Trimethoxyphenylsilane

Endpoint summary

Key value for chemical safety assessment

Genetic toxicity in vitro

Description of key information

Gene mutation (Bacterial reverse mutation assay/ Ames test): negative with and without metabolic activation in S. typhimurium: TA 98, TA 100, TA 1535, TA 1537 and Escherichia coli: WP2 uvrA (according to EEC directive L251, 27, 137 1984).

Mammalian gene mutagenicity (in vitro mouse lymphoma L5178Y cell gene mutation test): read-across from structural analogue substance trichlorophenylsilane (CAS: 98-13-5): negative with and without metabolic activation. (according to OECD TG 476).

Mammalian cytogenicity (Chinese hamster lung fibroblasts V79 cell chromosome aberration assay): positive with metabolic activation (according to OECD TG 473).

Link to relevant study records

Reference

Reference 1

Endpoint:

in vitro gene mutation study in bacteria

Type of information:

experimental study

Adequacy of study:

key study

Study period:

Not stated.

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

test procedure in accordance with national standard methods with acceptable restrictions

Remarks:

The study was conducted according to an EU test method but full details are not available. It was compliant with GLP. The restrictions were that no units for concentration of the test material was provided and only the positive control with activation was not adequate to test S9 efficacy.

Qualifier:

according to guideline

Guideline:

other: EEC directive L251, 27, 137 1984

Deviations:

yes

Remarks:

no Units for concentration of the test material was provided and the only positive control with activation was not adequate to test S9 efficacy.

GLP compliance:

yes

Type of assay:

bacterial reverse mutation assay

Target gene:

his operon for S. typhimurium strains and trp operon for E. coli strains.

Species / strain / cell type:

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

Species / strain / cell type:

E. coli WP2

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:

312.5, 625, 1250, 2500 and 5000 µg/plate - with and without metabolic activation.

Vehicle / solvent:

- Vehicle(s)/solvent(s) used: Ethanol.

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

other: 2-Anthramine

Remarks:

with metabolic activation: All strains; 10 µg/plate

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

methylmethanesulfonate

Remarks:

without metabolic activation:TA-1537; 50 µg/plate

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

2-nitrofluorene

Remarks:

without metabolic activation: TA-98; 10 µg/plate

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

9-aminoacridine

Remarks:

without metabolic activation: TA-1537; 50 µg/plate

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

sodium azide

Remarks:

without metabolic activation: TA-1535, TA-100; 10 µg/plate

Details on test system and experimental conditions:

METHOD OF APPLICATION: in medium (plate incorporation)

DURATION
- Expression time (cells in growth medium): 72 hours

NUMBER OF REPLICATIONS: triplicates each in two independent experiments.

DETERMINATION OF CYTOTOXICITY
- Method: Not reported.

METABOLIC ACTIVATION SYSTEM: S-9 mix was prepared in accordance with published procedures (Ames, et al, 1975; Matsushima, et al, 1976), using a 9, 000 x g supernatant prepared from Sprague-Dawley adult male rat liver induced by Aroclor 1254 five days prior to kill.

Evaluation criteria:

Not reported

Statistics:

Not reported

Species / strain:

E. coli WP2

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

not specified

Vehicle controls validity:

valid

Untreated negative controls validity:

not applicable

Positive controls validity:

valid

Species / strain:

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

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

not specified

Vehicle controls validity:

valid

Untreated negative controls validity:

not applicable

Positive controls validity:

valid

Additional information on results:

Not reported

Conclusions:

Interpretation of results: negative with and without metabolic activation

In a bacterial mutagenicity assay according to EEC directive L251, 27, 137 1984 and to GLP, no mutagenic effect was seen in any of the strains tested. Appropriate solvent and positive controls were included and gave expected results. The test substance is non-mutagenic in test strains used.

Reference 2

Endpoint:

in vitro cytogenicity / chromosome aberration study in mammalian cells

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2008-05-15 to 2008-06-20

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 473 (In Vitro Mammalian Chromosome Aberration Test)

Version / remarks:

1997

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: Commission Directive 2000/32/EC, L1362000, Annex 4A: ”Mutagenicity – In vitro Mammalian Chromosome Aberration Test“, dated May 19, 2000.

