Tetraethyl orthosilicate

Endpoint summary

Key value for chemical safety assessment

Genetic toxicity in vitro

Description of key information

The genetic toxicity studies for tetraethyl orthosilicate (CAS 78-10-4, EC No. 201-083-8) were conducted according to the appropriate OECD guidelines, or to protocols that are similar to OECD guidelines. The studies were conducted in compliance with GLP, except possibly BRRC 1981 and the published Lionti et al. 2014, for which information on GLP is not available.

 

Gene mutation assessed as weight of evidence (Bacterial reverse mutation assay / Ames test): negative with and without activation in Salmonella typhimurium TA98, TA100, TA1535, TA1537 and TA1538 (similar to OECD Test Guideline 471) (Hüls AG 1993).

 

Gene mutation (Bacterial reverse mutation assay / Ames test): negative with and without activation in Salmonella typhimurium strains TA 98, TA 100, TA1535, TA1537 or Escherichia coli WP2 (OECD Test Guideline 471) (Lionti et al. 2014).

 

Cytogenicity in mammalian cells: negative in CHO cells (OECD Test Guideline 473) (BioReliance 2002).

 

Mutagenicity in mammalian cells: negative in CHO cells (similar to OECD Test Guideline 476) (BRRC 1981).

Link to relevant study records

Reference

Reference 1

Endpoint:

in vitro cytogenicity / chromosome aberration study in mammalian cells

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1993-01-29 to 1993-03-22

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)

GLP compliance:

yes

Type of assay:

in vitro mammalian chromosome aberration test

Target gene:

Histidine operon (S. typhimurium strains); tryptophan operon (E. coli).

Species / strain / cell type:

Chinese hamster Ovary (CHO)

Metabolic activation:

with and without

Metabolic activation system:

Aroclor induced rat liver S9

Test concentrations with justification for top dose:

125 to 1500 µg/mL (without activation, 4 and 20h exposure), and 500 to 2080 µg/mL (witn activation 4 hour exposure)

Vehicle / solvent:

- Vehicle(s)/solvent(s) used: DMSO
- Justification for choice of solvent: based on infomation provided by the Sponsor and compatibility with the target cells.

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

mitomycin C

Remarks:

(without activation)

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

cyclophosphamide

Remarks:

(with activation)

Details on test system and experimental conditions:

METHOD OF APPLICATION: in medium

DURATION

- Exposure duration: 4h / 20h (-S9), 4h (+S9)

- Expression time (cells in growth medium): 20h

- Fixation time (start of exposure up to fixation or harvest of cells): 20h

NUMBER OF REPLICATIONS: duplicate flasks

NUMBER OF CELLS EVALUATED: 200 metaphase spreads (100 per duplicate flask), per concentration.

DETERMINATION OF CYTOTOXICITY

- Method: percentage total growth

Evaluation criteria:

Cells examined for numerical and structural aberrations, and statistical significance calculated. For the result to be positive, the increase in aberrations must be statistically significant and dose related.

Toxicity is defined as a 50 % or greater reduction in cell growth.

Statistics:

The number and type of aberrations found, the percentage of structurally and numerically damaged cells (% aberrant cells) in the total population examined and mean aberrations per cell were calculated for each group. Fisher's exact test was used to compare pairwise the percent aberrant cells of each treatment group with that of the solvent control.

Statistical analysis of the percent aberrant cells was performed using the Fisher's exact test. Fisher's test was used to compare pairwise the percent aberrant cells of each treatment group with that of the solvent control. In the event of a positive Fisher's test at any test article dose level, the Cochran-Armitage test was used to measure dose-responsiveness.

Species / strain:

Chinese hamster Ovary (CHO)

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Remarks:

With metabolic activation: 1250 µg/ml; Without metabolic activation: 1250 µg/ml

Vehicle controls validity:

valid

Untreated negative controls validity:

not applicable

Positive controls validity:

valid

Additional information on results:

TEST-SPECIFIC CONFOUNDING FACTORS
- Effects of pH: at highest test concentration was 7.4
- Effects of osmolality: checked

RANGE-FINDING/SCREENING STUDIES: Substantial toxicity (i.e., at least 50% cell growth inhibition, relative to the solvent control) was observed at dose level 2080 pg/mL in the non-activated 4 and 20 hour exposure groups and in the S9 activated 4 hour exposure group.


