Trichloro(hexadecyl)silane

Endpoint summary

Key value for chemical safety assessment

Genetic toxicity in vitro

Description of key information

Only a reliable bacterial mutagenicity study and a reliable mammalian mutagenicity study in vitro are available for the registered substance trichloro(hexadecyl)silane (CAS 5894-60-0), however, reliable data are available for the structural analogue substance trimethoxy(hexadecyl)silane (CAS 16415-12-6) for in vitro cytogenicity in mammalian cells.

Gene mutation (Bacterial reverse mutation assay/ Ames test): S. typhimurium TA 100, TA 98, TA 1535, TA 1537 and TA 102: Negative with and without metabolic activation for trichloro(hexadecyl)silane (according to OECD TG 471).

In vitro cytogenicity (Chinese hamster ovary (CHO) cell chromosome aberration assay): Negative with and without metabolic activation for the structural analogue substance trimethoxy(hexadecyl)silane (CAS 16415-12-6) (according to OECD TG 473).

In vitro mammalian mutagenicity (Mouse Lymphoma Assay): L5178Y cells: Negative with and without metabolic activation for trichloro(hexadecyl)silane (according to OECD TG 476).

Link to relevant study records

Reference

Reference 1

Endpoint:

in vitro cytogenicity / chromosome aberration study in mammalian cells

Type of information:

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

Adequacy of study:

key study

Study period:

02 Sep 2004 to 03 Dec 2004

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

Species / strain:

Chinese hamster Ovary (CHO)

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Remarks:

Experiment 1: cytotoxicity at 650 µg/mL (+S9) and 1300 µg/mL (±S9); Experiment 2: cytotoxicity at 10.2, 20.3 and 40.6 µg/mL (-S9). Precipitation was observed in the culture medium at 650 and 1300 µg/mL at the start and end of treatment.

Vehicle controls validity:

valid

Untreated negative controls validity:

not examined

Positive controls validity:

valid

Conclusions:

Interpretation of results: negative

The source substance was tested to OECD 473 (1997) under GLP. The source substance did not induce any statistically significant, dose-related increases in the frequency of cells with chromosomal aberrations either in the presence or absence of metabolic activation or after various exposure times. The source as well as the target substance were therefore considered to be non-clastogenic to CHO cells in vitro under the conditions of the test.

Reference 2

Endpoint:

in vitro gene mutation study in mammalian cells

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2011-10-20 to 2012-01-31

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 476 (In Vitro Mammalian Cell Gene Mutation Test)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method B.17 (Mutagenicity - In Vitro Mammalian Cell Gene Mutation Test)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EPA OPPTS 870.5300 - In vitro Mammalian Cell Gene Mutation Test

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: IWGT Recommendations

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

BAYERISCHES LANDESAMT FÜR GESUNDHEIT UND LEBENSMITTELSICHERHEIT

Type of assay:

in vitro mammalian cell gene mutation tests using the thymidine kinase gene

Target gene:

Thymidine kinase

Species / strain / cell type:

mouse lymphoma L5178Y cells

Details on mammalian cell type (if applicable):

- Type and identity of media: RPMI
- Properly maintained: Yes
- Periodically checked for Mycoplasma contamination: yes
- Periodically "cleansed" against high spontaneous background: yes

Metabolic activation:

with and without

Metabolic activation system:

Phenobarbital and ß-Naphthoflavone-induced rat liver S9 mix

Test concentrations with justification for top dose:

Pre-experiment I
- 0.100, 0.500, 2.500, 5.000, 7.500 and 10.000 mM (with and without metabolic activation)

Pre-experiment II
- 0.005, 0.010, 0.050, 0.100, 0.200 and 0.500 mM (without metabolic activation (24 h long-term exposure))

Experiment I
- 0.002, 0.005, 0.010, 0.020, 0.040, 0.080, 0.100, 0.200 mM (without metabolic activation)
- 0.020, 0.040, 0.080, 0.100, 0.200, 0.300, 0.500, 0.800 mM (with metabolic activation)

Experiment II
- 0.010, 0.020, 0.050, 0.100, 0.150, 0.200, 0.300, 0.350 mM (without metabolic activation)
- 0.015, 0.030, 0.050, 0.150, 0.250, 0.350, 0.450, 0.550, 1.150 mM (with metabolic activation)

Vehicle / solvent:

Based on the results of the solubility test THF was used as solvent (0.5% THF v/v). Different test item stock solutions were prepared and added to the samples. To reach a final concentration of 0.5% THF v/v in the samples the test item stock solution was diluted in RPMI + 5% HS for short-term exposure or RPMI + 7.5% HS for long-term exposure. After adding the THF stock solution to cell culture medium precipitate formed. The pH value was adjusted to physiological range with 1 M NaOH. The solvent was compatible with the survival of the cells and the activity of the S9 mix.

