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Toxicological information

Genetic toxicity: in vitro

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Endpoint:
in vitro gene mutation study in bacteria
Remarks:
Type of genotoxicity: gene mutation
Type of information:
read-across based on grouping of substances (category approach)
Adequacy of study:
key study
Study period:
8 May 1992 to 1 June 1992
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
There is no indication of the duration of the incubation period in Experiment 2. This is not expected to effect the validity of the results. Read across to a study result from an investigation using a similar material is justified for members of the Epoxidised Oils and Derivatives group. Four epoxidised oils (linseed, soybean, 2-ethylhexyl tallate and fatty acids, C14-C22, 2-ethylhexylesters) have been identified as sharing common structural and functional similarities, recognised in an OECD SIDS review as a single category, and therefore justifying read-across between data for different members of the group. Consequently data sharing between ESBO epoxidised soybean oil and epoxidised linseed oil is commonly utilised in the preparation of this dossier and other read-across bridges are used for other members of the EOD group where appropriate.
Justification for type of information:
Read across to a study result from an investigation using a similar material is justified for members of the Epoxidised Oils and Derivatives group. Four epoxidised oils and esters (linseed, soybean,9-octadecanoate propylene glycol ester and 2-ethylhexyl tallate ester ETP). The C14-C22, 2-ethylhexylesters are listed as similar products on the market to ETP based on fatty acids from other naturally occurring fatty acids. This group of epoxies are identified as sharing common structural and functional similarities, recognised in an OECD SIDS review as a single category, and therefore justifying read-across between data for different members of the group. Consequently data sharing between ESBO epoxidised soybean oil, ELO epoxidised Linseed oil and ETP epoxidised 2ethylhexyl tallate and fatty acids, C14-C22, 2-ethylhexylesters, epoxidised is commonly utilised in the preparation of this dossier. Read-across bridges are used for members of the EOD group where appropriate, is justified based on similar toxicity profiles and structural and functional similarities.

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1992
Report Date:
1992

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to
Guideline:
OECD Guideline 471 (Bacterial Reverse Mutation Assay)
Qualifier:
according to
Guideline:
other: EEC Annex V Test B14
Qualifier:
according to
Guideline:
other: UKEMS Guidelines
GLP compliance:
yes
Type of assay:
bacterial reverse mutation assay

Test material

Reference
Name:
Unnamed
Type:
Constituent
Type:
Constituent
Type:
Constituent
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): Epoxidised Soybean Oil
- Abbreviation: ESBO
- Alias name: Reoplast 39
- Physical state: Clear yellow Liquid
- Lot/batch No.: 08380306
- Expiration date of the lot/batch: July 1994
- Stability under test conditions: Stable
- Storage condition of test material: Dark at room temperature
- Other:
- Colour value (Gardner): 1 - 2
- Refractive Index at 20 °C: 1.4731
- Iodine Value: 4.3 g J2/100g
- Acid Value: 0.27 mg KOH/g
- Oxirane Value: 6.4 %

Method

Target gene:
histidine gene
Species / strain
Species / strain / cell type:
S. typhimurium, other: TA98; TA100; TA 1535; TA1537 and TA102
Additional strain / cell type characteristics:
other: biotin and histidine required for growth
Metabolic activation:
with and without
Metabolic activation system:
mammalian liver post-mitochondrial fraction (S9)
Test concentrations with justification for top dose:
Please see Table 1 and 2 below.
An initial toxicity range-finder was carried out in TA100 strain only, using final concentrations of Epoxidised Soybean Oil at 8, 40, 200, 1000 and 5000 µg/plate plus a solvent and a positive control. These treatments were non-toxic and the same dose range was used for experiment 1. For experiment 2 treatments, the dose range was narrowed to 312.5 - 5000 µg/plate in order to investigate those concentrations most likely to exhibit a mutagenic response.
Vehicle / solvent:
Test chemical solutions were prepared by dissolving Epoxidised Soybean Oil in analytical grade acetone, immediately prior to assay to give the required maximum concentration treatment solution. Further dilutions were then made using acetone. The test chemical solutions were protected from light and used within approximately 4 hours of the initial formulation of the test agent.
Controls
Untreated negative controls:
yes
Remarks:
solvent acetone
Positive controls:
yes
Remarks:
Please Table 2 below
Details on test system and experimental conditions:
An initial toxicity range-finder was carried out in TA100 strain only, using final concentrations of Epoxidised Soybean Oil at 8, 40, 200, 1000 and 5000 µg/plate plus a solvent and a positive control. These treatments were non-toxic and the same dose range was used for experiment 1.

Five strains of bacteria were used in this study. For all assays, bacteria were cultured for about 10 hours at 37 °C in nutrient broth (containing ampicillin for strains TA98 and TA100 and ampicillin and tetracycline for strain TA102). Bacteria were taken from vials of frozen cultures, which had been checked for strain characteristics (histidine dependence, rfa character and resistance to ampicillan (TA98 and TA100) or ampicillin plus tetracycline (TA102). Checks were carried out according to Maron and Ames and De Serres and Shelby. For all treatments, cultures were used within 2 hours of the end of the incubation period.

