Orthoperiodic acid

Endpoint summary

Key value for chemical safety assessment

Genetic toxicity in vitro

Description of key information

Ames Test (Gijsbrechts, 2018)

Under the conditions of this study, it was concluded that the test material was mutagenic.

Micronucleus Assay (read-across; Poul et al., 2004)

Potassium iodidate had no significant chromosome damaging effects in the cytokinesis-block micronucleus test. No clastogenicity was noted.

 

Micronucleus Assay (read-across; Risher and Keit, 2009)

The publication reported that sodium iodate showed no mutagenic activity by the micronucleus test using mouse bone marrow.

 

Mouse Lymphoma Assay (read-across; Kessler et al., 1980)

Under the conditions of the study, solutions of potassium iodide at concentrations of 0.1–10 mg/mL did not cause mutagenic effects in L5178Y mouse lymphoma cells or transforming activity in Balb/c3T3 cells grown in culture.

 

Comet Assay (read-across; Poul et al., 2004)

Under the conditions of the study, potassium iodate had no clastogenic activity in CHO cells for concentrations up to 10 mM.

Link to relevant study records

Reference

Reference 1

Endpoint:

in vitro gene mutation study in bacteria

Type of information:

experimental study

Adequacy of study:

key study

Study period:

01 January 2018 to 22 January 2018

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 471 (Bacterial Reverse Mutation Assay)

Version / remarks:

1997

Deviations:

no

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

2008

Deviations:

no

GLP compliance:

yes

Type of assay:

bacterial reverse mutation assay

Target gene:

- Histidine requirement in the Salmonella typhimurium strains (Histidine operon).
- Tryptophan requirement in the Escherichia coli strain (Tryptophan operon).

Species / strain / cell type:

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

Details on mammalian cell type (if applicable):

- Type and identity of media: Samples of frozen stock cultures of bacteria were transferred into enriched nutrient broth (Oxoid LTD, Hampshire, England) and incubated in a shaking incubator (37 ± 1 °C, 150 rpm), until the cultures reached an optical density of 1.0 ± 0.1 at 700 nm (10^9 cells/mL). Freshly grown cultures of each strain were used for testing.
- Properly maintained: Yes. The Salmonella typhimurium strains are regularly checked to confirm their histidine requirement, crystal violet sensitivity, ampicillin resistance (TA98 and TA100), UV sensitivity and the number of spontaneous revertants. Stock cultures of the strains were stored in liquid nitrogen (-196 °C).

MEDIA USED
- Agar plates (ø 9 cm) containing 25 mL glucose agar medium. Glucose agar medium contained per litre: 18 g purified agar in Vogel-Bonner Medium E, 20 g glucose. The agar plates for the test with the Salmonella typhimurium strains also contained 12.5 μg/plate biotin and 15 μg/plate histidine

- Top agar: Milli-Q water containing 0.6 % (w/v) bacteriological agar and 0.5 % (w/v) sodium chloride was heated to dissolve the agar. Samples of 3 mL top agar were transferred into 10 mL glass tubes with metal caps. Top agar tubes were autoclaved for 20 min at 121 ± 3 °C.

Species / strain / cell type:

E. coli WP2 uvr A

Details on mammalian cell type (if applicable):

- Type and identity of media: Samples of frozen stock cultures of bacteria were transferred into enriched nutrient broth (Oxoid LTD, Hampshire, England) and incubated in a shaking incubator (37 ± 1 °C, 150 rpm), until the cultures reached an optical density of 1.0 ± 0.1 at 700 nm (10^9 cells/mL). Freshly grown cultures of each strain were used for testing.
- Properly maintained: Yes. The strain is regularly checked to confirm the tryptophan requirement, UV-sensitivity and the number of spontaneous revertants. Stock cultures were stored in liquid nitrogen (-196 °C).

MEDIA USED
Agar plates
Agar plates (ø 9 cm) containing 25 mL glucose agar medium. Glucose agar medium contained per litre: 18 g purified agar in Vogel-Bonner Medium E, 20 g glucose. The agar plates for the test with the Escherichia coli strain contained 15 μg/plate tryptophan.

Top agar
Milli-Q water containing 0.6 % (w/v) bacteriological agar and 0.5 % (w/v) sodium chloride was heated to dissolve the agar. Samples of 3 mL top agar were transferred into 10 mL glass tubes with metal caps. Top agar tubes were autoclaved for 20 min at 121 ± 3 °C.

Metabolic activation:

with and without

Metabolic activation system:

S9-mix (rat liver S9-mix induced by Aroclor 1254)

Test concentrations with justification for top dose:

- Dose range finding study (TA100 and WP2uvrA only): 1.7, 5.4, 17, 52, 164, 512, 1600 and 5000 μg/plate (with and without S9-mix)
- Experiment 1 (TA1535, TA1537 and TA98): 52, 164, 512, 1600 and 5000 μg/plate (with and without S9-mix)
- Experiment 2 (TA100, TA1535 and WP2uvrA): 52, 164, 512, 1600 and 5000 μg/plate (TA100: with and without S9-mix, TA1535 and WP2uvrA: with S9-mix only)

Vehicle / solvent:

- Vehicle(s)/solvent(s) used: Milli-Q water
- Justification for choice of solvent/vehicle: A solubility test was performed based on visual assessment. The test material was dissolved in Milli-Q water.

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

Remarks:

Milli-Q water

True negative controls:

no

Positive controls:

yes

Positive control substance:

4-nitroquinoline-N-oxide

2-nitrofluorene

sodium azide

methylmethanesulfonate

other: ICR-191; 2-aminoanthracene

Details on test system and experimental conditions:

METHOD OF APPLICATION: in agar (plate incorporation)

DOSE RANGE FINDING TEST/ MUTATION ASSAY
- Selection of an adequate range of doses was based on a dose-range finding test with the strains TA100 and WP2uvrA, both with and without S9-mix. Eight concentrations, 1.7, 5.4, 17, 52, 164, 512, 1600 and 5000 µg/plate were tested in triplicate.
The highest concentration of the test material used in the subsequent mutation assays was 5000 µg/plate. At least five different doses (increasing with approximately half-log steps) of the test material were tested in triplicate in each strain in the absence and presence of S9-mix.
The negative control (vehicle) and relevant positive controls were concurrently tested in each strain in the presence and absence of S9-mix.

