Registration Dossier

Environmental fate & pathways

Endpoint summary

Administrative data

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Additional information

L5 is expected to hydrolyse with a half-life 30.3 days at pH 7 and 25°C (read-across from structurally-related substance L4).

A half-life of 9 days for reaction with hydroxyl radicals in air has been calculated for L5. Phototransformation in water and soil are not expected to be significant removal processes for L5.

Biodegradation of 0% in 28 days has been read-across from a structurally-related substance L3.

Data are available for degradation in soil simulation testing, read across from the structurally-related substance L4. Half-lives (closed tubes) of 3.7 d at 32% RH and at 22°C to 106.6 d at 100% RH and at 22°C (estimated to be 42 days when corrected for amount of L4 predicted to be in headspace at this RH) have been determined for Michigan Londo soil.

The main degradation products were dimethylsilanediol and trimethylsilanol. In open systems, the volatilisation of L4 was the predominant process for removal of L4 from soil at 100% RH, with a volatilisation half-life of 4 days, almost 10 times faster than the degradation of L4 at the same moisture level in the closed system.

In exposure modelling (EUSES 2.1.2) a half-life value of 10 days at 20°C will be used, based on the value of 10 d (#1) (92% RH 22°C Closed). This is an estimate. The exact value is not significant in respect of the overall risk characterisation for soil.

Data are available for degradation in sediment simulation testing, read across from the structurally-related substance HMDS. Whilst the degradation of L5 may be expected to be slower than HMDS, since the degradation half-life for HMDS leads to a conclusion of ‘vP’ for the sediment compartment based on a worst-case half-life of 192 d at 12 °C, it is reasonable to read-across the conclusion of ‘vP’ in sediment for L5.

Degradation rate in water:

Hydrolysis half-life 30.3d at pH 7 and 25°C (read-across). No significant biodegradation (read-across)

Degradation rate in sediment:

Half-life in sediment: >192 d at 12 °C (based on read-across)

Degradation rate in soil:

Michigan Londo soil, half-lives (closed tubes) 3.7 d at 32% RH and at 22°C to 106.6 d at 100% RH and at 22°C (estimated to be 42 days when corrected for amount of L4 predicted to be in headspace at this RH) (read-across)

In exposure modelling (EUSES 2.1.2) a half-life value of 10 days at 20°C will be used.

Degradation rate in air:

Rate constant for reaction with OH radicals in air: 1.8 E-12 cm3molecule-1second-1 (half-life 9 days) (Calculated)