Trimethoxyoctadecylsilane

Endpoint summary

Key value for chemical safety assessment

Genetic toxicity in vitro

Description of key information

Genetic toxicity in vitro:

Bacterial mutagenicity (Ames test, OECD 471, WoE): S. typhimurium TA 98, TA 100, TA 102, TA 1535, TA 1537 and E. coli WP2 uvrA: negative with and without metabolic activation (RA from CAS 70851-50-2 and CAS 16415-12-6). Nevertheless, no final decision on classification for genetic toxicity according to Regulation (EC) 1272/2008 or Directive 67/548/EEC can be made, as no information on mutagenicity and clastogenicity in mammalian cells/in vivo is available.

Link to relevant study records

Reference

Reference 1

Endpoint:

in vitro gene mutation study in bacteria

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

2002-05-13 to 2002-09-19

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 471 (Bacterial Reverse Mutation Assay)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

Freie und Hansestadt Hamburg, Behörde für Arbeit, Gesundheit uns SozialesFreie und Hansestadt Hamburg, Behörde für Arbeit, Gesundheit uns Soziales, Germany

Type of assay:

bacterial reverse mutation assay

Target gene:

His operon

Species / strain / cell type:

S. typhimurium TA 1535, TA 1537, TA 98, TA 100 and TA 102

Additional strain / cell type characteristics:

not applicable

Metabolic activation:

with and without

Metabolic activation system:

Aroclor 1254-induced rat liver S9

Test concentrations with justification for top dose:

Preliminary toxicity test:
- 0.316, 1, 3.16, 10, 31.6, 100, 316, 1000, 3160 and 5000 µg/plate (highest recommended concentration) (without metabolic activation, TA 100)

Experiment I+II:
- 3.16, 10, 31.6, 100 and 316 µg/plate (highest suitable concentration due to toxicity observed in the preliminary toxicity study) (without metabolic activation)

Vehicle / solvent:

- Vehicle(s)/solvent(s) used: acetone
- Justification for choice of solvent/vehicle: The vehicle was chosen due to its solubility properties and relative non-toxicity to bacteria.

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

other: -S9: Sodium azide (NaN), 2-nitro-fluorene (2-NF), 9-amino-acridine (9-AA), methyl methane sulfonate (MMS); +S9: 2-anthracene amide (2-AA), cyclophosphamide (CPA)

Remarks:

NaN: 10 µg/plate (TA 100, TA 1535), 2-NF: 10 µg/plate (TA 98), 9-AA: 100 µg/plate (TA 1537), MMS: 1300 µg/plate (TA 102), 2-AA: 2 µg/plate (TA 98, TA 102, TA 1537), CPA: 1500 µg/plate (TA 100, TA 1535)

Details on test system and experimental conditions:

METHOD OF APPLICATION: in agar (plate incorporation); pre-incubation

DURATION
- Pre-incubation period: 60 min
- Exposure duration: 48 hours

NUMBER OF REPLICATIONS: 3 plates for each test concentration in 2 independent experiments

DETERMINATION OF CYTOTOXICITY
- Method: Background lawn assessment, revertant colony counts

Evaluation criteria:

A result is positive if the number of revertants is significantly increased compared with the solvent control to at least 2-fold of the solvent control for TA 98, TA 100 and TA 102 and 3-fold of the solvent control for TA 1535 and TA 1537 in both experiments. Positive results have to be reproducible and the histidine independence of the revertants has to be confirmed by streaking on histidine-free agar plates. Cytotoxicity is defined as a reduction in the number of colonies by > 50% compared with the solvent control and/or a sparse background lawn.

Statistics:

MANN and WHITNEY and Spearman’s rank.