MUTATION ASSAY
- The above mentioned dose-range finding study with two tester strains is reported as a part of the mutation assay. In the second part of this experiment, the test material was tested both in the absence and presence of S9-mix in the tester strains TA1535, TA1537 and TA98. Top agar in top agar tubes was melted by heating to 45 ± 2 °C. The following solutions were successively added to 3 mL molten top agar: 0.1 mL of a fresh bacterial culture (109 cells/mL) of one of the tester strains, 0.1 mL of a dilution of the test material in Milli-Q water and either 0.5 mL S9-mix (in case of activation assays) or 0.5 mL 0.1 M phosphate buffer (in case of non-activation assays). The ingredients were mixed on a Vvortex mixer and the content of the top agar tube was poured onto a selective agar plate. After solidification of the top agar, the plates were inverted and incubated in the dark at 37.0 ± 1.0 °C for 48 ± 4 h. After this period revertant colonies (histidine independent (His+) for Salmonella typhimurium bacteria and tryptophan independent (Trp+) for Escherichia coli) were counted. An additional direct plate assay was performed with the tester strains TA100, WP2uvrA and TA1535.
In compliance with the OECD guideline No 471, there is no requirement for verification of a clear positive response. Since the test results of the mutation experiment showed clear positive responses, the follow-up experiment (pre-incubation assay) was not performed.

NUMBER OF REPLICATIONS: Testing was performed in triplicate

COLONY COUNTING
The revertant colonies were counted automatically with the Sorcerer Colony Counter. Plates with sufficient test material precipitate to interfere with automated colony counting were counted manually. Evidence of test material precipitate on the plates and the condition of the bacterial background lawn were evaluated when considered necessary, macroscopically and/or microscopically by using a dissecting microscope.

Evaluation criteria:

ACCEPTABILITY OF THE ASSAY
The assay is considered acceptable if it meets the following criteria:
a) The vehicle control and positive control plates from each tester strain (with or without S9-mix) must exhibit a characteristic number of revertant colonies when compared against relevant historical control data generated at the testing facility.
b) The selected dose range should include a clearly toxic concentration or should exhibit limited solubility as demonstrated by the preliminary toxicity range-finding test or should extend to 5 mg/plate.
c) No more than 5 % of the plates are lost through contamination or some other unforeseen event. If the results are considered invalid due to contamination, the experiment will be repeated.

DATA EVALUATION
- In addition to the criteria stated below, any increase in the total number of revertants should be evaluated for its biological relevance including a comparison of the results with the historical control data range.
- A test material is considered negative (not mutagenic) in the test if:
a) The total number of revertants in the tester strain TA100 or WP2uvrA is not greater than two (2) times the concurrent vehicle control, and the total number of revertants in tester strains TA1535, TA1537 or TA98 is not greater than three (3) times the concurrent vehicle control.
b) The negative response should be reproducible in at least one follow-up experiment.
- A test material is considered positive (mutagenic) in the test if:
a) The total number of revertants in the tester strain TA100 or WP2uvrA is greater than two (2) times the concurrent vehicle control, or the total number of revertants in tester strains TA1535, TA1537, TA98 is greater than three (3) times the concurrent vehicle control.
b) In case a follow up experiment is performed when a positive response is observed in one of the tester strains, the positive response should be reproducible in at least one follow up experiment.

Key result

Species / strain:

E. coli WP2 uvr A

Metabolic activation:

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

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Vehicle controls validity:

valid

Untreated negative controls validity:

not applicable

Positive controls validity:

valid

Key result

Species / strain:

S. typhimurium, other: TA 98, TA 100, TA 1535 & TA 1537

Metabolic activation:

with and without

Genotoxicity:

positive

Remarks:

In tester strain TA100 and TA1535, in the presence of S9-mix.

Cytotoxicity / choice of top concentrations:

cytotoxicity

Remarks:

Cytotoxicity, as evidenced by a reduction of the bacterial background lawn, was observed in the tester strains TA1537, TA98 and TA1537, TA98 and TA100 in the absence of S9-mix and in tester strains TA1537, TA98 and WP2uvrA in the presence of S9-mix.

Vehicle controls validity:

valid

Untreated negative controls validity:

not applicable

Positive controls validity:

valid

Additional information on results:

- The test material was initially tested in the tester strains TA100 and WP2uvrA as a dose-range finding test with concentrations of 1.7, 5.4, 17, 52, 164, 512, 1600 and 5000 µg/plate in the absence and presence of S9-mix. Based on the results of the dose-range finding test, the following dose-range was selected for the mutation assay with the tester strains, TA1535, TA1537 and TA98 in the absence and presence of S9-mix: 52, 164, 512, 1600 and 5000 μg/plate.

DIRECT PLATE ASSAY
- Precipitate: Precipitation of the test material on the plates was not observed at the start or at the end of the incubation period in any tester strain.
- Toxicity: To determine the toxicity of the test material, the reduction of the bacterial background lawn, the increase in the size of the microcolonies and the reduction of the revertant colonies were observed.
- Cytotoxicity, as evidenced by a reduction of the bacterial background lawn, was observed in the tester strains TA1537, TA98 and TA100 in the absence of S9-mix and in tester strains TA1537, TA98 and WP2uvrA in the presence of S9-mix.
Mutagenicity:
- In tester strain WP2uvrA, the test material induced an up to 2.2-fold increase in the number of revertant colonies in the presence of S9-mix. The increase observed was within the historical control data range and was not dose-related.
- In tester strain TA100, the test material induced up to 3.0-fold dose-related increases in the number of revertant colonies in the presence of S9-mix. The increases observed were above the laboratory historical control data ranges and more than two-fold the concurrent solvent control. In the absence of S9-mix, the test item induced dose-related increases. However, the increases were only 1.6-fold and within the historical control data range.
- In tester strain TA1535, the test material induced an up to 3.3-fold increase in the number of revertant colonies in the presence of S9-mix. The increase observed was above the laboratory historical control data ranges and more than three-fold the concurrent solvent control.

ADDITIONAL DIRECT PLATE ASSAY
To verify the mutagenic responses observed in the mutation assay, an additional experiment was performed. In this additional mutation experiment the test item was tested at a concentration range of 52 to 5000 µg/plate in tester strain TA100 in the absence of S9-mix and the tester strains TA100, WP2uvrA and TA1535 in the presence of S9-mix.
- Precipitate: Precipitation of the test material on the plates was not observed at the start or at the end of the incubation period.
- Toxicity: Cytotoxicity, as evidenced by a reduction in the bacterial background lawn and the presence of microcolonies, was observed in the tester strains TA100 and WP2uvrA in the presence of S9-mix.
Mutagenicity:
-In tester strain TA100, the test material induced up to 1.9-fold dose-related increases in the number of revertant colonies in the presence of S9-mix. The increases observed were above the laboratory historical control data ranges but less than 2-fold the concurrent solvent control. In the absence of S9-mix, the test material induced dose-related increases, however, the increases were only 1.5-fold and within the historical control data range.
- In tester strain TA1535, the test material induced an up to 2.5-fold increase in the number of revertant colonies in the presence of S9-mix. The increase observed was above the laboratory historical control data ranges but less than 3-fold the concurrent solvent control.


