Bis(D-gluconato-O1,O2)zinc

Endpoint summary

Key value for chemical safety assessment

Genetic toxicity in vitro

Description of key information

Several studies are identified in a read-across approach and demonstrate the absence of genetic toxicity in vitro. The study reported by Amacher and Paillet (in L5178Y/TK+/- cells) is the main study used in the assessement, considering that the relevance of gene mutation study in bacteria for inroganic compound is relative, and considering the reliability of available genotoxicity studies in mammalian cells.

Link to relevant study records

Reference

Reference 1

Endpoint:

in vitro gene mutation study in mammalian cells

Type of information:

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

Adequacy of study:

key study

Study period:

1980

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

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

Justification for type of information:

REPORTING FORMAT FOR THE ANALOGUE APPROACH
The read-across hypothesis is instantaneous dissociation of zinc gluconate into zinc cations (Zn2+) and gluconate anions in aqueous media (environmental compartments and body fluids). Thus, for endpoints where no zinc gluconate data exist, the assessment of the (eco-) toxicological effects can be based on available data of dissociable zinc compounds and gluconate derivatives.
The assessment of human and environmental toxicology is mainly based on the zinc ion, which is considered to be toxicologically more relevant than the gluconate ion (see complete justification report attached).
All of the zinc based read-across partners have in common that they dissociate into zinc and the respective counter ion in aqueous media as described above. The same is true for all of the gluconate based read-across partners, as they dissociate into the gluconate anion and the respective counter ion in aqueous media.
The gluconate derivatives are tentatively ignored for the purpose of this read-across due to the role of gluconates as common additives or nutritional supplements in food and due to the fact that gluconate/gluconic acid is a ubiquitous metabolic product/substrate in mammals with proven low toxicity. As a normal metabolic product of glucose metabolism, 25–30 g are being produced daily in humans. It can safely be concluded that systemic toxicity need not be expected to arise from gluconates/gluconic acid when assessing the potential effects of zinc gluconate. Nevertheless, the lack of toxicological relevance of gluconates is addressed in sufficient detail in the final read-across report targeted at supporting this dossier.
When resorting to dissociable zinc read-across partners, there is a risk of confounding effects that might actually be attributable to the counter ion. The dissociation products of the aforementioned zinc compounds are glycerol, sulphate and chloride ions. The counter ions of the gluconates are sodium, calcium and manganese. All these ions play an important role in the physiology of man and other species. Considering this information, the respective counter ions (calcium, sodium, manganese) are unlikely to contribute to any confounding effects hence do need to be further addressed in this report.

Taking into account the global approach and the detailed explanation (including data matrix and analysis for each endpoint) provided in the report attached, the present read-across is considered relevant.

Reason / purpose for cross-reference:

read-across source

Key result

Species / strain:

mouse lymphoma L5178Y cells

Metabolic activation:

without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

not specified

Vehicle controls validity:

valid

Untreated negative controls validity:

not specified

Positive controls validity:

not specified

Additional information on results:

Graph showing Average trifluorothymidine resistance (TFTRes) mutant counts versus test material has been attached as 'attached

Conclusions:

Interpretation of results: negative
The test material was found to be non-mutagenic under the test conditions.

Executive summary:

A study was conducted to assess the potential mutagenicity of test material in the mouse lymphoma thymidine kinase locus using the cell line L5178Y.

The mouse lymphoma cells (TK+/-) were treated with test material at 1.21 - 12.13 µg/mL for 3 h. 48 h after treatment, cells were treated with 4 µg/mL trifluorothymidine (TFT) for 7 d. Colonies growing in the presence of triflurothymidine (TFT resistant) were counted. TFT resistant colonies were scored as mutants.

The test material was found to be non-mutagenic under the test conditions.

