1-methyl-N,N',N''-tris(1-methylpropyl)silanetriamine

Endpoint summary

Key value for chemical safety assessment

Genetic toxicity in vitro

Description of key information

Bacterial reverse mutation assay: the substance 1-Methyl-N,N',N''-tris(1-methylpropyl)silanetriamine was negative with and without activation in S. typhimurium strains TA 98, TA100, TA1535, TA1537 and TA 1538 (OECD TG 471) (Wacker, 1989).

Link to relevant study records

Reference

Endpoint:

in vitro gene mutation study in bacteria

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1989-05-10 to 1989-10-31

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Remarks:

The restrictions were that the range of strains does not comply with the current guideline.

Qualifier:

according to guideline

Guideline:

OECD Guideline 471 (Bacterial Reverse Mutation Assay)

Version / remarks:

1981

Deviations:

yes

Remarks:

The range of strains does not comply with the current guideline

GLP compliance:

yes

Type of assay:

bacterial reverse mutation assay

Species / strain / cell type:

S. typhimurium TA 1535, TA 1537, TA 98 and TA 100

Species / strain / cell type:

S. typhimurium TA 1538

Metabolic activation:

with and without

Metabolic activation system:

biphenyl polychloride induced rat liver S9

Test concentrations with justification for top dose:

0.1, 0.5, 1, 2.5 and 5 ml/plate

Vehicle / solvent:

- Vehicle(s)/solvent(s) used: Acetone

- Justification for choice of solvent/vehicle: no justification given in study report.

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

other: 2-aminoanthracene

Remarks:

All strains (with activation)

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

2-nitrofluorene

Remarks:

TA 98, TA 1538 (without activation)

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

methylmethanesulfonate

Remarks:

TA 100 (without activation)

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

ethylmethanesulphonate

Remarks:

TA 1535 (without activation)

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

9-aminoacridine

Remarks:

TA 1537 (without activation)

Details on test system and experimental conditions:

ACTIVATION: Cofactors were added to the S9 mix to reach the following concentrations: 8 mM MgCl2, 33 mM KCl, 5 mM Glucose-6-phosphate, 4 mM NADP in 100 mM potassium-phosphate-buffer pH 7.4. The concentration of S9 in the mix was 5%, and 0.5 ml of S9 mix were added to test substance, overlay agar and bacterial suspension giving a final concentration of approximately 1% S9 in the plates.

METHOD OF APPLICATION: in agar (plate incorporation)

DURATION

- Exposure duration: 48 hours

NUMBER OF REPLICATIONS: 3 plates for each test concentration; experiment repeated

DETERMINATION OF CYTOTOXICITY
- Method: reduction in mean number of revertants, background lawn assessment

Evaluation criteria:

A result is positive if the number of colonies apparent in the presence of the test article is greater or equal to twice the number of colonies apparent in the negative control.

Statistics:

The mean number of colonies apparent in the dishes and the standard deviation were calculated.

Key result

Species / strain:

S. typhimurium TA 1535, TA 1537, TA 98 and TA 100

Metabolic activation:

without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Remarks:

from 2.5 mg/plate (Strain TA98 without metabolic activation)

Vehicle controls validity:

valid

Untreated negative controls validity:

not applicable

Positive controls validity:

valid

Key result

Species / strain:

S. typhimurium TA 1538

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Remarks:

2.5 mg/plate

Vehicle controls validity:

valid

Untreated negative controls validity:

not applicable

Positive controls validity:

valid

Additional information on results:

COMPARISON WITH HISTORICAL CONTROL DATA: Results were within range of historical control data

Table 2: Dose range-finding study Number of revertants per plate (2 plates)

	TA100 (-MA)
Conc. (mg/dish)	Plate 1	Plate 2	Cytotoxic (yes/no)
0*	87	95	No
0.05	103	83	No
0.1	81	85	No
0.5	98	77	No
1	80	74	No
2.5	96	91	No
5	103	99	No

*solvent control with Acetone

Table 3: Experiment 1 Plate incorporation Number of revertants per plate (mean of 3 plates)