DISCUSSION
- The negative control values were within the laboratory historical control data ranges.
- The strain-specific positive control values were within the laboratory historical control data ranges indicating that the test conditions were adequate and that the metabolic activation system functioned properly, except the response for TA1537 (absence of S9-mix in the first experiment). The purpose of the positive control is as a reference for the test system, where a positive response is required to check if the test system functions correctly. Since the value was more than 200 times greater than the concurrent solvent control values, this deviation in the mean plate count of the positive control had no effect on the results of the study.
- In the absence of S9-mix, no biologically relevant increases in the number of revertant colonies were observed.
- In the presence of S9-mix, the test material induced increases in the number of revertant colonies in the tester strains TA1535, TA100 and WP2uvrA. The increases were reproducible in the tester strains TA1535 and TA100. The increases were above the laboratory historical control data range in both the initial and the additional mutation experiment, but were only more than two- and three-fold in the initial experiment.
- Taken together, since 3.0- to 3.3-fold increases were observed in the presence of S9-mix in the tester strains TA100 and TA1535, respectively, and the results were reproducible, these increases are considered biologically relevant and the test item is mutagenic

Dose-Range Finding Test: Mutagenic Response of the test material in the Salmonella typhimurium Reverse Mutation Assay and in the Escherichia coli Reverse Mutation Assay 

Dose (µg/plate)	Mean number of revertant colonies/3 replicate plates (± S.D.) with one Salmonella typhimurium and one Escherichia coli strain.
	TA100					WP2uvrA
Without S9-mix
Positive control	748	±	13		1243		±	80
Solvent control	81	±	18		37		±	5
1.7	84	±	12		32		±	7
5.4	80	±	14		41		±	2
17	91	±	12		33		±	2
52	88	±	16		32		±	4
164	102	±	29		41		±	5
512	114	±	21		31		±	10
1600	129	±	20	^n	33		±	6
5000	99	±	58	^s m NP	23		±	4	^n NP
With S9-mix
Positive control	1251	±	39		439		±	44
Solvent control	71	±	7		24		±	7
1.7	91	±	4		53		±	13
5.4	79	±	12		38		±	5
17	87	±	3		42		±	7
52	73	±	16		33		±	12
164	108	±	9		35		±	8
512	136	±	16		52		±	15
1600	184	±	15		50		±	9
5000	212	±	18	^n NP	23		±	7	^n m NP

 

NP	No precipitate
m	Bacterial background lawn moderately reduced
n	Normal bacterial background lawn
s	Bacterial background lawn slightly reduced

 

Mutation Experiment: Mutagenic Response of the test material in the Salmonella typhimurium Reverse Mutation Assay 

Dose (µg/plate)		Mean number of revertant colonies/3 replicate plates (± S.D.) with different strains of Salmonella typhimurium.
		TA1535					TA1537					TA98
Without S9-mix
Positive control	1057		±	31		1407		±	85		1231		±	150
Solvent control	14		±	2		6		±	2		14		±	3
52	14		±	4		8		±	2		16		±	3
164	11		±	2		6		±	4		12		±	2
512	12		±	6		6		±	2		14		±	2
1600	13		±	6		3		±	2	^n	18		±	2	^n
5000	16		±	4	^n NP	5		±	8	^m NP	19		±	9	^s NP
With S9-mix
Positive control	330		±	26		399		±	72		1604		±	122
Solvent control	10		±	4		7		±	3		24		±	9
52	16		±	8		8		±	1		24		±	8
164	19		±	8		10		±	2		19		±	4
512	27		±	3		7		±	1		27		±	8
1600	33		±	10		5		±	1	^n	30		±	13	^n
5000	23		±	6	^n NP	7		±	3	^s NP	21		±	4	^s NP

 

NP	No precipitate
m	Bacterial background lawn moderately reduced
n	Normal bacterial background lawn
s	Bacterial background lawn slightly reduced

 

Additional Mutation Experiment: Mutagenic Response of the test material in the Salmonella typhimurium Reverse Mutation Assay and in the Escherichia coli Reverse Mutation Assay 

Dose (µg/plate)	Mean number of revertant colonies/3 replicate plates (± S.D.) with different strains of Salmonella typhimurium and one Escherichia coli strain.
	TA1535					TA100					WP2uvrA
Without S9-mix
Positive control					919		±	60
Solvent control					109		±	11
52					121		±	7
164					118		±	12
512					127		±	15
1600					155		±	4
2500					163		±	21
5000					104		±	41	^n NP
With S9-mix
Positive control	439	±	12		2379		±	41		514		±	6
Solvent control	13	±	2		124		±	12		44		±	19
52	13	±	6		125		±	11		38		±	10
164	11	±	3		134		±	16		47		±	2
512	14	±	6		179		±	8		56		±	12
1600	26	±	6		236		±	22		55		±	12
2500	32	±	1		235		±	34	^n	56		±	5	^n
5000	19	±	6	^n NP					^e NP MC					^e NP MC

 

MC	Microcolonies
NP	No precipitate
e	Bacterial background lawn extremely reduced
n	Normal bacterial background lawn

  

Conclusions:

Under the conditions of this study, it was concluded that the test material was mutagenic.

Executive summary:

The genetic toxicity of the test material was investigated in accordance with the standardised guidelines OECD 471 and EU Method B13/14, under GLP conditions.

The objective of this study was to determine the potential of the test material and/or its metabolites to induce reverse mutations at the histidine locus in several strains of Salmonella typhimurium (S. typhimurium; TA98, TA100, TA1535, and TA1537), and at the tryptophan locus of Escherichia coli (E. coli) strain WP2uvrA in the presence or absence of an exogenous mammalian metabolic activation system (S9). 

The test material was dissolved in Milli-Q water.  

In the dose range finding study, the test material was initially tested up to concentrations of 5000 µg/plate in the strains TA100 and WP2uvrA in the direct plate assay. The test material did not precipitate on the plates at this dose level. Cytotoxicity, as evidenced by a reduction in the bacterial background lawn, was observed in tester strain TA100 in the absence of S9-mix and in strain WP2uvrA in the presence of S9-mix.