Reference 2

Endpoint:

in vitro cytogenicity / chromosome aberration study in mammalian cells

Type of information:

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

Adequacy of study:

weight of evidence

Study period:

July 1977

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

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

Justification for type of information:

REPORTING FORMAT FOR THE ANALOGUE APPROACH
The read-across hypothesis is instantaneous dissociation of zinc gluconate into zinc cations (Zn2+) and gluconate anions in aqueous media (environmental compartments and body fluids). Thus, for endpoints where no zinc gluconate data exist, the assessment of the (eco-) toxicological effects can be based on available data of dissociable zinc compounds and gluconate derivatives.
The assessment of human and environmental toxicology is mainly based on the zinc ion, which is considered to be toxicologically more relevant than the gluconate ion (see complete justification report attached).
All of the zinc based read-across partners have in common that they dissociate into zinc and the respective counter ion in aqueous media as described above. The same is true for all of the gluconate based read-across partners, as they dissociate into the gluconate anion and the respective counter ion in aqueous media.
The gluconate derivatives are tentatively ignored for the purpose of this read-across due to the role of gluconates as common additives or nutritional supplements in food and due to the fact that gluconate/gluconic acid is a ubiquitous metabolic product/substrate in mammals with proven low toxicity. As a normal metabolic product of glucose metabolism, 25–30 g are being produced daily in humans. It can safely be concluded that systemic toxicity need not be expected to arise from gluconates/gluconic acid when assessing the potential effects of zinc gluconate. Nevertheless, the lack of toxicological relevance of gluconates is addressed in sufficient detail in the final read-across report targeted at supporting this dossier.
When resorting to dissociable zinc read-across partners, there is a risk of confounding effects that might actually be attributable to the counter ion. The dissociation products of the aforementioned zinc compounds are glycerol, sulphate and chloride ions. The counter ions of the gluconates are sodium, calcium and manganese. All these ions play an important role in the physiology of man and other species. Considering this information, the respective counter ions (calcium, sodium, manganese) are unlikely to contribute to any confounding effects hence do need to be further addressed in this report.

Taking into account the global approach and the detailed explanation (including data matrix and analysis for each endpoint) provided in the report attached, the present read-across is considered relevant.

Reason / purpose for cross-reference:

read-across source

Species / strain:

lymphocytes: Human

Metabolic activation:

without

Genotoxicity:

ambiguous

Remarks:

Chromosome fragments observed, but no significant difference with control.

Cytotoxicity / choice of top concentrations:

not specified

Additional information on results:

There were more chromosome fragments in all trated groups compared to controls especially in the cultures harvested after 48h, but this difference was not significant. Severe aberrations such as dicentric chromosomes were recorded only in lymphocyte cultures treated with the lowest concentration of zinc chloride (3 x 10-5 M) added at time 0, regardless whether the cultures were fixed after 48h or 72h. The findings were not significant statistically when compared to the controls only.

Chromosome analysis of leucocyte cultures contaminated by zinc chloride

Duration of the culture (h)	Dose of salt administered (M)	Interval of time between initiation of the culture and salt administration (h)	Number of cells analysed	Numerical aberrations		Structural aberrations	Type and number of structural aberrations
				Aneuploid cells	Cells in endoreduplication		Chromatid aberrations	Chromosome aberrations
							Gap	Gap	Fragment	Dicentric
48	0	-	100	3	0	1	1
	3 X 10^-4	0	100	1	0	2	2
		24	100	4	0	4	2		2
	3 X 10^-5	0	100	4	0	3	3			1
		24	100	4	0	4	2		2
72	0	-	100	2	0	3	3
	3 X 10^-4	0	100	3	0	0
		24	100	6	0	4	3		1
	3 X 10^-5	0	100	4	0	5	3			2
		24	100	2	1	3	2	1

Conclusions:

Results are ambigous because there is no statistical significance with controls (found to be insignificant when compared to only controls in chi-square analysis) and no dose response observed. Consequently, the results are not positive in line with current OECD guideline 473.

Executive summary:

A chromosome aberration test was conducted on human lymphocyte cultures to determine the mutagenic potential of Zinc chloride.

The toxic concentration was determined in normal stimulated human lymphocyte cultures and was found to be 3.10^-3M for zinc chloride. Furthermore 3 subtoxic doses of each salt (2, 10 and 100 times less than the toxic dose: 1.5 X 10^-3, 3 X 10^-5and 3 X 10^-4M) were added to 48- and 72-h cultures at 0 h and 24 h after initiation. Chromosome preparations were made and 100 well spread metaphases from each culture were analysed for the presence of numerical and structural aberrations. The most common aberration found for all tested metal salts was the occurrence of chromosome fragments. Dicentric chromosomes were only recorded in lymphocyte cultures treated with the lowest concentration of zinc chloride (3.10^-5M) added at time 0, regardless whether the cultures were fixed after 48 or 72 h.