Key result

Species / strain:

other: S. typhimurium TA 98, TA 100, TA 1535, TA 1537 and TA 102

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Remarks:

at 316 μg/plate (experiment I+II with and without S9-mix)

Vehicle controls validity:

valid

Untreated negative controls validity:

not examined

Positive controls validity:

valid

Additional information on results:

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

Table 1: Dose range-finding study Number of revertants per plate (2 plates)

	TA100
Conc. (µg/plate)	Plate 1	Plate 2	Cytotoxic (yes/no)
0*	148	140	No
0.316	160	151	No
1	148	141	No
3.16	153	149	No
10	138	141	No
31.6	162	149	No
100	132	162	No
316	171	157	Yes
1000	0	0	Yes
3160	0	0	Yes
5000	0	0	Yes

*: solvent control with acetone

MA: metabolic activation

Table 2: Experiment 1 Plate incorporation Number of revertants per plate (mean of 3 plates)

	TA98			TA100			TA102
Conc. µg/plate	— MA	+ MA	Cytotoxic (yes/no)	— MA	+  MA	Cytotoxic (yes/no)	— MA	+ MA	Cytotoxic (yes/no)
0*	30.3	39	No	152.3	164.7	No	273.7	275.7	No
3.16	34.7	38.3	No	152	159.7	No	275.7	278	No
10	26.3	33.3	No	155	164.3	No	274.3	266	No
31.6	26.7	39	No	149	169	No	270	273	No
100	22.7	36.3	No	152	162	No	270.7	262.7	No
316	31.7	36	Yes	150	164.7	Yes	272.3	260.7	Yes
Positive control	726.3	736.3	No	1091.7	1093.3	No	1105.3	1115	No

*: solvent control with acetone

MA: metabolic activation

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

	TA1535			TA1537
Conc. µg/plate	— MA	+  MA	Cytotoxic (yes/no)	— MA	+ MA	Cytotoxic (yes/no)
0*	17.3	17.7	No	4	5	No
3.16	16	15	No	4	3.7	No
10	17.3	18	No	2.7	4	No
31.6	15.7	12	No	3	3.3	No
100	16	17	No	3.7	4.7	No
316	15.3	18.3	Yes	3	4.3	Yes
Positive control	529.3	530.7	No	518.3	528.3	No

*: solvent control with acetone

MA: metabolic activation

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

	TA98			TA100			TA102
Conc. µg/plate	— MA	+ MA	Cytotoxic (yes/no)	— MA	+ MA	Cytotoxic (yes/no)	— MA	+  MA	Cytotoxic (yes/no)
0*	32	35.3	No	151.3	176.7	No	271.7	287.7	No
3.16	31	35	No	136.3	162.3	No	285	260.3	No
10	30.7	36	No	146.7	165	No	278	269.3	No
31.6	25.3	26.7	No	161	171	No	278	268.3	No
100	25	27	No	152	170.7	No	274	271.3	No
316	26.7	32.7	Yes	157	173.3	Yes	277	292	Yes
Positive control	876.7	1062.3	No	1300.3	1264	No	1294.3	1267.3	No

*: solvent control with acetone

MA: metabolic activation

Table 5: Experiment 2 Preincubation Number of revertants per plate (mean of 3 plates)

	TA1535			TA1537
Conc. µg/plate	— MA	+ MA	Cytotoxic (yes/no)	— MA	+ MA	Cytotoxic (yes/no)
0*	15.3	14.7	No	4	3.3	No
3.16	15	12.3	No	3	4	No
10	11.3	12.3	No	2.3	4	No
31.6	12	14.3	No	3.3	4.7	No
100	13.7	12.7	No	3	4	No
316	12	12	Yes	3	4	Yes
Positive control	491.7	451	No	443.3	446.7	No

*: solvent control with acetone

MA: metabolic activation

Conclusions:

In a reliable test, conducted according to OECD 471 in compliance with GLP, no mutagenic effect was observed for the test substance tested up to cytotoxic concentration in any of the test strains in two independent experiments without and with metabolic activation. The test substance is non-mutagenic in the tester strains used and under the conditions of the test.

