Dichloro(methyl)(vinyl)silane

Endpoint summary

Key value for chemical safety assessment

Effects on fertility

Effect on fertility: via oral route

Dose descriptor:

NOAEL

250 mg/kg bw/day

Additional information

There are no reproductive toxicity data on dichloro(methyl)(vinyl)silane or its hydrolysis product, methyl(vinyl)silanediol, so good quality data for the related substance trimethoxyvinylsilane have been used to assess the reproductive toxicity of dichloro(methyl)(vinyl)silane.

Dichloro(methyl)(vinyl)silane hydrolyses rapidly in contact with water (half-life <1 minute at pH 7), generating HCl and methyl(vinyl)silanediol. Trimethoxy(vinyl)silane (CAS 2768 -02 -7) hydrolyses more slowly at pH 7 (half-life ca.0.2 hours), but under acidic conditions such as in the stomach following ingestion, much more rapid hydrolysis can be expected based on experience with other methoxysilanes. The relevant hydrolysis products are methanol and vinylsilanetriol. The silanol hydrolysis products for the registered substance and the surrogate substance are therefore similar in chemical structure, the only difference being the replacement of -CH₃with an extra Si-OH group. Both have high water solubility and very low log K_ow(log K_ow-0.05 and -2.0, respectively). Acute oral toxicity data for other related silanols [e.g. dimethylsilanediol and methylsilanetriol (as the potassium salt)] indicate there are no significant toxicological differences between silanediol and silanetriol analogues. Data obtained via the oral route for trimethoxyvinylsilane are therefore considered appropriate for read-across to trichloro(methyl)(vinyl)silane.

Short description of key information:
There are no repeated dose toxicity data on dichloro(methyl)(vinyl)silane or its hydrolysis product, methyl(vinyl)silanediol, so good quality data for the related substance trimethoxyvinylsilane have been used to assess the reproductive toxicity of dichloro(methyl)(vinyl)silane.

In an oral OECD 422 study ( Hashima Labs, no date) in rats, trimethoxyvinylsilane was administered by gavage at doses up to 1000 mg/kg bw/day, and no effects on reproductive parameters were observed for males up to 1000 mg/kg. For females, a low number of oestrous cases was reported for the high dose groups.. The NOAEL was therefore 250 mg/kg bw/day for females.

Effects on developmental toxicity

Description of key information

There are no repeated dose toxicity data on dichloro(methyl)(vinyl)silane or its hydrolysis product, methyl(vinyl)silanediol, so good quality data for the related substance trimethoxyvinylsilane have been used to assess the developmental toxicity of dichloro(methyl)(vinyl)silane.
Exposure of pregnant CD® rats during organogenesis to trimethoxyvinylsilane by inhalation resulted in slight maternal toxicity at 100 and 300 ppm as evidenced by concentration-dependent reductions in gestational body weight gain (gd 6-9).  There was evidence of slightly delayed development in fetuses from the 300 ppm group as indicated by delayed ossification in several skeletal districts.  No exposure-related embryotoxicity or teratogenicity was observed in this study (BRRC, 1993). The observed variations are not considered toxicological, particularly in the presence of maternal toxicity, and therefore the NOAEC is 300 ppm (approx. 1730 mg/m3). 

Effect on developmental toxicity: via inhalation route

Dose descriptor:

NOAEC

1 730 mg/m³

Additional information

There are no developmental toxicity data on dichloro(methyl)(vinyl)silane or its hydrolysis product, methyl(vinyl)silanediol, so good quality data for the related substance trimethoxy(vinyl)silane have been used to assess the developmental toxicity of dichloro(methyl)(vinyl)silane.

For the inhalation route, the hydrolysis rate of trimethoxy(viny)lsilane in the respiratory tract and lungs is unknown, but is likely to be slower than that of dichloro(methyl)(vinyl)silane. For dichloro(methyl)(vinyl)silane, the species absorbed following inhalation exposure are mainly hydrolysis products, whereas for trimethoxyvinylsilane, absorption of the parent substance may be more significant. Trimethoxyvinylsilane has a higher log K_owvalue (1.08) therefore the proportion of inhaled material which is systemically absorbed is likely to be greater than for dichloro(methyl)(vinyl)silane. Nevertheless, in the absence of other data, the inhalatory NOAEL for trimethoxy(vinyl)silane is considered to represent a reasonable worst-case for read-across to dichloro(methyl)(vinyl)silane.

The HPV SIAR for methanol concludes the following: " High concentrations of methanol may cause specific malformations in organogenesis in pre-natal development of rodents. In the rat, the NOAEL (inhalation for 7 hours per day) was determined to be 6.5 mg/l, based on observance of malformations as well as slight decreased body weights. This corresponds to a maternal methanol blood level of 1000 to 2170 mg/l". Therefore the variations observed when trimethoxyvinylsilane was inhaled are unlikely to be due to methanol.

Justification for classification or non-classification

The available data on read-across substance trimethoxyvinylsilane suggest that dichloro(methyl)(vinyl)silane does not require classification for effects on reproduction or development.