Reaction mass of zinc oxide and zinc peroxide

Endpoint summary

Key value for chemical safety assessment

Genetic toxicity in vitro

Link to relevant study records

Reference

Reference 1

Endpoint:

in vitro transformation study in mammalian cells

Type of information:

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

Adequacy of study:

supporting study

Justification for type of information:

REPORTING FORMAT FOR THE ANALOGUE APPROACH

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
The target substance Zinc peroxide and the source substances Zinc oxide, Zinc Chloride, Zinc sulfate, Zinc nitrate are ionic and consist of the Zinc2+ cation and the respective anion.
The read-across is based on the assumption that the zinc cation (as measure for dissolved zinc species) is the determining factor for (eco)toxicity.
For further details, see Justification for read-across attached to IUCLID chapter 13

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
See Justification for read-across attached to IUCLID chapter 13

3. ANALOGUE APPROACH JUSTIFICATION
See Justification for read-across attached to IUCLID chapter 13

4. DATA MATRIX
See Justification for read-across attached to IUCLID chapter 13

Reason / purpose for cross-reference:

read-across: supporting information

Reason / purpose for cross-reference:

read-across source

Type of assay:

in vitro mammalian cell transformation assay

Species / strain / cell type:

other: Syrian hamster embryo cells

Details on mammalian cell type (if applicable):

No data

Additional strain / cell type characteristics:

not specified

Metabolic activation:

without

Metabolic activation system:

no data

Species / strain:

other: Syrian hamster embryo cells

Metabolic activation:

without

Genotoxicity:

positive

Remarks:

at 1 and 3 μg/ml

Cytotoxicity / choice of top concentrations:

not specified

Vehicle controls validity:

not specified

Untreated negative controls validity:

not specified

Positive controls validity:

not specified

Additional information on results:

None

None

Conclusions:

Interpretation of results: Positive without metabolic activation.

Reference 2

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

Justification for type of information:

REPORTING FORMAT FOR THE ANALOGUE APPROACH

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
The target substance Zinc peroxide and the source substances Zinc oxide, Zinc Chloride, Zinc sulfate, Zinc nitrate are ionic and consist of the Zinc2+ cation and the respective anion.
The read-across is based on the assumption that the zinc cation (as measure for dissolved zinc species) is the determining factor for (eco)toxicity.
For further details, see Justification for read-across attached to IUCLID chapter 13

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
See Justification for read-across attached to IUCLID chapter 13

3. ANALOGUE APPROACH JUSTIFICATION
See Justification for read-across attached to IUCLID chapter 13

4. DATA MATRIX
See Justification for read-across attached to IUCLID chapter 13

Reason / purpose for cross-reference:

read-across: supporting information

Reason / purpose for cross-reference:

read-across source

Type of assay:

DNA damage and repair assay, unscheduled DNA synthesis in mammalian cells in vitro

Species / strain / cell type:

other: Syrian hamster embryo cells

Details on mammalian cell type (if applicable):

No data

Additional strain / cell type characteristics:

not specified

Metabolic activation:

not specified

Metabolic activation system:

no data

Species / strain:

other: Syrian hamster embryo cells

Metabolic activation:

without

Genotoxicity:

positive

Remarks:

>1 µg/ml

Cytotoxicity / choice of top concentrations:

not specified

Vehicle controls validity:

not specified

Untreated negative controls validity:

not specified

Positive controls validity:

not specified

Conclusions:

Interpretation of results: Positive without metabolic activation.

Reference 3

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

Justification for type of information:

REPORTING FORMAT FOR THE ANALOGUE APPROACH

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
The target substance Zinc peroxide and the source substances Zinc oxide, Zinc Chloride, Zinc sulfate, Zinc nitrate are ionic and consist of the Zinc2+ cation and the respective anion.
The read-across is based on the assumption that the zinc cation (as measure for dissolved zinc species) is the determining factor for (eco)toxicity.
For further details, see Justification for read-across attached to IUCLID chapter 13

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
See Justification for read-across attached to IUCLID chapter 13

3. ANALOGUE APPROACH JUSTIFICATION
See Justification for read-across attached to IUCLID chapter 13

4. DATA MATRIX
See Justification for read-across attached to IUCLID chapter 13

Reason / purpose for cross-reference:

read-across: supporting information

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across source

Key result

Species / strain:

S. typhimurium, other: all tested strains

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

not specified

Vehicle controls validity:

not specified

Untreated negative controls validity:

valid

Positive controls validity:

valid

Reference 4

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

Justification for type of information:

REPORTING FORMAT FOR THE ANALOGUE APPROACH

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
The target substance Zinc peroxide and the source substances Zinc oxide, Zinc Chloride, Zinc sulfate, Zinc nitrate are ionic and consist of the Zinc2+ cation and the respective anion.
The read-across is based on the assumption that the zinc cation (as measure for dissolved zinc species) is the determining factor for (eco)toxicity.
For further details, see Justification for read-across attached to IUCLID chapter 13

