2-methylbutan-2-ol

Endpoint summary

Key value for chemical safety assessment

Genetic toxicity in vitro

Description of key information

2-Methylbutan-2-ol is not mutagenic in vitro in bacteria (two Ames tests) and in mammalian cells (HPRT assay). An in vitro chromosome aberration assay in mammalian V79 cells with 2-Methylbutan-2-ol demonstrated that the test sustance has no potential to induce chromosome aberrations.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (negative)

Genetic toxicity in vivo

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

Ames

In a reverse gene mutation assay the bacteria strains TA 1535, TA 1537, TA 98 and TA 100 of S.Typhimurium and and Escherichia coli WP2 uvrA were exposed to 2 -Methylbutan-2 -ol at concentrations of 33 µg - 5000 µg/plate in the precence and the absence of metabolic activation applying both the standard plate and the pre-incubation method (BASF SE, 2012). A biologically relevant increase in the number of his+ or trp+ revertants was not observed in the standard plate test or in the preincubation test either without S9 mix or after the addition of a metabolizing system. According to the results of the present key study, the test substance 2 -Methylbutan-2 -ol is not mutagenic in the S.Typhimurium/Escherichia coli reverse mutation assay under the experimental conditions chosen here.

2 -Methylbutan-2 -ol was further investigated using the gene mutation studies in bacterial (Salmonella typhimurium: TA 1535, TA 1537, TA 1538) and in Saccharomyces cerevisae ( Rowe and McCollister, 1982). In both test no genotoxicity could be observed with and without metabolic activation.

In vitro mammalian cell gene mutation test (HPRT test)

2-Methylbutan-2-ol was assessed for its potential to induce gene mutations at the HPRT locus using V79 cells of the Chinese hamster according to OECD guideline 476 (Harlan CCR GmbH, 2012). The assay was performed in two independent experiments with identical experimental procedures, using two parallel cultures each. The first experiment was performed with and without liver microsomal activation and a treatment period of 4 hours. The second experiment was performed with a treatment period of 24 hours in the absence of metabolic activation and 4 hours in the presence of metabolic activation. The cell cultures were evaluated at the following concentrations:

 

Experiment I:

without S9 mix: 27.5; 55.0; 220; 440; 880 µg/mL

with S9 mix: 27.5; 55.0; 110.0; 220; 880 µg/mL

Experiment II:

without S9 mix: 27.5; 55.0; 110; 220; 440; 880 µg/mL 

with S9 mix: 27.5; 55.0; 110; 220; 440; 880 µg/mL 

 

No precipitation of the test item was observed in all experiments up to the maximum concentration. No relevant cytotoxic effects occurred up to the maximum concentration of 880 µg/mL (appro. 10 mM) with and without metabolic activation. No relevant and reproducible increase in mutant colony numbers/10E6 cells was observed in the main experiments up to the maximum concentration. The mutant frequency remained well within the historical range of solvent controls. An increase of the induction factor reaching the threshold of three times the mutation frequency of the corresponding solvent control was observed in the second culture of the second experiment without metabolic activation at 110 µg/mL. However, the isolated increase was judged as biologically irrelevant fluctuation as it was neither reproduced in the parallel culture under identical experimental conditions nor dose dependent as indicated by the lacking statistical significance. No significant dose dependent trend of the mutation frequency was indicated by linear regression analysis. The positive controls showed a district increase in induced mutant colonies. In conclusion, under the experimental conditions reported, the test item did not induce gene mutations at the HPRT locus in V79 cells and therefore, 2-Methylbutan-2-ol, was considered to be non-mutagenic in this HPRT assay.

In vitro mammalian chromosome aberration test

In a chromosome aberration assay (Harlan CCR GmbH, 2012, OECD 473, GLP compliance) 2-Methylbutan-2-ol was tested in Chinese Hamster V79 cells. The highest applied concentration (880 µg/mL; approx. 10 mM) was chosen with regard to the molecular weight of the test item and with respect to the current guideline. Two independent experiments of the chromosome aberration assay were performed. In Experiment I the exposure period was 4 hours with and without S9 mix cells were fixed and stained after 18 hours. In Experiment II the exposure period was 4 hours with S9 mix and 24 hours without S9 mix cells were fixed and stained after 18 hours (- S9 mix) and after 28 hours (+ S9 mix). Cytotoxicity was indicated by reduced cell numbers. The cell numbers were determined microscopically by counting 10 defined fields per coded slide. Furthermore, mitotic index (% cells in mitosis) was determined. Breaks, fragments, deletions, exchanges, and chromosome disintegrations were recorded as structural chromosome aberrations. Gaps were recorded as well but not included in the calculation of the aberration rates. 100 well spread metaphases per culture were evaluated for cytogenetic damage on coded slides. Only metaphases with characteristic chromosome numbers of 22 ± 1 were included in the analysis. No precipitation in the culture medium nor an influence of the test item on osmolarity or pH value was observed. No relevant cytotoxicity, indicated by reduced mitotic indices and/or reduced cell numbers could be observed in either experimental part, up to the highest applied concentration.In both experiments, in the absence and presence of S9 mix, no biologically relevant increase in the number of cells carrying structural chromosome aberrations was observed. The aberration rates of the cells after treatment with the test item (0.0 - 2.5 % aberrant cells, excluding gaps) were within the range of the solvent control values (0.5 - 2.5 % aberrant cells, excluding gaps) and within the range of the laboratory historical solvent control data. No evidence of an increase in polyploid metaphases was noticed after treatment with the test item as compared to the control cultures. In both experiments, either EMS or CPA were used as positive controls and showed distinct increases in cells with structural chromosome aberrations. In conclusion, it can be stated that under the experimental conditions reported, the test item 2-Methylbutan-2-ol did not induce structural chromosomal aberrations in V79 cells of the Chinese hamster in vitro, when tested up to the highest required concentration.

Justification for classification or non-classification

Based on the available data 2 -Methylbutan-2-ol is not subject to C&L regarding genetic toxicity according to Directive 67/548/EEC and Regulation 1272/2008/EC.