Selenium disulphide

Endpoint summary

Key value for chemical safety assessment

Genetic toxicity in vitro

Description of key information

Genetic toxicity in vitro - Bacterial Reverse Mutation Assay

Selenium Disulphide is considered to be non-mutagenic in this Salmonella typhimurium and Escherichia coli reverse mutation assay.

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:

04 July 2018 - 01 August 2018

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Justification for type of information:

GLP study conducted to recent guidelines.

Qualifier:

according to guideline

Guideline:

OECD Guideline 471 (Bacterial Reverse Mutation Assay)

Deviations:

no

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Type of assay:

bacterial reverse mutation assay

Specific details on test material used for the study:

Identification: Selenium Disulphide
Batch: PMC/285/16
CAS No.: 7488-56-4
EINECS No. / EC No.: 231-303-8
Purity: 100%
Physical State / Appearance: Solid, orange
Expiry Date: 24 November 2026
Storage Conditions: At room temperature
Stability in Solvent: Not indicated by the Sponsor

Target gene:

Histidine and tryptophan

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/β-naphthoflavone induced rat liver S9

Test concentrations with justification for top dose:

In the pre-experiment the concentration range of the test item was 3 – 5000 μg/plate. The pre-experiment is reported as experiment I. Since no relevant toxic effects were observed 5000 μg/plate was chosen as maximal concentration. The concentration range included two logarithmic decades.

The following concentrations were tested in experiment II:
All strains with and without S9 mix: 33; 100; 333; 1000; 2500; and 5000 μg/plate

Due to a weak increase in revertant rates with TA 98 in the absence of S9 mix a confirmatory experiment with closer spacing was performed.
Experiment IIa:

Strain TA 98 without S9 mix: 658; 988; 1481; 2222; 3333; and 5000 μg/plate

Vehicle / solvent:

1% [w/v] Methylcellulose in deionized water

In a preliminary solubility trial several solvents (e.g. deionised water, DMSO, ethanol, acetone, DMF, THF and 1% [w/v] Methylcellulose) were used to find a suitable one to prepare an applicable test item preparation. The test item showed a low solubility in all solvents. However, 1% (w/v) Methylcellulose in deionised water was found to be the most suitable one which led to a fine suspension of the test item which appeared to be homogeneous. On the day of the experiment, the test item Selenium Disulphide was suspended in 1% [w/v] Methylcellulose in deionized water. To obtain a fine suspension a porcelain mortar was used (for details see raw data). The solvent was chosen because of its solubility properties and its relative nontoxicity to the bacteria (Maron et al.; 1981).

All formulations were prepared freshly before treatment and used within two hours of preparation.

Untreated negative controls:

other:

Remarks:

Based on historical data

Negative solvent / vehicle controls:

yes

Remarks:

Vehicle only

True negative controls:

not specified

Positive controls:

yes

Positive control substance:

sodium azide

methylmethanesulfonate

other: 4-nitro-o-phenylene-diamine; 2-aminoanthracene

Details on test system and experimental conditions:

Pre-Experiment for Toxicity
To evaluate the toxicity of the test item a pre-experiment was performed with all strains used. Eight concentrations were tested for toxicity and mutation induction with each 3 plates. The experimental conditions in this pre-experiment were the same as described for the experiment I below (plate incorporation test).
Toxicity of the test item results in a reduction in the number of spontaneous revertants (below a factor of 0.5) or a clearing of the bacterial background lawn.

Dose Selection
In the pre-experiment the concentration range of the test item was 3 – 5000 μg/plate. The pre-experiment is reported as experiment I. Since no relevant toxic effects were observed 5000 μg/plate was chosen as maximal concentration. The concentration range included two logarithmic decades.
The following concentrations were tested in experiment II:
All strains with and without S9 mix: 33; 100; 333; 1000; 2500; and 5000 μg/plate
Due to a weak increase in revertant rates with TA 98 in the absence of S9 mix a confirmatory experiment with closer spacing was performed.
Experiment IIa:
Strain TA 98 without S9 mix: 658; 988; 1481; 2222; 3333; and 5000 μg/plate