COMPARISON WITH HISTORICAL CONTROL DATA: The percentage of cells with structural aberrations in the test article-treated groups was statistically increased above that of the solvent control at dose level 1250 pg/mL (p

Remarks on result:

other: No mutagenic potential

For the chromosome aberration assay, CHO cells were seeded at approximately 5 x l0 5 cells/25 cm² flask and were incubated at 37+/- 1C  in a humidified atmosphere of 5+/-1% CO2 in air for 16-24 hours.

Treatment time: 4hrs, S9: none, Toxicity at highest dose scored: 52% at 1250 µg/ml; Mitotic index reduction: 4%
Treatment time: 20 hrs, S9: none, Toxicity at highest dose scored: 56% at 1250 µg/ml; Mitotic index reduction: none
Treatment time: 4 hrs, S9: yes, Toxicity at highest dose scored: 54% at 1250 µg/ml; Mitotic index reduction: 10%

The percentage of structurally damaged cells in the mitomycin (positive  control in non-activated system) treatment (15%) was statistically  significant.
The percentage of structurally damaged cells in the cyclophosphamide  (positive control in activated system) treatment (14%) was statistically  significant.

Table 1 Summary of results (200 cells scored)

Treatment µg/ml	Metabolic activation	Treatment time (h)	Mean mitotic index	Aberrations per cell (mean (±SD)	Cells with aberrations %
					numerical	Structural
0*	-	4	15.7	0.015 ± 0.122	3.0	1.5
250	-	4	16.0	0.005 ± 0.071	2.5	0.5
750	-	4	15.2	0.005 ± 0.071	3.0	0.5
1250	-	4	15.0	0.000 ± 0.000	2.5	1.0
Positive control	-	4	15.5	0.130 ± 0.484	4.0	10.0
0*	+	4	16.6	0.000 ± 0.000	2.0	0.0
250	+	4	15.1	0.005 ± 0.071	2.5	0.5
750	+	4	15.7	0.000 ± 0.000	1.5	0.0
1250	+	4	14.9	0.030 ± 0.198	3.5	2.5
Positive control	+	4	13.5	0.200 ± 0.576	3.0	14.0
0*	-	20	15.6	0.000 ± 0.000	2.0	1.0
250	-	20	14.8	0.000 ± 0.000	3.5	0.0
750	-	20	15.6	0.010 ± 0.141	2.0	0.5
1250	-	20	15.9	0.005 ± 0.071	2.5	0.5
Positive control	-	20	15.3	0.210 ± 0.598	3.5	15.0

* solvent control with DMSO

Conclusions:

Tetraethyl orthosilicate has been tested in a reliable study conducted according to OECD Test Guideline 473 in compliance with GLP (reliability score 1). No increase in the number of structural and numerical chromosome aberrations in CHO cells was observed. Appropriate positive and solvent controls were included and gave expected results. It is concluded that the test substance is negative for the induction of chromosome aberrations 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

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Remarks:

Tables of results are not included in the copy of the report available to the reviewer.

Qualifier:

equivalent or similar to guideline

Guideline:

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

GLP compliance:

no

Type of assay:

mammalian cell gene mutation assay

Species / strain / cell type:

Chinese hamster Ovary (CHO)

Metabolic activation:

with and without

Metabolic activation system:

Aroclor induced rat liver S9

Test concentrations with justification for top dose:

up to 0.15% by volume, equivalent to 1.5 µg/ml

Vehicle / solvent:

- Vehicle(s)/solvent(s) used: DMSO;
- Justification for choice of solvent/vehicle: none given in study report

Untreated negative controls:

yes

Remarks:

cell culture medium

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

N-dimethylnitrosamine

Remarks:

with activation

Untreated negative controls:

yes

Remarks:

cell culture medium

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

ethylmethanesulphonate

Remarks:

without activation

Details on test system and experimental conditions:

METHOD OF APPLICATION: in medium

DURATION
- Exposure duration: 5 hours minimum
- Expression time (cells in growth medium): 7-10 days
- Selection time (if incubation with a selection agent): Not specified
- Fixation time (start of exposure up to fixation or harvest of cells): 9-12 days

SELECTION AGENT (mutation assays):
Not specified

NUMBER OF REPLICATIONS: no information; 10 concentrations tested

DETERMINATION OF CYTOTOXICITY
- Method: relative total growth

Evaluation criteria:

A dose-related increase in the number of revertants relative to control values was considered positive.