Reference 2

Endpoint:

in vitro gene mutation study in bacteria

Type of information:

experimental study

Adequacy of study:

key study

Study period:

14 Dec 2010 - 07 Jan 2011

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 471 (Bacterial Reverse Mutation Assay)

Version / remarks:

1997

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

Ministerium für Arbeit, Gesundheit und Soziales des Landes Nordrhein-Westfalen, Düsseldorf, Germany

Type of assay:

bacterial reverse mutation assay

Target gene:

S. typhimurium strains: his operon
E. coli strain: trp operon

Species / strain / cell type:

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

Additional strain / cell type characteristics:

not applicable

Species / strain / cell type:

E. coli WP2 uvr A

Additional strain / cell type characteristics:

not applicable

Metabolic activation:

with and without

Metabolic activation system:

cofactor supplemented post-mitochondrial fraction (S9-mix), prepared from the livers of rats treated with Aroclor 1254

Test concentrations with justification for top dose:

Experiment I+II:
- 62, 185, 556, 1667, 5000 µg/plate (highest recommended concentration) (with and without metabolic activation)
Experiment III:
- 1000, 2000, 3000, 4000, 5000 µg/plate (with and without metabolic activation)

Vehicle / solvent:

- Vehicle/solvent used: acetone

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

other: -S9: sodium azide (NaN), 9-aminoacridine (9-AA), 2-nitrofluorene (2-NF), 4-nitroquinoline 1-oxide (4-NQO); +S9: 2-aminoanthracene (2-AA), benzo(a)pyrene (Ba(a)P)

Remarks:

NaN: 2 µg/plate (TA 100, TA 1535), 9-AA: 50 µg/plate (TA 1537), 2-NF: 4 µg/plate, 4-NQO: 1 µg/plate (E. coli WP2 uvrA), 2-AA: 7 µg/plate (TA 1535, TA 1537), 2 µg/plate (TA 100), 10 µg/plate (E. coli WP2 uvrA), Ba(a)P: 30 µg/plate (TA 98)

Details on test system and experimental conditions:

METHOD OF APPLICATION: in agar (plate incorporation)

DURATION
- Exposure duration: 48 h

NUMBER OF REPLICATIONS: triplicates in 3 independent experiments (test substance); six plates per experiment for the solvent control

DETERMINATION OF CYTOTOXICITY
- Method: growth of background lawn

Evaluation criteria:

A test substance producing no biologically relevant positive response in any one of the bacterial strains tested is considered to be non-mutagenic in this system. A biologically relevant response is described as follows: If the number of revertants is at least twice the spontaneous reversion rate for TA 1535, TA 98, TA 100 or WP2 uvrA (or three times for TA 1537) and/or if there is a concentration related increasing number of revertants over the range tested.

Statistics:

Mean values and standard deviations were calculated.

Key result

Species / strain:

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

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity nor precipitates, but tested up to recommended limit concentrations

Vehicle controls validity:

valid

Untreated negative controls validity:

not examined

Positive controls validity:

valid

Key result

Species / strain:

E. coli WP2 uvr A

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity nor precipitates, but tested up to recommended limit concentrations

Vehicle controls validity:

valid

Untreated negative controls validity:

not examined

Positive controls validity:

valid

Additional information on results:

TEST-SPECIFIC CONFOUNDING FACTORS
- Precipitation: Precipitation of the test substance was observed at concentrations ≥ 1000 µg/plate.

COMPARISON WITH HISTORICAL CONTROL DATA
- Historical control data were given in the study report. The results of the solvent control cultures lied within the range of the historical control data.

OTHER
- Revertant counts higher than 1000 were counted and calculated as 1000.
- Study plan amendment: Due to invalid positive and solvent controls for the strains Salmonella typhimurium TA 100 and Escherichia coli WP2 uvrA parts of the first experiment had to be repeated (=second experiment).

Table 1: Mean values of experiment 1 and 2.