Experimental Performance
For each strain and dose level, including the controls, three plates were used.
Experiment I (Plate Incorporation)
The following materials were mixed in a test tube and poured onto the selective agar plates:
100 μL Test solution at each dose level (solvent or reference mutagen solution (positive control)),
500 μL S9 mix (for test with metabolic activation) or S9 mix substitution buffer (for test without metabolic activation),
100 μL Bacteria suspension.
2000 μL Overlay agar

Experiment II and IIa (Pre-Incubation)
The following materials were mixed in a test tube and incubated at 37°C for 60 minutes.
100 μL Test solution at each dose level (solvent or reference mutagen solution (positive control)),
500 μL S9 mix (for test with metabolic activation) or S9 mix substitution buffer (for test without metabolic activation),
100 μL Bacteria suspension (cf. 3.4.3 Precultures),
After pre-incubation 2.0 mL overlay agar (45°C) was added to each tube.
The mixture was poured on minimal agar plates. After solidification the plates were incubated upside down for at least 48 hours at 37°C in the dark.
In parallel to each test a sterile control of the test item was performed and documented in the raw data. Therefore, 100 μL of the stock solution, 500 μL S9 mix / S9 mix substitution buffer were mixed with 2.0 mL overlay agar and poured on minimal agar plates.

Rationale for test conditions:

The test conditions were based on the OECD/EU test guidelines

Evaluation criteria:

The Salmonella typhimurium and Escherichia coli reverse mutation assay is considered acceptable if it meets the following criteria:
• regular background growth in the negative and solvent control;
• the spontaneous reversion rates in the negative and solvent control are in the range of our historical data;
• the positive control substances should produce an increase above the threshold of twofold (strains TA 98, TA 100, and WP2 uvrA) or threefold (strains TA 1535 and TA 1537) the colony count of the corresponding solvent control;
• a minimum of five analysable dose levels should be present with at least three dose levels showing no signs of toxic effects, evident as a reduction in the number of revertants below the indication factor of 0.5.

A test item is considered as a mutagen if a biologically relevant increase in the number of revertants of twofold or above (strains TA 98, TA 100, and WP2 uvrA) or threefold or above (strains TA 1535 and TA 1537) the spontaneous mutation rate of the corresponding solvent control is observed.

A dose dependent increase is considered biologically relevant if the threshold is reached or exceeded at more than one concentration.

An increase of revertant colonies equal or above the threshold at only one concentration is judged as biologically relevant if reproduced in an independent second experiment.

A dose dependent increase in the number of revertant colonies below the threshold is regarded as an indication of a mutagenic potential if reproduced in an independent second experiment. However, whenever the colony counts remain within the historical range of negative and solvent controls such an increase is not considered biologically relevant.

Key result

Species / strain:

S. typhimurium TA 1535

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Vehicle controls validity:

valid

Untreated negative controls validity:

not applicable

Positive controls validity:

valid

Key result

Species / strain:

S. typhimurium TA 1537

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Vehicle controls validity:

valid

Untreated negative controls validity:

not applicable

Positive controls validity:

valid

Key result

Species / strain:

S. typhimurium TA 98

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Vehicle controls validity:

valid

Untreated negative controls validity:

not applicable

Positive controls validity:

valid

Key result

Species / strain:

S. typhimurium TA 100

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Vehicle controls validity:

valid

Untreated negative controls validity:

not applicable

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:

no cytotoxicity

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Additional information on results:

The test item Selenium Disulphide was assessed for its potential to induce gene mutations according to the plate incorporation test (experiment I) and the pre-incubation test (experiment II and IIa) using Salmonella typhimurium strains TA 1535, TA 1537, TA 98, TA 100, and the Escherichia coli strain WP2 uvrA.

The assay was performed in three independent experiments with and/or without liver microsomal activation. Each concentration and the controls were tested in triplicate. The test item was tested at the following concentrations:

Pre-Experiment/Experiment I: All strains with and without S9 mix: 3; 10; 33; 100; 333; 1000; 2500; and 5000 μg/plate

Experiment II: All strains with and without S9 mix: 33; 100; 333; 1000; 2500; and 5000 μg/plate

Experiment IIa:
Strain TA 98 without S9 mix: 658; 988; 1481; 2222; 3333; and 5000 μg/plate

The test item precipitated in the overlay agar in the test tubes from 333 to 5000 μg/plate in experiment I and II and from 658 to 5000 μg/plate in experiment IIa. Precipitation of the test item in the overlay agar on the incubated agar plates was observed from 2500 to 5000 μg/plate in experiment I and II and from 3333 to 5000 μg/plate in experiment IIa.