Statistics:

Student's t-test

Species / strain:

Chinese hamster Ovary (CHO)

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Remarks:

variable, toxicity observed at several concentrations tested

Vehicle controls validity:

valid

Untreated negative controls validity:

not specified

Positive controls validity:

valid

Additional information on results:

COMPARISON WITH HISTORICAL CONTROL DATA: mutant frequencies for solvent controls were in an acceptable and low range compared with historical control values,

ADDITIONAL INFORMATION ON CYTOTOXICITY: Percentage survival was dose related for concentrations between 9 - 12 µg/ml. Less cytotoxicity was observed at two higher doses, and no survival was obtained at the highest dose. This unusual response may indicate possible phase separations characteristic of some organosilicon materials in aqueous media.

Remarks on result:

other: No mutagenic potential

The test material did not produce a dose-related increase in the frequency of mutants/10 E+06 viable cells over the range of concentrations tested either with or without activation. Two concentrations tested without activation showed a statistically significant mutant frequency relative to solvent control. Small increases in mutant frequency at other dose levels were not considered to be biologically significant because occasional increases of similar magnitude have been obtained in previous tests with solvent or negative controls. The biological significance of the weak responses obtained at the 1.4 and 1.1 µg/ml concentrations tested without activation was doubtful because the effects were produced at non-consecutive doses and were within the range of variations observed in historical negative control data.

Conclusions:

Tetraethyl orthosilicate has been tested in a reliable study according to a protocol that is similar to OECD Test Guideline 476 (reliability score 2). There was no information on GLP compliance. Weak responses (increase in the number of revertants relative to the solvent control ) were obtained at the 1.4 and 1.1 µg/ml concentrations tested without activation in Chinese hamster ovary cells. The biological significance of these results was doubtful because the effects were produced at non-consecutive doses and were within the range of variations observed in historical negative control data. It is therefore considered that the test substance is negative for the induction of mutations in mammalian cells under the conditions of this test.

Reference 3

Endpoint:

in vitro gene mutation study in bacteria

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

1993-01-29 to 1993-03-22

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Remarks:

The restrictions are that the range of strains does not comply with current guidelines.

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

Cited as Directive 84/449/EEC, B.14

Deviations:

yes

Remarks:

range of stains differs from current guideline

GLP compliance:

yes

Type of assay:

bacterial reverse mutation assay

Species / strain / cell type:

S. typhimurium, other: TA98, TA100, TA1535, TA1537 and TA1538

Metabolic activation:

with and without

Metabolic activation system:

phenobarbiturate activated S9

Test concentrations with justification for top dose:

8, 40, 200, 1000, 5000 µg/plate

Vehicle / solvent:

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

Untreated negative controls:

yes

Remarks:

water

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:

yes

Remarks:

water

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

other: Sodium trinitride

Remarks:

TA 100, TA 1535 (without activation)

Untreated negative controls:

yes

Remarks:

water

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

9-aminoacridine

Remarks:

TA 1537 (without activation)

Untreated negative controls:

yes

Remarks:

water

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

cyclophosphamide

Remarks:

TA 100 (with activation)

Details on test system and experimental conditions:

METHOD OF APPLICATION: in agar; preincubation

DURATION

- Preincubation period: 30 minutes

- Exposure duration: 96 hours

NUMBER OF REPLICATIONS: 3 per test concentration; Plate incorporation test was repeated in two preincubation assays (only two strains tested in final assay)

DETERMINATION OF CYTOTOXICITY

- Method: relative total growth

Evaluation criteria:

Substances that do not show a mutagenic effect at a concentration of 5000 µg/plate are considered to be non-mutagenic.

Statistics:

Revertant colonies counted, and mean / standard deviation calculated using a computer program written by BIOSYS Co.

Species / strain:

S. typhimurium TA 98

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 applicable

Positive controls validity:

valid

Species / strain:

S. typhimurium TA 100

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 applicable

Positive controls validity:

valid

Species / strain:

S. typhimurium TA 1535

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 applicable

Positive controls validity:

valid

Species / strain:

S. typhimurium 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 applicable

Positive controls validity:

valid

Species / strain:

S. typhimurium TA 1538

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 applicable

Positive controls validity:

valid

Additional information on results:

No precipitation or cytotoxicity were observed during the course of the test.

