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Key value for chemical safety assessment

Genetic toxicity in vitro

Description of key information

Gene mutation (Bacterial reverse mutation assay / Ames test): S. typhimurium TA 1535, TA 1537, TA 98, TA 100, and TA 102: negative with and without metabolic activation (similar to OECD TG 471)
Mammalian cytogenicity (CHO chromosome aberration assay, RA from CAS 157923-74-5: negative with and without metabolic activation (according to OECD TG 473)
Mammalian Mutagenicity (HPRT Test, RA from CAS 36957-84-3): negative with and without metabolic activation (similar to OECD TG 476)

Link to relevant study records

Referenceopen allclose all

Endpoint:
in vitro gene mutation study in bacteria
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
Qualifier:
equivalent or similar to guideline
Guideline:
OECD Guideline 471 (Bacterial Reverse Mutation Assay)
Version / remarks:
(1997)
Deviations:
yes
Remarks:
(no strain was included for detection of oxidising or cross-linking substances)
GLP compliance:
yes
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
Species / strain / cell type:
S. typhimurium TA 1538
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:
0.05-5 mg/plate
Vehicle / solvent:
- Solvent: ethanol
Untreated negative controls:
yes
Negative solvent / vehicle controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
other: +S9: 2-anthramine (TA 98, TA 100, TA 1535, TA 1537, TA 1538); -S9: 2-nitrofluorene (TA98); methyl methanesulfonate (TA 100); ethyl methanesulfonate (TA 1535); 9-aminoacridine (TA 1537); 2-nitrofluorene (TA 1538)
Details on test system and experimental conditions:
METHOD OF APPLICATION: in agar (plate incorporation)

DURATION
- Exposure duration: 48 h

NUMBER OF REPLICATIONS: 3


DETERMINATION OF CYTOTOXICITY
- Cytotoxicity was determined in a preliminary study using strain TA 98 and also within the main study cytotoxicity was determined. No further information was given about the method applied.


POSITIVE CONTROLS:
+S9: 2-anthramine (TA 98, TA 100, TA 1535, TA 1537, TA 1538: 0.002 mg/plate)
-S9: 2-nitrofluorene (TA98: 0.001 mg/plate); methyl methanesulfonate (TA 100: 0.1 mg/plate); ethyl methanesulfonate (TA 1535: 10 mg/plate); 9-aminoacridine (TA 1537: 0.05 mg/plate); 2-nitrofluorene (TA 1538: 0.001 mg/plate)
Evaluation criteria:
No significant effects: number of colonies after treatment with test substance is less than 2-fold the number of colonies of the solvent control.
Significant effects: number of colonies after treatment with test substance is at least 2-fold the number of colonies of the solvent control.
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:
cytotoxicity
Remarks:
-S9: TA 98, TA 1535 (5 mg/plate), TA 100, TA 1537, TA 1538 (1 and 5 mg/plate); +S9: TA 1537 (5 mg/plate)
Vehicle controls validity:
valid
Untreated negative controls validity:
not applicable
Positive controls validity:
valid
Additional information on results:
RANGE-FINDING/SCREENING STUDIES:
In a preliminary study the test substance was applied to bacteria (TA 98) from 0.5 to 100 mg/plate. Cytotoxicity was observed from 5 mg/plate upwards.

Table 1: Test results of experiment 1.

With or without S9-Mix

Test substance concentration

Mean number of revertant colonies per plate

(μg/plate)

(average of 3 plates ± Standard deviation)

 

 

 

 

TA 98

TA 100

TA1535

TA1537

TA1538

–

0

28±4

83±4

9±3

5±1

22±1

–

50

25±1

91±5

9±4

4±1

26±1

–

100

26±8

90±11

6±2

5±0

23±4

–

500

21±5

101±9

7±0

6±2

19±5

–

1000

21±2

78±6

11±4

8±5

26±4

–

5000

T

53±8

5±1

T

5±2

Positive controls, –S9

Name

2-NF

MMS

EMS

9-AA

2-NF

Concentrations (μg/plate)

1

100

10000

50

1

Mean No. of colonies/plate (average of 3)

472

299

1035

131

248

+

0

39±4

112±12

13±5

5±2

34±9

+

50

35±5

107±2

8±2

7±4

40±4

+

100

36±5

107±20

8±2

5±2

35±13

+

500

37±1

108±6

12±3

7±2

33±3

+

1000

34±7

102±8

10±3

4

33±8

+

5000

36±3

111±4

9±4

4±2

38±7

Positive controls, +S9

Name

2-A

2-A

2-A

2-A

2-A

Concentrations (μg/plate)

2

2

2

2

2

Mean No. of colonies/plate (average of 3)

554

1528

239

63

298

Table 2: Test results of experiment 2.

With or without S9-Mix

Test substance concentration

Mean number of revertant colonies per plate

(μg/plate)

(average of 3 plates ± Standard deviation)

 

 

 

 

TA 98

TA 100

TA1535

TA1537

TA1538

–

0

28±5

78±7

7±2

6±2

32±6

–

50

28±3

81±16

7±3

5±2

32±4

–

100

29±2

73±17

7±3

4±1

30±3

–

500

27±6

73±8

7±3

5±1

25±3

–

1000

28±6

T

5±3

2±1

7±6

–

5000

T

T

7±1

T

T

Positive controls, –S9

Name

2-NF

MMS

EMS

9-AA

2-NF

Concentrations (μg/plate)

1

100

10000

50

1

Mean No. of colonies/plate (average of 3)