Results are ambigous because there is no statistical significance with controls and no dose response observed. Consequently, the results are not positive in line with current OECD guideline 473.

Reference 3

Endpoint:

in vitro gene mutation study in mammalian cells

Type of information:

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

Adequacy of study:

weight of evidence

Study period:

1979

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

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

Justification for type of information:

REPORTING FORMAT FOR THE ANALOGUE APPROACH
The read-across hypothesis is instantaneous dissociation of zinc gluconate into zinc cations (Zn2+) and gluconate anions in aqueous media (environmental compartments and body fluids). Thus, for endpoints where no zinc gluconate data exist, the assessment of the (eco-) toxicological effects can be based on available data of dissociable zinc compounds and gluconate derivatives.
The assessment of human and environmental toxicology is mainly based on the zinc ion, which is considered to be toxicologically more relevant than the gluconate ion (see complete justification report attached).
All of the zinc based read-across partners have in common that they dissociate into zinc and the respective counter ion in aqueous media as described above. The same is true for all of the gluconate based read-across partners, as they dissociate into the gluconate anion and the respective counter ion in aqueous media.
The gluconate derivatives are tentatively ignored for the purpose of this read-across due to the role of gluconates as common additives or nutritional supplements in food and due to the fact that gluconate/gluconic acid is a ubiquitous metabolic product/substrate in mammals with proven low toxicity. As a normal metabolic product of glucose metabolism, 25–30 g are being produced daily in humans. It can safely be concluded that systemic toxicity need not be expected to arise from gluconates/gluconic acid when assessing the potential effects of zinc gluconate. Nevertheless, the lack of toxicological relevance of gluconates is addressed in sufficient detail in the final read-across report targeted at supporting this dossier.
When resorting to dissociable zinc read-across partners, there is a risk of confounding effects that might actually be attributable to the counter ion. The dissociation products of the aforementioned zinc compounds are glycerol, sulphate and chloride ions. The counter ions of the gluconates are sodium, calcium and manganese. All these ions play an important role in the physiology of man and other species. Considering this information, the respective counter ions (calcium, sodium, manganese) are unlikely to contribute to any confounding effects hence do need to be further addressed in this report.

Taking into account the global approach and the detailed explanation (including data matrix and analysis for each endpoint) provided in the report attached, the present read-across is considered relevant.

Species / strain:

other: Syrian hamster embryonic cells

Metabolic activation:

not applicable

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Remarks:

Reduced cloning efficiency by 20-25 % relative to control

Vehicle controls validity:

valid

Untreated negative controls validity:

not examined

Positive controls validity:

valid

Additional information on results:

Number of replicates: Each experimental point was repeated 3 to 7 times with cells that originated from different animals; but since the results were consistent, only one set of data for each chemical is presented in the report.

Conclusions:

Interpretation of results: negative
Under the test conditions, the test material was found to be non-transforming at 20 µg/mL.

Executive summary:

A Syrian hamster embryo (SHE) cell assay was conducted to evaluate the morphologic transformation inducing ability of the test material using hamster embryo cells (HEC). No guideline or GLP compliance was documented in the study report.

The assay involved 7 to 8 d treatment of the SHE cells, seeded with 300 cells from a secondary culture with an irradiated layer of SHE feeder cells (6 x 10⁴), with the test material (upto 20 µg/mL) in Dulbecco's modified Eagle's medium, supplemented with 10% fetal bovine serum. Colonies were then fixed, stained and scored for morphological transformations.

At the highest concentrations (20 µg/mL), cloning efficiency was reduced by 20 to 25% relative to the control. No morphological transformations were observed in the test cultures.

Under the test conditions, the test material was found to be non-transforming at 20 µg/mL.

