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Administrative data

Key value for chemical safety assessment

Genetic toxicity in vitro

Description of key information

Under the conditions of this study, the test material was considered to be non-mutagenic.

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:
15 March 2017 to 31 March 2017
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 471 (Bacterial Reverse Mutation Assay)
Version / remarks:
1997
Deviations:
no
Qualifier:
according to
Guideline:
EU Method B.13/14 (Mutagenicity - Reverse Mutation Test Using Bacteria)
Version / remarks:
2008
Deviations:
no
Qualifier:
according to
Guideline:
EPA OPPTS 870.5100 - Bacterial Reverse Mutation Test (August 1998)
Deviations:
no
Qualifier:
according to
Guideline:
other: Japanese Ministry of Economy, Trade and Industry, Japanese Ministry of Health, Labour and Welfare and Japanese Ministry of Agriculture, Forestry and Fisheries.
Deviations:
no
GLP compliance:
yes (incl. certificate)
Type of assay:
bacterial reverse mutation assay
Specific details on test material used for the study:
- The test material was accurately weighed and approximate half-log dilutions prepared in sterile distilled water by mixing on a vortex mixer on the day of each experiment. Formulated concentrations were adjusted to allow for the stated water/impurity content (1.4 %) of the test material.
- All formulations were used within four hours of preparation and were assumed to be stable for this period. Analysis for concentration, homogeneity and stability of the test material formulations is not a requirement of the test guidelines and was, therefore, not determined. This is an exception with regard to GLP and has been reflected in the GLP compliance statement.
Target gene:
S. typhimurium: Histidine locus
E. coli: Tryptophan locus
Species / strain / cell type:
S. typhimurium TA 1535, TA 1537, TA 98 and TA 100
Details on mammalian cell type (if applicable):
CELLS USED
- All of the Salmonella strains are histidine dependent by virtue of a mutation through the histidine operon and are derived from S. typhimurium strain LT2 through mutations in the histidine locus. Additionally due to the "deep rough" (rfa-) mutation they possess a faulty lipopolysaccharide coat to the bacterial cell surface thus increasing the cell permeability to larger molecules. A further mutation, through the deletion of the uvrB- bio gene, causes an inactivation of the excision repair system and a dependence on exogenous biotin. In the strains TA98 and TA100, the R-factor plasmid pKM101 enhances chemical and UV-induced mutagenesis via an increase in the error-prone repair pathway. The plasmid also confers ampicillin resistance which acts as a convenient marker (Mortelmans and Zeiger, 2000).
- Source: University of California, Berkeley, on culture discs, on 04 August 1995 and British Industrial Biological Research Association, on a nutrient agar plate, on 17 August 1987.
- All of the strains were stored at approximately -196 °C in a Statebourne liquid nitrogen freezer, model SXR 34.

MEDIA USED
- In this assay, overnight sub-cultures of the appropriate coded stock cultures were prepared in nutrient broth (Oxoid Limited; lot number 1865318 05/21) and incubated at 37 °C for approximately 10 hours. Each culture was monitored spectrophotometrically for turbidity with titres determined by viable count analysis on nutrient agar plates.
Species / strain / cell type:
E. coli WP2 uvr A
Details on mammalian cell type (if applicable):
CELLS USED
- In addition to a mutation in the tryptophan operon, the E. coli tester strain contains a uvrA- DNA repair deficiency which enhances its sensitivity to some mutagenic compounds. This deficiency allows the strain to show enhanced mutability as the uvrA repair system would normally act to remove and repair the damaged section of the DNA molecule (Green and Muriel, 1976 and Mortelmans and Riccio, 2000).
- Source: University of California, Berkeley, on culture discs, on 04 August 1995 and British Industrial Biological Research Association, on a nutrient agar plate, on 17 August 1987.
- All of the strains were stored at approximately -196 °C in a Statebourne liquid nitrogen freezer, model SXR 34.