Deviations:

no

GLP compliance:

yes

Type of assay:

other: in vitro mammalian chromosome aberration test

Species / strain / cell type:

Chinese hamster lung fibroblasts (V79)

Metabolic activation:

with and without

Metabolic activation system:

cofactor supplemented post-mitochondrial fraction (S9 mix), prepared from the livers of rats treated with Phenobarbital/beta-Naphthoflavone.

Test concentrations with justification for top dose:

Without activation: 63.9-2045.0 µg/mL; with activation 31.9-1022.5 µg/mL

Vehicle / solvent:

- Vehicle(s)/solvent(s) used: ethanol
- Justification for choice of solvent/vehicle: The solvent was chosen for its solubility properties and its relative non-toxicity to the cell cultures.

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

ethylmethanesulphonate

Remarks:

without metabolic activation: final concentration: 900 µg/mL

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

cyclophosphamide

Remarks:

with metabolic activation: final concentration: 1.4 µg/mL

Details on test system and experimental conditions:

METHOD OF APPLICATION: in medium in Quadriperm dishes

DURATION
- Preincubation period: none
- Exposure duration: 4 hours
- Expression time (cells in growth medium): 14 hours
- Fixation time (start of exposure up to fixation or harvest of cells): 18 hours

SPINDLE INHIBITOR (cytogenetic assays):
STAIN (for cytogenetic assays): Giemsa

NUMBER OF REPLICATIONS: duplicate cultures (2 chambers per test group)

NUMBER OF CELLS EVALUATED: at least 100 per culture

DETERMINATION OF CYTOTOXICITY
- Method: mitotic index; other: reduced cell mumbers

OTHER EXAMINATIONS:
- Determination of polyploidy: yes
- Determination of endoreplication: yes

OTHER: a preliminary test to evaluate cytotoxicity was carried out to determine suitable dose range for the assay.

Evaluation criteria:

A test item is classified as clastogenic if:
a) the number of induced structural chromosome aberrations is not in the range of the laboratory’s historical control data range;
and b) either a concentration-related or a significant increase of the number of structural chromosome aberrations is observed.

Statistics:

Fisher’s exact test

Species / strain:

Chinese hamster lung fibroblasts (V79)

Metabolic activation:

with

Genotoxicity:

positive

Cytotoxicity / choice of top concentrations:

cytotoxicity

Remarks:

at 511.3 µg/mL and above with S9

Vehicle controls validity:

valid

Untreated negative controls validity:

not applicable

Positive controls validity:

valid

Species / strain:

Chinese hamster lung fibroblasts (V79)

Metabolic activation:

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 applicable

Positive controls validity:

valid

Additional information on results:

TEST-SPECIFIC CONFOUNDING FACTORS: none. A non-interfering precipitate was observed at 2055.0 µg/mL

RANGE-FINDING/SCREENING STUDIES: significant toxicity was observed in the preliminary cytotoxicity test at concentrations of 1022.5 and 2045.0 µg/mL

CYTOTOXICITY: cytotoxic concentrations did not produce sufficient cells with analysable chromosomes to be included in the analysis.


COMPARISON WITH HISTORICAL CONTROL DATA: control results fall within the range of historical controls. All values of cultures treated with test substance in the presence of metabolic activation showed increases in the number of cells with aberrations excluding gaps clearly exceeded the control values.

