2,4-dimethyl-6-(1-methyl-pentadecyl)phenol

Endpoint summary

Additional information

Ames Test

The mutagenic potential of the test substance was investigated in a GLP-compliant Ames test (Ciba-Geigy, 1991) according to OECD guideline 471, performed with Salmonella typhimurium TA 98, TA 100, TA 1535, TA 1537 and Escherichia coli strain WP2 uvrA in the presence and absence of a metabolic activation system (S9 mix). Based on the results in the dose finding test, the maximum tested concentration in the main test was 5000 µg/plate with and without S9-mix. None of the tested concentrations led to an increase in the incidence of either histidine- or tryptophan-prototrophic mutants by comparison with the negative control either with or without metabolic activation. The bacterial background lawn was not reduced at all concentrations tested and no decrease in the number of revertants was observed. This result was confirmed in a second independent experiment. Therefore, based on the results of these experiments and on standard evaluation criteria, it is concluded that the test article and its metabolites did not induce gene mutations in the strains of S. typhimurium and E. coli used.

This finding is supported by the results of a second Ames study (Ciba-Geigy, 1990). In this stusy, three tester strains were used (S. typhimurium TA1537, TA100 and TA98). When tested at concentrations of up to 5000 µg/0.1ml, the test article did not cause an increase in the number of revertant both in the absence and presence of S9-metabolic activation.

HPRT Test

The test substance was tested for mutagenic effects on V79 Chinese hamster cells in vitro following OECD guideline 476 and in compliance with GLP (Ciba-Geigy, 1995). The cells were treated with the test item dissolved in DMSO in the experiments with metabolic activation for 5 hours and in the experiments without metabolic activation for 21 hours. The results of each experiment were confirmed in a second and independent experiment (confirmatory experiment). A preliminary range finding test was run assessing cytotoxicity. The test substance was tested at concentrations up to 320.0 µg/ml. Higher concentrations were not applied due to solubility limitations in the culture medium. Based on the results of the toxicity screening study, 320.0 µg/ml with and without metabolic activation was chosen as highest concentration for the first mutagenicity assay. In the presence and absence of metabolic activation, no significant increase in mutant frequency was observed at any concentration level tested in the original or the confirmatory experiment in comparison with the negative control. The positive controls induced a clear increase in mutant frequency. In both mutagenicity experiments with metabolic activation and in the confirmatory experiment without activation the required degree of toxicity of 50 to 90% was not reached. However, higher concentrations of the test compound were not suitable for application in this assay, since the respective stock solutions in DMSO were not miscible with culture medium. Based on the results of two independently performed experiments and under the given experimental conditions, it is concluded that the test article and its metabolites did not show any mutagenic activity in this forward mutation system.

Chromosome Aberration

In a chromosome aberration test (Ciba-Geigy, 1992) according to OECD 473 and in compliance with GLP, the substance was investigated for clastogenic effects on Chinese hamster ovary cells (CHO) at various concentrations (5.08 - 20.31 µg/ml without, and 162.5 - 650 µg/ml with a metabolic activation system). The cells were incubated with the test substance for 3 hours in the presence and for 18 or 42 hours in the absence of S9-mix. Two hundred metaphases whenever possible were examined from the vehicle control and from the cultures treated with the various concentrations of test material. At least fifty metaphases each from the appropriate positive controls were analyzed. In studies performed without metabolic activation using 18 and 42 hours incubation no biologically significant increase in the number of specific chromosome aberrations was observed in comparison with the corresponding negative control. In the three experiments performed in the presence of a metabolic activation system (3 hours treatment and 15 respectively 39 hours recovery time), no biologically significant increase in the number of specific chromosome aberrations was observed in comparison with the corresponding negative control. The number of chromosome aberrations was within the historical control range at all doses assessed. It is concluded that under the given experimental conditions no evidence of clastogenic effects was obtained in Chinese hamster ovary cells in vitro treated with the test substance.

Short description of key information:
The test item was studied for genotoxicity in bacterial and mammalian cell lines for gene mutation and in CHO cells for clastogenicity. Each of the test showed the absence of a genotoxic potential.

Endpoint Conclusion: No adverse effect observed (negative)

Justification for classification or non-classification

Dangerous Substance Directive (67/548/EEC)

The available experimental test data is reliable and suitable for the purpose of classification under Directive 67/548/EEC. Based on the present data, classification for genetic toxicity is not warranted under Directive 67/548/EEC.

 

Classification, Labeling, and Packaging Regulation (EC) No. 1272/2008

The available experimental test data are reliable and suitable for the purpose of classification under Regulation (EC) No.1272/2008. Based on the present data, classification for genetic toxicity is not warranted under Regulation (EC) No.1272/2008.