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In vitro

There are no data available on the in vitro genotoxic potential of octane. However, reliable data are available on structurally-related substances. Thus, read-across based on a category approach was conducted.

The in vitro genotoxicity of normal-heptane (CAS No. 142-82-5) has been assessed in different test systems.

A bacterial reverse mutation assay (Ames test) was conducted with normal-heptane following a protocol similar to OECD 471. The pre-incubation procedure was performed with Salmonella typhimurium strains TA 1535, TA 1537, TA 1538, TA 98 and TA 100, and Escherichia coli strains WP2 and WP2 uvr A. The strains were exposed to concentrations of 0, 3.91, 7.81, 15.6, 31.3, 62.5, 125, and 250 µg/mL for 48 -72 h both with and without metabolic activation. No significant increases in the ratio of mutations over controls was seen. Therefore, the test substance was not mutagenic in either the presence or absence of metabolic activation (Shell Chemicals, 1983; Brooks et al., 1988).

The potential of normal-heptane to cause chromosomal aberrations in rat liver RL4 cells was tested with a method comparable to OECD 473. Cells were exposed to concentrations of 0, 2.5, 5, and 10 µg/mL of test substance for 22 h, and then examined for chromosomal aberrations including polyploidy, chromatid gaps, and chromatid exchanges. No cytotoxicity was observed. A significant increase in chromatid gaps was seen at 10 µg/mL. However, this effect was neither dose-dependent nor accompanied by an increase in any other aberration type, and therefore not considered to be treatment-related. Under the conditions of this study, the test material was not clastogenic (Shell Chemicals, 1983; Brooks et al., 1988).

Iso-octane (CAS No. 540-84-1) was tested in a mammalian cell gene mutation assay performed according to OECD 476. The test material was prepared by adding iso-octane at a final concentration of 5 % v/v in culture (DMEM) medium and stirred overnight at room temperature in a foil wrapped, capped parafilm-sealed bottle to saturate the medium. Human lymphoblastoid cells (TK6) were exposed to 100 or 50 % of this saturated DMEM medium with and without metabolic activation for 3 h and allowed for expression for 4 to 8 days. Both with and without metabolic activation, iso-octane did not induce significant increases in the mutation frequency at the thymidine kinase locus and cell survival in iso-octane-saturated medium was greater than 50-60 %. Based on the study design there was no incidence of increased genetic toxicity caused by the test substance (Richardson et al., 1986).


In vivo

The in vivo genotoxicity of different category members has been tested.

Hydrocarbons, C7-C9, isoalkanes showed no evidence of genotoxicity in a dominant lethal study with rats. Hydrocarbons, C7-C9, n-alkanes, isoalkanes, cyclics were not clastogenic to mouse bone marrow cells. Iso-octane did not induce unscheduled DNA synthesis in rat hepatocyte cultures.

Based on the category approach, these results suggest that octane is not expected to induce genotoxicity in vivo.

Short description of key information:
The available data indicate that octane is not genotoxic.
In vitro:
Negative Ames test with S. typhimurium TA 1535, TA 1537, TA 1538, TA 98 and TA 100, and E. coli WP2 and WP2 uvr A, with and without metabolic activation.
Negative results in mammalian chromosomal aberration and gene mutation tests, the latter with and without metabolic activation.
In vivo:
Negative in dominant lethal, micronucleus and unscheduled DNA synthesis assays.

Endpoint Conclusion: No adverse effect observed (negative)

Justification for classification or non-classification

Based on read-across from structurally related substances within a category approach, the available data on the genotoxic potential of octane are conclusive but not sufficient for classification.