Untreated negative controls:

yes

Remarks:

treatment medium

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

other: -S9-mix: Ethylmethanesulfonate (EMS): 200 and 300 µg/ml; Methylmethanesulfonate (MMS): 10 µg/ml; +S9-mix: Benzo[a]pyrene (BaP): 3.5 µg/ml

Details on test system and experimental conditions:

METHOD OF APPLICATION: Dissolved in tetrahydrofuran and diluted with RPMI cell culture medium, where precipitate was formed.

DURATION: 4 h (short-term exposure), 24 h (long-term exposure)
Expression time (cells in growth medium): 48 h
Selection time (if incubation with selection agent): about 14 days

SELECTION AGENT ( mutation assay) 5 µg/ml trifluorothymidine

NUMBER OF REPLICATIONS: two separate experiments (I+II) with single exposure; cells were seeded in 4 plates and evaluated

NUMBER OF CELLS SEEDED: 2000 cells per well

DETERMINATION OF CYTOTOXICITY: relative total growth (RTG)

ACTIVATION: Phenobarbital and ß-Naphthoflavone-induced rat liver S9 mix included S9 to give a final protein concentration in the cultures of 0.75 mg/ml, and the following cofactors: 8 mM MgCl2; 33 mM KCl; 5 mM Glucose-6-phosphate; 5 mM NADP in 100 mM sodium-phosphate-buffer pH 7.4.

Evaluation criteria:

The test item is considered mutagenic if following criteria are met:
-The induced mutant frequency meets or exceeds the Global Evaluation factor (GEF) of 126 mutants per 10xE+06 cells
- A dose-dependent increase in mutant frequency is detected.

Besides, combined with a positive effect in the mutant frequency, an increased occurrence of small colonies (≥40% of total colonies) is an indication for potential clastogenic effects and/or chromosomal aberrations.
According to the OECD guideline, the biological relevance is considered first for the interpretation of results. Statistical methods might be used as an aid in evaluation the test result.
A test item is considered to be negative if the induced mutant frequency is below the GEF and the trend test is negative.

Statistics:

The non-parametric Mann-Whitney test is applied to the mutation data to prove the dose groups for any significant difference in mutant frequency compared to the negative /solvent controls.

Species / strain:

mouse lymphoma L5178Y cells

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Remarks:

at 0.200 and 0.350 mM (experiment II with and without S9-mix)

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Additional information on results:

Full study data tables are attached and summarized data is provided in the field "Any other information on results incl. tables".

Table 1: Summary: Experiment I and II, with metabolic activation

Test Group	Conc. [mM]	RCE [%]	RTG [%]	MF [mutants/ 106 cells]	IMF [mutants/ 106 cells]	GEF exceeded	Statistical Significance*	Precipitate
Experiment I
C1	0	105.4	128.9	90.7	/	/	/	-
C2		91.7	110.8
S1	0	100.0	100.0	81.7	/	/	/	-
S2					/	/	/	-
4	0.020	105.4	109.2	58.7	-23.0	-	-	-
5	0.040	97.5	110.7	106.2	24.6	-	-	-
6	0.080	98.2	108.6	77.2	-4.5	-	-	-
7	0.100	106.1	116.7	70.7	-11.0	-	-	-
8	0.200	88.8	95.3	93.2	11.5	-	-	+
9	0.300	98.9	83.9	105.5	23.8	-	-	+
11	0.500	83.8	25.0	87.7	6.0	-	-	+
12	0.800	60.6	7.6	78.7	-3.0	-	-	+
B[a]P	3.5	93.1	86.6	613.8	532.1	+	+	-
Experiment II
C1	0	103.6	104.9	91.8	/	/	/		-
C2		101.4	120.9		/	/	/		-
S1	0	100.0	100.0	109.7	/	/	/		-
S2					/	/	/		-
1	0.015	97.8	107.5	111.0	1.3	-	-		-
2	0.030	97.1	109.9	113.6	3.9	-	-		-
3	0.050	101.4	128.0	80.0	-29.7	-	-		-
4	0.150	101.4	127.1	134.0	24.2	-	-		-
5	0.250	93.5	95.1	129.9	20.2	-	-		-
6	0.350	92.8	63.6	172.7	63.0	-	+		-
7	0.450	33.1	2.2	132.6	22.9	-	-		+
8	0.550	67.6	7.8	127.7	17.9	-	-		+
14	1.150	91.4	8.3	112.0	2.3	-	-		+
B[a]P	3.5	90.6	76.8	742.1	632.4	+	+		-

