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Endpoint summary

Additional information

Weight-of-Evidence for genotoxicity was obtained from bacterial/mammalian gene mutation and chromosome aberration toxicity studies with read-across substances. A read-across justification based on molecular, physicochemical and toxicological properties was written as a separate document provided under Section 13 (Assessment reports). The following data were used:

- Bacterial mutagenicity testing was conducted on Epoxidized Soybean Oil (ESBO) in Salmonella typhimurium strains TA 98, TA 100, TA 1535, TA 1537 and TA 1538 without metabolic activation (Heath and Reilly, 1982). In this case, enzyme activation was determined not to be necessary. ESBO was not mutagenic in any of the tester strains used at any of the levels incorporated into the assay. The number of revertants produced after incorporation of these agentia into the system was not markedly different from control plates.

- Bacterial mutagenicity testing was conducted on Fatty acids, tall-oil, epoxidized, 2-ethylhexylesters (ETP) in Salmonella typhimurium strains TA 98, TA 100, TA 1535, TA 1537 and Escherichia coli WP2 uvrA with and without metabolic activation (RCC-CCR, 2005). ETP did not induce gene mutations by base pair changes or frameshifts in the genome of the strains used. ETP was not mutagenic in this S. typhimurium and E. coli reverse mutation assay.

- Epoxidised soybean oil (ESBO) was tested in an in vitro cytogenetics assay in human lymphocyte cultures with and without metabolic activation up to highest dose of 55 ug/mL, which was close to the solubility limit (Hazleton, 1992a). In Experiment 1, treatment without metabolic activation was continuous for 20 hours; treatment with metabolic activation was for 3 hours only followed by a 17 hour recovery period prior to harvest. Up to the highest concentration of 55ug/mL, there was no mitotic inhibition in the absence of S-9 and approximately 14% in its presence, although this was not clearly dose-related. Experiment 2 included a delayed sampling time: treatment without metabolic activation was continuous for 20 or 44 hours; treatment with metabolic activation was for 3 hours followed by a 17 or 41 hour recovery period. The highest concentration of 55 ug/mL induced 47% and 25% mitotic inhibition in the absence and presence of metabolic activation, respectively. ESBO with and without metabolic activation resulted in frequencies of cells with aberrations which were similar to or not significantly different from negative controls and fell within negative historical control ranges. It was concluded that ESBO did not induce chromosome aberrations in cultured human peripheral blood lymphocytes when tested up to its limit of solubility in both the absence and presence of metabolic activation.

- Fatty acids, tall-oil, epoxidized, 2-ethylhexylesters (ETP) was tested to induce structural chromosome aberrations in V79 cells in the absence and the presence of metabolic activation in two independent experiments at one preparation interval (18 hrs) in Experiment I and at two preparation intervals (18 hrs and 28 hrs) in Experiment II (RCC-CCR, 2005b). In a pre-test on toxicity, precipitation of the test item after 4 hours treatment was observed at 32.8 ug/mL and above in the absence and the presence of S9 mix. Using reduced cell numbers as an indicator for toxicity in the pre-test, clear toxic effects were observed after 4 hours treatment with 4200 ug/mL in the absence of S9 mix; therefore, 4200 ug/mL was chosen as the top concentration in Experiment 1 in the absence of S9 mix. Since no relevant toxicity was observed in the pre-test on toxicity in the presence of S9 mix, the test item was tested up to a concentration exhibiting clear test item precipitation as recommended in OECD 473; therefore, 100 ug/mL was chosen as the top concentration in Experiment I in the presence of S9 mix. Cytotoxicity indicated by reduced cell numbers of about and below 50% of control was observed in Experiment II, after 18 and 28 hours continuous treatment in the absence of S9 mix. Since no relevant toxicity was observed in the pre-test on toxicity in the presence of S9 mix, the test item was tested up to a concentration exhibiting clear test item precipitation as recommended in the OECD Guideline 473.

In both independent experiments, neither a statistically significant nor a biologically relevant increase in the number of cells carrying structural chromosomal aberrations was observed after treatment with the test item. No relevant increase in the frequencies of polyploid metaphases was found after treatment with the test item as compared to the frequencies of the controls. It was concluded that ETP was considered to be non-clastogenic in this chromosome aberration test with and without S9 mix when tested up to cytotoxic and/or precipitating concentrations.

- Epoxidised Soybean Oil (ESBO) was assayed for its ability to induce mutation at the tk locus (5-trifluorothymidineresistance) in mouse lymphoma cells in 2 independent experiments, each conducted in the absence and presence of metabolic activation (Monsanto Health Lab, 1986). In both experiments, 5000 µg/mL in the absence and presence of S-9 was used, which yielded at least 83.2% relative survival.

In the absence of metabolic activation, reproducible statistically significant and dose-related increases in mutant frequency were not observed in the 2 experiments over the dose range 312.5 to 2500 µg/mL. At 5000 µg/mL, a positive point was obtained in Experiment 1 and due to heterogeneity in the data this dose was excluded from analysis in Experiment 2. However, if each of the replicate cultures at 5000 µg/mL in Experiment 2 are considered in turn, neither yields a statistically significant increase in mutant frequency. This, combined with the fact that there were no absolute increases in mutant numbers in Experiment 1 at 5000 µg/mL and that carry-over of the test compound was a problem at this dose, suggests that the increased mutant frequency seen in Experiment 1 was not the result of chemically induced mutation. In the presence of S-9, no statistically significant increases in mutant frequency were observed at any dose level tested in Experiment 1 or 2. It was concluded that, ESBO failed to demonstrate an ability to induce mutation at the tk locus of L5178Y mouse lymphoma cells in the absence and presence of S-9.

 

In conclusion, the toxicity pattern of 'fatty acids, C16 -18 and C18 -unsaturated isopentyl esters, epoxidized' is also considered to be comparable to ESBO and ETP, and does not to have potential for bacterial/mammalian mutagenicity nor chromosome aberration potential. Based on the absence of in vitro genotoxic potential, no further in vivo testing was required.

Justification for selection of genetic toxicity endpoint
Weight-of-Evidence from read-across substances; this endpoint was considered as first priority endpoint.

Short description of key information:
Weight of evidence for absence of genotoxic potential was available from Epoxidized Soybean Oil (ESBO) which was negative for bacterial and gene mutation and for chromosome aberration potential in in vitro studies. Additional weight of evidence for absence of genotoxic potential was available from Fatty acids, tall-oil, epoxidized, 2-ethylhexylesters (ETP) which was negative for bacterial and gene mutation and for chromosome aberration potential in in vitro studies. Based on these data, the toxicity pattern of 'fatty acids, C16 -18 and C18 -unsaturated isopentyl esters, epoxidized' is also considered to be comparable to ESBO and ETP, and does not to have potential for bacterial/mammalian mutagenicity nor chromosome aberration potential. Based on the absence of in vitro genotoxic potential, no further in vivo testing was requiered.

Endpoint Conclusion: No adverse effect observed (negative)

Justification for classification or non-classification

Based on the results and according to the EC criteria for classification and labelling according to CLP regulation (EC No. 1272/2008 of 16 December 2008), 'fatty acids, C16 -18 and C18 -unsaturated isopentyl esters, epoxidized' does not have to be classified and has no obligatory labelling requirement for mutagenic potential.