No polyploidy was observed in any culture

Table 1 Summary of results of chromosome aberration study

Activation	Concentration µg/ml	Cell numbers %	Mitotic index %	Aberrant cells inc gaps	Aberrant cells exc gaps	Aberrant cells with exchanges
Without activation	Solvent control	100	100	2.5	1.0	0
	Positive control	NT	115.4	15.5	12.5*	7.5
	127.8	103.1	138.5	1.5	1.5	0.5
	255.6	93.5	1.2.0	3.0	2.0	0
	511.3	89.3	102.4	0	0	0
With activation	Solvent control	100	100	2.5	2.5	0.5
	Positive control	NT	72.8	18.5	16.5*	7.5
	127.8	81.7	89.0	8.5	7.5*	5.5
	255.6	55.1	78.0	14.5	13.5*	6.5
	511.3	64.6	69.1	18.0	16.0*	5.0

NT not tested * Aberration frequency statistically significantly higher than corresponding control values (p < 0.05)                                                                                                                               

Table 2 Results of chromosome analysis without activation (total of 200 cells scored)

Treatment		Solvent control	Positive control	Low dose 127.8 µg/mL	Mid dose 255.6 µg/mL	High dose 511.3  µg/mL
Cytotoxicity		no	no	no	no	no*
Chromatid aberrations	break	2	12	3	3	0
	fragment	0	2	0	0	0
	deletion	0	0	0	0	0
	exchange	0	21	1	0	0
Chromosome aberrations	break	0	4	0	0	0
	fragment	0	1	0	1	0
	deletion	0	0	0	0	0
	exchange	0	0	0	0	0
mitotic index %		100	115.4	138.5	102.0	102.4

*cultures treated with toxic concentrations did not have sufficient analysable chromosomes to be included in the analysis

Table 3 Results of chromosome analysis with activation (total of 200 cells scored)

Treatment		Solvent control	Positive control	Low dose 127.8 µg/mL	Mid dose 255.6 µg/mL	High dose 511.3 µg/mL
Cytotoxicity		no	no	no	no	no
Chromatid aberrations	break	5	19	3	16	25
	fragment	0	0	0	0	0
	deletion	0	0	0	0	0
	exchange	1	15	11	15	10
Chromosome aberrations	break	0	1	0	2	2
	fragment	0	0	1	0	0
	deletion	0	0	0	0	0
	exchange	0	0	0	1	0
mitotic index  %		100	72.8	89.0	78.0	69.1

Conclusions:

Interpretation of results :
positive with metabolic activation
negative without metabolic activation

Trimethoxyphenylsilane CAS 2996-92-1 has been tested in a valid in vitro cytogenicity study according to OECD 473 and under GLP. A statistically significant, dose dependent increase in the number of cells with aberrations excluding gaps was detected in the evaluated concentration tested in the presence of activation. Appropriate solvent and positive controls were included and gave expected results. It is concluded by the authors of the study that this result is biologically significant and that trimethoxyphenylsilane is positive for the induction of structural chromosome aberrations (clastogenic) under the conditions of the test.

Reference 3

Endpoint:

in vitro gene mutation study in mammalian cells

Type of information:

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

Adequacy of study:

key study

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:

mouse lymphoma L5178Y cells

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Remarks:

600 µg/ml

Vehicle controls validity:

valid

Untreated negative controls validity:

not applicable

Positive controls validity:

valid

Conclusions:

Interpretation of results: negative with and without activation

Executive summary:

An in vitro mammalian mutagenicity study is available from the structural analogue trichloro(phenyl)silane. In this test the structural analogue did not show any genotoxic potential and thus this is also estimated for trimethoxy(phenyl)silane. As explained in the justification for type of information, the differences in molecular structure between the target and the source are unlikely to lead to differences in genetic toxicity that are higher than the typical experimental error of the test method.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed (positive)

Genetic toxicity in vivo

Description of key information

Chromosome aberration (rat erythrocyte micronucleus assay, inhalation: vapour): read-across from the structural analogue substance dimethoxymethylphenylsilane (CAS: 3027-21-2): negative (according to OECD TG 413).

Link to relevant study records

Reference

Endpoint:

in vivo mammalian somatic cell study: cytogenicity / erythrocyte micronucleus

Type of information:

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

Adequacy of study:

key study

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

Sex:

male/female

Genotoxicity:

negative

Toxicity:

yes

Remarks:

reduction in PCE:NCE ratio relative to control

Vehicle controls validity:

valid

Negative controls validity:

valid

Positive controls validity:

not examined

Conclusions:

Interpretation of results: negative

Executive summary:

An in vivo mammalian micronucleus study is available from the structural analogue dimethoxymethyl(phenyl)silane CAS 3027 -21 -2. In this test the structural analogue did not show any genotoxic potential and thus this is also estimated for trimethoxy(phenyl)silane. As explained in the justification for type of information, the differences in molecular structure between the target and the source are unlikely to lead to differences in genetic toxicity that are higher than the typical experimental error of the test method.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (negative)

Additional information

Studies were chosen as key when the available study was of relevance and of sufficient quality for classification, labelling and for risk assessment.

