N-[3-(dimethoxymethylsilyl)-2-methylpropyl]ethylenediamine

Endpoint summary

Additional information

The substance is subject to rapid hydrolysis under the conditions of aquatic toxicity tests and it is therefore likely that exposure will have been to its hydrolysis products. Methanol is non-toxic to aquatic organisms at the concentrations it would be found at in the tests reported below.

READ-ACROSS JUSTIFICATION

In order to reduce animal testing read-across is proposed to fulfill up to REACH Annex IX requirements for the registered substance from substances that have similar structure and physicochemical properties. Ecotoxicological studies are conducted in aquatic medium or in moist environments; therefore the hydrolysis rate of the substance is particularly important since after hydrolysis occurs the resulting product has different physicochemical properties and structure.

In moist medium, N-[3-(dimethoxymethylsilyl) -2-methylpropyl]ethylenediaminehydrolyses very rapidly (half-life 15 min at room temperature and pH 7) to N-[3-(dihydroxymethylsilyl) -2-methylpropyl]ethylenediamine.

N-[3-(dihydroxymethylsilyl) -2-methylpropyl]ethylenediamine a silanetriol with log K_ow of -1.0. The non-silanol hydrolysis product methanol is not expected to contribute to any adverse effects at the relevant dose levels. This is discussed further below.

In the following paragraphs the read-across approach for N-[3-(dimethoxymethylsilyl) -2-methylpropyl]ethylenediamine is assessed for each surrogate substance taking into account structure, hydrolysis rate and physico-chemical properties.

·             Read-across from N-(3-(trimethoxysilyl)propyl)ethylenediamine (CAS 1760-24-3) to N-[3-(dimethoxymethylsilyl) -2-methylpropyl]ethylenediamine (CAS 23410-40-4)

Data are available for short-term toxicity of the registered substance to fish, aquatic invertebrates and algae. A 96 hours LC₅₀ value of 200 ppm has been determined for effects on mortality of Lepomis macrochirus.

A 48-h EC₅₀ value of 81 mg/l has been determined for effects on mobility of Daphnia magna. A 96-hour EC₅₀ value of 8.8 mg/l and NOEC of 3.1 mg/l have been determined for effects on growth rate of Pseudokirchneriella subcapitata.

A 21-day NOEC of ≥1 ppm (≥1 mg/l) has been determined for the effects of the test substance on survival and reproduction of Daphnia magna in a long-term test. A data waiver is applicable for long-term toxicity to fish.

The aquatic toxicity studies were conducted at pH 8 and above in many cases. The neutral form of the amine, i. e. the un-ionised form, is more toxic than the ionised form. This pattern of toxicity is consistent with ammonia, where the un-ionised form, NH₃, is more toxic than the ionised form, NH₄. The difference in toxicity is due to bioavailability, where the un-ionised form can cross cell membranes more readily than the ionised form. Therefore, for waters having a pH closer to 7 it is likely that the study results overestimate the toxicity of the registered substance.

·   Considerations on the non-silanol hydrolysis product:

Methanol and is well characterised in the public domain literature and are not hazardous at the concentrations relevant to the studies; the short-term EC₅₀ and LC₅₀ values for methanol are in excess of 1000 mg/l (OECD 2004a - SIDS for methanol). Therefore, at the loading rates experienced in these tests it is unlikely that the presence of either would significantly affect the results of the tests.