(1RS,4Z,8E,12RS)-13-oxabicyclo[10.1.0]trideca-4,8-diene

Genetic toxicity: in vitro

Administrative data

Endpoint:

in vitro gene mutation study in bacteria

Remarks:

Type of genotoxicity: gene mutation

Type of information:

experimental study

Adequacy of study:

key study

Study period:

26-06-2019 to 19-07-2019

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

Guideline study performed under GLP. All relevant validity criteria were met.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2019

Report date:

2019

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 471 (Bacterial Reverse Mutation Assay)

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

Test guideline 3

Qualifier:

according to guideline

Guideline:

EPA OPPTS 870.5100 - Bacterial Reverse Mutation Test (August 1998)

Deviations:

no

Test guideline 4

Qualifier:

according to guideline

Guideline:

JAPAN: Guidelines for Screening Mutagenicity Testing Of Chemicals

Version / remarks:

Japanese Ministry of Economy, Trade and Industry, Japanese Ministry of Health, Labor and Welfare and Japanese Ministry of Agriculture, Forestry and Fisheries (24 November 2000)

Deviations:

no

Test guideline 5

Qualifier:

according to guideline

Guideline:

other: ICH S2(R1) guideline

Version / remarks:

June 2012 (ICH S2(R1) Federal Register

Deviations:

not specified

GLP compliance:

yes (incl. QA statement)

Remarks:

inspected: August 2018 ; signature: November 2018

Type of assay:

bacterial reverse mutation assay

Test material

Test material information

Constituent 1

Reference substance name:

(1RS,4Z,8E,12RS)-13-oxabicyclo[10.1.0]trideca-4,8-diene

EC Number:

951-761-9

Cas Number:

55722-64-0

Molecular formula:

C12H18O

IUPAC Name:

(1RS,4Z,8E,12RS)-13-oxabicyclo[10.1.0]trideca-4,8-diene

Test material form:

liquid

Specific details on test material used for the study:

- Physical state: Liquid
- Storage condition of test material: Approximately 4 °C in the dark under nitrogen
- Other: clear colourless

Method

Target gene:

histidine or tryptophan locus

Species / strain

Species / strain 1

Species / strain / cell type:

E. coli WP2 uvr A

Additional strain / cell type characteristics:

not applicable

Species / strain 2

Species / strain / cell type:

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

Additional strain / cell type characteristics:

not applicable

Metabolic activation:

with and without

Metabolic activation system:

Type and composition of metabolic activation system: Rat liver S9
- source of S9: Purchased from recognised supplier (dates within full study report) ; S9 Microsomal fraction: Lot No. Lot No. 4061
- method of preparation of S9 mix: Documented in the full study report. Stored at -196ºC
- concentration or volume of S9 mix and S9 in the final culture medium: 10% S9
- quality controls of S9 (e.g., enzymatic activity, sterility, metabolic capability): A Certificate of S9 QC and Production Certificate including Activity is presented in the full study report. Additionally, concurrent positive control substances all produced marked increases in the number of revertant colonies and the activity of the S9 fraction was found to be satisfactory

Test concentrations with justification for top dose:

Experiment 1 (pre-incubation method): 0, 1.5, 5, 15, 50, 150, 500, 1500 and 5000 µg/plate
Experiment 2 (pre-incubation method): Eight to ten test item dose levels were selected in Experiment 2 in order to achieve both a minimum of four non-toxic doses and the toxic/guideline limit of the test item. The dose levels were selected based on the results of Experiment 1.
All strains (absence of S9-mix): 0.5, 1.5, 5, 15, 50, 75, 100, 150 µg/plate.
All strains (presence of S9-mix): 0.5, 1.5, 5, 15, 50, 75, 100, 125, 150, 175, 500 µg/plate.

Vehicle / solvent:

- Vehicle(s)/solvent(s) used: dimethylsulphoxide (DMSO)
- Justification for choice of solvent/vehicle: The test item was immiscible in sterile distilled water at 50 mg/mL but was fully miscible in DMSO at the same concentration in solubility checks performed. DMSO was selected as the vehicle.
- Other: Formulated concentrations were adjusted/increased to allow for the stated water/impurity content. See 'Test Material Information' for further details.

Controls

Controls 1

Untreated negative controls:

yes

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

4-nitroquinoline-N-oxide

9-aminoacridine

N-ethyl-N-nitro-N-nitrosoguanidine

Remarks:

Without metabolic activation S9

Controls 2

Untreated negative controls:

yes

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

benzo(a)pyrene

other: 2-Aminoanthracene

Remarks:

With metabolic activation S9

Details on test system and experimental conditions:

METHOD OF APPLICATION: Experiment 1. in medium; in agar (pre-incubation) ; Experiment 2. in medium; in agar (pre-incubation).
The choice of application was due to the test item to either have unknown volatility or was suspected to be volatile, therefore all testing was performed using the pre-incubation method (20 minutes at 37 ± 3 °C) except for the untreated controls.

