Registration Dossier

Environmental fate & pathways

Endpoint summary

Administrative data

Description of key information

Additional information

MS-Silane is a UVCB comprised of 12 chlorosilanes and 1 non-chlorinated silane. Dichloro(dimethyl)silane is the most prevalent substance and accounts for 20 -35% of MS-Silane. It hydrolyses rapidly under environmentally relevant conditions to dimethylsilanediol and hydrogen chloride (HCL) with t1/2of <0.3 min at 1.5oC. Chlorotrimethylsilane makes up 0-15% of MS-Silane and hydrolyses rapidly under environmentally relevant conditions to trimethylsilanediol and hydrogen chloride (HCL) with t1/2of <0.2 min at 1.5oC. Data are also available for similar chlorosilanes: trichloromethyl (t1/2of <0.2 min at 1.5oC), tetrachlorodimethyl (t1/2of <0.2 min at 1.5oC). 

Chlorosilanes in general exhibit rapid hydrolysis due to the size of the silica atom and the nature of the bond. Therefore, the environmental fate properties of the silanols will be discussed as exposure to the environment to the hydrolysis products rather than the parent substance. The environmental properties of HCL will not be discussed as it will be buffered to various extents, dependent on the buffering capacity of different compartments in the environment. The predicted environmental concentrations of MS-Silane indicate that the buffering capacity of the environment is sufficient.  At pH 7 it is found as water and the chloride ion, which do not need to be further discussed.