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
See Justification for read-across attached to IUCLID chapter 13

3. ANALOGUE APPROACH JUSTIFICATION
See Justification for read-across attached to IUCLID chapter 13

4. DATA MATRIX
See Justification for read-across attached to IUCLID chapter 13

Reason / purpose for cross-reference:

read-across: supporting information

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across source

Species / strain:

other: Human dental pulp cells (D824 cells); Syrian hamster embryo cells

Metabolic activation:

without

Genotoxicity:

positive

Cytotoxicity / choice of top concentrations:

not specified

Vehicle controls validity:

not specified

Untreated negative controls validity:

not specified

Positive controls validity:

not specified

Reference 5

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

Justification for type of information:

REPORTING FORMAT FOR THE ANALOGUE APPROACH

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
The target substance Zinc peroxide and the source substances Zinc oxide, Zinc Chloride, Zinc sulfate, Zinc nitrate are ionic and consist of the Zinc2+ cation and the respective anion.
The read-across is based on the assumption that the zinc cation (as measure for dissolved zinc species) is the determining factor for (eco)toxicity.
For further details, see Justification for read-across attached to IUCLID chapter 13

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
See Justification for read-across attached to IUCLID chapter 13

3. ANALOGUE APPROACH JUSTIFICATION
See Justification for read-across attached to IUCLID chapter 13

4. DATA MATRIX
See Justification for read-across attached to IUCLID chapter 13

Reason / purpose for cross-reference:

read-across: supporting information

Reason / purpose for cross-reference:

read-across source

Type of assay:

in vitro mammalian cell gene mutation tests using the thymidine kinase gene

Target gene:

Thymidine kinase

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

Conclusions:

Interpretation of results: negative

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (negative)

Genetic toxicity in vivo

Link to relevant study records

Reference

Endpoint:

genetic toxicity in vivo, other

Remarks:

in vivo mammalian somatic cell study: cytogenicity

Type of information:

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

Adequacy of study:

weight of evidence

Justification for type of information:

REPORTING FORMAT FOR THE ANALOGUE APPROACH

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
The target substance Zinc peroxide and the source substances Zinc oxide, Zinc Chloride, Zinc sulfate, Zinc nitrate are ionic and consist of the Zinc2+ cation and the respective anion.
The read-across is based on the assumption that the zinc cation (as measure for dissolved zinc species) is the determining factor for (eco)toxicity.
For further details, see Justification for read-across attached to IUCLID chapter 13

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
See Justification for read-across attached to IUCLID chapter 13

3. ANALOGUE APPROACH JUSTIFICATION
See Justification for read-across attached to IUCLID chapter 13

4. DATA MATRIX
See Justification for read-across attached to IUCLID chapter 13

Reason / purpose for cross-reference:

read-across: supporting information

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across source

Type of assay:

other: in vivo mammalian somatic cell study: cytogenicity

Sex:

male/female

Genotoxicity:

negative

Toxicity:

not specified

Vehicle controls validity:

valid

Negative controls validity:

not specified

Positive controls validity:

not specified

Conclusions:

Interpretation of results: negative

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (negative)

Additional information

No data on genotoxicity are available for the target substance Zinc peroxide. However, reliable data are available for Zinc compounds as well as on hydrogen peroxide. A justification for read-across is attached to IUCLID section 13.

 

Data on Zinc

Non-human information

Several in vitro and in vivo studies are available on the genotoxicity of zinc oxide. Data on other zinc compounds have also to be considered, as the basic assumption is made that after intake all zinc compounds (including metallic zinc) are changed (at least in part) to the ionic species and that it is this zinc cation that is the determining factor for the biological activities of the zinc compounds.

The genotoxicity of soluble and slightly soluble zinc compounds has been extensively investigated in a wide range of in vitro and in vivo studies. The in vitro investigations included non-mammalian and mammalian test systems covering the endpoints of gene mutation, chromosomal aberrations, sister chromatid exchange, unscheduled DNA synthesis (UDS), as well as cell transformation. Available in vivo genotoxicity assays included the micronucleus test, sister chromatid exchange (SCE) and chromosomal aberration test and the dominant lethal mutation assay in mouse or rat as well as investigations for sex-linked recessive lethal mutation in drosophila melanogaster.

The investigated zinc compounds did not increase the mutation frequencies in the majority of bacterial or mammalian cell culture systems. For example, zinc chloride, zinc sulphate, zinc bis(dihydrogen phosphate), zinc oxide or zinc monoglycerolate were consistently negative in the Ames test. While zinc chloride was also negative for gene mutations in the mouse lymphoma assays, there was some evidence that zinc oxide, zinc acetate or zinc monoglycerolate induced in the absence of metabolic activation the formation of mutation colonies. Several reviewers noted, however, that these mutations were observed at cytotoxic concentrations and that the analysis did not distinguish between big and small colonies which could be caused by gene mutation or chromosomal aberrations (Thompson et al.,1989, WHO, 2001; EU RAR, 2004; MAK, 2009).