Remarks on result:

other: No mutagenic potential

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

Conc. (µl/ml)	TA 98			TA 100			TA 1535
	- MA	+ MA	Cytotoxic (yes/no)	- MA	+ MA	Cytotoxic (yes/no)	- MA	+ MA	Cytotoxic (yes/no)
Negative Control	28	52	No	105	120	No	5	11	No
0*	28	44	No	87	90	No	8	10	No
8	20	42	No	100	107	No	9	5	No
40	20	41	No	92	97	No	6	9	No
200	24	44	No	97	104	No	7	10	No
1000	26	45	No	99	107	No	6	9	No
5000	21	30	No	96	101	No	10	9	No
Positive control	97	-	No	450(AZ) 106(CP)	304	No	367	-	No

*solvent control with DMSO

 

 

Table 2b : Experiment 1 Plate incorporation Number of revertants per plate

Conc. (µl/ml)	TA 1537			TA 1538
	- MA	+ MA	Cytotoxic (yes/no)	- MA	+ MA	Cytotoxic (yes/no)
Negative Control	10	17	No	21	20	No
0*	10	11	No	24	30	No
8	10	13	No	19	31	No
40	12	12	No	17	21	No
200	7	11	No	21	26	No
1000	7	14	No	20	28	No
5000	11	11	No	21	24	No
Positive control	94	-	No	82	NT	No

*solvent control with DMSO

NT: not tested

 

 

 

Table 3a: Experiment 2 Pre incubation Number of revertants per plate (mean of 3 plates

Conc. (µl/ml)	TA 98			TA 100			TA 1535
	- MA	+ MA	Cytotoxic (yes/no)	- MA	+ MA	Cytotoxic (yes/no)	- MA	+ MA	Cytotoxic (yes/no)
Negative Control	218	534	No	105	103	No	9	9	No
0*	296	571	No	92	86	No	11	9	No
8	326	622	No	96	104	No	11	10	No
40	314	561	No	83	88	No	6	11	No
200	329	628	No	98	111	No	7	13	No
1000	422	631	No	106	98	No	7	9	No
5000	252	258	No	96	100	No	5	11	No
Positive control	227	-	No	442(AZ) 102(CP)	362	No	371	-	No

 

*solvent control with DMSO

 

Table 3b: Experiment 2 Pre incubation Number ofrevertants per plate

Conc. (µl/ml)	TA 1537			TA 1538
	- MA	+ MA	Cytotoxic (yes/no)	- MA	+ MA	Cytotoxic (yes/no)
Negative Control	9	16	No	23	25	No
0*	7	13	No	19	26	No
8	9	14	No	21	29	No
40	8	14	No	17	24	No
200	10	13	No	17	26	No
1000	8	15	No	15	30	No
5000	3	18	No	15	27	No
Positive control	109	-	No	88	-	No

*solvent control with DMSO

Conclusions:

Tetraethyl orthosilicate (CAS No. 78-10-4) has been tested in a reliable study according to an appropriate EU guideline (84/449/EEC B 14), in compliance with GLP (reliability score 2). No evidence of increase in the number of revertants relative to solvent control was observed in Salmonella typhimurium TA98, TA100, TA1535, TA1537 and TA1538, when tested up to limit concentrations. Appropriate concurrent solvent (DMSO), negative (water) and positive controls were included, and the expected responses were observed. It is concluded that the test substance is not mutagenic to bacteria under the conditions of this test.

Reference 4

Endpoint:

in vitro gene mutation study in bacteria

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

1993-01-29 to 1993-03-22

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Remarks:

GLP compliance not specified

Qualifier:

according to guideline

Guideline:

OECD Guideline 471 (Bacterial Reverse Mutation Assay)

GLP compliance:

not specified

Remarks:

The source of this test is published literature; publications often do not include information on GLP status. Due to the lack of information on GLP status for this test, a weight of evidence approach has been taken for bacterial mutagenicity.

Type of assay:

bacterial reverse mutation assay

Target gene:

Histidine operon (S. typhimurium strains); tryptophan operon (E. coli).