Table 2: Summary: Experiment I and II, without metabolic activation

Test Group	Conc. [mM]	RCE [%]	RTG [%]	MF [mutants/ 10xE+06 cells]	IMF [mutants/ 10xE+06 cells]	GEF exceeded	Statistical Significance*	Precipitate
Experiment I
C1	0	93.5	91.1	58.6	/	/	/	-
C2		99.7	112.4		/	/	/	-
S1	0	100.0	100.0	62.5	/	/	/	-
S2					/	/	/	-
1	0.002	94.2	109.4	56.8	-5.8	-	-	-
2	0.005	96.9	111.0	46.8	-15.7	-	-	-
3	0.010	90.8	91.0	82.8	20.2	-	-	-
4	0.020	109.2	109.3	44.0	-18.5	-	-	-
5	0.040	91.5	90.5	77.5	14.9	-	-	-
6	0.080	95.6	89.6	78.3	15.7	-	-	-
7	0.100	99.7	79.8	69.9	7.4	-	-	-
8	0.200	74.4	16.8	80.4	17.8	-	-	+
EMS	300	87.4	92.4	506.6	444.1	+	+	-
MMS	10	86.7	83.3	416.3	353.8	+	+	-
Experiment II
C1	0	91.5	134.0	83.4	/	/	/	-
C2		98.6	142.4		/	/	/	-
S1	0	100.0	100.0	68.6	/	/	/	-
S2					/	/	/	-
4	0.010	102.8	100.6	53.1	-15.5	-	-	-
5	0.020	89.4	83.2	89.3	20.7	-	-	-
6	0.050	84.4	93.7	106.1	37.5	-	-	-
7	0.100	96.5	85.6	71.5	2.9	-	-	-
8	0.150	90.8	91.8	95.4	26.8	-	-	-
9	0.200	89.4	38.9	87.3	18.6	-	-	-
11	0.300	95.7	34.8	57.6	-11.0	-	-	+
12	0.350	98.6	6.9	70.3	1.7	-	-	+
EMS	200	70.9	42.5	1763.5	1694.9	+	+	-
MMS	10	61.7	42.1	776.2	707.6	+	+	-

C: Negative Controls

S: Solvent Controls

RCE: Relative Cloning Efficiency = [(mean value positive cultures / mean value positive cultures of corresponding controls) x 100]

RTG: Relative Total Growth = (RSG x RCE)/100

MF: Mutant Frequency = {-ln [negative cultures/total wells (selective medium)] / -ln [negative cultures/total wells (non selective medium)]}x800

IMF: Induced Mutant Frequency = mutant frequency sample – mean value mutant frequency corresponding controls

GEF: Global Evaluation Factor (126); +: GEF exceeded, -: GEF not exceeded

*Statistical significant difference in mutant frequency compared to negative/solvent controls (Mann Whitney test , p<0.05). +: significant; -not significant

B[a]P: Benzo[a]pyrene [μg/ml]

EMS: Ethylmethanesulphonate [μg/ml]

MMS: Methylmethanesulphonate [μg/ml]

Conclusions:

Interpretation of results: negative

Trichloro(hexadecyl)silane has been tested in a study conducted according to OECD 476 and in compliance with GLP. No test-substance induced increase in the mutant frequency was observed with or without metabolic activation when the substance was tested up to cytotoxic concentration in L5178Y cells. Appropriate solvent, negative and positive controls were included and gave expected results. It is concluded that the test substance is negative for mutagenicity to mammalian cells under the conditions of the test.