MEDIA USED
- In this assay, overnight sub-cultures of the appropriate coded stock cultures were prepared in nutrient broth (Oxoid Limited; lot number 1865318 05/21) and incubated at 37 °C for approximately 10 hours. Each culture was monitored spectrophotometrically for turbidity with titres determined by viable count analysis on nutrient agar plates.
Metabolic activation:
with and without
Metabolic activation system:
S9-Mix
Test concentrations with justification for top dose:
1.5, 5, 15, 50, 150, 500, 1500 and 5000 μg/plate for Experiments 1 and 2.
Eight test material concentrations were selected in Experiment 2 in order to achieve both four non-toxic dose levels and the toxic limit of the test material following the change in test methodology from plate incorporation to pre-incubation.
Vehicle / solvent:
- Vehicle(s)/solvent(s) used: Sterile distilled water
- Justification for choice of solvent/vehicle: The test material was fully miscible in sterile distilled water at 50 mg/L in solubility checks performed in-house. Sterile distilled water was therefore selected as the vehicle.
Untreated negative controls:
yes
Negative solvent / vehicle controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
9-aminoacridine
N-ethyl-N-nitro-N-nitrosoguanidine
benzo(a)pyrene
other: 4-Nitroquinoline-1-oxide (0.2 μg/plate for TA98 in the absence of S9-mix) and 2-Aminoanthracene (1 μg/plate for TA100, 2 μg/plate for TA1535 and TA1537 and 10 μg/plate for WP2uvrA, in the presence of S9-mix)
Remarks:
The sterility controls were performed in triplicate: Top agar and histidine/biotin or tryptophan -S9-mix; Top agar and histidine/biotin or tryptophan +S9-mix; and The maximum dosing solution of the test material -S9-mix only (test in singular only).
Details on test system and experimental conditions:
EXPERIMENT 1: PLATE INCORPORATION METHOD
- Doses: 1.5, 5, 15, 50, 150, 500, 1500 and 5000 μg/plate
- Without Metabolic Activation: 0.1 mL of the appropriate concentration of test material or solvent vehicle or appropriate positive control was added to 2 mL of molten, trace amino-acid supplemented media containing 0.1 mL of one of the bacterial strain cultures and 0.5 mL of phosphate buffer. These were then mixed and overlayed onto a Vogel-Bonner agar plate. Negative (untreated) controls were also performed on the same day as the mutation test. Each concentration of the test material, appropriate positive, vehicle and negative controls, and each bacterial strain, was assayed using triplicate plates.
- With Metabolic Activation: The procedure was the same as described above, except that following the addition of the test material formulation and bacterial culture, 0.5 mL of S9-mix was added to the molten, trace amino-acid supplemented media instead of phosphate buffer.
- Incubation and Scoring: All of the plates were incubated at 37 ± 3 °C for approximately 48 hours and scored for the presence of revertant colonies using an automated colony counting system. The plates were viewed microscopically for evidence of thinning (toxicity).

EXPERIMENT 2: PRE-INCUBATION METHOD
- Doses: 1.5, 5, 15, 50, 150, 500, 1500 and 5000 μg/plate
- Without Metabolic Activation: 0.1 mL of the appropriate bacterial strain culture, 0.5 mL of phosphate buffer and 0.1 mL of the test material formulation or solvent vehicle or 0.1 mL of appropriate positive control were incubated at 37 ± 3 °C for 20 minutes (with shaking) prior to addition of 2 mL of molten, trace amino-acid supplemented media and subsequent plating onto Vogel-Bonner plates. Negative (untreated) controls were also performed on the same day as the mutation test employing the plate incorporation method. All testing for this experiment was performed in triplicate.
- With Metabolic Activation: The procedure was the same as described previously (see 3.3.3.2) except that following the addition of the test material formulation and bacterial strain culture, 0.5 mL of S9-mix was added to the tube instead of phosphate buffer, prior to incubation at 37 ± 3 °C for 20 minutes (with shaking) and addition of molten, trace amino-acid supplemented media. All testing for this experiment was performed in triplicate.
- Incubation and Scoring: All of the plates were incubated at 37 ± 3 °C for approximately 48 hours and scored for the presence of revertant colonies using an automated colony counting system. The plates were viewed microscopically for evidence of thinning (toxicity). Several manual counts were required due to revertant colonies spreading slightly, thus distorting the actual plate count.

