other clinical signs of toxicity were observed. It was therefore concluded by the study authors that the test substance was not irritating to the skin.

In a reliable eye irritation study not conducted to GLP), Organofunctional Silane Y-9616 (gamma-mercaptopropyltrimethoxysilane) was not irritating to the eyes of New Zealand white rabbits (BRRC 1990). No corneal injury or iritis was observed in any of the eyes. Within one hour minor transient conjunctival irritation (redness) was observed in 5/6 animals from the highest dose volume group (0.1 ml). All eyes were normal within 48 hours. No other effects were reported.

Data to which reliability could not be assigned are available for the registered substance but insufficient study details were presented (Carnegie-Mellon 1976). These are included as supporting data.

Read-across justification

The registration substance and the read-across substance are structurally-related substance which belong to a small analogue group of alkoxysilanes containing thiol groups (see Section 1.4). The two substances hydrolyse to produce a common hydrolysis product, 3-(trihydroxysily)propanethiol and ethanol and methanol, respectively.

No in vivo irritation data are available for any other members of the analogue group. However, read-across from the methoxy to ethoxy analogues is supported by a large dataset for non-functional alkyl alkoxysilanes which show no differences in irritation properties between corresponding pairs of alkoxysilanes, as indicated in the table below:

Example skin and eye irritation results for pairs of alkyl alkoxysilanes

CAS Number

1185-55-3

2031-67-6

1067-25-0

2550-02-9

3069-40-7

2943-75-1

2768-02-7

78-08-0

Chemical Name

Trimethoxy(methyl)silane

Triethoxy(methyl)silane

Trimethoxypropylsilane

Triethoxypropylsilane

Trimethoxyoctylsilane

Triethoxyoctylsilane

Trimethoxyvinylsilane

Triethoxy(vinyl)silane

Molecular weight (parent)

136.22

178.31

164.28

206.36

234.41

276.5

148.24

190.32

Skin irritation

Not irritant

Not irritant

Irritant

Irritant

Irritant

Irritant

Not irritant

Not irritant

Eye irritation

Not irritant

Not irritant

Not irritant

 

Not irritant

 

Not irritant

Not irritant

 

Additional results are available in a supporting report attached in Section 13 of the IUCLID 5 dossier (PFA 2013t).


Justification for classification or non-classification

Based on the lack of effects in the available data read across from the structurally analogous 3-trimethoxysilylpropane-1-thiol (CAS 4420-74-0), no classification is required for skin or eye irritation according to Regulation (EC) No 1272/2008.