Epoxidised Soybean Oil was tested for mutation in 5 strains of Salmonella typhurium at the concentrations detailed in Table 1. Triplicate plates with and without S-9 mix were used. Negative (solvent) and positive controls were included in both assays, in quintuplicate without and with S-9 mix. In each experiment, bacterial strains were treated with diagnostic mutagens in triplicate in the absence of S-9. The activity of the S-9 mix used in each experiment was confirmed by AAN treatments (again in triplicate) of at least one strain in the presence of S-9.

Because the results of the first experiment were negative, treatments in the presence of S-9 in Experiment 2 included a pre-incubation step, where the quantities of test chemical or control solution, bacteria and S-9 mix detailed, were mixed together and incubated for 1 hour at 37 °C, before the addition of 2.5 mL molten agar at 46 °C. Plating of these treatments then proceeded as for the normal plate-incorporation procedure. In this way, it was hoped to increase the range of mutagenic chemicals that could be detected in the assay.

Colony Counting:
Colonies were counted electronically using a Seescan Colony Counter or manually where minor agar damage might have interfered with automatic counting, and the background lawn inspected for signs of toxicity.
Evaluation criteria:
Acceptance Criteria:
The assay was considered valid if the following criteria were met:
i) the mean negative control counts fell within the normal range as defined in Appendix 4
ii) the positive control chemicals induced clear increases in revertant numbers confirming discrimination between different strains, and an active S-9.
iii) no more than 5 % of the plates were lost through contamination or some other unforeseen event

Evaluation criteria:
A test compound was considered to be mutagenic if
i) the assay was valid
ii) Dunnett's test gave a significant response (p <= 0.01), and the data set showed a significant dose-correlation
iii) the positive responses described in (ii) were reproducible
Statistics:
The m-statistic was first calculated to check that the data were Poisson-distributed and then Dunnett's test was used to compare the counts of each dose with the control. The presence or otherwise of a dose response was then checked by linear regression analysis.

Results and discussion

Test resultsopen allclose all
Species / strain:
S. typhimurium TA 102
Metabolic activation:
with
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
cytotoxicity
Untreated negative controls validity:
valid
Positive controls validity:
valid
Species / strain:
S. typhimurium TA 102
Metabolic activation:
without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
no cytotoxicity
Untreated negative controls validity:
valid
Positive controls validity:
valid
Species / strain:
S. typhimurium TA 1535, TA 1537, TA 98 and TA 100
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
no cytotoxicity
Untreated negative controls validity:
valid
Positive controls validity:
valid
Additional information on results:
Toxicity:
Only treatments of strain TA102 in Experiment 2 (+ S-9 only) showed signs of toxicity (as indicated by thinning of the background bacterial lawn) in this study. In this case, toxic effects were seen mostly at the 3 highest doses. It would appear that the use of a pre-incubation step particularly enhanced the toxicity of the test agent to this test strain.

Range-finder and Experiment 1 treatments were carried out using final concentrations of Epoxidised SOybean Oil at 8, 40, 200, 1000 and 5000 µg/plate, Precipitation, in the form of oil droplets, was observed at concentrations of 1000 and 5000 µg/plate. For experiment 2, testing was again carried out up to maximum concentration of 5000 µg/plate (despite the observation of precipitation), as it was possible that the compund formed an emulsion within the test system and it was felt important to maximise the exposure of the cells to this. A narrowed dose range was also used in this experiment (312.5 - 5000 µg/plate) in order to examine those doses most likely to exhibit a mutagenic response. Oil droplets were observed on test plates in this experiment, following treatments of 1250 µg/plate and above.

Mutation:
The individual plate counts were averaged to give mean values. From the data it can be seen that mean solvent control counts fell within the normal historical range, that the positive control chemicals all induced large increases in revertant numbers in the appropriate strains, and that < 5 % of plates were lost, leaving adequate numbers of plates at all treatments. The study was accepted as valid.

The mutation data were evaluated as follows:
No treatment with Epoxidised Soybean Oil of any of the tester strains, earlier in the absence or presence of S-9, resulted in a significant increase in revertant numbers. The data obtained therefore gave no indication of an ability of the test agent to induce mutation.
Remarks on result:
other: strain/cell type: S. typhimurium TA 102
Remarks:
Migrated from field 'Test system'.

Any other information on results incl. tables

No further information

Applicant's summary and conclusion

Conclusions:
It is concluded that Epoxidised Soybean Oil failed to induce mutation in 5 strains of Salmonella typhimurium, when treated up to a maximum concentration of 5000 µg/plate, in the absence and presence of a rat liver metabolic activation system.
Executive summary:

Epoxidised Soyban Oil was assayed for mutation in 5 -histidine-requiring strains (TA98, TA100, TA1535, TA1537 and TA102) of Salmonella typhimurium, both in the absence and presence of metabolic activation by an Aroclor 1254 induced rat liver post-mitochondrial fraction (S-9), in two separate experiments.

It was concluded that Epoxidised Soybean Oil failed to induce mutation in 5 strains of Salmonella typhimurium, when treated up to a maximum concentration of 5000 µg/plate, in the absence and presence of a rat liver metabolic activation system.