Registration Dossier

Ecotoxicological information

Endpoint summary

Administrative data

Description of key information

Additional information

N-[3-(trimethoxysilyl)propyl]butylamine hydrolyses rapidly in contact with water (half-life approximately 4.0 h at 25°C and pH 7), to produce N-[3-(trihydroxysilyl)propyl]butylamine and methanol. Methanol is considered non-hazardous at the concentrations at which it would be present in the studies assessed. Therefore, the hazard assessment for the environment, including sediment and soil compartments, is based on the properties of the hydrolysis product, in accordance with REACH guidance.

The registered substance is part of a group of organosilicones, the toxicity of which is determined by a non-polar narcosis mechanism of toxicity, and as such log Kowdrives toxicity. Additional information is given in a supporting report Application of Category - Analogue - QSAR for Reconsile (PFA, 2013a) attached in Section 13 of the IUCLID 5 dossier.

Measured short-term data are available for fish, invertebrates and algae for the toxicity of N-[3-(trimethoxysilyl)propyl]butylamine(CAS No. 31024-56-3).

A limit test was conducted for each of the three trophic levels. No effects were observed at the nominal test concentration of 50 mg/l for Oncorhynchus mykiss (OECD Guideline 203 Fish, Acute Toxicity Test, Springborn Smithers 2008a), of 25 mg/l for Daphnia magna (OECD Guideline 202 Daphnia sp. Acute Immobilisation Test, Springborn Smithers 2008b) and of 1 mg/l for Pseudokirchnerella subcapitata (OECD Guideline 201 Alga, Growth Inhibition Test, Springborn Smithers 2008c). The results are expressed relative to nominal test substance concentration. No effects could be detected up to the highest tested concentration but the maximum concentration used (50 mg/1 for fish, 25 mg/l for invertebrates and 1 mg/l for the algae) was well below the predicted solubility of the substance (130000 mg/l) and so does not provide an accurate representation of the likely toxicity of the substance. Therefore it was considered appropriate to read across from the structurally analogous substance, N-ethyl-3-trimethoxysilyl-2-methylpropanamine (CAS No. 227085-51-0).

READ-ACROSS JUSTIFICATION

In order to reduce animal testing read-across is proposed to fulfil up to REACH Annex IX requirements for the registered substance from substances that have similar structure and physico-chemical 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 physico-chemical properties and the structure is altered.

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

·        Read-across from N-ethyl-3-trimethoxysilyl-2-methylpropanamine (CAS No. 227085-51-0) to N-[3-(trimethoxysilyl)propyl]butylamine.

Both substances are member of an analogue group of the amino substances structural class. For the following endpoints read-acrossdata from the structural related substance N-ethyl-3-trimethoxysilyl-2-methylpropanamine were used for the assessment of the aquatic toxicity.Reliable short-term toxicity tests results with freshwater organisms were available for fish, invertebrates and algae.A limit test was conducted at a test concentration of 100 mg/l and no effects were observed at this concentration to Zebra Fish(Brachydanio rerio).Daphnia magnawere exposed to the test substance for 48 hours in a static test system. At test termination an EC50> 100 mg/l was recorded and a 72-h ErC50>100 mg/l and NOEC of 22 mg/l were determined in a guideline test conducted according to GLP for the freshwater algaeScenedesmus suspicatus.

·        Considerations on the non-silanol hydrolysis products:

Methanol is well characterised in the public domain literature and is not hazardous at the concentrations relevant to the studies; the short-term EC50and LC50values for this substance is in excess of 1000 mg/l (OECD2004a - SIDS for methanol).

 

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

Chemical Name

N-[3-(trimethoxysilyl)propyl]butylamine

N-ethyl-3-trimethoxysilyl-2-methylpropanamine

CAS Number

31024-56-3

227085-51-0

Si hydrolysis product

N-[3-(trihydroxysilyl)propyl]butylamine

N-ethyl-3-trihydroxysilyl-2-methylpropanamine

Molecular weight (parent)

235.40

221,37

Molecular weight (hydrolysis product)

193.32

179.29

log Kow(parent)

Log Kow 2.2 (QSAR)

Log Kow 1.6 (QSAR)

log Kow(silanol hydrolysis product)

Log Kow -0.9 (QSAR)

Log Kow -1.48 (QSAR)

Water sol (parent)

1.3E+04 mg/l at 20°C (QSAR)

6.98E+04 04 mg/l at 20°C (QSAR)

Water sol (silanol hydrolysis product))

1E+06 mg/l at 20°C (QSAR)

1E+06 mg/l at 20°C (QSAR)

Vapour pressure (parent)

0.76 Pa at 25°C (QSAR)

14.4 Pa at 25°C

Vapour pressure (hydrolysis product)

1.2E-05 Pa at 25°C (QSAR)

5.26E-005 Pa at 25°C (QSAR)

Hydrolysis t1/2at pH 7 and 20°C-25°C

4.0 h

4.7 h

Hydrolysis t1/2at pH 4 and 25°C

0.2 h

0.3h

Hydrolysis t1/2at pH 9 and 25°C

0.07 h

n/a

Short-term toxicity to fish (LC50)

> 50 mg/l(highest tested concentration)

> 100 mg/l

Short-term toxicity to aquatic invertebrates (EC50)

> 25mg/l(highest tested concentration)

> 100 mg/l

Algal inhibition (ErC50and NOEC)

> 1 mg/l(highest tested concentration)

ErC50> 100 mg/l

NOEC of 22 mg/l

 

Long-term toxicity to aquatic invertebrates (NOEC)

n/a

n/a