	TA98			TA100			TA1538
Conc. mg/dish	— MA	+ MA	Cytotoxic (yes/no)	— MA	+ MA	Cytotoxic (yes/no)	— MA	+ MA	Cytotoxic (yes/no)
0*	24	28	No	95.3	101	No	41.3	43	No
0.1	23	31.3	No	87.7	99	No	34.7	44	No
0.5	25.3	37	No	88.7	98.3	No	37.7	47.7	No
1	29.7	29	No	98	104.7	No	25	38.7	No
2.5	26.7	31.3	Yes	78.7	97.3	No	21	35	No
5	27.3	40	Yes	84	99.3	Yes	7.3	24.3	Yes
Positive control	551.5	1135.5	No	308.5	1538	No	240	1258	No

*solvent control with Acetone

Table 3: Experiment 1 Plate incorporation Number of revertants per plate (mean of 3 plates)

	TA1535			TA1537
Conc. mg/dish	—  MA	+ MA	Cytotoxic (yes/no)	— MA	+ MA	Cytotoxic (yes/no)
0*	8.3	10.7	No	10	10.3	No
0.1	9	11.7	No	13.7	10	No
0.5	7	9.7	No	12	8.3	No
1	8.3	9.3	No	10	9	No
2.5	9	8.7	No	7.3	8.7	No
5	3	10	Yes	3	5	Yes
Positive control	1002.5	185	No	331.5	93.5	No

*solvent control with Acetone

Table 4: Experiment 2 Plate incorporation Number of revertants per plate (mean of 3 plates)

	TA98			TA100			TA1538
Conc. mg/dish	— MA	+ MA	Cytotoxic (yes/no)	— MA	+ MA	Cytotoxic (yes/no)	— MA	+  MA	Cytotoxic (yes/no)
0*	30	24.3	No	109	107	No	41.3	43	No
0.1	18	32.3	No	113.7	111.3	No	34.7	44	No
0.5	26.7	24.3	No	117.7	127.3	No	37.7	47.7	No
1	23.3	25.3	No	107.7	104.7	No	25	38.7	No
2.5	17.7	32.3	Yes	147	124.7	No	21	35	Yes
5	3.3	20	Yes	64.3	92.3	Yes	7.3	24.3	Yes
Positive control	408.5	1106	No	293.5	1118.5	No	240	1258	No

*solvent control with Acetone

Table 4: Experiment 2 Plate incorporation Number of revertants per plate (mean of 3 plates)

	TA1535			TA1537
Conc. mg/dish	—  MA	+ MA	Cytotoxic (yes/no)	— MA	+ MA	Cytotoxic (yes/no)
0*	11.3	11.7	No	11.3	7.7	No
0.1	9.7	10.3	No	11	8	No
0.5	10	13.7	No	10	9	No
1	8.7	15	No	12.3	8.3	No
2.5	11	10	No	5.7	8.7	Yes
5	7.7	8	Yes	0.3	9.3	Yes
Positive control	1295.5	133	No	216.5	62.5	No

*solvent control with Acetone

Conclusions:

1-Methyl-N,N',N''-tris(1-methylpropyl)silanetriamine has been tested for mutagenicity to bacteria in a study conducted according to OECD 471 (1981) and in compliance with GLP. No test-substance induced increase in the number of revertants was observed for the test substance up to limit concentrations in Salmonella typhimurium strains TA98, TA100, TA1535, TA1537 or TA 1538 without and with metabolic activation in two independent experiments. It is concluded that the the test substance is not mutagenic to bacteria under the conditions of the test.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (negative)

Additional information

1-Methyl-N,N',N''-tris(1-methylpropyl)silanetriamine has been tested in a valid bacterial reverse mutation assay, according to the OECD TG 471 (1989), and under GLP, using Salmonella typhimurium strains TA 98, TA 100, TA 1535, TA 1537 or TA 1538 (Wacker, 1989).

No increase in the number of revertants was observed in any test strain, with or without metabolic activation in two separate experiments up to limit concentrations. Appropriate positive and solvent controls were added and gave expected results. It was concluded that the test substance is negative for mutagenicity to bacteria under the conditions of the test. The study is considered reliability 2 due to the lack of inclusion of a bacterial strain capable of detecting cross-linking or oxidising mutagens.