DURATION
- Exposure duration:
Experiment 1. All of the plates were pre-incubated in sealed, small volume containers, by application of 0.1 mL of the appropriate bacterial strain culture, 0.5 mL of phosphate buffer OR S9-mix (as appropriate) and 0.1 mL of the test item formulation, vehicle or 0.1 mL of appropriate positive control were incubated at 37 ± 3 ºC for 20 minutes (with shaking) prior to addition of 2 mL of molten amino-acid supplemented media. All of the plates were sealed in anaerobic jars or bags (one jar/bag for each concentration of test item/vehicle) during the incubation procedure (37 ± 3 ºC for approximately 48 to 72 hours) to minimize potential losses of the test item from the plates. After incubation, the plates were scored for the presence of revertant colonies using an automated colony counting system. The plates were viewed microscopically for evidence of thinning (toxicity). Manual counts may be performed, where automated counting cannot be performed: e.g. colonies spreading, colonies on the edge of the plates and artefacts on the plates, thus distorting the actual plate count.

Experiment 2. 0.1 mL of the appropriate bacterial strain culture, 0.5 mL of phosphate buffer OR S9-mix (as appropriate) and 0.1 mL of the test item formulation, vehicle or 0.1 mL of appropriate positive control were incubated at 37 ± 3 ºC for 20 minutes (with shaking) prior to addition of 2 mL of molten amino-acid supplemented media Subsequently, the procedure for incubation and duration was the same as in Experiment 1.

SELECTION AGENT (mutation assays): histidine-deficient agar

NUMBER OF REPLICATIONS: 3

DETERMINATION OF CYTOTOXICITY
- Method: relative total growth

Rationale for test conditions:

In accordance with the OECD TG 471 guidelines.

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:
1. A dose-related increase in mutant frequency over the dose range tested (De Serres and Shelby, 1979).
2. A reproducible increase at one or more concentrations.
3. Biological relevance against in-house historical control ranges.
4. 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)).
5. Statistical analysis of data as determined by UKEMS (Mahon et al., 1989).
A test item is considered non-mutagenic (negative) in the test system if the above criteria are not met.
In instances of data prohibiting definitive judgement about test item activity are reported as equivocal.

Statistics:

Statistical methods (Mahon, et al.); as recommended by the UKEMS Subcommittee on Guidelines for Mutagenicity Testing, Report - Part III (1989).
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.

Results and discussion

Test results

Test results 1

Key result

Species / strain:

E. coli WP2 uvr A

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Remarks:

See table 1 and 2

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Test results 2

Key result

Species / strain:

S. typhimurium TA 98

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Remarks:

See table 1 and 2

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Test results 3

Key result

Species / strain:

S. typhimurium TA 100

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Remarks:

See table 1 and 2

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Test results 4

Key result

Species / strain:

S. typhimurium TA 1535

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Remarks:

See table 1 and 2

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Test results 5

Key result

Species / strain:

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

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Remarks:

See table 1 and 2

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Test results 6

Key result

Species / strain:

S. typhimurium TA 1537

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Remarks:

See table 1 and 2

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Additional information on results:

HISTORICAL CONTROL DATA (with ranges, means and standard deviation and confidence interval (e.g. 95%)
- Positive historical control data: The current Positive HCD dataset is presented in the full study report.
- Negative (solvent/vehicle) historical control data: The current background spontaneous revertant counts in concurrent untreated controls and/or or vehicle controls ; historic negative controls are presented in the full study report.

Any other information on results incl. tables

Table 1 : Test Results: Experiment 1 with and without metabolic activation and results of concurrent positive controls