NUMBER OF REPLICATIONS: 3

ACCEPTABILITY CRITERIA
The reverse mutation assay may be considered valid if the following criteria are met:
- All bacterial strains must have demonstrated the required characteristics as determined by their respective strain checks according to Ames et al., (1975), Maron and Ames (1983), Mortelmans and Zeiger (2000), Green and Muriel (1976) and Mortelmans and Riccio (2000).
- All tester strain cultures should exhibit a characteristic number of spontaneous revertants per plate in the vehicle and untreated controls (negative controls). Acceptable ranges are presented as follows: TA1535: 7 to 40; TA100: 60 to 200; TA1537: 2 to 30; TA98: 8 to 60; WP2uvrA: 10 to 60
- All tester strain cultures should be in the range of 0.9 to 9 x 10^9 bacteria per mL.
- Diagnostic mutagens (positive control chemicals) must be included to demonstrate both the intrinsic sensitivity of the tester strains to mutagen exposure and the integrity of the S9-mix. All of the positive control chemicals used in the study should induce marked increases in the frequency of revertant colonies, both with or without metabolic activation.
- There should be a minimum of four non-toxic test material dose levels.
- There should be no evidence of excessive contamination.
Evaluation criteria:
EVALUATION CRITERIA
There are several criteria for determining a positive result. Any, one, or all of the following can be used to determine the overall result of the study:
- A dose-related increase in mutant frequency over the dose range tested (De Serres and Shelby, 1979).
- A reproducible increase at one or more concentrations.
- Biological relevance against in-house historical control ranges.
- Statistical analysis of data as determined by UKEMS (Mahon et al., 1989).
- Fold increase greater than two times the concurrent solvent control for any tester strain (especially if accompanied by an out-of-historical range response (Cariello and Piegorsch, 1996)).
A test material will be considered non-mutagenic (negative) in the test system if the above criteria are not met.
Although most experiments will give clear positive or negative results, in some instances the data generated will prohibit making a definite judgment about test material activity. Results of this type will be reported as equivocal.
Statistics:
Statistical significance was confirmed by using Dunnetts Regression Analysis (* = p < 0.05) for those values that indicate statistically significant increases in the frequency of revertant colonies compared to the concurrent solvent control.
Key result
Species / strain:
S. typhimurium, other: ta98, ta100, TA1535 and TA1537
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
Key result
Species / strain:
E. coli WP2 uvr A
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
Additional information on results:
MUTATION TEST
- Prior to use, the master strains were checked for characteristics, viability and spontaneous reversion rate (all were found to be satisfactory). The amino acid supplemented top agar and the S9-mix used in both experiments was shown to be sterile. The test material formulation was also shown to be sterile.
- Results for the negative controls (spontaneous mutation rates) were considered to be acceptable. These data are for concurrent untreated control plates performed on the same day as the Mutation Test.
- The maximum dose level of the test material in the first experiment was selected as the maximum recommended dose level of 5000 μg/plate. In the first mutation test (plate incorporation method), the test material caused a visible reduction in the growth of the bacterial background lawns of all of the tester strains initially from 1500 μg/plate in the absence of S9-mix and at 5000 μg/plate in the presence S9-mix. These results were not indicative of toxicity sufficiently severe enough to prevent the test material being tested up to the maximum recommended dose level of 5000 μg/plate in the second mutation test. The test material again induced a toxic response in the second mutation test (pre-incubation method), with weakened bacterial background lawns noted to all of the tester strains in both the absence and presence of S9-mix at 5000 μg/plate. The sensitivity of the bacterial tester strains to the toxicity of the test material varied slightly between strain type, exposures with or without S9-mix and experimental methodology. No test material precipitate was observed on the plates at any of the doses tested in either the presence or absence of S9-mix.
- There were no significant increases in the frequency of revertant colonies recorded for any of the bacterial strains, with any dose of the test material, either with or without metabolic activation (S9-mix) in Experiment 1 (plate incorporation method). Similarly, no toxicologically significant increases in the frequency of revertant colonies were recorded for any of the bacterial strains, with any dose of the test material, either with or without metabolic activation (S9-mix) in Experiment 2 (pre-incubation method). Small but statistically significant increases in TA100 revertant colony frequency were observed in the absence of S9-mix at 150 and 1500 μg/plate in the second mutation test. These increases were considered to be of no biological relevance because there was no evidence of a dose-response relationship or reproducibility. Furthermore, the individual revertant colony counts at the statistically significant dose levels were within the in-house historical untreated/vehicle control range for the tester strain and the maximum fold increase was only 1.3 times the concurrent vehicle control.
- The vehicle (sterile distilled water) control plates gave counts of revertant colonies within the normal range. All of the positive control chemicals used in the test induced marked increases in the frequency of revertant colonies, both with or without metabolic activation. Thus, the sensitivity of the assay and the efficacy of the S9-mix were validated.