The plates incubated with the test item showed normal background growth up to 5000 μg/plate with and without S9 mix in all strains used.

No toxic effects, evident as a reduction in the number of revertants (below the indication factor of 0.5), occurred in the test groups with and without metabolic activation.

No substantial increase in revertant colony numbers of any of the four tester strains TA 1535, TA 1537, TA 100, and E.coli WP2 uvrA was observed following treatment with Selenium Disulphide at any concentration level, neither in the presence nor absence of metabolic activation (S9 mix).

In addition, tester strain TA 98 showed no relevant increase in revertant rates in experiment I in the absence and presence of metabolic activation and in experiment II in the presence of metabolic activation.

In experiment II in the absence of S9 mix a dose-related increase in revertant colony numbers was obtained with TA 98. At 5000 μg/plate the revertant rate (58.7 revertants per plate; factor 2.1) exceeded the range of the historical negative control data (13 – 43 revertants per plate) and slightly exceeded the threshold of twofold compared to the respective solvent control (28.0 revertants per plate). This observation occurred at a dose which showed fine precipitates on the agar plates. In this experiment scoring was done automatically whereas in the previous experiment I manual scoring of TA 98 and TA 100 colony numbers was done at high doses due to discrepancies between the values measured by the automatic scoring system and the colony counts on the plates determined by eye. Since scoring bias could not be excluded, and in accordance with the evaluation criteria defined in 3.7.3, a confirmatory experiment, designated experiment IIa, was performed to corroborate the finding in experiment II. A closer dose spacing (dilution factor 1.5) was applied in the repeat experiment with TA 98 in the absence of metabolic activation. In experiment IIa no biologically relevant increase in revertant rates was observed when tested up to the highest required dose of 5000 μg/plate. The highest revertant colony number was obtained at the top dose of 5000 μg/plate (39.0 revertants per plate). This value was clearly within the range of the historical negative control data (13 – 43 revertants per plateand below the threshold of twofold compared to the respective solvent control (23.3 revertants per plate). Fine precipitation of the test item onto the plates was observed at 3333 and 5000 μg/plate. The revertant colonies of these two dose groups were scored manually to prevent misleading data due to possible interference with precipitates.

Finally, the observation of a slight increase in revertant rates in TA 98 in the absence of S9 mix was not reproduced in the confirmatory experiment IIa with narrow dose setting. The observation in experiment II occurred only at a dose which showed fine precipitates onto the agar plates while scored automatically. In experiment I and IIa the colony numbers were scored manually to prevent misleading data due to possible interference with precipitation. Thus, it cannot be precluded that the slightly increased revertant rates in experiment II are based on erroneous automatic scoring procedure. In accordance with the evaluation criteria, due to the lack of reproducibility in the findings in experiment II in tester strain TA 98 in the absemce of S9 mix has to be regarded as not biologically relevant.


Appropriate reference mutagens were used as positive controls. They showed a distinct in-crease in induced revertant colonies.

