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Administrative data

Description of key information

Acute oral, dermal and inhalation toxicity data are available for constituents of amino functional alkoxysilanes, and a related substance, as described in the discussion below.

Key value for chemical safety assessment

Acute toxicity: via oral route

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed

Acute toxicity: via inhalation route

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed

Acute toxicity: via dermal route

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed

Additional information

Amino functional alkoxysilanes is a multiconstituent substance which is the reaction mass of tri-(methoxy/ethoxy) methylsilane and amino-functional (methoxy/ethoxy)-silanes. The identity and abundance of the constituents have been determined by GC analysis. A detailed description of the composition can be found in Section 1.2 of the Chemical Safety Report; in broad terms the composition can be described as shown below:

 

General name and structure

Canonical SMILES

Range

A

Tri-(methoxy/ethoxy)-methylsilane

 

Constituent A1:CO[Si](OC)(OC)C

Constituent A2:CCO[Si](OC)(OC)C

Constituent A3:CCO[Si](OCC)(OC)C

50-80%

B

Octa-alkoxy-methyl-aminotrialkylsilane

 

Constituent B1

CO[Si](OC(COCCC[Si](OC)(OC)OC)CNCCC[Si](OC)(OC)OC)(OC)C

Constituent B2

CCO[Si](CCCNCC(O[Si](OC)(OC)C)COCCC[Si](OC)(OC)OC)(OC)OC

Constituent B3

CCO[Si](OCC)(CCCNCC(O[Si](OC)(OC)C)COCCC[Si](OC)(OC)OC)OC

Constituent B4

CCO[Si](OCC)(OCC)CCCNCC(O[Si](OC)(OC)C)COCCC[Si](OC)(OC)OC

Constituent B5

CCO[Si](CCCOCC(O[Si](OC)(OC)C)CNCCC[Si](OCC)(OCC)OCC)(OC)OC

Constituent B6

CCO[Si](OCC)(CCCOCC(O[Si](OC)(OC)C)CNCCC[Si](OCC)(OCC)OCC)OC

Constituent B7

CCO[Si](OCC)(OCC)CCCNCC(O[Si](OC)(OC)C)COCCC[Si](OCC)(OCC)OCC

5-20%

C

Cyclo-silylalkylamine

 

Constituent C1

CO[Si](CCCOCC1CNCCC[Si](O1)(OC)OC)(OC)OC

Constituent C2

CCO[Si]1(OC)CCCNCC(O1)COCCC[Si](OC)(OC)OC

Constituent C3

CCO[Si]1(CCCNCC(O1)COCCC[Si](OC)(OC)OC)OCC

Constituent C4

CCO[Si](CCCOCC1CNCCC[Si](O1)(OCC)OCC)(OC)OC

Constituent C5

CCO[Si](OCC)(CCCOCC1CNCCC[Si](O1)(OCC)OCC)OC

5-20%

D

(3-aminopropyl)tri(methoxy/ethoxy)silane

 

Constituent D1:NCCC[Si](OC)(OC)OC

Constituent D2:NCCC[Si](OCC)(OC)OC

Constituent D3 :NCCC[Si](OCC)(OCC)OC

Constituent D4 :NCCC[Si](OCC)(OCC)OCC

0-10%

Impurities

Higher molecular weight alkoxy organosilicon Impurities

No individual impurities present above 1%.

Mol Wt 600-930 g/mol

0-10%

 

Smaller alkoxysilane impurities

No individual impurities present above 1%.

Mol Wt 120-272 g/mol

0-5%

 

Methanol

 

0-7%

 

Ethanol

 

0-2%

TOTAL

 

 

100%

No acute toxicity data are available for the registered substance itself. However, data are available for a number of the substances that are representative of Constituents A and D, and it is therefore possible to determine the appropriate classification of the substance based on the rules for mixtures specified in Regulation (EC) No 1272/2008.

The available data are summarised in the table below, and are then discussed in more detail:

Constituent identity

Structure

Acute oral LD50(mg/kg bw)

Acute dermal LD50(mg/kg bw)

Acute inhalation LC50(mg/l)

Trimethoxy(methyl) silane

MeSi(OMe)3

11685

>9500

>42.1

3-aminopropyl(trimethoxy)silane

(MeO)3Si(CH2)3NH2

3030

11300

-

Triethoxy(methyl) silane

 

MeSi(OEt)3

>2007

>2007

13.5

3-aminopropyl(triethoxy)silane

(EtO)3Si(CH2)3NH2

1490-2690

4080

-

N-ethyl-3-trimethoxysilyl-2-methyl-propanamine

(MeO)3SiCH2HC2(CH2)CH2NHCH2CH3

>2000

>2000

-

 

Trimethoxy(methyl) silane (CAS 1185-55-3)

The key study for trimethoxy(methyl) silane (CAS 1185-55-3) for acute oral toxicity in rat reports an LD50 value of 11685 mg/kg in rat (Mellon, 1963). Clinical signs of toxicity were sluggishness and unsteady gait post-dosing. At necropsy, gross examination revealed congested lungs, mottled livers with prominent acini and some haemorrhage and congestion of the gastrointestinal tract.