Table 1: Summary of Experiment 1

± S9 Mix

Concentration

(µg/plate)

Mean number of colonies/plate

Base-pair Substitution Type

Frameshift Type

TA100

TA1535

WP2uvrA

TA98

TA1537

-

Solvent

1.5

5

15

50

150

500

1500

5000

97

116

111

114

106

108

102

103

119

17

19

15

16

16

16

13

12

8

35

38

37

41

42

37

32

36

40

17

18

20

18

24

16

15

17

20

11

12

9

8

8

11

9

10

7

+

Solvent

1.5

5

15

50

150

500

1500

5000

113

117

121

102

115

99

113

108

94

15

13

12

9

15

11

12

11

13

46

46

47

42

43

49

46

41

49

27

25

24

24

29

18

22

20

17

10

13

12

9

11

10

11

10

4

Positive Controls

-

Name

ENNG

ENNG

ENNG

4NQO

9AA

Concentration (µg/plate)

3

5

2

0.2

80

Mean no. colonies/plate

530

580

829

212

325

+

Name

2AA

2AA

2AA

BP

2AA

Concentration (µg/plate)

1

2

10

5

2

Mean no. colonies/plate

1270

265

422

274

314

ENNG = N-ethyl-N’-nitro-N-nitrosoguanidine

4NQO = 4-Nitroquinoline-1-oxide

9AA = 9-aminoacridine

2AA = 2-aminoanthracene

BP = benzo(a)pyrene

Table 2: Summary of Experiment 2

± S9 Mix

Concentration

(µg/plate)

Mean number of colonies/plate

Base-pair Substitution Type

Frameshift Type

TA100

TA1535

WP2uvrA

TA98

TA1537

-

Solvent

1.5

5

15

50

150

500

1500

5000

99

105

88

101

111

123

114

122

0

14

13

15

15

16

15

13

14

0

36

37

36

31

36

29

38

45

0

20

19

18

23

22

20

21

20

0

15

15

15

15

13

13

13

11

0

+

Solvent

1.5

5

15

50

150

500

1500

5000

93

97

101

90

71

67

79

74

77

11

13

10

13

11

9

13

10

9

48

45

46

43

47

45

41

50

37

27

29

27

33

28

27

27

20

18

20

13

12

17

16

16

17

17

0

Positive Controls

-

Name

ENNG

ENNG

ENNG

4NQO

9AA

Concentration (µg/plate)

3

5

2

0.2

80

Mean no. colonies/plate

552

331

634

173

188

+

Name

2AA

2AA

2AA

BP

2AA

Concentration (µg/plate)

1

2

10

5

2

Mean no. colonies/plate

1391

221

256

124

276

ENNG = N-ethyl-N’-nitro-N-nitrosoguanidine

4NQO = 4-Nitroquinoline-1-oxide

9AA = 9-aminoacridine

2AA = 2-aminoanthracene

BP = benzo(a)pyrene

Conclusions:
Under the conditions of this study, the test material was considered to be non-mutagenic.
Executive summary:

The genetic toxicity of the test material was investigated in accordance with the standardised guidelines OECD 471, EU Method B13/14, EPA OCSPP 870.5100 and the major Japanese Regulatory Authorities including METI, MHLW and MAFF, under GLP conditions in the Bacterial Reverse Mutation Test.

Salmonella typhimurium strains TA1535, TA1537, TA98 and TA100 and Escherichia coli strain WP2uvrA were treated with the test material using both the Ames plate incorporation and pre-incubation methods at eight dose levels, in triplicate, both with and without the addition of a rat liver homogenate metabolizing system (10% liver S9 in standard co-factors). The dose range for Experiment 1 was predetermined and was 1.5 to 5000 μg/plate. The experiment was repeated on a separate day (pre-incubation method) using fresh cultures of the bacterial strains and fresh test material formulations. The dose range was the same as Experiment 1 (1.5 to 5000 μg/plate). Eight test material concentrations were selected in Experiment 2 in order to achieve both four non-toxic dose levels and the toxic limit of the test material following the change in test methodology.

The vehicle (sterile distilled water) control plates gave counts of revertant colonies within the normal range. All of the positive control chemicals used in the test induced marked increases in the frequency of revertant colonies, both with or without metabolic activation. Thus, the sensitivity of the assay and the efficacy of the S9-mix were validated.

The maximum dose level of the test material in the first experiment was selected as the maximum recommended dose level of 5000 μg/plate. In the first mutation test (plate incorporation method), the test material caused a visible reduction in the growth of the bacterial background lawns of all of the tester strains initially from 1500 μg/plate in the absence of S9-mix and at 5000 μg/plate in the presence S9-mix. These results were not indicative of toxicity sufficiently severe enough to prevent the test material being tested up to the maximum recommended dose level of 5000 μg/plate in the second mutation test. The test material again induced a toxic response in the second mutation test (pre-incubation method), with weakened bacterial background lawns noted to all of the tester strains in both the absence and presence of S9-mix at 5000 μg/plate. The sensitivity of the bacterial tester strains to the toxicity of the test material varied slightly between strain type, exposures with or without S9-mix and experimental methodology. No test material precipitate was observed on the plates at any of the doses tested in either the presence or absence of S9-mix.