In the first mutation experiment, the test material was tested up to concentrations of 5000 µg/plate in the strains TA1535, TA1537 and TA98. The test material did not precipitate on the plates at this dose level. Cytotoxicity, as evidenced by a reduction in the bacterial background lawn, was observed in the tester strains TA1537 and TA98 in the absence and presence of S9-mix.

In tester strain WP2uvrA, the test material induced an up to 2.2-fold increase in the number of revertant colonies in the presence of S9-mix. The increase observed was within the historical control data range and was not dose-related.

In tester strain TA100, the test material induced up to 3.0-fold dose-related increases in the number of revertant colonies in the presence of S9-mix. The increases observed were above the laboratory historical control data ranges and more than two-fold the concurrent solvent control. In the absence of S9-mix, the test item induced dose-related increases. However, the increases were only 1.6-fold and within the historical control data range.

In tester strain TA1535, the test material induced an up to 3.3-fold increase in the number of revertant colonies in the presence of S9-mix. The increase observed was above the laboratory historical control data ranges and more than three-fold the concurrent solvent control.

To verify the mutagenic responses observed in the first mutation experiment, an additional experiment was performed. In the additional experiment the test item was tested at a concentration range of 52 to 5000 μg/plate in tester strain TA100 in the absence of S9-mix and the tester strains TA100, WP2uvrA and TA1535 in the presence of S9-mix. The test material did not precipitate on the plates at this dose level. Cytotoxicity, as evidenced by a reduction in the bacterial background lawn and the presence of microcolonies, was observed in the tester strains TA100 and WP2uvrA in the presence of S9-mix.

In tester strain TA100, the test material induced up to 1.9-fold dose-related increases in the number of revertant colonies in the presence of S9-mix. The increases observed were above the laboratory historical control data ranges.

In tester strain TA1535, the test material induced an up to 2.5-fold increase in the number of revertant colonies in the presence of S9-mix. The increase observed was above the laboratory historical control data ranges. In this study, acceptable responses were obtained for the negative and strain-specific positive control items indicating that the test conditions were adequate and that the metabolic activation system functioned properly.

In the absence of S9-mix, no biologically relevant increases in the number of revertant colonies were observed.

In the presence of S9-mix, the test material induced increases in the number of revertant colonies in the tester strains TA1535, TA100 and WP2uvrA. The increases were reproducible in the tester strains TA1535 and TA100. The increases were above the laboratory historical control data range in both the initial and the additional mutation experiment, but were only more than two- and three-fold in the initial experiment.

Taken together, since 3.0- to 3.3-fold increases were observed in the presence of S9-mix in the tester strains TA100 and TA1535, respectively, and the results were reproducible, these increases are considered biologically relevant and the test material is mutagenic.

Under the conditions of this study, it was concluded that the test material was mutagenic.

Reference 2

Endpoint:

in vitro DNA damage and/or repair study

Type of information:

experimental study

Adequacy of study:

key study

Study period:

not reported

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Remarks:

The study was conducted on the read across substance, potassium iodate. Investigations on the gastric hydrolysis of the registration substance indicate a chemical reaction of periodate to iodate thereby confirming the validity of the read across.

Reason / purpose for cross-reference:

other: read across: target

Qualifier:

no guideline available

Principles of method if other than guideline:

The alkaline comet assay was performed according to Tice et al. (2000). Cells were collected by trypsination, suspended in pre-warmed low melting point (LMP) agarose (0.5 % in PBS) and deposited on a conventional microscope slide (initially dipped in 1 % agarose and dried) pre-coated with normal agarose (0.8 % in PBS). Slides were put in a lysis solution (2.5 M NaCl, 0.1 M EDTA, 10 mM Tris pH10, 10 % DMSO and 1 % Triton 100) for 1 hour at about 5 °C. DNA was allowed to unwind in electrophoresis buffer (0.3 M NaOH, 1 mM EDTA, pH 13.6) for 40 minutes at room temperature. Slides were then placed into a horizontal electrophoresis tank and exposed to 0.7 V/cm (300 mA) for 24 minutes. After electrophoresis, slides were washed twice in neutralization buffer (0.4 M Tris, pH 7.5) and dehydrated in ethanol for 5 minutes. After staining with ethidium bromide, 50 randomly selected cells per slide were submitted to image analysis. Olive tail moment (OTM), defined as the product of the distance between the barycentres of the head and tail by the proportion of DNA in the tail, was used to evaluate the extent of DNA damage in individual cells. Highly damaged cells (HDC) were characterised by an extensive DNA fragmentation which allowed 90 % of the DNA to migrate during electrophoresis, forming the comet tail. Median values of OTM were calculated without taking HDC into account. Each dose was tested in duplicate and at least two independent assays were performed. Etoposide (0.5 mg/mL), a well known inhibitor of topoisomerase II inducing DNA double strand breaks, was used as positive control. In parallel to the assessment of DNA damage, cell viability was measured using the Trypan blue exclusion method. Cell viability was expressed as proportion of total cells.

GLP compliance:

not specified

Type of assay:

comet assay

Species / strain / cell type:

Chinese hamster Ovary (CHO)

Details on mammalian cell type (if applicable):

Chinese hamster ovary (CHO-K1) cells were purchased from Eurobio (France). They were routinely maintained from stocks stored in liquid nitrogen. CHO cells were grown at 37 °C in a humidified atmosphere at 5% CO2 in air, in HAM’S F12 medium with L-glutamine supplemented with 10 % fetal calf serum (FCS), penicillin (50 UI/mL) and streptomycine (50 mg/mL). Cells were subcultured 24 hours before treatment.

Test concentrations with justification for top dose:

0.625, 1.25, 2.5, 5 and 10 mM

Vehicle / solvent:

For test material formulations culture medium was used as vehicle.
For positive control Etoposide (0.5 mg/mL) was dissolved in DMSO.

Untreated negative controls:

yes

Remarks:

culture medium

Negative solvent / vehicle controls:

no

True negative controls:

no

Positive controls:

yes

Positive control substance:

other: Etoposide

Details on test system and experimental conditions:

The alkaline comet assay was performed according to Tice et al. (2000). Cells were collected by trypsination, suspended in pre-warmed low melting point (LMP) agarose (0.5 % in PBS) and deposited on a conventional microscope slide (initially dipped in 1 % agarose and dried) pre-coated with normal agarose (0.8 % in PBS). Slides were put in a lysis solution (2.5 M NaCl, 0.1 M EDTA, 10 mM Tris pH10, 10 % DMSO and 1 % Triton 100) for 1 hour at about 5 °C. DNA was allowed to unwind in electrophoresis buffer (0.3 M NaOH, 1 mM EDTA, pH 13.6) for 40 minuttes at room temperature. Slides were then placed into a horizontal electrophoresis tank and exposed to 0.7 V/cm (300 mA) for 24 minutes. After electrophoresis, slides were washed twice in neutralization buffer (0.4 M Tris, pH 7.5) and dehydrated in ethanol for 5 minutes. After staining with ethidium bromide, 50 randomly selected cells per slide were submitted to image analysis.
Each dose was tested in duplicate and at least two independent assays were performed. Etoposide (0.5 mg/mL), a well known inhibitor of topoisomerase II inducing DNA double strand breaks, was used as positive control.