In order to address the missing strain, data are read-across from the related substances 1,1-dimethyl-N,N'-bis(1-methylpropyl)silanediamine CAS 93777-98-1 and N,N',N''-tributyl-1-methylsilanetriamine CAS 16411-33-9, both of which gave negative results with and without metabolic activation in all strains tested (Bioservice, 2004a and 2004b).

Non-testing methods including read-across from surrogate substances are able to provide information on genetic toxicity (REACH Guidance part 07a, R.7.7.3). In the case of genetic toxicity the presence or absence of functional groups that are known to be related to genetic toxicity is considered important, as the presence or absence of reactive groups and molecular substructures is associated with mutagenic and carcinogenic properties of chemicals (Benigni and Bossa, 2006). Consideration is therefore given to the structural similarity, particularly presence or absence of structural alerts for genetic toxicity, when selecting surrogate substances for genetic toxicity endpoints.

Read-across hypothesis

The hypothesis is that that source (read-across) substances and registration (target) substance have similar systemic toxicological properties because they hydrolyse to similar silanol hydrolysis products, methylsilanetriol and dimethylsilanediol and similar amines, n-butylamine and sec-butylamine. None of the substances or hydrolysis products have structural alerts for genetic toxicity.

Read-across justification

(a) Structural similarity of parent substance and silicon-containing hydrolysis products

The target and source substances are structurally similar and hydrolyse rapidly to methylsilanetriol or dimethylsilanediol.

The registered substance (target) 1-methyl-N,N',N''-tris(1-methylpropyl)silanetriamine CAS 37697-65-7 hydrolyses very rapidly (hydrolysis half-lives at 25°C, < 2 min at pH 4 and pH7 and 5.0 min at pH9). The products of hydrolysis are the amine-functional leaving group, sec-butylamine (CAS 13952-84-6) and the silanol, methylsilanetriol (CAS 2445-53-6).

N,N',N''-Tributyl-1-methylsilanetriamine CAS 16411-33-9 hydrolyses very rapidly (hydrolysis half-lives at 25°C, < 2 min at pH 4, 7 and 9). The products of hydrolysis are the amine-functional leaving group, n-butylamine (CAS 109-73-9) and the silanol, methylsilanetriol (CAS 2445-53-6). This source substance has the same silanol hydrolysis product as the target substance and a similar amine-functional leaving group.

1,1-Dimethyl-N,N'-bis(1-methylpropyl)silanediamine CAS 93777-98-1 hydrolyses rapidly (hydrolysis half-lives at 25°C, < 2 min at pH 4, 7 and 9). The products of hydrolysis are the amine-functional leaving group, sec-butylamine (CAS 13952-84-6) and the silanol, dimethylsilanediol (CAS 1066-42-8). This source substance has the same amine-functional leaving group as the target substance and a similar silanol hydrolysis product.

 (b) Lack of structural alerts

None of the substances or hydrolysis products has structural alerts for genotoxicity (Benigni et al, 2008).

(c) Lack of genetic toxicity of the silicon hydrolysis product

Dimethylsilanediol is not mutagenic in a study which included an appropriate 5^th strain (unpublished data). No data are available for methylsilanetriol, but other substances which also hydrolyse to methylsilanetriol give negative results in appropriate strains.

(d) Lack of genetic toxicity of the non-silicon hydrolysis product.

The non-silicon hydrolysis product of the registered product, sec-butylamine does not have data in the disseminated dossier from a bacterial mutagenicity study which tested an appropriate strain. However, a wide range of in vitro and in vivo data are presented which conclude that the substance is not a genetic toxin.

The data available for the rapidly hydrolysing read-across substances indicates that sec-butylamine is not of concern for genetic toxicity.

Benigni and Bossa (2006). Current Computer-Aided Drug Design 2, (2), 169-176.

Benigni et al (2008). The Benigni/Bossa rule base for mutagenicity and carcinogenicity JR Scientific report EUR 23241 EN

Justification for classification or non-classification

Based on the available bacterial mutagenicity data, 1-methyl-N,N',N''-tris(1-methylpropyl)silanetriamine does not require classification for mutagenicity according to Regulation (EC) No 1272/2008.