S9-Mix (-)	Dose Level Per Plate	Number of revertants (mean) +/- SD
		Base-pair substitution strains						Frameshift strains
		TA100		TA1535		WP2uvrA		TA98		TA1537
	Solvent Control (DMSO)	108 07 98	(104) 5.5#	15 25 16	(19) 5.5	28 31 27	(29) 2.1	15 20 16	(17) 2.6	9 11 11	(10) 1.2
	1.5 µg	115 110 103	(112) 2.9	20 14 26	(20) 6.0	35 28 21	(28) 7.0	18 19 15	(17) 2.1	9 6 9	(8) 1.7
	5 µg	103 122 107	(111) 10.0	15 15 16	(15) 0.6	26 37 27	(30) 6.1	9 19 20	(6) 6.1	11 14 8	(11) 3.0
	15 µg	100 119 119	(113) 11.0	29 13 15	(19) 8.7	25 24 35	(28) 6.1	14 14 18	(15) 2.3	10 6 17	(11) 5.6
	50 µg	126 163 165	(151) 22.0	18 11 19	(16) 4.4	33 19 37	(30) 9.5	11 21 17	(16) 5.0	8 17 12	(12) 4.5
	150 µg	0 V 0 V 0 V	(0) 0.0	15 S 14 S 12 S	(14) 1.5	25 S 29 S 21 S	(25) 4.0	8 S 15 S 9 S	(11) 3.8	10 S 6 S 5 S	(7) 2.6
	500 µg	0 V 0 V 0 V	(0) 0.0	8 S 21 S 23 S	(17) 8.1	0 V 0 V 0 V	(0) 0.0	0 V 0 V 0 V	(0) 0.0	11 S 5 S 5 S	(7) 3.5
	1500 µg	0 T 0 T 0 T	(0) 0.0	0 T 0 T 0 T	(0) 0.0	0 V 0 V 0 V	(0) 0.0	0 T 0 T 0 T	(0) 0.0	0 T 0 T 0 T	(0) 0.0
	5000 µg	0 T 0 T 0 T	(0) 0.0	0 T 0 T 0 T	(0) 0.0	0 V 0 V 0 V	(0) 0.0	0 T 0 T 0 T	(0) 0.0	0 T 0 T 0 T	(0) 0.0
Positive controls S9-Mix (-)	Name Dose Level No. of Revertants	ENNG		ENNG		ENNG		4NQO		9AA
		3 µg		5 µg		2 µg		0.2 µg		80 µg
		588 538 571	(566) 25.4	1337 1433 1383	(1384) 48.0	514 527 478	(506) 25.4	191 182 187	(187) 4.5	181 179 248	(203) 39.3
S9-Mix (+)	Dose Level Per Plate	Number of revertants (mean) +/- SD
		Base-pair substitution strains						Frameshift strains
		TA100		TA1535		WP2uvrA		TA98		TA1537
	Solvent Control (DMSO)	96 109 104	(103) 6.6#	11 15 11	(12) 2.3	47 35 28	(37) 9.6	20 18 20	(19) 1.2	15 15 17	(16) 1.2
	1.5 µg	103 91 98	(97) 6.0	11 14 15	(13) 2.1	40 35 30	(35) 5.0	18 18 24	(20) 6.7	11 12 12	(12) 0.6
	5 µg	99 116 107	(107) 8.5	9 11 16	(12) 3.6	30 37 37	(35) 4.0	27 15 16	(19) 6.7	13 11 15	(13) 2.0
	15 µg	102 115 103	(107) 7.2	14 7 7	(9) 4.0	41 37 49	(42) 6.1	22 36 22	(27) 8.1	20 14 10	(15) 5.0
	50 µg	100 101 101	(101) 0.6	20 16 13	(16) 3.5	32 45 32	(36) 7.5	23 17 22	(21) 3.2	11 13 8	(11) 2.5
	150 µg	208 S 227 S 121 S	(185) 56.5	10 9 4	(8) 3.2	43 32 29	(35) 7.4	17 19 20	(19) 1.5	7 10 11	(9) 2.1
	500 µg	0 T 0 T 0 T	(0) 0.0	0 V 0 V 0 V	(0) 0.0	0 V 0 V 0 V	(0) 0.0	15 S 21 S 17 S	(18) 3.1	0 V 0 V 0 V	(0) 0.0
	1500 µg	0 T 0 T 0 T	(0) 0.0	0 T 0 T 0 T	(0) 0.0	0 V 0 V 0 V	(0) 0.0	0 T 0 T 0 T	(0) 0.0	0 T 0 T 0 T	(0) 0.0
	5000 µg	0 T 0 T 0 T	(0) 0.0	0 T 0 T 0 T	(0) 0.0	0 V 0 V 0 V	(0) 0.0	0 T 0 T 0 T	(0) 0.0	0 T 0 T 0 T	(0) 0.0
Positive controls S9-Mix (+)	Name Dose Level No. of Revertants	2AA		2AA		2AA		BP		2AA
		1 µg		2 µg		10 µg		5 µg		2 µg
		1263 964 1024	(1084) 158.2	234 230 235	(233) 2.6	148 139 132	(140) 8.0	112 139 121	(124) 13.7	234 205 220	(220) 14.5