 

The key bacterial mutagenicity study on trimethoxyphenylsilane was conducted in compliance with GLP and according to EEC directive L251, 27, 137, 1984 (now B.13/14). No evidence for a test-substance related increase in the number of revertants was observed in Salmonella typhimurium TA 98, TA 100, TA 1535, TA 1537 and Escherichia coli WP2 and WP2 uvrA strains. Appropriate positive and solvent controls were included and gave expected results. Under the conditions of this study, trimethoxyphenylsilane was concluded to be non-mutagenic in the Salmonella typhimurium/E. coli strains (Dow Corning Corporation, 1991a).

 

No measured data are available to assess the in vitro mammalian mutagenicity potential of the registered substance, trimethoxyphenylsilane, however, reliable data are available for the structural analogue substance, trichlorophenylsilane (CAS: 98-13-5). Both substances hydrolyse in contact with water to generate the common silanol hydrolysis product, phenylsilanetriol, and it is therefore considered that read-across between the substances is appropriate. The other hydrolysis products, methanol and hydrogen chloride are not genotoxic.

The key in vitro cytogenicity study on trimethoxyphenylsilane was conducted in compliance with GLP and according to OECD TG 473. A statistically significant, dose dependent increase in the number of cells with aberrations excluding gaps was detected in the evaluated concentration in the presence of metabolic activation.Appropriate positive and solvent controls were included and gave expected results.It was therefore concluded that this result is biologically significant and that trimethoxyphenylsilane is positive for the induction of structural chromosome aberrations (clastogenic) under the conditions of the test (Hoffmann, H.2008).

The key in vitro mammalian cell gene mutation study on the structural analogue substance trichlorophenylsilane (CAS: 98-13-5) was conducted in compliance with GLP and according to OECD TG 476. No increase in mutant frequency was observed at any concentration with and without metabolic activation at 4 hours treatment and without metabolic activation at 24 hours treatment. Expected results were obtained with positive and negative controls. It was concluded that the structural analogue substance, trichlorophenylsilane is negative for the induction of mutations in L5178Y cells under the conditions of the test (Flanders, L.2010).

 

 

No measured data are available to assess the in vivo cytogenicity potential of the registered substance, trimethoxyphenylsilane, however reliable data are available for the structural analogue substance dimethoxymethylphenylsilane (CAS: 3027-21-2). Since both substances hydrolyse in contact with water to generate structurally related silanol hydrolysis products,phenylsilanetriol and methylphenylsilanediol, it is considered that read-across between the substances is appropriate. The other hydrolysis products, methanol is not genotoxic.

 

The key in vivo cytogenicity study on the structural analogue substance dimethoxymethylphenylsilane (CAS: 3027-21-2)wasperformed as part of a 14-day repeat dose inhalation toxicity study in compliance with GLP and according to OECD TG 413. The test substance was not genotoxic under the conditions of the test. Appropriate positive and solvent controls were included and gave expected results (Dow Corning Corporation, 1991b). The potential for clastogenicity observed in the in vitro assay with the registered substance was not confirmed in an in vivo chromosome aberration assay with the structural analogue substance dimethoxymethylphenylsilane, therefore the overall assumption is that the registered substance is neither mutagenic not cytogenic. 

Justification for classification or non-classification

Based on the available in vitro and in vivo data on mutagenicity of the registered substance and the structural analogue substances, trichlorophenylsilane (CAS: 98-13-5) and dimethoxymethylphenylsilane (CAS: 3027-21-2), trimethoxyphenylsilane is not classified for mutagenicity according to Regulation (EC) 1272/2008 or Directive 67/548/EEC.