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All Ames tests were negative. The chromosomal aberration tests had ambiguos results; this is also the case for SCE and comet assays.A gene mutation assay in chinese hamster V79 cells in vitro (V79/HPRT) with thymol was negative with and without metabolic activation.

Several MNT (micronuleus tests) were conducted. One MNT based on OECD 475 had a positive result. However, a critical evaluation of the test procedure revealed some drawbacks and deviations to the actual guideline. First of all the documentation did not comply with the current standards. Additional the number of test animal was lower as required by the actual guideline. Effects were examined at an early stage, the type of aberration was not decribed and individual animals date were missing. Therefore the test has some essential limitation and is not regarded as not reliable.

In 2 additional NMTs (mammalian erythrocyte micronuleus tests) which fully complies with a reliable study a negative test result was found.The result is supported by a SLRL test (sex-linked recessive lethal test for mutagenesis in Drosphila melanogaster) which was also negative.

Overall, no clear evidence for a mutagenic potential of thymol was found.

Short description of key information:
Several Ames test, chromosomal aberration test, SCE's (sister chromatid exchange), comet assays, a HPRT assay and some special tests were available, Additional several in-vivo micronuleus assays and a SLRL were available/published.

Endpoint Conclusion: No adverse effect observed (negative)

Justification for classification or non-classification

Based on a weight of evidence consideration a classification is not justified