methylpentane

Endpoint summary

Additional information

The first in vitro study evaluated the mutagenicity of vapors of commercial hexane (52% n-hexane). According to the study report (API, 1989; Klimisch score =2 since a read across approach was followed) plates of S. typhimurium were exposed for seven to eight hours to test atmospheres of 0, 600, 1000, 3000, 6000, or 9000 ppm of test substance.The test substance did not produce a positive response in any of the test strains.

Two in vitro studies determined the mutagenicity of commercial hexane (52% n-hexane) in Chinese hamster ovary (CHO) cells. In one study CHO cells were exposed to concentrations of 0, 0.132, 0.098, 0.063, 0.0362, or 0.0122 ul/ml both with and without metabolic activation for 5 hours (API, 1990; Klimisch score =2 since a read across approach was followed). The cells were then analyzed for mutation frequency. The test substance was found not to be mutagenic both in the presence and absence of metabolic activation. However, the test substance was cytotoxic at concentrations of 0.063 ul/ml or greater.

In the second in vitro study CHO cells were exposed to concentrations of commercial hexane (52% n-hexane) of 0, 0.015, 0.034, 0.074, 0.123, and 0.416 ul/ml without metabolic activation and 0, 0.014, 0.022, 0.056, 0.118, and 0.251 ul/ml with metabolic activation (Daughtrey, 1984; Klimisch score =2 since a read across approach was followed). 0.5 ug/ml triethylenemelamine was used a positive control without metabolic activation and 50 ug/ml cyclophosphamide was used as a positive control with metabolic activation. Negative and positive controls were found to be valid and no significant increase in chromosome aberrations were found. The test substance was however found to be cytotoxic at concentrations of 0.074 ul/ml or greater. The test substance is not clastogenic.

An in vivo study determined the effect of inhalation exposure of commercial hexane (52% n-hexane) on rat bone marrow (Daughtrey, 1994; Klimisch score =2 since a read across approach was followed). Groups of 5 male and 5 female rats were exposed to 0, 900, 3000, and 9000 ppm of test substance vapor for 6 hrs/day for 5 days. 0.5 mg/kg triethylenemelamine was used as a positive control substance. Animals were sacrificed 3 or 21 hours after exposure, and the bone marrow from their femurs examined for cell aberrations. Because no statistically significant increases in cell aberrations were identified, in any of the test groups, the test substance was classified as not mutagenic.

All studies were conducted in a manner similar or equivalent to currently established OECD guidelines.

 

Short description of key information:
Three in vitro genetic toxicity studies and one in vivo genetic toxicity study were read across based on data for commercial hexane (52% n-hexane).

All genetic toxicity tests, both in vitro and in vivo, were negative.

Genetic Toxicity in vitro - Bacterial reverse mutation assay (OECD TG 471) - Negative
Genetic Toxicity in vitro - In vitro Mammalian Chromosome Aberration Test (OECD TG 473) - Negative
Genetic Toxicity in vitro - In vitro Mammalian Cell Gene Mutation Test (OECD TG 476) - Negative

Genetic Toxicity in vivo - Mammalian Bone Marrow Chromosome Aberration Test (OECD TG 475) – Not Mutagenic

Endpoint Conclusion: No adverse effect observed (negative)

Justification for classification or non-classification

The negative results using in vitro and in vivo genotoxicity assays do not warrant the classification of this substance as genotoxic under the new Regulation (EC) 1272/2008 on classification, labeling and packaging of substances and mixtures (CLP) or under the Directive 67/518/EEC for dangerous substances and Directive 1999/45/EC for preparations.