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The test item SIKA Hardener MH was tested for mutagenic activity in a bacterial reverse mutation assay according to EU Method B13/14/OECD Guideline 471.

Five bacterial strains, Salmonella typhimurium TA98, TA100, TA1535, TA1537 and Escherichia coli WP2 uvrA were used to investigate the mutagenic potential of Sika Hardener MH in two independent experiments, in a plate incorporation test (experiment I, Initial Mutation Test) and in a pre-incubation test (experiment II, Confirmatory Mutation Test). Each assay was conducted with and without metabolic activation (S9 Mix). The concentrations, including the controls, were tested in triplicate.

In the performed experiments positive and negative (vehicle) controls were run concurrently. The revertant colony numbers of vehicle control plates with and without S9 Mix demonstrated the characteristic mean number of spontaneous revertants in the vehicle controls. The reference mutagens showed a distinct increase of induced revertant colonies. In the performed experimental phases there were at least five analyzable concentrations and a minimum of three non-toxic dose levels at each tester strain. The validity criteria of the study were fulfilled.

No biologically relevant increases were observed in revertant colony numbers of any of the five test strains following treatment with Sika Hardener MH at any concentration level, either in the presence or absence of metabolic activation (S9 Mix) in the performed experiments. Sporadic increases in revertant colony numbers compared to the vehicle control values and/or revertant colony numbers above the actual historical control data ranges were observed in both independently performed main experiments.

There was no tendency of higher mutation rates with increasing concentrations beyond the generally acknowledged border of biological relevance in the performed experiments.

In the Confirmatory Mutation Test following the pre-incubation procedure inhibitory effect of the test item was observed in all examined bacterial strains and included the lower revertant colony numbers than the revertant colony numbers of the vehicle controls (that were often below the corresponding historical control data ranges) and reduced or slightly reduced background lawn development. No revertant growth was observed in S. typhimurium TA100 at 5000 μg/plate, without metabolic activation (-S9 Mix).

The reported data of this mutagenicity assay shows that under the experimental conditions reported the test item did not induce gene mutations by frameshift or base-pair substitution in the genome of the strains used. Therefore, Sika Hardener MH was considered non-mutagenic in this bacterial reverse mutation assay (ToxiCoop, 2011).

Justification for selection of genetic toxicity endpoint
Only one study available.

Short description of key information:
The test item SIKA Hardener MH was tested for mutagenic activity in a bacterial reverse mutation assay according to EU Method B13/14/OECD Guideline 471. The test item SIKA Hardener MH showed no mutagenic activity in the bacterial reverse mutation assay.

Endpoint Conclusion: No adverse effect observed (negative)

Justification for classification or non-classification

Based on results of in vitro genetic toxicity study, SIKA Hardener MH was not classified and labelled as genotoxic according to Directive 67/548/EEC (DSD) and to Regulation (EC) No 1272/2008 (CLP).