Summary of Experiment I
Metabolic Activation	Test Group		Dose Level (per plate)	Revertant Colony Counts (Mean ± SD)
				TA 1535		TA 1537		TA 98	TA 100	WP2 uvrA
Without Activation	1% Methylcellulose			9 ± 3		11 ± 1		26 ± 6	188 ± 5	44 ± 6
	Untreated			12 ± 4		14 ± 6		27 ± 1	180 ± 12	42 ± 11
	Selenium		3 µg	10 ± 1		12 ± 3		29 ± 7	186 ± 23	44 ± 11
	Disulphide		10 µg	13 ± 3		11 ± 2		26 ± 9	177 ± 19	45 ± 3
			33 µg	9 ± 2		10 ± 2		28 ± 3	189 ± 7	45 ± 4
			100 µg	11 ± 3		12 ± 3		27 ± 7	182 ± 25	48 ± 7
			333 µg	11 ± 3		11 ± 1		29 ± 8	190 ± 28	39 ± 6
			1000 µg	12 ± 3		10 ± 0		33 ± 4	183 ± 7	47 ± 15
			2500 µg	7 ± 2^P		16 ± 5^P		37 ± 2^P M	204 ± 5^P M	43 ± 16^P
			5000 µg	10 ± 3^P		17 ± 3^P		41 ± 5^P M	237 ± 5^P M	51 ± 9^P
	NaN3		10 µg	1168 ± 65					1797 ± 254
	4-NOPD		10 µg					426 ± 21
	4-NOPD		50 µg			74 ± 13
	MMS		2.0 µL							814 ± 83
With Activation	1% Methylcellulose			11 ± 1		14 ± 3		48 ± 8	206 ± 3	54 ± 12
	Untreated			12 ± 4		13 ± 3		48 ± 1	214 ± 4	54 ± 10
	Selenium		3 µg	12 ± 3		12 ± 3		42 ± 8	173 ± 25	50 ± 3
	Disulphide		10 µg	11 ± 4		13 ± 6		46 ± 4	189 ± 11	43 ± 5
			33 µg	11 ± 4		13 ± 1		49 ± 8	202 ± 16	50 ± 5
			100 µg	13 ± 2		12 ± 3		39 ± 4	191 ± 21	51 ± 10
			333 µg	13 ± 2		14 ± 2		45 ± 10	202 ± 19	44 ± 4
			1000 µg	11 ± 1		16 ± 4		49 ± 5	187 ± 12	39 ± 8
			2500 µg	11 ± 1^P		18 ± 6^P		38 ± 3^P M	160 ± 2^P M	44 ± 5^P
			5000 µg	12 ± 2^P		13 ± 3^P		35 ± 2^P M	195 ± 8^P	51 ± 5^P
	2-AA		2.5 µg	211 ± 21		414 ± 17		2280 ± 240	3770 ± 167
	2-AA		10.0 µg							217 ± 21
Key to Positive Controls					Key to Plate Postfix Codes
NaN3 2-AA 4-NOPD MMS		sodium azide 2-aminoanthracene 4-nitro-o-phenylene-diamine methyl methane sulfonate			P M		Precipitate Manual count

 

 

Summary of Experiment II
Metabolic Activation	Test Group		Dose Level (per plate)	Revertant Colony Counts (Mean ± SD)
				TA 1535		TA 1537		TA 98	TA 100	WP2 uvrA
Without Activation	1% Methylcellulose			10 ± 1		19 ± 3		28 ± 8	209 ± 5	53 ± 2
	Untreated			16 ± 4		20 ± 6		29 ± 8	199 ± 27	62 ± 7
	Selenium		33 µg	10 ± 4		21 ± 4		28 ± 8	203 ± 29	49 ± 3
	Disulphide		100 µg	12 ± 3		23 ± 6		22 ± 6	194 ± 11	58 ± 5
			333 µg	9 ± 2		21 ± 5		20 ± 4	215 ± 10	43 ± 11
			1000 µg	11 ± 5		21 ± 5		22 ± 2	220 ± 23	57 ± 3
			2500 µg	9 ± 1^P		20 ± 7^P		40 ± 12^P	249 ± 17^P	51 ± 5^P
			5000 µg	11 ± 1^P		27 ± 0^P		59 ± 1^P	278 ± 17^P	58 ± 11^P
	NaN3		10 µg	1241 ± 8					1641 ± 171
	4-NOPD		10 µg					399 ± 36
	4-NOPD		50 µg			100 ± 5
	MMS		2.0 µL							803 ± 42
With Activation	1% Methylcellulose			11 ± 2		24 ± 3		39 ± 5	204 ± 19	65 ± 6
	Untreated			12 ± 2		25 ± 4		42 ± 10	213 ± 9	70 ± 3
	Selenium		33 µg	11 ± 1		24 ± 2		35 ± 7	202 ± 20	47 ± 5
	Disulphide		100 µg	13 ± 6		26 ± 2		34 ± 3	213 ± 5	48 ± 6
			333 µg	12 ± 2		23 ± 3		41 ± 6	202 ± 12	53 ± 5
			1000 µg	11 ± 2		21 ± 2		35 ± 5	206 ± 26	51 ± 7
			2500 µg	13 ± 2^P		25 ± 5^P		38 ± 7^P	213 ± 17^P	50 ± 8^P
			5000 µg	14 ± 1^P		22 ± 3^P		46 ± 5^P	222 ± 25^P	63 ± 5^P
	2-AA		2.5 µg	182 ± 25		248 ± 28		1673 ± 143	2410 ± 100
	2-AA		10.0 µg							200 ± 23
Key to Positive Controls					Key to Plate Postfix Codes
NaN3		sodium azide			P		Precipitate
2-AA		2-aminoanthracene
4-NOPD		4-nitro-o-phenylene-diamine
MMS		methyl methane sulfonate