573

270

835

116

548

+

0

43±10

118±4

9±5

6±1

38±3

+

50

41±5

107±13

11±2

5±3

47±11

+

100

43±2

101±14

8±2

5±1

38±10

+

500

44±14

101±11

9±5

5±3

42±9

+

1000

46±11

98±17

9±1

6±2

49±4

+

5000

43±8

109±5

11±2

6±1

41±12

Positive controls, +S9

Name

2-A

2-A

2-A

2-A

2-A

Concentrations (μg/plate)

2

2

2

2

2

Mean No. of colonies/plate (average of 3)

673

1337

185

35

579

 

MMS = methyl methanesulfonate

EMS = ethyl methanesulfonate

9AA = 9-aminoacridine

2-A = 2-anthramine

T = cytotoxic

Conclusions:
Interpretation of results: negative

In a bacterial mutagenicity assay similar to OECD 471 and GLP, no mutagenic effect was observed for the test substance tested up to the top dose of 5000 µg/plate in any of the test strains in two independent experiments without and with metabolic activation. The test substance is non-mutagenic under the applied conditions.
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
Justification for type of information:
see attached document for justification of read-across
Reason / purpose for cross-reference:
read-across source
Species / strain:
Chinese hamster lung fibroblasts (V79)
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
Conclusions:
Interpretation of results: negative
One study is available from the structural analogue 4-amino-3,3-dimethylbutyltrimethoxysilane (CAS 157923-74-5). In this study it was observed that the source substance does not induce chromosomal aberration in mammalian cells. 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 the genetic toxicity potential that are higher than the typical experimental error of the test method.
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:
see attached document for justification of read-across
Reason / purpose for cross-reference:
read-across source
Type of assay:
other: mammalian cell gene mutation assay
Species / strain:
Chinese hamster Ovary (CHO)
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
cytotoxicity
Remarks:
reduced cloning efficiency at 2 mg/ml in 1 experiment (decrease of 20%)
Vehicle controls validity:
valid
Untreated negative controls validity:
valid
Positive controls validity:
valid
Conclusions:
Interpretation of results: negative
One study is available from the structural analogue 2-(triethoxysilyl)propylamine (CAS 36957-84-3). In this study it was observed that the source substance does not induce chromosomal aberration in mammalian cells. 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 the genetic toxicity potential that are higher than the typical experimental error of the test method.
Endpoint conclusion
Endpoint conclusion:
no adverse effect observed (negative)

Genetic toxicity in vivo

Endpoint conclusion
Endpoint conclusion:
no study available

Additional information

Data are available from a bacterial mutagenicity study on N-[3-(trimethoxysilyl)propyl]butylamine (CAS 31024-56-3). No further information is available for the registered substance, however, reliable data are available for the closely related substances, 4-amino-3,3-dimethylbutyltrimethoxysilane (CAS 157923-74-5) and 2-(triethoxysilyl)propylamine (CAS 36957-84-3). 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 an analogue substance has been applied to support the human health hazard assessment of N-[3 -(trimethoxysilyl)propyl]butylamine (CAS 31024 -56 -3). Details on read across justifications can be found in the attached justification in the respective target entry and in the overall justification for grouping of substances attached in IUCLID Section 13.

 

 

Discussion of results:

In vitro genotoxicity

In the available key study (Hazleton France, 1989) N-[3-(trimethoxysilyl)propyl]butylamine (CAS 31024-56-3) was tested for bacterial mutagenicity similar to the OECD TG 471, and in compliance with GLP. No test-substance related increase in the number of revertants was observed when tested in two independent experiments with and without metabolic activation up to the top concentration of 5000 µg/plate in Salmonella typhimurium strains TA 1535, TA 1537, TA 1538, TA 98, and TA 100 in the plate incorporation assay. Appropriate solvent and positive controls were included and gave the expected results. It is concluded that the test substance is negative for mutagenicity to bacteria under the conditions of the test.

No data are available for mutagenicity to a bacterial strain capable of detecting cross-linking or oxidising mutagens. In view of the lack of genetic toxicity demonstrated in studies on mammalian cells, and the absence of structural features that indicate that such mutagenicity is likely, testing in an appropriate 5th strain is not considered necessary. In addition, the only silicon-containing substance which has given a positive result in a bacterial strain capable of detecting cross-linking or oxidising mutagens contains an epoxy- side-chain (which is associated with cross-linking mutagenicity), and this substance was positive in Salmonella typhimurium strains TA 100, TA 1535 as well as in E.coli WP2uvrA.

 

In the available key study (RCC, 2001) 4-amino-3,3-dimethylbutyltrimethoxysilane (CAS 157923-74-5) was tested for cytogenicity according to the OECD TG 473, and in compliance with GLP. The test substance did not induce structural chromosomal aberrations in the Chinese hamster lung fibroblasts (V79) cell line with and without metabolic activation up to limit concentrations. Appropriate solvent and positive controls were included into the test and gave expected results. It is concluded that 4-amino-3,3-dimethylbutyltrimethoxysilane (CAS 157923-74-5) is negative for the induction of chromosome aberrations under the conditions of the test.

 

In the available key study (Bushy Run Research Center, 1985) 2-(triethoxysilyl)propylamine (CAS 36957-84-3) was tested for mammalian mutagenicity (HPRT Test) similar to the OECD TG 476, and in compliance with GLP. No increase in mutant frequency was observed at any concentration up to cytotoxicity with and without metabolic activation at 5 hours treatment. Expected results were obtained with positive, solvent, and negative controls. It is concluded that 2-(triethoxysilyl)propylamine (CAS 36957-84-3) is negative for the induction of mutations in Chinese hamster Ovary cells (CHO) under the conditions of the test.

 

In vivo genotoxicty

No data available.

Justification for classification or non-classification

The available in vitro genotoxicity data are reliable and suitable for classification. Based on this data, classification for mutagenicity according to Regulation (EC)1272/2008 is not warranted.