Evaluation criteria:

Olive tail moment (OTM), defined as the product of the distance between the barycentres of the head and tail by the proportion of DNA in the tail, was used to evaluate the extent of DNA damage in individual cells. Highly damaged cells (HDC) were characterised by an extensive DNA fragmentation which allowed 90 % of the DNA to migrate during electrophoresis, forming the comet tail. Median values of OTM were calculated without taking HDC into account.
In parallel to the assessment of DNA damage, cell viability was measured using the Trypan blue exclusion method. Cell viability was expressed as proportion of total cells.

Statistics:

In the alkaline comet assay, data were expressed as the median values of OTM (S.D.) for each slide. Comparisons between control and treated cell cultures were made using ANOVA and Dunnett’s one sided test.

Key result

Species / strain:

Chinese hamster Ovary (CHO)

Remarks:

CHO-K1

Metabolic activation:

not applicable

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Vehicle controls validity:

valid

Untreated negative controls validity:

not applicable

Positive controls validity:

valid

Additional information on results:

The results showed that the comet assay failed to detect the presence of DNA damage after a treatment of cells by potassium iodate for concentrations up to 10 mM.
The slight increase in tail moment observed at 10 mM was found not to be statistically singificant from the control.

Conclusions:

Interpretation of results: negative

Under the conditions of the study, potassium iodate had no clastogenic activity in CHO cells for concentrations up to 10 mM.

Executive summary:

The mutagenic effects of potassium iodate were evaluated in vitro using the alkaline comet assay at concentration of 0.625, 1.25, 2.5, 5 and 10 mM. Cell viability was measured using the Trypan blue exclusion method and expressed as proportion of total cells. The test results showed that potassium iodate did not induce DNA damage, or cytotoxicity, in the alkaline comet assay for doses up to 10 mM.

Reference 3

Endpoint:

in vitro DNA damage and/or repair study

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Study conducted on read-across material.

Justification for type of information:

A read-across justification report (RAAF) will be added to Section 13 as soon as possible.

Reason / purpose for cross-reference:

read-across source

Key result

Species / strain:

Chinese hamster Ovary (CHO)

Remarks:

CHO-K1

Metabolic activation:

not applicable

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Vehicle controls validity:

valid

Untreated negative controls validity:

not applicable

Positive controls validity:

valid

Reference 4

Endpoint:

in vitro cytogenicity / micronucleus study

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Study conducted on read-across material.

Justification for type of information:

A read-across justification report (RAAF) will be added to Section 13 as soon as possible.

Reason / purpose for cross-reference:

read-across source

Key result

Species / strain:

Chinese hamster Ovary (CHO)

Remarks:

CHO-K1

Metabolic activation:

not applicable

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Vehicle controls validity:

valid

Untreated negative controls validity:

not applicable

Positive controls validity:

valid

Reference 5

Endpoint:

in vitro cytogenicity / micronucleus study

Type of information:

experimental study

Adequacy of study:

key study

Study period:

not reported

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Remarks:

The study was conducted on the read across substance, potassium iodate. Investigations on the gastric hydrolysis of the registration substance indicate a chemical reaction of periodate to iodate thereby confirming the validity of the read across.

Reason / purpose for cross-reference:

other: read across: target

Qualifier:

equivalent or similar to guideline

Guideline:

other: OECD Guideline 487 (In Vitro Mammalian Cell Micronucleus Test)

Deviations:

yes

Remarks:

all cultures were treated without metabolic activation

Principles of method if other than guideline:

Exponentially growing CHO-K1 cells were plated in a six-well plate on glass coverslips (1.5105 cells/well) and cultured 24 hours prior to treatment. Duplicate coverslips were established for each experiment, and at least two independent experiments were performed. The cells were exposed to the test material at different concentrations for 3 hours in a Foetal Calf Serum (FCS) free medium. At the end of treatment, cells were washed twice with Phosphate Buffered Saline (PBS) before a 20 hour incubation in fresh medium containing 10 % of FCS and 3 mg/mL of cytochalasin B. Thereafter, cells were washed twice with PBS and allowed to recover for 1.5 hours in 10 % FCS fresh medium. Cells were fixed with cold methanol, stained with acridine orange (62.5 mg/mL) for 5 minutes and mounted in Sorensen buffer. Slides were coded and blindly examined under an epifluorescence microscope at 1000 magnification under oil immersion. One thousand (1000) binucleated cells were scored for each slide. Methyl methanesulphonate (MMS) (30 mg/mL), a well known alkylating agent, was used as positive control. Cytotoxicity was measured by the binucleated cell ratio between treated and control slides.

GLP compliance:

not specified

Type of assay:

in vitro mammalian cell micronucleus test

Species / strain / cell type:

Chinese hamster Ovary (CHO)

Details on mammalian cell type (if applicable):

Chinese hamster ovary (CHO-K1) cells were purchased from Eurobio (France). They were routinely maintained from stocks stored in liquid nitrogen. CHO cells were grown at 37 °C in a humidified atmosphere at 5% CO2 in air, in HAM’S F12 medium with L-glutamine supplemented with 10 % fetal calf serum (FCS), penicillin (50 UI/mL) and streptomycine (50 mg/mL). Cells were subcultured 24 hours before treatment.

Test concentrations with justification for top dose:

0.625, 1.25, 2.5, 5 and 10 mM

Vehicle / solvent:

For test material formulations culture medium was used as vehicle.
For positive control, methyl methanesulphonate (MMS) (30 µg/mL) was dissolved in culture medium.

