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Administrative data

Description of key information

In a combined oral gavage OECD 422 study with tris(2-methoxyethoxy)vinylsilane in rats there were no test article-related effects on mean body weights, body weight gains or food consumption in the toxicity phase females. Haematological effects were observed in both sexes in the 250 mg/kg/day toxicity phase group. These findings correlated with the microscopic finding of hypocellularity in the sternal bone marrow, in which aggregates of mature granulocytes were absent. Serum chemistry parameters in the 250 mg/kg/day toxicity phase male and female groups were observed. Test article-related macroscopic changes, microscopic changes and/or reductions in organ weights were observed in the 75 mg/kg/day group males and the 250 mg/kg/day group males and females. The NOAEL for tris(2-methoxyethoxy)vinylsilane for male systemic toxicity is 25 mg/kg/day. Based on effects on hematology and serum chemistry parameters and effects on lymphoid tissues for females at 250 mg/kg/day, which were similar to the effects noted for males, the NOAEL for female systemic toxicity is 75 mg/kg/day.
The effects on hematology parameters included decreased blood cell counts and changes in the granulocyte and erythroid series. Serum chemistry showed decreased albumin, protein and globulin.
In a 14-week whole-body inhalation study (Dodd, DE and WJ Kintigh) in which rats were exposed to concentration of the read-across substance trimethoxyvinylsilane up to 400 ppm, a concentration of 100 ppm was a LOAEC (effects included decreased urine osmolality and sodium, potassium and chloride concentrations in males and slight decrease in body weight and body weight gain in females), and 10 ppm (58 mg/m3) was a NOAEC.
No reliable data are available for the dermal route.

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Endpoint conclusion
Dose descriptor:
NOAEL
25 mg/kg bw/day
Study duration:
subacute
Species:
rat

Additional information

The key study for repeated dose toxicity via the oral route is the only available guideline study for the submission substance for this endpoint. The test was conducted in accordance with OECD 422 and in compliance with GLP, and was therefore assigned Reliability 1.

The subchronic inhalation toxicity endpoint for tris(2-methoxyethoxy) vinylsilane CAS 1067-53-4 is read across from trimethoxyvinylsilane CAS 2768-02-7, for which a subchronic inhalation study with reliability 1 is available.

The read-across is justified on the grounds that both substances yield the same hydrolysis product, vinylsilanetriol. Both substances are rapidly hydrolysed in contact with water; the hydrolysis half-lives are 0.2 h intrimethoxyvinylsilane versus 1 h in tris (2-methoxyethoxy)vinylsilane.

 

The other hydrolysis products are methoxyethanol,CAS 109-86-4, for tris(2-methoxyethoxy)vinylsilane and methanol for trimethoxyvinylsilane. Methoxyethanol is a known to be toxic to reproduction, with both developmental and fertility effects in both male and female rodents. Data for reproductive and developmental toxicity are discussed in section 5.9; it is proposed to classify tris(2-methoxyethoxy)vinylsilane as Repr. Cat. 3 (R62) according to EU Directive 67/548/EEC and Repro. Cat. 2, H361f according to Regulation 1272/2008. Subacute toxicity endpoints are not considered to be affected by the fertility toxic properties. Methanol has no significant toxicological effects in rats and rabbits used in standard laboratory tests.

For the derivation of DNELs the original oral OECD 422 study is used as a worst case. The less severe DNELs derived from thetrimethoxyvinylsilane study are considered further evidence that the silanol hydrolysis product does not exhibit further toxicological effects in a subchronic study. This is illustrated in the table below.

Table 5.8: DNELs derived from the inhalation studying of trimethoxyvinylsilane and those derived from the subacute study of tris(2-methoxyethoxy) vinylsilane:

Trimethoxyvinylsilane

Tris(2-methoxyethoxy) vinylsilane

Workers

DNEL (long-term, inhalation): 4.9 mg/m3

DNEL (long-term, inhalation): 1.2 mg/m3

DNEL (long-term, dermal): 0.69 mg/kg/day

DNEL (long-term, dermal): 0.17 mg/kg/day

Consumers

DNEL (long-term, inhalation): 1.04 mg/m3

DNEL (long-term, inhalation): 0.37 mg/m3

DNEL (long-term, dermal): 0.3 mg/kg/day

DNEL (long-term, dermal): 0.10 mg/kg/day

DNEL (long-term, oral): 0.3 mg/kg/day

DNEL (long-term, oral): 0.10 mg/kg/day

 

Justification for classification or non-classification

Based on the available OECD 422 study, there is no proposal to classify tris(2 -methoxyethoxy)vinylsilane for specific target organ toxicity following repeated exposure. Classification for reproductive effects is discussed in Section 7.8.