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Dimethoxydimethylsilane (CAS 1112-39-6) hydrolyses rapidly in contact with water (DT50: <0.6 h), to dimethylsilanediol and methanol. The ECHA guidance R.16 states that “for substances where hydrolytic DT50 is less than 12 h, environmental effects are likely to be attributed to the hydrolysis product rather than to the parent itself” (ECHA, 2016).

One study is available for the hydrolysis product, dimethylsilanediol, investigating the effect of the test item on soil microflora in a respiration test and a soil nitrogen transformation test. As no statistically significant inhibition was observed in both tests, dimethylsilanediol is not expected to cause any significant long-term effects when applied to agricultural soils at levels up to 300 ppm.

Methanol is considered as not harmful to the environment (OECD SIDS, 2004). Thus, methanol is not considered to contribute to the overall environmental toxicity of the target substance.

No further testing for the toxicity to terrestrial organisms is considered necessary because:

- The substance hydrolyses rapidly and its hydrolysis product has a Log Kow< 3, therefore, partitioning to the terrestrial compartment is expected to be minimal.

- The substance is used under highly controlled conditions and, therefore, exposure of soil is low.

- The risk characterisation ratio (RCR) for soil is <1 indicating a low risk for terrestrial organisms.