Untreated negative controls:

yes

Remarks:

culture medium

Negative solvent / vehicle controls:

no

True negative controls:

no

Positive controls:

yes

Positive control substance:

methylmethanesulfonate

Details on test system and experimental conditions:

Exponentially growing CHO-K1 cells were plated in a six-well plate on glass coverslips (1.5105 cells/well) and cultured 24 hours prior to treatment. Duplicate coverslips were established for each experiment, and at least two independent experiments were performed. The cells were exposed to the test material at different concentrations for 3 hours in a Foetal Calf Serum (FCS) free medium. At the end of treatment, cells were washed twice with Phosphate Buffered Saline (PBS) before a 20 hour incubation in fresh medium containing 10 % of FCS and 3 mg/mL of cytochalasin B. Thereafter, cells were washed twice with PBS and allowed to recover for 1.5 hours in 10 % FCS fresh medium. Cells were fixed with cold methanol, stained with acridine orange (62.5 mg/mL) for 5 minutes and mounted in Sorensen buffer.

Evaluation criteria:

Slides were coded and blindly examined under an epifluorescence microscope at 1000 magnification under oil immersion. Criteria for cells and micronuclei scoring were as follows:
- The cells should be binucleated with an intact nuclear membrane and should be situated within the same cytoplasmic boundary.
- Micronuclei should be morphologically identical to but smaller than nuclei, their diameter usually varied between 1/6th and 1/3rd of the mean diameter of the main nuclei.
- Micronuclei should be readily distinguished and not be linked to the main nuclei via nucleoplasmic bridges.
- Cells showing chromatin condensation or nuclear fragmentation with an intact cytoplasmic membrane were classified as apoptotic cells.
One thousand (1000) binucleated cells were scored for each slide. The frequencies of binuclei, or binuclei with micronuclei and of apoptotic cells were estimated. Cytotoxicity was measured by the bincleated cell ratio between treated and control slides.

Statistics:

In the cytokinesis-block micronucleus assay data were expressed as the percentage of binucleated cells with micronuclei. Comparisons between control and treated cell cultures were made using ANOVA and Dunnett’s one sided test.

Key result

Species / strain:

Chinese hamster Ovary (CHO)

Remarks:

CHO-K1

Metabolic activation:

not applicable

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Vehicle controls validity:

valid

Untreated negative controls validity:

not applicable

Positive controls validity:

valid

Additional information on results:

Potassium iodate did not induce any increase in the frequency of binucleated cells with micronuclei for doses ranging from 0.625 to 10 mM. Furthermore, no clastogenic effects of the compound were noted in cells that had completed one nuclear division.

Conclusions:

Interpretation of results: negative

Potassium iodidate had no significant chromosome damaging effects in the cytokinesis-block micronucleus test. No clastogenicity was noted.

Executive summary:

The mutagenic potential of the test material was investigated in a cytokinesis-block micronucleus assay at test concentrations of 0.625, 1.25, 2.5, 5 and 10 mM. Concurrent positive and negative controls were included. Under the conditions of the study, potassium iodate did not induce any increase in the frequency of binucleated cells with micronuclei for doses ranging from 0.625 to 10 mM. Furthermore, no clastogenic effects of the compound were noted in cells that had completed one nuclear division.

Reference 6

Endpoint:

in vitro cytogenicity / micronucleus study

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Study conducted on read-across material.

Justification for type of information:

A read-across justification report (RAAF) will be added to Section 13 as soon as possible.

Reason / purpose for cross-reference:

read-across source

Key result

Species / strain:

mammalian cell line, other: mouse bone marrow

Metabolic activation:

not specified

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

not specified

Reference 7

Endpoint:

in vitro cytogenicity / micronucleus study

Type of information:

experimental study

Adequacy of study:

key study

Study period:

not reported

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

data from handbook or collection of data

Remarks:

Data from a report from a recognised body reviewed by a panel of experts. Although there is limited detail on materials and methods included in the publication, the conclusions drawn from the cicads document are considered to be reliable and representative of the mutagenic potential of the substance.

Reason / purpose for cross-reference:

other: read across: target

Qualifier:

no guideline available

Principles of method if other than guideline:

A micronucleus test was conducted although the publication includes no detail on the materials and methods used in the study.

GLP compliance:

not specified

Type of assay:

in vitro mammalian cell micronucleus test

Species / strain / cell type:

mammalian cell line, other: mouse bone marrow

Key result

Species / strain:

mammalian cell line, other: mouse bone marrow

Metabolic activation:

not specified

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

not specified

Sodium iodate showed no mutagenic activity by the micronucleus test using mouse bone marrow.

Conclusions:

Interpretation of results: negative

The publication reported that sodium iodate showed no mutagenic activity by the micronucleus test using mouse bone marrow. No information is provided on experimental materials and methods.

Executive summary:

The publication reported that sodium iodate showed no mutagenic activity by the micronucleus test using mouse bone marrow.

No information is provided on experimental materials and methods.

Reference 8

Endpoint:

in vitro gene mutation study in mammalian cells

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Study conducted on read-across material.

Justification for type of information:

A read-across justification report (RAAF) will be added to Section 13 as soon as possible.

Reason / purpose for cross-reference:

read-across source

Species / strain:

mouse lymphoma L5178Y cells

Metabolic activation:

without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

not determined

Vehicle controls validity:

not applicable

Untreated negative controls validity:

valid

Positive controls validity:

valid

Species / strain:

other: BALB/c 3T3

Metabolic activation:

without

Genotoxicity:

other: no transforming activity

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Vehicle controls validity:

not applicable

Untreated negative controls validity:

valid

Positive controls validity:

valid

Reference 9

Endpoint:

in vitro gene mutation study in mammalian cells

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

Not reported

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Remarks:

The study was conducted with the read across substance, potassium iodide. Investigations on the gastric hydrolysis of the registration substance indicate a chemical reaction of periodate to iodate, while toxicokinetic investigations on iodate indicate a chemical reaction of iodate to iodide, thereby confirming the validity of the read across.

Reason / purpose for cross-reference:

other: read across: target

Qualifier:

equivalent or similar to guideline

Guideline:

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

Qualifier:

equivalent or similar to guideline

Guideline:

EU Method B.21 (In Vitro Mammalian Cell Transformation Test)

GLP compliance:

no

Remarks:

Study pre-dates GLP

Type of assay:

mammalian cell gene mutation assay

Target gene:

thymidine kinase (TK) locus

Species / strain / cell type:

mouse lymphoma L5178Y cells

Details on mammalian cell type (if applicable):

The L5178Y mouse-lymphoma cells were originally derived from a methylcholanthrene induced lymphoma (Fischer, 1958). The L5178Y cell line used was supplied by the Food and Drug Administration, Washington, D.C, USA.

Species / strain / cell type:

other: BALB/c 3T3

Details on mammalian cell type (if applicable):

Balb/c 3T3 cells (Litton Bionetics, Kensington, Maryland, USA.), derived from done A31 of the Balb/c 3T3 line, were used for the transformation studies. The cells were grown in Eagle's Minimal Essential Medium with Eagle's- Salts (EMEM), supplemented with 10% fetal calf serum and 1 % 200 mM glutamine (Gibco). Stock cultures were maintained at 75% confluence. The maintenance medium was EMEM with 5% fetal calf serum.

