N-[3-(triethoxysilyl)propyl]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. Ethanol 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 VIII 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 (triethoxysilyl) propyl]ethylenediamine (CAS 5089-72-5) hydrolyses rapidly (half-life 165 min at room temperature and pH 7) to N-[3-(trihydroxysilyl) propyl]ethylenediamine.

The non-silanol hydrolysis product ethanol 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 (triethoxysilyl) propyl]ethylenediamine (CAS 5089-72-5) 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 (triethoxysilyl) propyl]ethylenediamine (CAS 5089-72-5)

Both, the registered substance and the read across substance N-(3-(trimethoxysilyl) propyl) ethylenediamine hydrolyse rapidly and have the same hydrolysis product. The only difference is the alcohol which is ethanol for the registered substance and methanol for the read across substance. Apart from the same hydrolysis product, other phys. -chem. data suppose that similar behaviour can also be expected for the parent constituents, as their molecular weights and log Kow are comparable.

Data are available for short-term toxicity of the read across substance to fish, aquatic invertebrates and algae.

A 96 hours LC50 value of 597 mg/L has been determined for effects on mortality of Brachidanio rerio.

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.

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 products:

Methanol and ethanol are 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 these substances are in excess of 1000 mg/l (OECD, 2004a - SIDS for methanol, CAS 67-56-1, OECD, 2004b - SIDS for ethanol, CAS 64-17-5).

Table7.1.1Key physicochemical parameters and ectoxicological data for the registered and surrogate substances.

CAS Number	5089-72-5	1760-24-3
Chemical Name	N-[3-(triethoxysilyl)propyl]ethylenediamine	N-(3-(trimethoxysilyl)propyl)ethylenediamine
Si hydrolysis product	N-[3-(trihydroxysilyl)propyl]ethylenediamine	N-[3-(trihydroxysilyl)propyl]ethylenediamine
Molecular weight (parent)	264.44	222.36
Molecular weight (silanol hydrolysis product)	180.28	180.28
log Kow(parent)	Log Kow 1.2 (QSAR)	not applicable
log Kow(silanol hydrolysis product)	Log Kow -3.4 (QSAR)	Log Kow -3.4 (QSAR)
Water sol (parent)	2.4E+05 mg/l at 20-25°C (QSAR)	Not relevant
Water sol (silanol hydrolysis product))	1.0E+06 mg/l at 20-25°C (QSAR)	1.0E+06 mg/l at 20-25°C (QSAR)
Vapour pressure (parent)	3.0E-02 Pa at 25°C (QSAR)	0.3 - 0.4 Pa at 20°C (measured)
Vapour pressure (hydrolysis product)	6.8E-06 Pa at 25°C (QSAR)	6.8E-06 Pa at 25°C (QSAR)
Hydrolysis t1/2 at pH 7 and 25°C	165 min	0.025 h
Hydrolysis t1/2 at pH 4 and 25°C	15 min	0.1 h
Hydrolysis t1/2 at pH 9 and 25°C	14 min	Not reported
Short-term toxicity to fish (LC50)	-	LC50 (96 h): 597 mg/l mortality Danio rerio
Short-term toxicity to aquatic invertebrates (EC50)	EC50 (48 h): 23 mg/l mobility Daphnia magna	EC50 (48 h): 81 mg/l mobility Daphnia magna
Algal inhibition (ErC50 and NOEC)	-	(72-h) EC50: 8.8 mg/l growth rate Pseudokirchneriella subcapitata,reliability 2 (72-h) NOEC: 3.1 mg/l growth rate Pseudokirchneriella subcapitata,reliability 2
Long-term toxicity to aquatic invertebrates (NOEC)	-	(21-day) NOEC: ≥1 ppm survival and reproduction Daphnia magna

 

References:

OECD (2004a): SIDS Initial Assessment Report for SIAM 19, Berlin, Germany, 18-20 October 2004, Methanol, CAS 67-56-1.

OECD (2004b): SIDS Initial Assessment Report for SIAM 19, Berlin, Germany, 19-22 October 2004, Ethanol, CAS 64-17-5.