There were no significant increases in the frequency of revertant colonies recorded for any of the bacterial strains, with any dose of the test material, either with or without metabolic activation (S9-mix) in Experiment 1 (plate incorporation method). Similarly, no toxicologically significant increases in the frequency of revertant colonies were recorded for any of the bacterial strains, with any dose of the test material, either with or without metabolic activation (S9-mix) in Experiment 2 (pre-incubation method). Small but statistically significant increases in TA100 revertant colony frequency were observed in the absence of S9-mix at 150 and 1500 μg/plate in the second mutation test. These increases were considered to be of no biological relevance because there was no evidence of a dose-response relationship or reproducibility. Furthermore, the individual revertant colony counts at the statistically significant dose levels were within the in-house historical untreated/vehicle control range for the tester strain and the maximum fold increase was only 1.3 times the concurrent vehicle control.

Under the conditions of this study, the test material was considered to be non-mutagenic.

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed (negative)

Genetic toxicity in vivo

Endpoint conclusion
Endpoint conclusion:
no study available

Additional information

The genetic toxicity of the test material was investigated in accordance with the standardised guidelines OECD 471, EU Method B13/14, EPA OCSPP 870.5100 and the major Japanese Regulatory Authorities including METI, MHLW and MAFF, under GLP conditions in the Bacterial Reverse Mutation Test. The study was awarded a reliability score of 1 in accordance with the criteria set forth by Klimisch et al. (1997).

Salmonella typhimurium strains TA1535, TA1537, TA98 and TA100 and Escherichia coli strain WP2uvrA were treated with the test material using both the Ames plate incorporation and pre-incubation methods at eight dose levels, in triplicate, both with and without the addition of a rat liver homogenate metabolizing system (10% liver S9 in standard co-factors). The dose range for Experiment 1 was predetermined and was 1.5 to 5000 μg/plate. The experiment was repeated on a separate day (pre-incubation method) using fresh cultures of the bacterial strains and fresh test material formulations. The dose range was the same as Experiment 1 (1.5 to 5000 μg/plate). Eight test material concentrations were selected in Experiment 2 in order to achieve both four non-toxic dose levels and the toxic limit of the test material following the change in test methodology.

The vehicle (sterile distilled water) control plates gave counts of revertant colonies within the normal range. All of the positive control chemicals used in the test induced marked increases in the frequency of revertant colonies, both with or without metabolic activation. Thus, the sensitivity of the assay and the efficacy of the S9-mix were validated.

The maximum dose level of the test material in the first experiment was selected as the maximum recommended dose level of 5000 μg/plate. In the first mutation test (plate incorporation method), the test material caused a visible reduction in the growth of the bacterial background lawns of all of the tester strains initially from 1500 μg/plate in the absence of S9-mix and at 5000 μg/plate in the presence S9-mix. These results were not indicative of toxicity sufficiently severe enough to prevent the test material being tested up to the maximum recommended dose level of 5000 μg/plate in the second mutation test. The test material again induced a toxic response in the second mutation test (pre-incubation method), with weakened bacterial background lawns noted to all of the tester strains in both the absence and presence of S9-mix at 5000 μg/plate. The sensitivity of the bacterial tester strains to the toxicity of the test material varied slightly between strain type, exposures with or without S9-mix and experimental methodology. No test material precipitate was observed on the plates at any of the doses tested in either the presence or absence of S9-mix.

There were no significant increases in the frequency of revertant colonies recorded for any of the bacterial strains, with any dose of the test material, either with or without metabolic activation (S9-mix) in Experiment 1 (plate incorporation method). Similarly, no toxicologically significant increases in the frequency of revertant colonies were recorded for any of the bacterial strains, with any dose of the test material, either with or without metabolic activation (S9-mix) in Experiment 2 (pre-incubation method). Small but statistically significant increases in TA100 revertant colony frequency were observed in the absence of S9-mix at 150 and 1500 μg/plate in the second mutation test. These increases were considered to be of no biological relevance because there was no evidence of a dose-response relationship or reproducibility. Furthermore, the individual revertant colony counts at the statistically significant dose levels were within the in-house historical untreated/vehicle control range for the tester strain and the maximum fold increase was only 1.3 times the concurrent vehicle control.

Under the conditions of this study, the test material was considered to be non-mutagenic.

Justification for classification or non-classification

In accordance with the criteria for classification as defined in Annex I, Regulation (EC) No. 1272/2008, the substance does not require classification with respect to genetic toxicity.