Metabolic activation:

without

Metabolic activation system:

Iodide is small ion, so the metabolic activation system is unnecessary to the test

Test concentrations with justification for top dose:

- Mutagenicity test: 0.1, 0.5, 1, 5 and 10 mg/mL
- Transformation test: 0.1, 0.5, 1, 5 and 10 mg/mL

Vehicle / solvent:

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

Untreated negative controls:

yes

Remarks:

media

Negative solvent / vehicle controls:

no

True negative controls:

no

Positive controls:

yes

Positive control substance:

N-dimethylnitrosamine

N-ethyl-N-nitro-N-nitrosoguanidine

ethylmethanesulphonate

Details on test system and experimental conditions:

Mutagenesis:
L5178Y cells (l x 10^6 cells/mL) in 50 mL sterile centrifuge tubes were incubated with the test compounds, EMS, MNNG, and DMN (the positive controls) or media (the negative control) for four hours at 37 °C. The cells were then washed three times in FMO and incubated in a roller drum for 48 hours. This incubation period allowed for the expression of induced mutations. The cells were then plated in FM with 20 % horse serum. To the media, 3.5 % Noble agar and 100 μg/mL BUdR were added. Colony formation was scored after 10 days incubation at 37 °C. In all of the experiments, the cloning efficiency of the control plates was found to be greater than 85 %. The number of mutant colonies / 1 x 10^3 cells was calculated for the media controls. The actual spontaneous mutation frequency was variable ranging for this series of experiments from 4-10 mutants/1 x 10^3 cells. For the purpose of calculations, this was designated as having a mutational frequency (MF) of one. All other mutational values were compared to this control value. A-MF of 2.5 or greater was considered a positive mutational event.

Transformation:
Doses of the compounds were tested for cytoxicity by plating 2 x 10^2 cells in 25 cm² tissue culture flasks (Falcon). The plating efficiency of the control was compared to that of the treated cells after seven days incubation. the doses that yielded 50 % of the control value and the next two lower dose multiples were used in the transformation assay. Ten thousand 3T3 cells were incubated for 48 hours with the test agents, MNNG (positive control) or media (negative control) in 25 cm² flasks. The cell sheet was then rinsed three times using Hank's Balanced Salt Solution (HBSS), and 5 mL of maintenance media was added to each flask. The cells were incubated for 21 days at 37 °C During this time the media was replaced twice weekly. After this incubation the cells were stained. Transformed foci were then counted. The number of foci formed in the presence of the test compounds were compared to the media control values. Only foci that exhibited the typical criss-cross pattern with overlapping and piling up of cells were considered to be transformed. Values of 2.5 times greater than that observed in the negative controls were considered to be positive transformational events.

Evaluation criteria:

Mutagenesis: All other mutational values were compared to this control value. A-MF of 2.5 or greater was considered a positive mutational event.

Transformation: Only foci that exhibited the typical criss-cross pattern with overlapping and piling up of cells were considered to be transformed. Values of 2.5 times greater than that observed in the negative controls were considered to be positive transformational events.

Statistics:

Student's T -Test was used to compare the difference between toxic group with negative control group.

Species / strain:

mouse lymphoma L5178Y cells

Metabolic activation:

without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

not determined

Vehicle controls validity:

not applicable

Untreated negative controls validity:

valid

Positive controls validity:

valid

Species / strain:

other: BALB/c 3T3

Metabolic activation:

without

Genotoxicity:

other: no transforming activity

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Vehicle controls validity:

not applicable

Untreated negative controls validity:

valid

Positive controls validity:

valid

Table 1: Mutagenicity of Iodide in the L5178Y Test System

Compound	Concentration	Mutational Frequency
Iodide (KI solution)	10 mg/mL	1
	5 mg/mL	0.76
	1 mg/mL	1.33
	500 μg/mL	1.67
	100 μg/mL	1
Negative control (Media)		1
EMS	500 μg/mL	12
MNNG	5 μg/mL	15

Table 2:  Effects of Iodide on the Transformation of Balb/c 313 Cells

Compound	Concentration	# of foci
Iodide (KI solution)	10 mg/mL	0.33
	5 mg/mL	2
	1 mg/mL	0.61
	500 μg/mL	0.61
	100 μg/mL	0.83
Negative control (Media)		1.22
MNNG	5 μg/mL	7.5

 

Conclusions:

Interpretation of results: negative in both mutagenicity and BALB/c 3T3 cell transformation assays

Under the conditions of the study, solutions of potassium iodide at concentrations of 0.1–10 mg/mL did not cause mutagenic effects in L5178Y mouse lymphoma cells or transforming activity in Balb/c3T3 cells grown in culture.

Executive summary:

The mutagenic potential to iodide was studied using the L5178Y mouse (TK+/-) lymphoma assay. The established mutagens ethylmethanesulphonate (EMS) and dimethylnitrosamine (DMN) were highly active in this assay, whereas iodide (KI) was inactive. Using the BALB/c3T3 transformation assay, the transformational capacities of these same agents, and the positive mutagen N-ethyl-N-nitro-N-nitrosoguanidine (MNNG), were assessed. All concentrations of the iodide tested were inactive in this assay. It can be concluded that potassium iodide did not possess any biologically significant mutagenic or cell transforming ability.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed (positive)

Genetic toxicity in vivo

Description of key information

Drosophila SLRL Assay (read-across; Risher and Keit, 2009)

The publication reported that sodium iodate showed no mutagenic activity by the recessive lethal test using Drosophila.

Link to relevant study records

Reference

Reference 1

Endpoint:

in vivo insect germ cell study: gene mutation

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

not reported

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

data from handbook or collection of data

Remarks:

Data from a report from a recognised body reviewed by a panel of experts. Although there is limited detail on materials and methods included in the publication, the conclusions drawn from the cicads document are considered to be reliable and representative of the mutagenic potential of the substance.

Reason / purpose for cross-reference:

other: read across: target

Qualifier:

no guideline available

GLP compliance:

not specified

Type of assay:

Drosophila SLRL assay

Species:

Drosophila melanogaster

Details on test animals or test system and environmental conditions:

No further information provided on test animals and environmental conditions.

Additional information on results:

Sodium iodate showed no mutagenic activity by the recessive lethal test using Drosophila.

