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Key value for chemical safety assessment

Genetic toxicity in vitro

Description of key information
Based on the information available for read-across substances hydrogen peroxide and magnesium hydroxide, the reaction mass of magnesium carbonate and magnesium hydroxide and magnesium oxide and magnesium peroxide will not exert any genotoxic effects in vivo.
Link to relevant study records
Reference
Endpoint:
in vitro gene mutation study in bacteria
Remarks:
Type of genotoxicity: gene mutation
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: The study was carried out in accordance with the principles layed down for the standard S. typhimurium plate-incorporation assay with metabolic activation by the S9 mix.
Principles of method if other than guideline:
Method: other: slightly modified from Ames, B.N. et al.: Mutation Research 31, 347-361 (1975)
GLP compliance:
not specified
Type of assay:
bacterial reverse mutation assay
Species / strain / cell type:
S. typhimurium TA 1535, TA 1537, TA 98 and TA 100
Additional strain / cell type characteristics:
not specified
Species / strain / cell type:
S. typhimurium TA 1538
Additional strain / cell type characteristics:
not specified
Species / strain / cell type:
E. coli WP2
Additional strain / cell type characteristics:
other: tryptophan-requiring
Metabolic activation:
with and without
Metabolic activation system:
S9 mix
Test concentrations with justification for top dose:
Without S9 mix: 0.0033 to 0.67 mg per plate in S. typhimurium strains TA1535, TA1538 and TA98; from 0.001 to 0.33 mg per plate in strains TA1537 nd TA100; from 0.033 to 3.3 mg per plate in E. coli strain WP2
With S9 mix: 0.01 to 3.3 mg per plate in all five S. typhimurium strains and from 0.01 to 30 mg per plate in E. coli strain WP2
Vehicle / solvent:
Hydrogen peroxide was dissolved in 0.067 M potassium or sodium phosphate buffer, pH 7
Untreated negative controls:
not specified
Negative solvent / vehicle controls:
not specified
True negative controls:
no
Positive controls:
yes
Positive control substance:
other: Without S9 mix: 2-nitrofluoren (TA98, TA1538), sodium azide (TA100, TA1535), 9-aminoacridine (TA1537), furylfuramide or N-methyl-N'-nitro-N-nitrosoguadinine (E. coli); With S9 mix: 2-Anthramine (all tested strains)
Details on test system and experimental conditions:
The S9 mix contained 10 % Aroclor 1254-induced S9 from male Sprague-Dawley rats. All platings were performed in duplicate and all tests were repeated. An additional test was performed with the test substance to see if the substance supported the growth of histidine-requiring strains of S. typhimurium in the absence of added histidine. In addition to the tested strains of S. typhimurium also strain SL4024 was used in this test.
Evaluation criteria:
Test results were considered valid only if the positive control compounds induced increases in mutant counts to at least twice background.
Species / strain:
S. typhimurium TA 100
Metabolic activation:
with and without
Genotoxicity:
positive
Cytotoxicity / choice of top concentrations:
not determined
Vehicle controls validity:
not specified
Untreated negative controls validity:
not specified
Positive controls validity:
valid
Remarks on result:
other: strain/cell type:
Remarks:
Migrated from field 'Test system'.
Conclusions:
Interpretation of results (migrated information):
positive in S. typhimurium TA100
negative in all other strains tested

Hydrogen peroxide was found to be mutagenic in an in-vitro Ames test performed with S. typhimurium TA100, whereas it was negative in Ames tests carried out with other S. typhimurium strains and with E. coli WP2 strain.
Executive summary:

The mutagenicity of hydrogen peroxide was tested in the Ames test with S. typhimurium strains TA98, 100, 1535, 1537 and 1538 and E. coli WP2 strain. The test substance was found to increase the number of revertant colonies of S. typhimurium TA100 significantly, both in the absence and the presence of S9 metabolic activation. The test was negative in all other strains tested in the study. It was concluded that hydrogen peroxide exhibits mutagenicity to S. typhimurium TA100 in the Ames test.

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed (negative)

Additional information

Additional information from genetic toxicity in vitro:

In order to be systemically available, a chemical needs to be absorbed, either via the oral, inhalatory or dermal route. Dissolution of solids is generally assumed to be a prerequisite for absorption. As the reaction mass of magnesium carbonate and magnesium hydroxide and magnesium oxide and magnesium peroxide is a solid inorganic multi-constituent substance, this means that Mg2+, OH-and hydrogen peroxide are the species to be taken into account when assessing its toxicity.

Hydrogen peroxide

In the EU Risk Assessment Report (2003) a thorough assessment on the genotoxic properties of hydrogen peroxide has been performed. It was concluded that hydrogen peroxide is a mutagen and genotoxicant as positive results were obtained in a variety of in vitro test systems, including Ames, gene mutation, DNA damage and repair and chromosomal aberrations testing.

In contrast, the available in vivo studies are not in support of a significant genotoxicity/mutagenicity for hydrogen peroxide under in vivo conditions. It is suggestes that cells are adapted to repair DNA damage caused by oxidants. In the EU Risk Assessment Report it is therefore concluded that hydrogen peroxide is not classified as a mutagen.

 

Magnesium dihydroxide

Three key studies are available that assess the different genotoxic aspects of magnesium hydroxide. All tests are carried out according to GLP and OECD and EU guidelines. In a valid reverse mutation assay with Salmonella Typhimurium and Eschericia Coli (Verspeek-Rip, 2010) all bacteria strains showed negative responses over the entire dose range. The second test (Buskens, 2010), a chromosome aberration test, showed that magnesium hydroxide did not induce clastogenic effects under the conditions of the test. Thirdly, an in vitro gene mutation test with mouse lymphoma cells (Verspeek-Rip, 2010) is available in which magnesium hydroxide did not induce a significant increase in the mutation frequency in the presence and absence of S9-mix. Therefore, the substance was concluded not to be mutagenic under the conditions of the test.

 

Based on the above information, it can be concluded that the reaction mass of magnesium carbonate and magnesium hydroxide and magnesium oxide and magnesium peroxide will not exert any genotoxic effects in vivo.

Justification for classification or non-classification

In accordance to EU Classification, Labelling and Packaging of Substances and Mixtures (CLP) Regulation (EC) No. 1272/2008, classification is not necessary for genotoxicity based on the available information for read-across substances hydrogen peroxide and magnesium hydroxide.