hydrolysis products of 3-(triethoxysilyl)propan-1-amine

Biodegradation in water: screening tests

Description of key information

76% oxygen consumption in 28 days (OECD 306), read across

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Additional information

There are no ready biodegradation data available for the substance hydrolysis product of 3-(triethoxysilyl)propan-1-amine >0.1 -<16% (EC no. 939-125-9). In order to fulfil the standard information requirements set out in Annex VIII, read-across from a structurally related substance (3-(triethoxysilyl)propan-1-amine, CAS no. 919-30-2), is conducted in accordance with Annex XI, 1.5, of Regulation (EC) No 1907/2006. This read across is justified as the parent material, 3-(triethoxysilyl)propan-1-amine, hydrolyses rapidly in water to form the target substance (hydrolysis product of 3-(triethoxysilyl)propan-1-amine >0.1 -<16% (EC no. 939-125-9). Therefore it can be expected that both substances have a similar behaviour under the aqueous condition during the eco- and toxicological testing. The hydrolysis product silanol and condensation products dimers, trimers and polymers of siloxanes have the similar functional group (-O-Si- or HO-Si-). Therefore, they are considered to be in one class of compounds and structural differences are not supposed to contribute to significant differences in activity, with respect to eco- and human toxicological endpoints. The other hydrolysis product is ethanol, being readily biodegradable and well characterised and not expected to have adverse effects on microorganisms.

A detailed analogue approach justification is provided in the technical dossier (Please refer to IUCLID Section 13 for further information).

Two studies investigating the biodegradability potential of 3-(triethoxysilyl)propan-1-amine (CAS no. 919-30-2) are available (Evonik 1994, 2005). The first test was conducted according to EU Method C4.A Dissolved organic carbon (DOC) Die-away test (92/69/EEC), under GLP conditions. The inoculum (non-adapted activated sludge from a sewage treatment plant) was exposed for 28 days to the test substance and biodegradation calculated based on DOC removal measurements. At the end of the experiment, the substance reached a biodegradation value of 67% and therefore, does not meet the criterion to be considered readily biodegradable (70% DOC). However, considering that within 7 days the biodegradation value for the substance was already 63% and the final value of 67%, almost reaching the pass value of 70% for readily biodegradable substances, 3-(triethoxysilyl)propan-1-amine indeed shows a potential for biodegradation in water. This estimation is supported by another test with seawater according to OECD guideline 306. This guideline is comparable to OECD 301D (closed bottle test). After 28 days the degradation was 76%. The Guidance on Information Requirements and Chemical Safety Assessment chapter 7b (ECHA 2016) states: “A result of >20% ThOD or DOC removal is indicative of potential for primary biodegradation in the marine environment, whereas a result of >60% ThOD or 70% DOC removal is indicative of potential for ultimate biodegradation in the marine environment (OECD, 2006). When a chemical attains >60% ThOD or >70% DOC removal in a biodegradability in seawater test (OECD 306), it can also be expected to fulfil the criteria for ready biodegradability.”

Therefore, 3-(triethoxysilyl)propan-1-amine (CAS no. 919-30-2) and thereby the target substance hydrolysis product of 3-(triethoxysilyl)propan-1-amine >0.1 -<16% (EC no. 939-125-9) can be regarded as readily biodegradable.