Species / strain / cell type:

S. typhimurium TA 1535, TA 1537, TA 98, TA 100 and E. coli WP2

Metabolic activation:

with and without

Metabolic activation system:

Phenobarbital/beta-naphthoflavone induced rat liver S9

Test concentrations with justification for top dose:

0, 313, 625, 1250, 2500, 5000 µg/plate

Vehicle / solvent:

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

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

2-nitrofluorene

Remarks:

2 µg/plate TA98 without metabolic activation

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

sodium azide

Remarks:

1 µg/plate TA100 and TA1535 without metabolic activation

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

other: ICR191

Remarks:

1 µg/plate TA1537 without metabolic activation

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

4-nitroquinoline-N-oxide

Remarks:

0.5 µg/plate E. coli WP2 uvrA (pKM101) without metabolic activation

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

other: 2-aminoanthracene

Remarks:

without metabolic activation; 2.5 µg/plate TA 1535, TA 1537, TA 98, TA 100 and 25 µg/plate E. coli WP2 uvrA (pKM101)

Details on test system and experimental conditions:

METHOD OF APPLICATION: in agar (plate incorporation)

DURATION
- Exposure duration: no information

SELECTION AGENT (mutation assays): histidine or tryptophan-deficient agar

NUMBER OF REPLICATIONS: triplicate plates

DETERMINATION OF CYTOTOXICITY
- Method: no information; concentrations were based on cytotoxicity evaluation

Evaluation criteria:

The test substance is considered positive when there is an increase in the number of revertants relative to the solvent control (≥ twofold for TA 98, TA100 and E.coli; ≥ threefold for TA 1535 or TA 1537).

Statistics:

Revertant colonies counted, and mean / standard deviation calculated using a computer program written by BIOSYS Co.

Species / strain:

S. typhimurium TA 98

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:

not specified

Untreated negative controls validity:

not applicable

Positive controls validity:

not specified

Species / strain:

S. typhimurium TA 100

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:

not specified

Untreated negative controls validity:

not applicable

Positive controls validity:

not specified

Species / strain:

S. typhimurium TA 1535

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:

not specified

Untreated negative controls validity:

not applicable

Positive controls validity:

not specified

Species / strain:

S. typhimurium 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:

not specified

Untreated negative controls validity:

not applicable

Positive controls validity:

not specified

Species / strain:

E. coli WP2

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:

not specified

Untreated negative controls validity:

not applicable

Positive controls validity:

not specified

Additional information on results:

No precipitation or cytotoxicity were observed during the course of the test.

Remarks on result:

other: No mutagenic potential

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

Conc. (µl/ml)	TA 98			TA 100			TA 1535
	- MA	+ MA	Cytotoxic (yes/no)	- MA	+ MA	Cytotoxic (yes/no)	- MA	+ MA	Cytotoxic (yes/no)
Negative Control	28	52	No	105	120	No	5	11	No
0*	28	44	No	87	90	No	8	10	No
8	20	42	No	100	107	No	9	5	No
40	20	41	No	92	97	No	6	9	No
200	24	44	No	97	104	No	7	10	No
1000	26	45	No	99	107	No	6	9	No
5000	21	30	No	96	101	No	10	9	No
Positive control	97	-	No	450(AZ) 106(CP)	304	No	367	-	No

*solvent control with DMSO

 

 

Table 2b : Experiment 1 Plate incorporation Number of revertants per plate

Conc. (µl/ml)	TA 1537			TA 1538
	- MA	+ MA	Cytotoxic (yes/no)	- MA	+ MA	Cytotoxic (yes/no)
Negative Control	10	17	No	21	20	No
0*	10	11	No	24	30	No
8	10	13	No	19	31	No
40	12	12	No	17	21	No
200	7	11	No	21	26	No
1000	7	14	No	20	28	No
5000	11	11	No	21	24	No
Positive control	94	-	No	82	NT	No

*solvent control with DMSO

NT: not tested

 

 

 

Table 3a: Experiment 2 Pre incubation Number of revertants per plate (mean of 3 plates

Conc. (µl/ml)	TA 98			TA 100			TA 1535
	- MA	+ MA	Cytotoxic (yes/no)	- MA	+ MA	Cytotoxic (yes/no)	- MA	+ MA	Cytotoxic (yes/no)
Negative Control	218	534	No	105	103	No	9	9	No
0*	296	571	No	92	86	No	11	9	No
8	326	622	No	96	104	No	11	10	No
40	314	561	No	83	88	No	6	11	No
200	329	628	No	98	111	No	7	13	No
1000	422	631	No	106	98	No	7	9	No
5000	252	258	No	96	100	No	5	11	No
Positive control	227	-	No	442(AZ) 102(CP)	362	No	371	-	No

 

*solvent control with DMSO

 