 

 

Summary of Experiment IIa
Metabolic Activation		Test Group	Dose Level (per plate)		Revertant Colony Counts (Mean ± SD)
					TA 98
Without Activation		1% Methylcellulose			23 ± 3
		Untreated			27 ± 7
		Selenium Disulphide	658 µg		26 ± 7
			988 µg		26 ± 4
			1481 µg		32 ± 5
			2222 µg		38 ± 2
			3333 µg		32 ± 4^P M
			5000 µg		39 ± 3^P M
		4-NOPD	10 µg		471 ± 10
Key to Positive Controls				Key to Plate Postfix Codes
4-NOPD	4-nitro-o-phenylene-diamine			P M		Precipitate Manual count

 

Conclusions:

In conclusion, it can be stated that during the described mutagenicity test and under the experimental conditions reported, the test item did not induce gene mutations by base pair changes or frameshifts in the genome of the strains used.

Executive summary:

The test item Selenium Disulphide was assessed for its potential to induce gene mutations according to the plate incorporation test (experiment I) and the pre-incubation test (experiment II and IIa) using Salmonella typhimurium strains TA 1535, TA 1537, TA 98, TA 100, and the Escherichia coli strain WP2uvrA.

 

The assay was performed in three independent experiments with and/or without liver microsomal activation. Each concentration and the controls were tested in triplicate. The test item was tested at the following concentrations:

 

Pre-Experiment/Experiment I (plate incorporation assay): All strains with and without S9 mix: 3; 10; 33; 100; 333; 1000; 2500; and 5000 μg/plate

 

Experiment II (pre-incubation assay): All strains with and without S9 mix: 33; 100; 333; 1000; 2500; and 5000 μg/plate

 

Experiment IIa (pre-incubation assay):

Strain TA 98 without S9 mix: 658; 988; 1481; 2222; 3333; and 5000 μg/plate

 

The test item precipitated in the overlay agar in the test tubes from 333 to 5000 μg/plate in experiment I and II and from 658 to 5000 μg/plate in experiment IIa. Precipitation of the test item in the overlay agar on the incubated agar plates was observed from 2500 to 5000 μg/plate in experiment I and II and from 3333 to 5000 μg/plate in experiment IIa.

 

The plates incubated with the test item showed normal background growth up to 5000 μg/plate with and without S9 mix in all strains used.

 

No toxic effects, evident as a reduction in the number of revertants (below the indication factor of 0.5), occurred in any strains with and without metabolic activation.

 

No relevant increase in revertant colony numbers was observed with the four tester strains TA 1535, TA 1537, TA 100, and E.coli WP2uvrA following treatment with Selenium Disulphide at any concentration level, neither in the presence nor absence of metabolic activation (S9 mix).

 

In addition, tester strain TA 98 showed no relevant increase in revertant rates in experiment I in the absence and presence of metabolic activation and in experiment II in the presence of metabolic activation. However, in experiment II in the absence of S9 mix the exposure with the test item led to a dose-related, slight increase in revertant colony numbers in TA 98 at the highest required dose. The finding occurred at a dose causing strong precipitation. Thus, it cannot be precluded that the slightly increased revertant rates in experiment II at top dose are based on the interference of the fine precipitates with scoring. Because of this finding, and in accordance with the evaluation criteria, this part of the experiment was repeated as experiment IIa.