ENNG  N-ethyl-N'-nitro-N-nitrosoguanidine

4NQO  4-Nitroquinoline-1-oxide

9AA      9-Aminoacridine

BP         Benzo(a)pyrene

2AA      2-Aminoanthracene

N/T      Not tested at this dose level

S            Sparse bacterial background lawn

V           Very weak bacterial background lawn

T            Toxic, no bacterial background lawn

#           Standard deviation

 

Table 2 : Test Results: Experiment 2 with and without metabolic activation and results of concurrent positive controls

S9-Mix (-)	Dose Level Per Plate	Number of revertants (mean) +/- SD
		Base-pair substitution strains						Frameshift strains
		TA100		TA1535		WP2uvrA		TA98 #2		TA1537
	Solvent Control (DMSO)	112 124 110	(115) 7.60#	13 10 13	(12) 1.7	22 21 24	(22) 1.5	18 23 17	(19) 3.2	6 10 14	(10) 4.0
	0.5 µg	114 112 116	(114) 2.0	14 12 10	(12) 2.0	20 19 25	(21) 3.2	6 19 15	(13) 6.7	10 5 7	(7) 2.5
	1.5 µg	124 122 107	(118) 9.3	21 9 13	(14) 6.1	20 18 20	(19) 1.2	17 18 24	(20) 3.8	11 10 14	(12) 2.1
	5 µg	109 108 129	(115) 11.8	9 16 18	(14) 4.7	26 22 23	(24) 2.1	13 17 17	(16) 2.3	9 9 8	(9) 0.6
	15 µg	115 118 113	(115) 2.5	11 10 9	(10) 1.0	21 19 17	(19) 2.0	13 19 22	(19) 4.6	15 11 13	(13) 2.0
	50 µg	99 S 107 S 110 S	(105) 5.7	16 10 12	(13) 3.1	18 21 24	(21) 3.0	22 12 15	(16) 5.1	9 15 11	(12) 3.1
	75 µg	111 S 95 S 114 S	(107) 10.2	0 V 0 V 0 V	(0) 0.0	15 17 20	(17) 2.5	12 26 14	(17) 7.6	9 13 7	(10) 3.1
	100 µg	0 V 0 V 0 V	(0) 0.0	0 V 0 V 0 V	(0) 0.0	25 S 20 S 16 S	(20) 4.5	19 S 11 S 13 S	(14) 4.2	7 S 9 S 3 S	(6) 3.1
	150 µg	0 V 0 V 0 V	(0) 0.0	0 V 0 V 0 V	(0) 0.0	0 V 0 V 0 V	(0) 0.0	0 V 0 V 0 V	(0) 0.0	0 V 0 V 0 V	(0) 0.0
Positive controls S9-Mix (-)	Name Dose Level No. of Revertants	ENNG		ENNG		ENNG		4NQO		9AA
		3 µg		5 µg		2 µg		0.2 µg		80 µg
		475 561 596	(544) 62.3	1098 1229 1410	(1246) 156.7	331 338 368	(346) 19.7	147 162 125	(145) 18.6	177 160 171	(169) 8.6
S9-Mix (+)	Dose Level Per Plate	Number of revertants (mean) +/- SD
		Base-pair substitution strains						Frameshift strains
		TA100		TA1535		WP2uvrA		TA98 #2		TA1537
	Solvent Control (DMSO)	120 110 107	(112) 6.8#	9 12 12	(11) 1.7	25 24 25	(25) 0.6	29 26 18	(24) 5.7	12 10 15	(12) 2.5
	0.5 µg	86 95 101	(94) 7.5	11 10 12	(11) 1.0	33 27 30	(30) 3.0	23 27 23	(24) 2.3	8 6 13	(9) 3.6
	1.5 µg	108 130 116	(118) 11.1	14 7 10	(10) 3.5	30 26 19	(25) 5.6	22 27 27	(25) 2.9	11 11 14	(12) 1.7
	5 µg	121 115 102	(113) 9.7	9 13 14	(12) 2.6	21 36 34	(30) 8.1	26 24 22	(24) 2.0	9 12 12	(11) 1.7
	15 µg	117 104 109	(110) 6.6	14 12 7	(11) 3.6	33 32 34	(33) 1.0	22 23 15	(20) 4.4	15 8 12	(12) 3.5
	50 µg	101 108 96	(102) 6.0	6 9 15	(10) 4.6	30 18 35	(28) 8.7	32 24 32	(29) 4.6	14 19 4	(12) 7.6
	100 µg	99 S 108 S 109 S	(105) 5.5	11 8 19	(13) 5.7	34 34 28	(32) 3.5	20 18 20	(19) 1.2	12 7 6	(8) 3.2
	125 µg	0 V 0 V 0 V	(0) 0.0	14 S 8 S 12 S	(11) 3.1	30 18 28	(25) 6.4	34 23 18	(25) 8.2	16 12 9	(12) 3.5
	150 µg	0 V 0 V 0 V	(0) 0.0	0 V 0 V 0 V	(0) 0.0	25 S 41 S 30 S	(32) 8.2	16 20 15	(17) 2.6	11 19 10	(13) 4.9
	175 µg	0 V 0 V 0 V	(0) 0.0	0 V 0 V 0 V	(0) 0.0	31 S 24 S 38 S	(31) 7.0	24 S 17 S 23 S	(21) 3.8	7 S 12 S 15 S	(11) 4.0
	500 µg	0 T 0 T 0 T	(0) 0.0	0 V 0 V 0 V	(0) 0.0	0 V 0 V 0 V	(0) 0.0	0 V 0 V 0 V	(0) 0.0	0 T 0 T 0 T	(0) 0.0
Positive controls S9-Mix (+)	Name Dose Level No. of Revertants	2AA		2AA		2AA		BP		2AA
		1 µg		2 µg		10 µg		5 µg		2 µg
		1471 1326 1373	(1390) 74.0	236 223 241	(233) 9.3	103 112 127	(114) 12.1	120 123 100	(114) 12.5	194 163 130	(162) 32.0