Reference 4

Endpoint:

in vitro gene mutation study in bacteria

Type of information:

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

Adequacy of study:

key study

Study period:

1980

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

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

Justification for type of information:

REPORTING FORMAT FOR THE ANALOGUE APPROACH
The read-across hypothesis is instantaneous dissociation of zinc gluconate into zinc cations (Zn2+) and gluconate anions in aqueous media (environmental compartments and body fluids). Thus, for endpoints where no zinc gluconate data exist, the assessment of the (eco-) toxicological effects can be based on available data of dissociable zinc compounds and gluconate derivatives.
The assessment of human and environmental toxicology is mainly based on the zinc ion, which is considered to be toxicologically more relevant than the gluconate ion (see complete justification report attached).
All of the zinc based read-across partners have in common that they dissociate into zinc and the respective counter ion in aqueous media as described above. The same is true for all of the gluconate based read-across partners, as they dissociate into the gluconate anion and the respective counter ion in aqueous media.
The gluconate derivatives are tentatively ignored for the purpose of this read-across due to the role of gluconates as common additives or nutritional supplements in food and due to the fact that gluconate/gluconic acid is a ubiquitous metabolic product/substrate in mammals with proven low toxicity. As a normal metabolic product of glucose metabolism, 25–30 g are being produced daily in humans. It can safely be concluded that systemic toxicity need not be expected to arise from gluconates/gluconic acid when assessing the potential effects of zinc gluconate. Nevertheless, the lack of toxicological relevance of gluconates is addressed in sufficient detail in the final read-across report targeted at supporting this dossier.
When resorting to dissociable zinc read-across partners, there is a risk of confounding effects that might actually be attributable to the counter ion. The dissociation products of the aforementioned zinc compounds are glycerol, sulphate and chloride ions. The counter ions of the gluconates are sodium, calcium and manganese. All these ions play an important role in the physiology of man and other species. Considering this information, the respective counter ions (calcium, sodium, manganese) are unlikely to contribute to any confounding effects hence do need to be further addressed in this report.

Taking into account the global approach and the detailed explanation (including data matrix and analysis for each endpoint) provided in the report attached, the present read-across is considered relevant.

Reason / purpose for cross-reference:

read-across source

Species / strain:

bacteria, other: Bacillus subtilis H17 Rec+ and M45 Rec-

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

not determined

Vehicle controls validity:

not specified

Untreated negative controls validity:

not specified

Positive controls validity:

not specified

Additional information on results:

ZnCl2 was tested among 121 metal compounds rec-assayed with cold incubation.

Conclusions:

The result is negative under tested conditions.

Executive summary:

The study present several metal compounds rec-assayed, including ZnCl2. ZnCl2 was tested with the Bacillus subtilis recombination assay (rec-assay) using spores of B. subtilis strains, H17 Rec+ (rec+ arg try) and M45 Rec- (rec45 arg try) strains.

Thawed culture cells, previously kept at -80 °C in broth culture with 50 % glycerol supplementation, were streaked on the dry surface of broth agar. Impregnated paper disks (16 mm diameter) with test material solution were placed over the starting points of the streaks. The plates were first kept at 4-5 °C for 24 h, and then incubated at 30 °C for about 20 h. Then the length of the inhibition zone was measured.

The test material did not show an increased lethal activity on Rec- in comparision with Rec+ cells and therefore did not cause cellular damage.

Under the given test conditions, the test material was found to be negative in B.subtilis recombination assay.

In combination with the already available publications, the data can be used for the purpose of REACH registration of zinc gluconate in a read-across approach and is considered to be reliable.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (negative)

Additional information

In vitro gene mutation study in bacteria :

Tests on the mutagenic potential of zinc compounds in bacteria are considered dispensable for principal considerations, since inorganic metal compounds are frequently negative in this assay due to limited capacity for uptake of metal ions (Guidance on information requirements and chemical safety assessment, Chapter R.7a, p. 565; HERAG facts sheet mutagenicity, Chapter 2.1). Consequently the genetic toxicity is mainly based on test in mammalian cells.

Justification for classification or non-classification

The main study considered on mammalian cells (Amacher et al.) assess the potential mutagenicity of test material in the mouse lymphoma thymidine kinase locus using the cell line L5178Y. The test material was found to be non-mutagenic under the test conditions. The interpretation of results of this study is that, in a read-across approach, zinc gluconate is considered negative.

Consequently, the substance is no classified.

Supporting studies are also reported on mammalian cells : Chromosome study in human lymphocytes after in vitro exposure (Deknudt et al.), Study of in vitro morphological transformation of Syrian Hamster Embryo Cells (SHE) (DiPaolo et al.).