[[(2-ethylhexyl)oxy]methyl]oxirane

Endpoint summary

Key value for chemical safety assessment

Genetic toxicity in vitro

Endpoint conclusion

Endpoint conclusion:

adverse effect observed (positive)

Genetic toxicity in vivo

Description of key information

Although the test substance produced a positive response in the gene mutation test on S. typhimurium TA1535, results of the gene mutation tests on mammalian cells in vitro and of the in vivo micronucleus tests in mice in rats gave a negative response. The target substance is therefore considered as negative for mutagenicity.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (negative)

Additional information

So far, he source substance oxirane, 2-((C12-14-alkyloxy)methyl)derivs (EC 271-846-8, C12-14GE) is used for read-across to assess genotoxicity of the target substance [[(2-ethylhexyl)oxy]methyl]oxirane (EC 219-553-6, EHGE) as both do share a common functional group (glycidylether) and both are manufactured by reacting an alcohol with epichlorohydrine to an alkyl glycidylether under alkalinic conditions Data derived with the source substance oxirane, 2-((C12-14-alkyloxy)methyl)derivs (EC 271-846-8, C12-14GE) are used for read-across to the target substance [[(2-ethylhexyl)oxy]methyl]oxirane (EC 219-553-6, EHGE) as outlined and justified in the endpoint study records, although having some limitations.

This information will be amended later by a new in vitro gene mutation study in bacteria and an in vitro cytogenicity / chromosome aberration study in mammalian cells, once decided upon, as proposed in our comments to ECHA communication/decision number CCH-D-2114606775-44-01/D. The goal is to further strengthen the read-across justification, supporting read-across of other endpoint study records, established based on studies with the SOURCE substance.

The currently available information is assessed/summarised as follows:

Gene mutation on bacteria

Reverse mutation test on bacteria (on S. typhimurium and on E. coli) is available and valid. Two tests have been realised according to protocol similar to the OECD guidelines.

The first study was conducted according to the OECD 471 guideline and in compliance with GLP, using the direct plate incorporation method in S. typhimurium TA98, TA 1535, TA1537, TA100 strains and E.coli WP2 bacteria, at doses of 3.3, 10, 33, 100, 333, 1000, 3333 µg/plate (and at higher concentrations during the preliminary test) (Valentine, 1997). In the mutagenicity assay, a positive response was observed with tester strain TA1535, with and without metabolic activation. All other strains were negative, with and without metabolic activation. Generally, precipitate was observed at >1000 µg per plate. Toxicity was observed at >1000 µg per plate in the presence of S9 activation only. Under the conditions of this study, the test substance was concluded to be positive in the Bacterial Reverse Mutation Assay with an Independent Repeat Assay.

In vitro gene mutation on mammalian cells

A valid gene mutation test on mammalian cells is available (CHO/HGPRT). This test has been established according to protocol similar to the OECD guidelines and delivered homogeneous negative results.

In the first study, test substance was tested in the CHO/HGPRT Mutation Assay in the absence and presence of metabolic activation, according to the OECD 476 guideline and in compliance with GLP (Richard, 1998). Without S9 activation, no cultures exhibited mutant frequencies of >40 mutants per 10⁶ clonable cells. With S9 activation, the mutant frequency of the highest dose seeded for mutant selection was elevated, though it was not >40 mutants per 10⁶ clonable cells; in the independent repeat assay the high dose exhibited a mutant frequency> 40 mutants per 10⁶ clonable cells; in the third assay, no cultures exhibited mutant frequencies of >40 mutants per 10⁶ clonable cells. This indicates that the high mutant frequency exhibited in the independent repeat with S9 activation was probably an artifact. There was no dose response in any of the mutagenesis assays. Therefore, the results of the CHO/HGPRT Mutation Assay indicate that, under the conditions of this study, test substance was concluded to be negative with and without S9 activation.

As results summarised above are ambiguous a new study with [[(2-ethylhexyl)oxy]methyl]oxirane is proposed to achieve more clarity.

In vivo micronucleus test

Two studies are available and valid and results indicate an absence of mutagenicity.

The first study was realised according to the OECD 474 guideline and in compliance with GLP (Ramadevi, 1997). Male and female mice were dosed with alkyl glycidyl ether at concentrations of 1000, 2000 or 4000 mg/kg body weight. No mortality was observed in any male or female mice in the micronucleus study. Clinical signs following dose administration included lethargy in male and female mice at all test article dose levels and piloerection in male and female mice at 4000 mg/kg. Bone marrow cells, collected 24, 48 and 72 hours after treatment, were examined microscopically for micronucleated polychromatic erythrocytes. Slight reductions (up to 11%) in the ratio of polychromatic erythrocytes to total erythrocytes were observed in some of the treated groups relative to the respective vehicle controls. No significant increase in micronucleated polychromatic erythrocytes in treated groups relative to the respective vehicle control group was observed in male or female mice at 24, 48 or 72 hours after dose administration. The results of the assay indicate that under the conditions described in this report, test substance did not induce a significant increase in micronucleated polychromatic erythrocytes in either male or female mice. Test substance was concluded to be negative in the mouse micronucleus assay.

In vivo chromosome aberration test

The second study was realised according to the OECD 475 guideline (Piper, 1979). In this in vivo chromosome aberration study male and female Sprague Dawley rats received a dose of 213.8, 712.5 and 2137.5 mg/kg bw/d on 5 consecutive days by intraperitoneal injection. In parallel a negative and a positive control was applied in the vehicle control group and the positive control group. No consistent structural or numerical cytogenetic aberrations in rat bone marrow cells were observed and also this study was rated negative for genotoxicity.

Conclusion

Although the source substance produced a positive response in the gene mutation test on S. typhimurium TA1535 tester strain, results of the gene mutation tests on mammalian cells in vitro and of thein vivo micronucleus tests in mice and chromosome aberration test in rats gave a negative response. The target substance 2-ethylhexyl glycidylether is concluded as negative for mutagenicity. However, further studies are currently in discussion to be performed to clarify further uncertainties.

Justification for classification or non-classification

Based on the results from read-across studies, the target substance is concluded to be negative for mutagenicity. Therefore, the target substance is not to be classified according to CLP (Regulation EC No. 1272/2008).