#2 : Experimental procedure repeated at a later date due to contamination in the original test

Applicant's summary and conclusion

Conclusions:

Interpretation of results:
negative
Under the conditions of this study, the test item was considered to be non-mutagenic in the presence and absence of S9 activation.

Executive summary:

The study was performed to the requirements of OECD Guideline 471, EU Method B13/14, US EPA OCSPP 870.5100 and Japanese guidelines for bacterial mutagenicity testing under GLP, to evaluate the potential mutagenicity of the test item in a bacterial reverse mutation assay using S.typhimurium strains TA98, TA100, TA1535, TA1537 and E.coli strain WP2uvrA- in both the presence and absence of S-9 mix. The test strains were treated with the test item using the Ames pre incubation method at up to ten 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 using fresh cultures of the bacterial strains and fresh test item formulations. Up to ten test item dose levels were selected in Experiment 2 in order to achieve a minimum of four non-toxic dose levels and the toxic limit of the test item. The dose range was amended following the results of Experiment 1 and ranged between 0.5 and 500 µg/plate, depending on bacterial strain type and presence or absence of S9-mix. The vehicle (DMSO) 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 item in the first experiment was selected as the maximum recommended dose level of 5000 μg/plate or the toxic limit of the test item depending on the strain type and presence of S9-mix.The maximum dose level of the test item in the first experiment was selected as the OECD TG 471 recommended dose level of 5000 μg/plate. In the first mutation test, the test item induced a visible reduction in the growth of the bacterial background lawns of all of the tester strains, initially from 150 μg/plate in both the absence and presence of metabolic activation (S9-mix). Based on the results of Experiment 1, the toxic limit was employed as the maximum concentration in the second mutation test. The test item once again induced a toxic response with a visible reduction in the growth of the bacterial background lawns noted for all of the tester strains, initially from 50 and 100 μg/plate in the absence and presence of metabolic activation (S9-mix), respectively. There were no biologically relevant increases in the frequency of revertant colonies recorded for any of the bacterial strains, with any dose of the test item, either with or without metabolic activation (S9-mix) in Experiment 1. One statistically significant value was noted (TA100 at 50 μg/plate in the absence of metabolic activation (S9-mix). However, this response was neither dose-related nor reproducible, and was within the in-house historical vehicle/untreated control range for the strain and, therefore considered of no biological relevance. A further statistical value was also noted (TA100 at 150 μg/plate in the presence of metabolic activation (S9-mix)), however this concentration exhibited toxicity as weakened bacterial background lawns therefore nullifying the statistical value.No significant increases in the frequency of revertant colonies were recorded for any of the bacterial strains, with any dose of the test item, either with or without metabolic activation (S9-mix) in Experiment 2. No precipitates were observed at any dose level in either the presence or absence of S9-mix. There were no biologically relevant increases in the frequency of revertant colonies recorded for any of the bacterial strains, with any dose of the test item, either with or without metabolic activation (S9‑mix). It was concluded that, under the conditions of this assay, the test item gave a negative, i.e. non-mutagenic response in S.typhimurium strains TA98, TA100, TA1535, TA1537 and E.coli strain WP2uvrA- in the presence and absence of S-9 mix.