Executive summary:

The test item Trichloro(hexadecyl)silane was assessed for its potential to induce mutations at the mouse lymphoma thymidine kinase locus using the cell line L5178Y.

The selection of the concentrations used in the main experiments was based on data from the pre-experiments. In experiment I 0.800 mM (with metabolic activation) and 0.200 mM (without metabolic activation) were selected as the highest concentrations. In experiment II 1.150 mM (with metabolic activation) and 0.350 mM (without metabolic activation) were selected as the highest concentrations. Experiment I with and without metabolic activation and experiment II with metabolic activation were performed as a 4 h short-term exposure assay. Experiment II without metabolic activation was performed as a 24 h long-term exposure assay.

The test item was dissolved in tetrahydrofuran (THF) and diluted in RPMI + 5% HS for short-term exposure or RPMI + 7.5% HS for long-term exposure. After adding the THF stock solution to cell culture medium precipitate formed.

The test item was investigated at the following concentrations:

Experiment I

with metabolic activation:

0.020, 0.040, 0.080, 0.100, 0.200, 0.300, 0.500, 0.800 mM

and without metabolic activation:

0.002, 0.005, 0.010, 0.020, 0.040, 0.080, 0.100, 0.200 mM

Experiment II

with metabolic activation:

0.015, 0.030, 0.050, 0.150, 0.250, 0.350, 0.450, 0.550, 1.150 mM

and without metabolic activation:

0.010, 0.020, 0.050, 0.100, 0.150, 0.200, 0.300, 0.350 mM

Precipitation of the test item was noted in pre-experiment I and II and in experiment I and II with and without metabolic activation.

Growth inhibition was observed in experiment I and II with and without metabolic activation.

In experiment I with metabolic activation the relative total growth (RTG) was 7.6% for the highest concentration (0.800 mM) evaluated. The highest concentration evaluated without metabolic activation was 0.200 mM with a RTG of 16.8%. In experiment II with metabolic activation the relative total growth (RTG) was 8.3% for the highest concentration (1.150 mM) evaluated. The highest concentration evaluated without metabolic activation was 0.350 mM with a RTG of 6.9%.Concentrations with RTG values below 10% were not considered for evaluation of mutagenicity.

In experiment I and II no biologically relevant increase of mutants was found after treatment with the test item (with and without metabolic activation).The Global Evaluation Factor (GEF; defined as the mean of the negative/vehicle mutant frequency plus one standard deviation; data gathered from ten laboratories) was not exceeded by the induced mutant frequency at any concentration. Concentrations with RTG values below 10% were not considered for evaluation of mutagenicity.

No dose-response relationship was observed.

In experiment I and II colony sizing showed no clastogenic effects induced by the test item under the experimental conditions (with and without metabolic activation).

EMS, MMS and B[a]P were used as positive controls and showed distinct and biologically relevant effects in mutation frequency. Additionally, MMS and B[a]P significantly increased the number of small colonies, thus proving the efficiency of the test system to indicate potential clastogenic effects.

This study is classified as acceptable. This study satisifies the requirements for Test Guidelines OPPTS 870.5300, OECD 476 for in vitro mutagenicity (mammalian forward mutation) data.

Reference 3

Endpoint:

in vitro gene mutation study in bacteria

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2002-05-07 to 2002-08-26

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 UND SOZIALES

Type of assay:

bacterial reverse mutation assay

Target gene:

His operon

Species / strain / cell type:

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

Additional strain / cell type characteristics:

other: uvr B-, rfa- (TA 98 & TA 100: pKM 101)

Species / strain / cell type:

S. typhimurium TA 102

Additional strain / cell type characteristics:

other: wild-type, rfa-, pKM 101

Metabolic activation:

with and without

Metabolic activation system:

Aroclor induced rat liver S9-mix

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 (without metabolic activation)
Experiment I:
- 10, 31.6, 100, 316 and 1000 μg/plate (with and without metabolic activation)
Experiment II:
- 10, 31.6, 100, 316 and 1000 μg/plate (with and without metabolic activation)

Vehicle / solvent:

- Vehicle(s)/solvent(s) used: ethylene glycol dimethylether
- Justification for choice of solvent/vehicle: The solvent was chosen because of 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-mix: sodium azide, 10 µg/plate (TA 100, TA 1535); 2-nitro-fluorene, 10 µg/plate (TA 98); 9-AA, 100 µg/plate (TA 1537); MMS, 1300 µg/plate (TA 102); +S9-mix: 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); preincubation

DURATION
- Preincubation period: 60 minutes
- Expression time (cells in growth medium): 48 hours

NUMBER OF REPLICATIONS: 3 plates per concentration in two independent experiments

DETERMINATION OF CYTOTOXICITY
- Method: other: reduced background lawn and/or a reduction in the number of revertant colonies by more than 50% compared with the solvent control

Evaluation criteria:

The test chemical 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 random samples on
histidine free agar plates.

Cytotoxicity is defined as a reduction in the number of colonies by more than 50% compared with the solvent control and/or a scarce background
lawn.

Statistics:

MANN and WHITNEY and Spearman's rank

Species / strain:

S. typhimurium TA 98

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Remarks:

316 and 1000 µg/plate (-S9, pre-incubation test)

Vehicle controls validity:

valid

Untreated negative controls validity:

not examined

True negative controls validity:

not examined

Positive controls validity:

valid

Species / strain:

S. typhimurium TA 100

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Remarks:

1000 µg/plate (-S9, plate incorporation test); 316 and 1000 µg/plate (-S9, pre-incubation test)

Vehicle controls validity:

valid

Untreated negative controls validity:

not examined

True negative controls validity:

not examined

Positive controls validity:

valid

Species / strain:

S. typhimurium TA 102

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Remarks:

316 and 1000 µg/plate (-S9, pre-incubation test)

Vehicle controls validity:

valid

Untreated negative controls validity:

not examined

True negative controls validity:

not examined

Positive controls validity:

valid

Species / strain:

S. typhimurium TA 1535

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Remarks:

1000 µg/plate (-S9, plate incorporation test); 316 and 1000 µg/plate (-S9, pre-incubation test)

Vehicle controls validity:

valid

Untreated negative controls validity:

not examined

True negative controls validity:

not examined

Positive controls validity:

valid

Species / strain:

S. typhimurium TA 1537

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Remarks:

1000 µg/plate (-S9 & +S9 , plate incorporation test); 316 and 1000 µg/plate (-S9, pre-incubation test)

Vehicle controls validity:

valid

Untreated negative controls validity:

not examined

True negative controls validity:

not examined

Positive controls validity:

valid

Additional information on results:

Full study data tables are attached as background material.

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

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

	TA100
Conc. (µg/plate)	Plate 1	Plate 2	Cytotoxic (yes/no)
0*	137	137	No
0.316	140	145	No
1	144	143	No
3.16	132	106	No
10	127	116	No
31.6	121	126	No
100	109	107	No
316	142	122	No
1000	175	170	Yes
3160	0	0	Yes
5000	0	0	Yes

*solvent control with DMSO

Table 3: 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*	38	36	No	123.3	131.3	No	271.7	278.3	No
10	44.7	34	No	150.7	133.7	No	259.3	279.7	No
31.6	43	37	No	136.0	138	No	269.7	284	No
100	41.7	30	No	131.7	148.7	No	275	280.7	No
316	46	28.7	No	156.0	143	No	253.7	266.3	No
1000	47	31	No	147.7	132.7	Yes	291.3	258	No
Positive control	1041.7	987.3	No	1271.3	1267	No	1223	1219	No

*solvent control with DMSO

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*	13.7	13	No	5	4	No
10	13.7	12.3	No	3.7	4.7	No
31.6	13	13	No	4.7	3	No
100	11.3	12	No	3	3.3	No
316	13.7	12.3	No	4	3.3	No
1000	12	11.7	Yes	4.7	5	Yes
Positive control	789	788.7	No	779.7	789.3	No