The key study for trimethoxy(methyl) silane (CAS 1185-55-3) for acute inhalation toxicity reports an LC50 value of >42.1 mg/l (Dow Corning Corporation, 2006). Clinical signs were urine staining, discoloured urine, faecal staining, head and muzzle soiling. Necropsy findings included urinary bladder calculi and kidney foci in both sexes, an enlarged kidney in one male, and abscessed prostrate glands in two males.

The key study for trimethoxy(methyl) silane (CAS 1185-55-3) for acute dermal toxicity reports an LD50 of >9500 mg/kg (Mellon, 1963). There were no clinical signs of toxicity and no abnormalities were detected at necropsy.

The substance is a major part of Constituents A. It also shares a common silanol hydrolysis product with the trisilane constituents (Constituents B) of the registered substance, methylsilanetriol.

3-Aminopropyl(triethoxy)silane (CAS 919-30-2)

The key acute oral study for 3-aminopropyl(triethoxy)silane (CAS 919-30-2), conducted in a manner similar to (the now deleted) OECD 401, involved gavage administration of one of three doses of the neat material to groups male and female rats. LD50 values of 2.83 and 1.57 ml/kg bw were reported for males and females, respectively (equivalent to 2.69 and 1.49 g/kg bw). Gross and microscopic examination revealed kidney damage, particularly in those that succumbed (BRRC, 1989).

The key inhalation study for 3-aminopropyl(triethoxy)silane (CAS 919-30-2) was conducted in a manner similar to OECD 403 (limit test). No overt toxicity was detected in rats of either sex exposed (whole body, 6 h) to the neat substantially saturated vapour. Mean measured concentrations of the test material were 5 and 16 ppm (around 45 and 144 mg/m3) for males and females, respectively; the corresponding concentrations of ethanol were 380 and 490 ppm (BRRC, 1982).

In the key acute dermal study for 3-aminopropyl(triethoxy)silane (CAS 919-30-2), using a method similar to OECD 402, the skin of male and female rabbits was in occluded 24-h contact with one of four doses. An LD50 of 4.29 ml/kg bw (4.08 g/kg bw) was reported with some evidence of overt toxicity at the lowest tested dose of 1 ml/kg bw (BRRC, 1989).

The substance is a minor constituent of the registered substance (Constituents D) and also shares the same silanol hydrolysis product as the other amino alkoxysilane constituents (Constituents D), 3-aminopropylsilanetriol.

3-(Trimethoxysilyl)propylamine (CAS 13822-56-5)

In the key acute oral toxicity study (BRRC, 1980) for 3-(trimethoxysilyl) propylamine, an LD50 value 2.97 ml/kg was determined for rats in a study that was carried out according to a protocol that was similar to OECD 401 but was not compliant with GLP. Clinical signs of toxicity included sluggishness and unsteady gait. Necropsy of animals that died during the study revealed purple-coloured glandular portions of the stomach. Based on a relative density of 1.02, the LD50 was ca. 3030 mg/kg.

In the key acute dermal toxicity study (BRRC, 1980) for 3-(trimethoxysilyl) propylamine, an LD50 value of 11.3 ml/kg was determined for rats in a study that was carried out according to a protocol that was similar to OECD 402 but was not compliant with GLP. No clinical signs of toxicity were reported, but severe local effects were observed at the higher dose levels of 8 and 16 ml/kg. In fatalities, necropsy findings were discoloured liver (mottled red and tan, white spots) and kidneys (tan). In survivors, discoloured livers (dark red) and kidneys (mottled tan and red). Based on a relative density of 1.02, the LD50 was ca. 11,526 mg/kg.

The substance is a constituent of the registered substance (Constituents D) and also shares the same silanol hydrolysis product as the other amino alkoxysilane constituents (Constituents D), 3-aminopropylsilanetriol.

