Dibutyl ether

Endpoint summary

Additional information

In vitro studies

The mutagenicity of dibutyl ether was investigated in a standard Salmonella /microsome test using Salmonella typhimurium strains TA97, TA98, TA100 and TA1535 both in the presence and the absence of a metabolic activation system (two different liver S9 mixes, produced from rats and hamsters pretreated with Aroclor 1254). The study performance meets currently valid guidelines. Dibutyl ether at concentrations of up to and including 667 µg/plate did not produce a doubling or a dose-dependent increase of the number of his+ revertants/plate in the Salmonella typhimurium strains used neither in absence nor in the presence of a metabolic activation system and was therefore judged as non mutagenic in this test system (Zeiger et al., 1992). Also in another Salmonella/microsome assay performed under GLP conditions following OECD TG 471 (1983) dibutyl ether at concentrations of up to and including 5000 µg/plate induced no mutations in Salmonella typhimurium strains TA98, TA100, TA1535 and TA1537 (BioChem, 1991b).

Dibutyl ether (purity > 99.3 %) was tested for its ability to induce chromosomal aberrations in a cytogenetic test using human peripheral lymphocytes in the presence and the absence of a metabolic activation system (liver S9 fractions of Aroclor 1254-induced rats). The study performed under GLP conditions and in accordance with directive 2000/32/EC, B.10 (2000) and OECD TG 473 (1997), gave no indications on clastogenic activity of dibutyl ether, which was tested up to and including the cytotoxic concentration level of 200 µg/ml. Only at the pronounced cytotoxic concentration of 200 µg dibutyl ether/ml medium an increase was noted in the number of aberrations. In the test without metabolic activation and 24-hour exposure, but not in the 4-hour experiment, a significant increase was noted in the number of aberrations to 12.5 % at this concentration. But in this experiment the mitotic index was only 0.09 and only 16 metaphases instead of 200 were scored, because no more metaphases of sufficient quality for evaluation were available due to cytotoxicity. In the tests with metabolic activation, and only in one of the two independent experiments, a marginal, though not significant, increase was noted in the number of aberrations to 5.3 % at the concentration level of 200 µg/ml. In this experiment the mitotic index was only 0.40 and only 151 metaphases instead of 200 were scored, because no more metaphases of sufficient quality for evaluation were available due to cytotoxicity. It is known that high cytotoxicity causes artefacts in the form of aberrations in vitro chromosomal tests. Hence the increase at the concentration of 200 µg dibutyl ether/ml medium is considered as artefact and not test item-related (Degussa AG, 2005c).

Justification for selection of genetic toxicity endpoint
No specific study was selected as all 3 in vitro studies were negative, with and without metabolic activation.

Short description of key information:
The mutagenicity of dibutyl ether was tested in a bacterial test system (two Ames tests performed according to OECD TG 471 and GLP, respectively under guideline-like conditions) and a mammalian test system (chromosomal aberration GLP test according to OECD TG 473 (1997) on human peripheral lymphocytes). The Ames test according to OECD TG 471 has been performed according to the former OECD TG 471 (1983) requiring the four Salmonella typhimurium strains used. The adopted OECD TG 471 (1997) requires the additional use of E. coli WP2 strains or Salmonella typhimurium TA 102 to detect certain oxidizing mutagens, cross-linking agents and hydrazines. However, dibutyl ether is not a highly reactive agent and is therefore not expected to be a cross-linking agent, has no oxidizing properties and is no hydrazine. Thus, a GLP test according to OECD TG 471 (1983) without E. coli WP2 strains or Salmonella typhimurium TA 102 together with a second test performed on the Salmonella typhimurium strains TA97, TA98, TA100 and TA1535, is considered as sufficient to evaluate the mutagenic activity of dibutyl ether in this bacterial test system.

Endpoint Conclusion: No adverse effect observed (negative)

Justification for classification or non-classification

In vitro, dibutyl ether was neither mutagenic in a bacterial test system (two tests, each performed according to OECD TG 471 (1983)) nor clastogenic in a mammalian test system (chromosomal aberration GLP test according to OECD TG 473 on human peripheral lymphocytes). Therefore, the substance does not need to be classified and labelled as a mutagen, according to the Regulation 1271/2008 and the Directive 67/548/EEC.