Hexyltrimethoxysilane

Endpoint summary

Key value for chemical safety assessment

Genetic toxicity in vitro

Description of key information

Ames test according to OECD TG 471: negative

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:

2018-01-25 to 2018-04-24

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:

21st July, 1997

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method B.13/14 (Mutagenicity - Reverse Mutation Test Using Bacteria)

Version / remarks:

May 30, 2008

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

Bayrisches Landesamt für Gesundheit und Lebensmittelsicherheit

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: The tester strains TA98, TA100 and TA102 contain the R-factor plasmid, pkM101

Species / strain / cell type:

S. typhimurium TA 102

Additional strain / cell type characteristics:

other: The tester strains TA98, TA100 and TA102 contain the R-factor plasmid, pkM101

Metabolic activation:

with and without

Metabolic activation system:

S9 liver microsomal fraction from phenobarbital / β naphthoflavone-induced male rats

Test concentrations with justification for top dose:

0.0100, 0.0316, 0.100, 0.316, 1.0, 2.5 and 5.0 µL/plate

Concentrations were selected based on the results of a preliminary experiment.

Vehicle / solvent:

- Vehicle(s)/solvent(s) used: DMSO
- Justification for choice of solvent/vehicle: DMSO was selected based on the solubility of the test material.

Untreated negative controls:

yes

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

sodium azide

methylmethanesulfonate

other: 4-nitro-o-phenylene-diamine (4-NOPD); 2-aminoanthracene (2AA)

Details on test system and experimental conditions:

METHOD OF APPLICATION: in agar for plate incorporation test (experiment I) and the pre-incubation test (experiment II)

DURATION
- Preincubation period: 60 min
- Exposure duration: 48 h

NUMBER OF REPLICATIONS: 3

DETERMINATION OF CYTOTOXICITY
- Method: Cytotoxicity can be detected by a clearing or rather diminution of the background lawn or a reduction in the number of revertants down to a mutation factor of approximately ≤ 0.5 in relation to the solvent control.

Evaluation criteria:

A test was considered acceptable if for each strain:
- the bacteria demonstrated their typical responses to ampicillin (TA98, TA100, TA102)
- the negative control plates (A. dest.) with and without S9 mix were within the historical control data range
- corresponding background growth on negative control, solvent control and test plates was observed
- the positive controls showed a distinct enhancement of revertant rates over the control plate
- at least five different concentrations of each tester strain were analysable.

A test item was considered as mutagenic if:
- a clear and dose-related increase in the number of revertants occurred and/or
- a biologically relevant positive response for at least one of the dose groups occurred in at least one tester strain with or without metabolic activation.

A biologically relevant increase was described as follows:
- if in tester strains TA 98, TA 100 and TA 102 the number of reversions was at least twice as high
- if in tester strains TA 1535 and TA 1537 the number of reversions ws at least three times higher than the reversion rate of the solvent control.

Statistics:

Not reported

Species / strain:

S. typhimurium TA 98

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Species / strain:

S. typhimurium TA 100

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Species / strain:

S. typhimurium TA 1535

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Species / strain:

S. typhimurium TA 1537

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Species / strain:

S. typhimurium TA 102

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:

valid

Positive controls validity:

valid

Additional information on results:

TEST-SPECIFIC CONFOUNDING FACTORS
- Precipitation: No precipitation of the test item was observed in any tester strain used in experiment I and II (with and without metabolic activation).

RANGE-FINDING/SCREENING STUDIES: The toxicity of the test item was determined with tester strains TA 98 and TA 100 in a pre-experiment. Eight concentrations (0.00316, 0.0100, 0.0316, 0.100, 0.316, 1.0, 2.5 and 5.0 µL/plate) were tested for toxicity and induction of mutations with three plates each. No toxicity was observed in the pre-experiment.

HISTORICAL CONTROL DATA (with ranges, means and standard deviation and confidence interval (e.g. 95%)
- Positive historical control data:
- Negative (solvent/vehicle) historical control data:

ADDITIONAL INFORMATION ON CYTOTOXICITY:
- Measurement of cytotoxicity used: In experiment I toxic effects of the test item were observed in tester strain TA 98 at concentrations of 1.0 µL/plate and higher (without metabolic activation) and in tester strain 1537 at a concentration of 5.0 µL/plate (with metabolic activation).

In experiment II toxic effects of the test item were noted in tester strains TA 98 and TA 100 at a concentration of 5.0 µL/plate (without metabolic activation) and at concentrations of 2.5 µL/plate and higher (with metabolic activation). In tester strain TA 1535 toxic effects of the test item were noted at concentrations of 2.5 µL/plate and higher (without metabolic activation) and at concentrations of 1.0 µL/plate and higher (with metabolic activation). In tester strain TA 1537 toxic effects of the test item were observed at a concentration of 5.0 µL/plate (with and without metabolic activation).

- Other observations when applicable: The reduction in the number of revertants down to a mutation factor of ≤ 0.5 found in experiment I in tester strain TA 100 at a concentration of 2.5 µL/plate (without metabolic activation) was regarded as not biologically relevant due to lack of a dose-response relationship.

Conclusions:

In conclusion, it can be stated that during the described mutagenicity test and under the experimental conditions reported, hexyltrimethoxysilane did not cause gene mutations by base pair changes or frameshifts in the genome of the tester strains used. Therefore, hexyltrimethoxysilane is considered to be non-mutagenic in this bacterial reverse mutation assay.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (negative)

Genetic toxicity in vivo

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

A key bacterial mutagenicity study according to OECD TG 471 and GLP is available for hexyl(trimethoxy)silane (CAS 3069-19-0). In general, no evidence for a test-substance related increase in the number of revertants was observed in any of the Salmonella typhimurium strains (TA 1535, TA1537, TA98, TA100 and TA102) in two independent experiments without and with metabolic activation. There was a reduction in the number of revertants down to a mutation factor of ≤ 0.5 in experiment I in tester strain TA 100 at a concentration of 2.5 µL/plate (without metabolic activation); however, this effect was regarded as not biologically relevant due to lack of a dose-response relationship. Additionally, cytoxicity effects were noted in both experiments. In experiment I toxic effects of the test item were observed in tester strain TA98 at concentrations of 1.0 µL/plate and higher (without metabolic activation) and in tester strain TA1537 at a concentration of 5.0 µL/plate (with metabolic activation). In experiment II toxic effects of the test item were noted in tester strains TA98 and TA100 at a concentration of 5.0 µL/plate (without metabolic activation) and at concentrations of 2.5 µL/plate and higher (with metabolic activation). In tester strain TA1535 toxic effects of the test item were noted at concentrations of 2.5 µL/plate and higher (without metabolic activation) and at concentrations of 1.0 µL/plate and higher (with metabolic activation). In tester strain TA1537 toxic effects of the test item were observed at a concentration of 5.0 µL/plate (with and without metabolic activation). Appropriate positive and solvent controls were included and gave expected results. Under the conditions of this study, the registered substance was concluded to be non-mutagenic in the strains tested (Eurofins, 2018).

No bacterial mutagenicity potential is also considered for the target substance CAS 3069-19-0.

Justification for classification or non-classification

Hexyltrimethoxysilane is considered to be non-mutagenic in this bacterial reverse mutation assay. However, no final decision on classification for genetic toxicity according to Regulation (EC) 1272/2008 can be made, as any information on chromosomal aberration and mutagenicity in mammalian cells/in vivo is available.