Triethoxy(methyl)silane (CAS 2031-67-6)

The acute oral toxicity study conducted in compliance with GLP and according to the now deleted OECD TG 401, reports an LD50 value of >2007 mg/kg bw for triethoxy(methyl) silane. There were no mortalities or marked systemic effect in rats at the limit dose of 2007 mg/kg bw (Hazleton France, 1995a).

The key acute inhalation toxicity study which was conducted in compliance with GLP and according to OECD TG 403 reports an LC50 of 13500 mg/m³ for triethoxy(methyl) silane vapour in rats after 4 hours. One animal from a total of ten died. The LC50was reported to be about 13.5 mg/l (13500 mg/m³) but would appear to be greater than this value (Hoechst, AG 1991). Ataxia, irregular respiration, stupor, altered gait, prostration, tonic convulsions, trembling and reduced spontaneous activity were seen in both sexes during the 14-day observation period. Gross pathological examination reports dark red, patchy lungs.

The key acute dermal toxicity study which was conducted in compliance with GLP and according to OECD TG 402, reports an LD50 value of >2007 mg/kg bw for triethoxy(methyl) silane. There were no mortalities or marked systemic effect in rats at the limit dose of 2007 mg/kg bw (24 hour exposure) (Hazelton France, 1992b).

The substance shares a common silanol hydrolysis product with the trisilane constituents (Constituent B) of the registered substance, methylsilanetriol.

N-ethyl-3-trimethoxysilyl-2-methyl-propanamine (CAS 227085-51-0)

Acute toxicity data are also available for N-ethyl-3-trimethoxysilyl-2-methyl-propanamine. Although not one of the name constituents, this substance is of relevance for the assessment since it shares the same ultimate silanol hydrolysis product as the trisilane and cyclo-trisilane constituents of the registered substance, N-ethyl-3-trihydroxysilyl-2-methylpropanamine (Constituents B and C). An acute oral LD50 of >2000 mg/kg bw (RCC 2001a) and acute dermal LD50 of >2000 mg/kg bw (RCC 2001b) are reported in reliable studies, conducted according to current OECD guidelines and under GLP.

The substance is relevant as it shares a silanol hydrolysis product with the trisilane constituents (Constituents B).

Conclusion for acute toxicity

It can be seen from the data summarised that the only constituent which meets the criteria for acute toxicity classification is 3-aminopropyl(triethoxy)silane (CAS 919-30-2), which is classified as Acute Toxic Category 4 (oral) in Annex VI of Regulation (EC) No 1272/2008.

Given the concentration of this constituent in the registered substance (0 to 10%) it does not contribute towards the overall classification according to the rules for mixtures specified in Regulation (EC) No 1272/2008.

For other simple alkoxy and aminofunctional alkoxy constituents with no available data, it can be assumed that these are also not classified for acute toxicity based on weight of evidence for a number of alkyl and amino alkoxysilanes for which measured data indicate no significant differences in acute toxicity properties between methoxy and ethoxy analogues containing the same alkyl or amine groups attached to silicon. Further details of the available data are given in supporting reports attached in Section 13 of IUCLID (PFA, 2013t and PFA, 2013v).

For the trisilane and cyclo-trisilane constituents, no measured data are available for the parent materials. However, these hydrolyse very rapidly, particularly following oral exposure (see Section 4.1), to silanols, methanol and ethanol. In view of the high molecular weight of these parent constituents (>500) it is not anticipated that these would be more hazardous than the simple amino alkoxysilanes or corresponding silanols and it is therefore assumed for the purposes of assessment that these would not contribute to the overall classification of the registered substance for acute systemic toxicity. Relevant data are available for alkoxysilanes producing the same silanols (methylsilanetriol,N-ethyl-3-trihydroxysilyl-2-methylpropanamine and 3-aminopropylsilanetriol), as well as methanol and ethanol and these do not contribute to the overall classification for acute toxicity.


Justification for classification or non-classification

Based on the available data for constituents of amino functional alkoxysilanes, no classification for acute oral, dermal or inhalation toxicity is required according to the rules for mixtures specified in Regulation (EC) No 1272/2008.

The only constituent for which any acute toxicity classification is required is 3-aminopropyl(triethoxy)silane (CAS 919-30-2) which is classified as Acute Toxic Category 4 (oral) in Annex VI of Regulation (EC) No 1272/2008. At a concentration ranging from 0 to 10 % in the registered substance, this constituent does not contribute towards the overall classification of the substance.

Since methanol is present in the registered substance at concentration ranging from 0 to 7%, classification STOT SE 2 (eyes and central nervous system) is required for amino functional alkoxysilanes according to Annex VI of Regulation (EC) No 1272/2008.