 

No relevant increase in mutation was observed in the confirmatory experiment performed with TA 98 under identical experimental conditions, but with a closer dose spacing and manual scoring of mutant colonies at high doses.

Therefore, due to lacking reproducibility the finding in experiment II in tester strain TA 98 in the absence of S9 mix has to be regarded as not biologically relevant.

 

Appropriate reference mutagens were used as positive controls and showed a distinct increase of induced revertant colonies.

 

In conclusion, it can be stated that during the described mutagenicity test and under the experimental conditions reported, the test item did not induce gene mutations by base pair changes or frameshifts in the genome of the strains used.

 

Therefore, Selenium Disulphide is considered to be non-mutagenic in this Salmonella typhimurium and Escherichia coli reverse mutation assay.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (negative)

Additional information

Genetic toxicity in vitro - Bacterial Reverse Mutation Assay

The test item Selenium Disulphide was assessed for its potential to induce gene mutations according to the plate incorporation test (experiment I) and the pre-incubation test (experiment II and IIa) usingSalmonella typhimuriumstrains TA 1535, TA 1537, TA 98, TA 100, and the Escherichia coli strain WP2uvrA.

 

The assay was performed in three independent experiments with and/or without liver microsomal activation. Each concentration and the controls were tested in triplicate. The test item was tested at the following concentrations:

 

Pre-Experiment/Experiment I (plate incorporation assay): All strains with and without S9 mix: 3; 10; 33; 100; 333; 1000; 2500; and 5000 μg/plate

 

Experiment II (pre-incubation assay): All strains with and without S9 mix: 33; 100; 333; 1000; 2500; and 5000 μg/plate

 

Experiment IIa (pre-incubation assay):

Strain TA 98 without S9 mix: 658; 988; 1481; 2222; 3333; and 5000 μg/plate

 

The test item precipitated in the overlay agar in the test tubes from 333 to 5000 μg/plate in experiment I and II and from 658 to 5000 μg/plate in experiment IIa. Precipitation of the test item in the overlay agar on the incubated agar plates was observed from 2500 to 5000 μg/plate in experiment I and II and from 3333 to 5000 μg/plate in experiment IIa.

 

The plates incubated with the test item showed normal background growth up to 5000 μg/plate with and without S9 mix in all strains used.

 

No toxic effects, evident as a reduction in the number of revertants (below the indication factor of 0.5), occurred in any strains with and without metabolic activation.

 

No relevant increase in revertant colony numbers was observed with the four tester strains TA 1535, TA 1537, TA 100, and E.coli WP2uvrA following treatment with Selenium Disulphide at any concentration level, neither in the presence nor absence of metabolic activation (S9 mix).

 

In addition, tester strain TA 98 showed no relevant increase in revertant rates in experiment I in the absence and presence of metabolic activation and in experiment II in the presence of metabolic activation. However, in experiment II in the absence of S9 mix the exposure with the test item led to a dose-related, slight increase in revertant colony numbers in TA 98 at the highest required dose. The finding occurred at a dose causing strong precipitation. Thus, it cannot be precluded that the slightly increased revertant rates in experiment II at top dose are based on the interference of the fine precipitates with scoring. Because of this finding, and in accordance with the evaluation criteria, this part of the experiment was repeated as experiment IIa.

 

No relevant increase in mutation was observed in the confirmatory experiment performed with TA 98 under identical experimental conditions, but with a closer dose spacing and manual scoring of mutant colonies at high doses.

Therefore, due to lacking reproducibility the finding in experiment II in tester strain TA 98 in the absence of S9 mix has to be regarded as not biologically relevant.

 

Appropriate reference mutagens were used as positive controls and showed a distinct increase of induced revertant colonies.

 

In conclusion, it can be stated that during the described mutagenicity test and under the experimental conditions reported, the test item did not induce gene mutations by base pair changes or frameshifts in the genome of the strains used.

 

Therefore, Selenium Disulphide is considered to be non-mutagenic in this Salmonella typhimurium and Escherichia coli reverse mutation assay.

Justification for classification or non-classification

Based on the available data and in accordance with Regulation (EC) 1272/2008, Selenium Disulphide does not meet the classification criteria for mutagenicity.