Reaction mass of 2-(3-ethylphenyl)oxirane and 2,2’-(1,3-phenylene)dioxirane and 2,2'-(1,4-phenylene)dioxirane

Endpoint summary

Additional information

A study was performed to assess the mutagenic potential of the submission substance using a bacterial/microsome test system (Ames plate incorporation method).The method conforms to the guidelines for bacterial mutagenicity testing published by the major Japanese Regulatory Authorities including METI, MHLW and MAFF. It also meets the requirements of the OECD Guidelines for Testing of Chemicals No. 471 "Bacterial Reverse Mutation Test", Method B13/14 of Commission Regulation (EC) Number 440/2008 of 30 May 2008 and the USA, EPA (TSCA) OPPTS harmonised guidelines.

Large, dose‑related and statistically significant increases in revertant colony frequency were observed in all of the bacterial strains (except TA1537) at the upper sub‑toxic dose levels of the test material, in both the absence and presence of S9. The increases in colony frequency at the upper sub-toxic test material dose levels were very large and in excess of the in-house historical control range of each strain. Smaller increases (within the range of the in-house historical range) were observed in TA1537 at 1500 µg/plate in both the presence and absence of S9. A reproducible response was evident for bacterial strains TA100 and WP2uvrA^-when taking the results of the Preliminary Toxicity Test into consideration. 

The test material was considered to be mutagenic under the conditions of this test.

A study was conducted to assess the clastogenic potential of the submission substance in human lymphocytes using the OECD Guidelines for Testing of Chemicals (1997) No. 473 "Genetic Toxicology: Chromosome Aberration Test" and Method B10 of Commission Regulation (EC) No. 440/2008 of 30 May 2008. The study design also meets the requirements of the UK Department of Health Guidelines for Testing of Chemicals for Mutagenicity.

The test material induced clear dose-related statistically significant increases in the frequency of cells with aberrations in the 4(20)-hour exposure groups in the absence and presence of metabolic activation in Experiment 1.The exposure groups for experiment 2 were performed. However, due to the clear un‑equivocal positive response achieved in experiment 1 the slides were not scored and no data is reported.

The test material was considered to be clastogenic to human lymphocytes in vitro.

The study was performed to assess the potential of the test material to produce damage to chromosomes or aneuploidy when administered to mice. The method was designed to comply with the 1997 OECD Guidelines for Testing of Chemicals No.474 "Micronucleus Test", Method B12 of Commission Regulation (EC) No. 440/2008 of 30 May 2008, the USA EPA, TSCA and FIFRA guidelines and the Japanese METI/MHLW guidelines for testing of new chemical substances.

The micronucleus test was conducted using the oral route in groups of seven mice (males) at the maximum tolerated dose (MTD) 360 mg/kg and with 180 and 90 mg/kg as the two lower dose levels. Animals were killed 24 or 48 hours later, the bone marrow was extracted, and smears preparations made and stained. Polychromatic (PCE) and normochromatic (NCE) erythrocytes were scored for the presence of micronuclei.

Further groups of mice were given a single oral dose of arachis oil (2 groups each of 7 mice) or dosed orally with cyclophosphamide (5 mice), to serve as vehicle and positive controls respectively. Vehicle control animals were killed 24 or 48 hours later, and positive control animals were killed after 24 hours. No statistically significant decreases in the PCE/NCE ratio were observed in the 24 or 48 -hour test material dose groups when compared to their concurrent control groups.

There was no evidence of a significant increase in the incidence of micronucleated polychromatic erythrocytes in animals dosed with the test material when compared to the concurrent vehicle control groups.

The positive control group showed a marked increase in the incidence of micronucleated polychromatic erythrocytes hence confirming the sensitivity of the system to the known mutagenic activity of cyclophosphamide under the conditions of the test.

The test material was considered to be non-genotoxic under the conditions of the test.

Short description of key information:
The submission substance is not classified with regard genetic toxicity. The substance was found to be mutagenic to bacterial cells (Ames study), clastogenic to human lymphocytes in vitro ( chromosome aberration study). However, any concerns regarding mutagenicity are mitigated by a negative (i.e. non-genotoxic) in-vivo mouse micronucleus study.

Endpoint Conclusion: Adverse effect observed (positive)

Justification for classification or non-classification

The submission substance is not classified with regard genetic toxicity. The substance was found to be mutagenic to bacterial cells (Ames study), clastogenic to human lymphocytes in vitro ( chromosome aberration study), however, any concerns regarding mutagenicity are mitigated by a negative (i.e. non-genotoxic) in-vivo mouse micronucleus study.