Table 3b: Experiment 2 Pre incubation Number ofrevertants per plate

Conc. (µl/ml)	TA 1537			TA 1538
	- MA	+ MA	Cytotoxic (yes/no)	- MA	+ MA	Cytotoxic (yes/no)
Negative Control	9	16	No	23	25	No
0*	7	13	No	19	26	No
8	9	14	No	21	29	No
40	8	14	No	17	24	No
200	10	13	No	17	26	No
1000	8	15	No	15	30	No
5000	3	18	No	15	27	No
Positive control	109	-	No	88	-	No

*solvent control with DMSO

Conclusions:

Tetraethyl orthosilicate has been tested for mutagenicity to bacteria in study conducted according to OECD Test Guideline 471 (reliability score 2), up to limit concentrations. No data are available on GLP compliance. No test substance induced increase in the number of revertants was observed in Salmonella typhimurium strains TA 98, TA 100, TA1535, TA1537 or Escherichia coli WP2 in the presence or absence of metabolic activation. Appropriate positive and solvent controls were included and gave expected results. 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

Information is available for tetraethyl orthosilicate from reliable studies for all the required in vitro endpoints. The results of the standard studies were in agreement and indicate tetraethyl orthosilicate is negative for genotoxicity. There are also results from an in vitro sister chromatid exchange (SCE) assay and from an unscheduled DNA synthesis (UDS) test. No biologically significant induction of SCEs was observed. The results of the UDS assay indicated that DNA damage had occurred as a result of exposure to the test substance. However, it is considered that this finding is not relevant as no effects were observed in the standard studies.

 

Tetraethyl orthosilicate has been tested in a reliable study according to a now superseded version of an appropriate EU guideline (84/449/EEC B 14), equivalent to OECD Test Guideline 471, in compliance with GLP (Hüls AG 1993). No evidence of increase in the number of revertants relative to solvent control was observed in Salmonella typhimurium TA98, TA100, TA1535, TA1537 and TA1538, when tested up to limit concentrations. Appropriate concurrent solvent (DMSO), negative (water) and positive controls were included, and the expected responses were observed. It is concluded that tetraethyl orthosilicate is not mutagenic to bacteria under the conditions of this test.

 

Information is available for the registered substance for mutagenicity to a bacterial strain capable of detecting cross-linking or oxidising mutagens from a recently published study in which tetraethyl orthosilicate was tested for mutagenicity to bacteria in study conducted according to OECD Test Guideline 471 (1997), up to limit concentrations (Lionti et al. 2014). No data are available on GLP compliance therefore this study was not chosen as the key study. No test substance induced increase in the number of revertants was observed in Salmonella typhimurium strains TA 98, TA 100, TA1535, TA1537 or Escherichia coli WP2 in the presence or absence of metabolic activation. Appropriate positive and solvent controls were included and gave expected results. It is concluded that tetraethyl orthosilicate is negative for mutagenicity to bacteria under the conditions of the test.

 

Tetraethyl orthosilicate has been tested in a reliable study conducted according to OECD Test Guideline 473 and in compliance with GLP (BioReliance 2002). No increase in the number of structural and numerical chromosome aberrations in Chinese hamster ovary (CHO) cells was observed. Appropriate positive and solvent controls were included and gave expected results. It is concluded that tetraethyl orthosilicate is negative for the induction of chromosome aberrations under the conditions of the test.

 

Tetraethyl orthosilicate has been tested in a reliable study conducted according to a protocol that is similar to OECD Test Guideline 476 (BRRC 1981). Weak responses (increase in the number of revertants relative to the solvent control) were obtained at the 1.4 and 1.1 µg/mL concentrations tested without activation in CHO cells. The biological significance of these results was doubtful because the effects were produced at non-consecutive doses and were within the range of variations observed in historical negative control data. It is therefore considered that tetraethyl orthosilicate is negative for the induction of mutations in mammalian cells under the conditions of this test.

 

Additional information is available from in vitro studies on UDS and SCE (BRRC 1981), with evidence of UDS. However, in the light of the negative results from the standard studies and the lack of genetic toxicity structural alerts, the UDS finding is considered not relevant. According to the guidance, results from the standard mutagenicity studies are generally of higher significance than the result of indicator tests such as UDS.

Justification for classification or non-classification

Based on the available in vitro information, tetraethyl orthosilicate does not require classification for germ cell mutagenicity according to Regulation (EC) No 1272/2008.