With or without S9-Mix	Test substance concentration (µg/plate)	Mean number of revertant colonies per plate (average of 3 plates ± Standard deviation)
		TA 1535	TA 1537	TA 98	TA 100	WP2 uvrA
–	0	9±3	4±3	20±4	207±34	17±6
–	62	7±3	3±1	23±6	202±30	16±3
–	185	10±2	3±3	24±3	219±26	19±4
–	556	6±3	8±3	20±1	222±39	15±5
–	1667, P	11±3	3±3	25±6	187±5	13±3
–	5000, P	9±5	5±3	27±3	200±9	12±2
Positive controls, –S9	Name	NaN3	9-AA	2-NF	NaN3	4-NQO
	Concentrations (µg/plate)	2	50	4	2	1
	Revertants per plate	677±107	328±45	363±64	1000±0	491±100
+	0	13±4	6±3	28±3	130±20	23±3
+	62	12±1	4±1	34±2	142±11	21±4
+	185	14±2	4±2	21±4	109±10	20±5
+	556	8±2	4±2	23±6	107±7	21±2
+	1667, P	12±2	4±3	28±6	129±12	19±4
+	5000, P	8±5	5±1	25±9	125±13	23±2
Positive controls, +S9	Name	2-AA	2-AA	B[a]P	2-AA	2-AA
	Concentrations (µg/plate)	7	7	30	2	10
	Revertants per plate	531±45	595±58	1000±0	1000±0	206±23

P: precipitation observed

 

Table 2: Results of experiment 3.

With or without S9-Mix	Test substance concentration (µg/plate)	Mean number of revertant colonies per plate (average of 3 plates ± Standard deviation)
		TA 1535	TA 1537	TA 98	TA 100	WP2 uvrA
–	0	9±2	4±1	21±4	105±12	20±6
–	1000, P	9±3	4±3	28±4	140±26	17±6
–	2000, P	13±5	1±1	22±4	134±33	28±11
–	3000, P	10±3	5±2	23±2	129±5	22±8
–	4000, P	10±4	2±2	19±1	137±21	25±1
–	5000, P	10±2	3±2	23±4	117±12	20±7
Positive controls, –S9	Name	NaN3	9-AA	2-NF	NaN3	4-NQO
	Concentrations (µg/plate)	2	50	4	2	1
	Revertants per plate	704±73	147±13	400±71	1000±0	613±41
+	0	9±2	4±1	21±4	105±12	20±6
+	1000, P	9±3	4±3	28±4	140±26	17±6
+	2000, P	13±5	1±1	22±4	134±33	28±11
+	3000, P	10±3	5±2	23±2	129±5	22±8
+	4000, P	10±4	2±2	19±1	137±21	25±1
+	5000, P	10±2	3±2	23±4	117±12	20±7
Positive controls, +S9	Name	2-AA	2-AA	B[a]P	2-AA	2-AA
	Concentrations (µg/plate)	7	7	30	2	10
	Revertants per plate	491±44	584±97	805±78	1000±0	274±103

 P: precipitation observed

Conclusions:

In a study performed according to OECD 471 and in compliance with GLP no mutagenic effect was observed for the test substance tested up to the limit concentration in any of the test strains in three independent experiments with and without metabolic activation.

Reference 3

Endpoint:

in vitro gene mutation study in bacteria

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

weight of evidence

Justification for type of information:

Please refer to the attached justification below and the overall justification for grouping of substances attached in IUCLID Section 13.

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across source

Statistics:

MANN and WHITNEY and Spearman’s rank.

Key result

Species / strain:

other: S. typhimurium TA 98, TA 100, TA 1535, TA 1537 and TA 102

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Remarks:

at 316 μg/plate (experiment I+II with and without S9-mix)

Vehicle controls validity:

valid

Untreated negative controls validity:

not examined

Positive controls validity:

valid

Key result

Species / strain:

S. typhimurium, other: TA 98, TA 100, TA 1535, TA 1537

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity nor precipitates, but tested up to recommended limit concentrations

Vehicle controls validity:

valid

Untreated negative controls validity:

not examined

Positive controls validity:

valid

Key result

Species / strain:

E. coli WP2 uvr A

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity nor precipitates, but tested up to recommended limit concentrations

Vehicle controls validity:

valid

Untreated negative controls validity:

not examined

Positive controls validity:

valid

Remarks on result:

other: CAS 70851-50-2, LPT 2002

Conclusions:

In two reliable tests, conducted according to OECD 471 in compliance with GLP, no mutagenic effect was observed for the source substances (dimethoxymethyl)(octadecyl)silane (CAS 70851-50-2) and hexadecyl(trimethoxy)silane (CAS 16415-12-6) tested up to cytotoxic concentration in any of the test strains in at least two independent experiments without and with metabolic activation. The source substances are non-mutagenic in the tester strains used and under the conditions of the test. As explained in the analogue justification, it is considered that the target and the source substances are unlikely to lead to differences in genetic toxicity potential.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (negative)

Genetic toxicity in vivo

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

No data on genetic toxicity (mutagenicity) in bacterial cells is avaiable for trimethoxyoctadecylsilane (CAS 3069-42-9).Therefore, the risk assessment was performed based on the available data from the source substance hexadecyltrimethoxysilane (CAS 16415-12-6) and dimethoxymethyloctadecylsilane (CAS 70851-50-2). In accordance with Regulation (EC) No. 1907/2006 Annex XI, 1.5 “Grouping of substances and read across” and following the Read across assessment framework (RAAF, ECHA 2017) read across from analogue substances has been applied to support the human health hazard assessment of trimethoxyoctadecylsilane (CAS 3069-42-9). 

 Genetic toxicity (mutagenicity) in bacteria in vitro

A reliable bacterial gene mutation study (Ames test) performed according to OECD 471 and in compliance with GLP with Hexadecyltrimethoxysilane (CAS 16415-12-6) is available (Evonik, 2011). The strains Salmonella typhimurium TA 1535, TA 1537, TA 98, TA 100 and E.coli WP2 uvr A were tested according to the plate incorporation procedure in the absence and presence of a metabolic activation system (Aroclor 1254-induced rat liver S9-mix). Three independent experiments were conducted in three repetitions at each concentration from 62 to 5000 µg/plate (experiment I and II) and 1000 to 5000 µg/plate (experiment III). Due to invalid positive and solvent controls for the strains Salmonella typhimurium TA 100 and Escherichia coli WP2 uvr A, parts of the first experiment had to be repeated (= second experiment). No significant increase in the number of revertants was observed in any of the tester strains with and without metabolic activation. No cytotoxicity was observed at any of the tested concentrations. Appropriate solvent (acetone) and positive controls were included and gave the expected results. Precipitation of the test material was noted at concentrations ≥1000 µg/plate. Based on the results of the study the test material was considered to be not mutagenic to bacteria under the conditions of the test.

 

A second reliable bacterial gene mutation study (Ames test) performed according to OECD 471 and in compliance with GLP with Dimethoxymethyloctadecylsilane (CAS 70851-50-2) is available (LPT, 2002). The strains Salmonella typhimurium TA 1535, TA 1537, TA 98, TA 100 and TA 102 were tested according to the plate incorporation (experiment I) and pre-incubation (experiment II) procedure in the absence and presence of a metabolic activation system (Aroclor 1254-induced rat liver S9-mix). Two independent experiments were conducted in three repetitions at each concentration from 3.16 to 316 µg/plate. No significant increase in the number of revertants was observed in any of the tester strains with and without metabolic activation. Cytotoxicity was observed at a concentration of 316 µg/plate with and without metabolic activation. Appropriate solvent (acetone) and positive controls were included into the test and gave the expected results. Precipitation of the test material was not noted at any tested concentration. Based on the results of the study the test material was considered to be not mutagenic to bacteria under the conditions of the test.

 

Based on the above study results with the structural analogue substances Hexadecyltrimethoxysilane (CAS 16415-12-6) and Dimethoxymethyloctadecylsilane (CAS 70851-50-2) sufficient evidence is given that the registered substance Trimethoxyoctadecylsilane (CAS 3069-42-9) is considered not to be mutagenic to bacteria.

Justification for classification or non-classification

Reliable data from structural analogue substances on genetic toxicity indicates that the registered substance does not meet the criteria for classification according to Regulation (EC) No. 1272/2008, and the available data are therefore conclusive but not sufficient for classification. Nevertheless, no final decision on classification for genetic toxicity according to Regulation (EC) 1272/2008 or Directive 67/548/EEC can be made, as no information on mutagenicity and clastogenicity in mammalian cells/in vivo is available