Conflicting information was further found when zinc compounds were examined for their potential to induce chromosomal aberrations or sister chromatid exchange in mammalian cell systems or when evaluated in the cell transformation assay. Positive as well as negative results were obtained in these cell systems with either soluble or slightly soluble zinc compounds. In those studies where chromosomal aberrations or sister chromatid exchange has been observed, these were generally considered to be weak and occurred only at high, often cytotoxic concentrations. Moreover, these positive in vitro findings have also to be seen in context of the impact that changes in zinc levels can have on cell system processes that are controlled by a strict metal homeostasis. A change of this metal homeostasis due to increased zinc levels, may lead to a binding of zinc to amino acids like cysteine and therefore to an inhibition of certain enzymes. This can lead to interactions with the energy metabolism, signal transmission and apoptotic processes which can lead to the observed clastogenic or aneugenic effects in in vitro systems (EU RAR, 2004; MAK, 2009).

In addition to above mentioned in vitro investigations, various soluble and slightly soluble zinc compounds have also been studied in a range of in vivo studies including the micronucleus test, SCE and chromosomal aberration test or dominant lethal mutation assay in mice or rats as well as in the Drosophila Melanogaster SLRL test. The zinc compounds were consistently negative in the micronucleus and in the assay with Drosophila Melanogaster. Zinc sulphate was further negative in a dominant lethal assay in rats.

Equivocal and sometimes contradicting results were found for the induction of chromosomal aberrations which have been studied in bone marrow cells harvest from animals exposed to zinc compounds zinc chloride, and zinc oxide. Negative findings for chromosome aberrations have been produced after intraperitoneal injection of zinc chloride into mice (Vilkina et al., 1978) or when rats were given zinc sulphate by gavage once or daily for 5 consecutive days (Litton Bionetics, 1974). In contrast, increased aberrations have been reported in rats after inhalation exposure to zinc oxide (Voroshilin et al., 1978), in rats after oral exposure to zinc chloride and in mice after multiple intraperitoneal injections of zinc chloride (Gupta et al., 1991). Moreover, increased chromosomal aberrations were found in calcium-deficient mice when fed zinc (in form of zinc chloride) via the diet (Deknudt, 1982). These equivocal finding likely a reflection of inter-study differences in routes, levels, and duration of zinc exposure, the nature of lesions scored (gaps compared to more accepted structural alterations) and great variability in the technical rigor of individual studies (WHO, 2001). The German MAK committee reviewed the existing in vivo evidence and concluded that particularly those studies indicating clastogenic effects involved a lot of methodological uncertainties which do not allow overruling those in vivo studies which did not provide any evidence for chromosomal aberrations in vivo. Moreover, the Dutch rapporteur of EU risk assessment of zinc compounds under the EU existing substance legislation considered the positive in vitro findings for chromosomal aberration and SCE assays to be overruled by the overall weight of evidence of negative in vivo tests for this endpoint (EU RAR, 2004).

 

Human information:

The only identified publicly available genotoxicity study in humans related to the identification of chromosomal aberrations in lymphocytes of 24 workers in a zinc smelting plant (Bauchinger et al.,1976). This study was, however, not suitable to draw any conclusions to the association of these effects with zinc exposure, as the workers displayed also increased blood levels of lead and cadmium, and the clastogenic effects were predominantly attributed to cadmium exposure. There were no further reports in the accessible literature on genotoxic effects of zinc compounds in human populations.

 

Data on hydrogen peroxide

Cited from theSummary Risk Assessment Report oin Hydrogen peroxide (2003):

“H2O2 is a mutagen and genotoxicant in a variety ofin vitrotest systems. Regardingin vivogenotoxicity, studies have explored DNA repair in liver cells of rats, as well as micronucleus formation in mice, all with a negative outcome. At low concentrations (0.2-3.2% solutions), and with a low application frequency on the skin of mice, H2O2 did not induce local genotoxicity or mutagenicity. The available studies are not in support of significant genotoxicity/mutagenicity of H2O2 underin vivoconditions.”

 

In the transformation/dissolution test conducted with the target source Zinc peroxide, it was demonstrated, that only low levels of hydrogen peroxide are released. Thus, high concentration effects of hydrogen peroxide are not relevant for the target substance.In the view of the high degradation capacity for hydrogen peroxide in blood, it is unlikely that hydrogen peroxide released from ZnO2 is systemically distributed, and therefore the endogenous steady state levels of hydrogen peroxide in tissues are unlikely to be affected.

 

Overall, the target substance Zinc peroxide is not considered to be mutagenic in vivo.

Justification for classification or non-classification

The overall weight of the evidence from the existing in vitro and in vivo genotoxicity assays suggests that zinc compounds do not have biologically relevant genotoxic activity. This conclusion is in line with those achieved by other regulatory reviews of the genotoxicity of zinc compounds (WHO, 2001; SCF, 2003; EU RAR, 2004, MAK, 2015). Hence, no classification and labelling for mutagenicity are required.