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Description of key information

There are no repeated dose oral, inhalation or dermal studies available for 1,2 -bis[dichloro(methyl)silyl]ethane. Data waivers are in place for oral and dermal repeated dose toxicity endpoints (see attachment to data waiver for repeated dose toxicity: oral).

 

Since the local corrosive effects of chlorosilanes would be significant, valid oral or inhalation studies according to the relevant guidelines are technically not feasible. It is also unlikely that any systemic effects would be observed at doses made sufficiently low to prevent the known corrosive effects and/or distress in the test species. Indeed, ECHA’s Executive Director made the following statement in his decision (No. ED/49/2015) for trichlorosilane “ECHA notes that the Contested Decision should not have provided the option of carrying out the PNDT study on the registered substance, which is corrosive and consequently can only be tested at very low concentrations. In a PNDT study, which normally requires high systematic availability of the tested substance, the very low concentrations would almost certainly lead to a negative result”.

 

To support this conclusion a 28-day inhalation study with another chlorosilane, dichloro(dimethyl)silane (CAS 75-78-5, WIL, 2014) is used to demonstrate that local effects are dominated by generation of the hydrolysis product, HCl, and that there are no adverse systemic effects.

 

In a well conducted 90-day gas inhalation study (Toxigenics, 1984) the systemic NOAEC for hydrogen chloride was 20 ppm based on decreased body weight following exposure to 50 ppm (6 hours/day, 5 days/week) in rats and mice. The main adverse findings related to irritant/corrosive effects on the nasal turbinates in mice, which was observed with a LOAEC of 10 ppm.

A good quality 90-day repeated inhalation study for hydrogen chloride has been used to assess the local effects of 1,2 -bis[dichloro(methyl)silyl]ethane

. In a 90-day repeated inhalation study with HCl, no serious adverse systemic effects were observed in rats and mice exposed up to 50 ppm (approximately 70 mg/m3) for 6 hours per day, 5 days per week (Toxigenics, 1983). The only significant adverse finding relating to systemic toxicity was decreased body weight at the highest dose level. Local effects on the nasal turbinates of mice were observed at all dose levels tested (10, 20 and 50 ppm). Testing with HCl at higher test concentrations is neither ethically nor technically feasible since severe corrosive effects would lead to discomfort and distress in the test animals. The author of this CSR considers that the apparent systemic effects at 50 ppm in the study were most likely secondary to local corrosive effects at this dose level.

Following uptake of HCl, hydrogen and chloride ions from will enter the body’s natural homeostatic processes and significant systemic effects are unlikely.

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Endpoint conclusion
Endpoint conclusion:
no study available

Repeated dose toxicity: inhalation - systemic effects

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed
Dose descriptor:
NOAEC
132 mg/m³
Study duration:
subacute
Species:
rat

Repeated dose toxicity: inhalation - local effects

Endpoint conclusion
Endpoint conclusion:
adverse effect observed
Dose descriptor:
LOAEC
15 mg/m³
Study duration:
subchronic
Species:
rat

Repeated dose toxicity: dermal - systemic effects

Endpoint conclusion
Endpoint conclusion:
no study available

Repeated dose toxicity: dermal - local effects

Endpoint conclusion
Endpoint conclusion:
no study available

Additional information

Justification for classification or non-classification

The available data indicate that 1,2 -bis[dichloro(methyl)silyl]ethane does not need to be classified for specific target organ toxicity according to Regulation (EC) No 1272/2008.