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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

Biodegradation in water, screening tests: The hydrolysis product 3-(trihydroxysilyl)propiononitrile is not expected to undergo any significant biodegradation.

Key value for chemical safety assessment

Additional information

No data are available for the submission substance, 3-(triethoxysilyl)propiononitrile. 3-(triethoxysilyl)propiononitrile

hydrolyses in contact with water (half-life 6.5 hours, measured) to give 3-(trihydroxysilyl)propiononitrile and ethanol.

A summary report of a ready biodegradation study is available for the related substance 3-(trimethoxysilyl)propiononitrile. It is considered appropriate to read across the ready biodegradation result for 3-(trimethoxysilyl)propiononitrile because the hydrolysis half-life (1.8 hrs, pH 7, predicted) indicates that, under conditions relevant to ready biodegradation assessment, it will hydrolyse to 3-(trihydroxysilyl)propiononitrile (3 carbons) and methanol (3 carbons). This is selected as the key study.

A biodegradation rate of 61% in 20 days is reported for 3-(trimethoxysilyl)propiononitrile (hydrolysis products: 3-(trihydroxysilyl)propiononitrile and methanol).

Methanol biodegrades rapidly and therefore the majority of the degradation observed for the test substance is considered to be the result of the biodegradation of methanol. Based on the 1:1 relation of the hydrolysis products with respect to the number of carbons,3-(trihydroxysilyl)propiononitrile is not expected to undergo any significant biodegradation.

This is supported by evidence that within a category of small molecule silicon-dominated organosilicon compounds, without reactive functional groups in the side chain, there is no evidence of any significant biodegradation in ready biodegradation tests (Data gap filling report for ready biodegradability of silicon-dominated substances PFA.151.004.022A).

The other hydrolysis product of the submission substance, ethanol, is expected to biodegrade rapidly (see Price 1974).