Conclusions:

Interpretation of results: negative

The publication reported that sodium iodate showed no mutagenic activity by the recessive lethal test using Drosophila. No information is provided on experimental materials and methods.

Executive summary:

The publication reported that sodium iodate showed no mutagenic activity by the recessive lethal test using Drosophila. No information is provided on experimental materials and methods.

Reference 2

Endpoint:

in vivo insect germ cell study: gene mutation

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Study conducted on read-across material.

Justification for type of information:

A read-across justification report (RAAF) will be added to Section 13 as soon as possible.

Reason / purpose for cross-reference:

read-across source

Additional information on results:

Sodium iodate showed no mutagenic activity by the recessive lethal test using Drosophila.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (negative)

Additional information

Genetic Toxicity In Vitro

Ames Test (Gijsbrechts, 2018)

The genetic toxicity of the test material was investigated in accordance with the standardised guidelines OECD 471 and EU Method B13/14, under GLP conditions. The study was awarded a reliability score of 1 in accordance with the criteria set forth by Klimisch et al. (1997).

The objective of this study was to determine the potential of the test material and/or its metabolites to induce reverse mutations at the histidine locus in several strains of Salmonella typhimurium (S. typhimurium; TA98, TA100, TA1535, and TA1537), and at the tryptophan locus of Escherichia coli (E. coli) strain WP2uvrA in the presence or absence of an exogenous mammalian metabolic activation system (S9). 

The test material was dissolved in Milli-Q water.  

In the dose range finding study, the test material was initially tested up to concentrations of 5000 µg/plate in the strains TA100 and WP2uvrA in the direct plate assay. The test material did not precipitate on the plates at this dose level. Cytotoxicity, as evidenced by a reduction in the bacterial background lawn, was observed in tester strain TA100 in the absence of S9-mix and in strain WP2uvrA in the presence of S9-mix.

In the first mutation experiment, the test material was tested up to concentrations of 5000 µg/plate in the strains TA1535, TA1537 and TA98. The test material did not precipitate on the plates at this dose level. Cytotoxicity, as evidenced by a reduction in the bacterial background lawn, was observed in the tester strains TA1537 and TA98 in the absence and presence of S9-mix.

In tester strain WP2uvrA, the test material induced an up to 2.2-fold increase in the number of revertant colonies in the presence of S9-mix. The increase observed was within the historical control data range and was not dose-related.

In tester strain TA100, the test material induced up to 3.0-fold dose-related increases in the number of revertant colonies in the presence of S9-mix. The increases observed were above the laboratory historical control data ranges and more than two-fold the concurrent solvent control. In the absence of S9-mix, the test item induced dose-related increases. However, the increases were only 1.6-fold and within the historical control data range.

In tester strain TA1535, the test material induced an up to 3.3-fold increase in the number of revertant colonies in the presence of S9-mix. The increase observed was above the laboratory historical control data ranges and more than three-fold the concurrent solvent control.

To verify the mutagenic responses observed in the first mutation experiment, an additional experiment was performed. In the additional experiment the test item was tested at a concentration range of 52 to 5000μg/plate in tester strain TA100 in the absence of S9-mix and the tester strains TA100, WP2uvrA and TA1535 in the presence of S9-mix. The test material did not precipitate on the plates at this dose level. Cytotoxicity, as evidenced by a reduction in the bacterial background lawn and the presence of microcolonies, was observed in the tester strains TA100 and WP2uvrA in the presence of S9-mix.

In tester strain TA100, the test material induced up to 1.9-fold dose-related increases in the number of revertant colonies in the presence of S9-mix. The increases observed were above the laboratory historical control data ranges.

In tester strain TA1535, the test material induced an up to 2.5-fold increase in the number of revertant colonies in the presence of S9-mix. The increase observed was above the laboratory historical control data ranges. In this study, acceptable responses were obtained for the negative and strain-specific positive control items indicating that the test conditions were adequate and that the metabolic activation system functioned properly.

In the absence of S9-mix, no biologically relevant increases in the number of revertant colonies were observed.

In the presence of S9-mix, the test material induced increases in the number of revertant colonies in the tester strains TA1535, TA100 and WP2uvrA. The increases were reproducible in the tester strains TA1535 and TA100. The increases were above the laboratory historical control data range in both the initial and the additional mutation experiment, but were only more than two- and three-fold in the initial experiment.

Taken together, since 3.0- to 3.3-fold increases were observed in the presence of S9-mix in the tester strains TA100 and TA1535, respectively, and the results were reproducible, these increases are considered biologically relevant and the test material is mutagenic.

Micronucleus Assay (read-across; Poul et al., 2004)

The mutagenic potential of the test material was investigated in a cytokinesis-block micronucleus assay at test concentrations of 0.625, 1.25, 2.5, 5 and 10 mM. Concurrent positive and negative controls were included. Under the conditions of the study, potassium iodate did not induce any increase in the frequency of binucleated cells with micronuclei for doses ranging from 0.625 to 10 mM. Furthermore, no clastogenic effects of the compound were noted in cells that had completed one nuclear division.

 

Micronucleus Assay (read-across; Risher and Keit, 2009)

The publication reported that sodium iodate showed no mutagenic activity by the micronucleus test using mouse bone marrow.

No information is provided on experimental materials and methods.

 

Mouse Lymphoma Assay (read-across; Kessler et al., 1980)

The mutagenic potential to iodide was studied using the L5178Y mouse (TK+/-) lymphoma assay. The established mutagens ethylmethanesulphonate (EMS) and dimethylnitrosamine (DMN) were highly active in this assay, whereas iodide (KI) was inactive. Using the BALB/c3T3 transformation assay, the transformational capacities of these same agents, and the positive mutagen N-ethyl-N-nitro-N-nitrosoguanidine (MNNG), were assessed. All concentrations of the iodide tested were inactive in this assay. It can be concluded that potassium iodide did not possess any biologically significant mutagenic or cell transforming ability.

 

Comet Assay (read-across; Poul et al., 2004)

The mutagenic effects of potassium iodate were evaluated in vitro using the alkaline comet assay at concentration of 0.625, 1.25, 2.5, 5 and 10 mM. Cell viability was measured using the Trypan blue exclusion method and expressed as proportion of total cells. The test results showed that potassium iodate did not induce DNA damage, or cytotoxicity, in the alkaline comet assay for doses up to 10 mM.

Under the conditions of this study, it was concluded that the test material was mutagenic.

Genetic Toxicity In Vivo

Drosophila SLRL Assay (read-across; Risher and Keit, 2009)

The publication reported that sodium iodate showed no mutagenic activity by the recessive lethal test using Drosophila.

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.