*solvent control with DMSO

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

	TA98			TA100			TA102
Conc. (µg/plate)	- M	+ MA	Cytotoxic (yes/no)	- MA	+ MA	Cytotoxic (yes/no)	- MA	+ MA	Cytotoxic (yes/no)
0*	37.3	38.3	No	114.7	134.7	No	277	259.3	No
10	41.3	28	No	108.3	104.7	No	252.3	281.3	No
31.6	36.3	37	No	134.3	114.7	No	256	268.7	No
100	33.3	37	No	120.3	134.3	No	248	278.7	No
316	46.7	30.7	Yes	132	151.3	Yes	260.3	272	Yes
1000	53.3	40.7	Yes	117.7	123.7	Yes	296.3	276	Yes
Positive control	637.7	654.7	No	997.3	976	No	1222	1226.3	No

*solvent control with DMSO

Table 4: 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*	14	17.3	No	5	6	No
10	14.3	13.3	No	4.7	6	No
31.6	13.7	13.7	No	4.7	5	No
100	13	13	No	5	5.3	No
316	12	13.7	Yes	5.3	5.3	Yes
1000	14	14	Yes	4.3	5	Yes
Positive control	902.3	900	No	377.3	381.3	No

*solvent control with DMSO

Conclusions:

Trichloro(hexadecyl)silane has been tested in compliance with OECD 471, under GLP conditions. No increase in the number of revertant colonies compared with the solvent control was observed for the test substance in any of the Salmonella typhimurium strains TA98, TA 100, TA102, TA 1535 and TA 1537 when tested with and without metabolic activation in either the initial plate incorporation or the repeat pre-incubation assay. It is concluded that the test substance is negative for mutagenicity to bacteria under the conditions of the test.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (negative)

Genetic toxicity in vivo

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

Only a reliable bacterial mutagenicity study and a reliable mammalian mutagenicity study in vitro are available for the registered substance trichloro(hexadecyl)silane (CAS 5894-60-0), however, reliable data are available for the structural analogue substance trimethoxy(hexadecyl)silane (CAS 16415-12-6) for in vitro cytogenicity in mammalian cells. Both substances have the ability to hydrolyse in contact with water to produce the same silanol hydrolysis product hexadecylsilanetriol. It is therefore considered that read-across between the substances is appropriate.

 

A key bacterial reverse mutation study conducted according to OECD TG 471 and in compliance with GLP is available for trichloro(hexadecyl)silane (CAS 5894-60-0). No increase in the number of revertant colonies compared with the solvent control was observed for the test substance in any of the Salmonella typhimurium strains TA 98, TA 100, TA 102, TA 1535 and TA 1537 when tested with and without metabolic activation in either the initial plate incorporation or the repeat pre-incubation assay. It was therefore concluded that the test substance is negative for mutagenicity to bacteria under the conditions of the test (LPT, 2002).

 

A key in vitro cytogenicity study conducted according to OECD TG 473 and in compliance with GLP is available for the structural analogue substance trimethoxy(hexadecyl)silane (CAS 16415-12-6). Trimethoxy(hexadecyl)silane did not induce any statistically significant, dose-related increases in the frequency of cells with chromosomal aberrations either in the presence or absence of metabolic activation or after various exposure times. Trimethoxy(hexadecyl)silane was therefore considered to be non-clastogenic to CHO cells in vitro under the conditions of the test (RTC, 2005).

 

In the key in vitro mammalian mutagenicity study (BSL, 2012), the test item trichloro(hexadecyl)silane (CAS 5894-60-0) was assessed for its potential to induce mutations at the mouse lymphoma thymidine kinase locus using the cell line L5178Y. The study was conducted according to OECD TG 476 and in compliance with GLP. No biologically relevant increase of mutants was found after treatment with the test item (with and without metabolic activation). The Global Evaluation Factor (GEF; defined as the mean of the negative/vehicle mutant frequency plus one standard deviation; data gathered from ten laboratories) was not exceeded by the induced mutant frequency at any concentration. Concentrations with RTG values below 10% were not considered for evaluation of mutagenicity. No dose-response relationship was observed. Colony sizing showed no clastogenic effects induced by the test item under the experimental conditions (with and without metabolic activation). Appropriate solvent and positive controls were included in the test and gave the expected results. It was therefore concluded that the test substance is not mutagenic to mammalian cells under the conditions of the test.

Justification for classification or non-classification

The available in vitro data on genetic toxicity of the registered substance and the structural analogue substance, trimethoxy(hexadecyl)silane (CAS 16415-12-6) do not meet the criteria for classification according to Regulation (EC) No. 1272/2008, and are therefore conclusive but not sufficient for classification.