Ethyl octanoate

Endpoint summary

Description of key information

The test item is not skin sensitising.

Key value for chemical safety assessment

Skin sensitisation

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not sensitising)

Additional information:

For this endpoint there are two older supporting human maximisation studies available on ethyl octanoate and three recent key in vitro skin sensitisation tests (in chemico DPRA, in vitro LuSens and in vitro h-CLAT test) on ethyl hexanoate, performed according to OECD guidelines and in compliance to GLP. Read-across (RA) was done from ethyl hexanoate to ethyl octanoate and the results on ethyl hexanoate are used for the classification of ethyl octanoate taking into account the human maximization studies on ethyl octanoate.

DPRA:

The reactivity of ethyl hexanoate towards synthetic cystein or lysine containing peptides was evaluated in the DPRA test according to OECD 442C. The percentage of depletion of cysteine- and lysine-peptides is calculated and used in a prediction model to assign the test item to one of four reactivity classes and discriminate between sensitisers and non-sensitisers.

The mean C- and K-peptide depletion was below 0.0%. Negative depletions are considered to be "zero" for the calculation of the mean peptide depletion. Ethyl hexanoate shows no chemical reactivity in the DPRA under the current test conditions.

Based on the result, and on the structural, chemical and toxicological similarities between ethyl hexanoate and ethyl octanoate, ethyl octanoate is not a sensitiser.

LuSens:

The keratinocyte activating potential of ethyl hexanoate was evaluated in the LuSens assay according to OECD 442D. Ethyl hexanoate was incubated with a luciferase reporter cell line (LuSens cells) for 48 hours at 37°C and the antioxidant response element (ARE) dependent luciferase activity was measured.

Ethyl hexanoate did not precipitate in the experiment and the acceptance criteria were met. Ethyl hexanoate did not induce a statistical significant increase in luciferase activity in LuSens cells in two consecutive concentrations, while the 70% viability was reached. From this it is concluded that ethyl hexanoate does not have keratinocyte activating potential.

Based on the result, and on the structural, chemical and toxicological similarities between ethyl hexanoate and ethyl octanoate, ethyl octanoate is not a sensitiser.

h-CLAT:

The potential of ethyl hexanoate to induce cell membrane markers CD86 and CD54 expression was evaluated in the human cell line activation test according to the new OECD 442E TG. Ethyl hexanoate was incubated with the human pro-monocytic cell line THP-1 for 24 hours at 37°C and the membrane markers expression was measured by flow cytometry through staining with FITC labeled anti-human-CD86/anti human CD54 antibody and propidium iodide.

Ethyl hexanoate was tested at concentrations of 566 μg/mL onwards and no precipitates were noticed in any concentration. Relative fluorescence intensity and concurrent relative viability were determined. Ethyl hexanoate induced CD54 expression in THP-1 cells with 83% viability. Therefore, it was concluded that ethyl hexanoate induces dendritic cell activation.

Based on the result, and on the structural, chemical and toxicological similarities between ethyl hexanoate and ethyl octanoate, ethyl octanoate induces dendritic cell activation.

Human maximisation test (see IUCLID 7.10.4) :

Two human maximisation tests with 25 volunteers were performed with ethyl octanoate to determine the contact-sensitizing potential of the test substance in humans.

In the first study the ages varied from 18 to 50 years and in the second study from 18 to 39 years.

Induction included 5 repeated 48 hour occlusive patch tests on the same skin site with a 24 hour rest period between removal and reapplication of the patch. Following a 2 week rest period after the last induction patch, challenge was done by a 48 -hour occluded patch with the maximum non-irritating concentration of the substance on a slightly irritated skin site. The challenge site was scored after 24 and 48 hours after patch removal and the sensitisation index was noted.

In the first test ethyl octanoate at 2% in petrolatum produced sensitisation reactions in two individuals, while in the second study no sensitisation reactions were observed in any of the volunteers.

Ethyl octanoate should not be considered as sensitiser as it is unlikely that this material would present a danger of contact-sensitization.

Conclusion:

To come to a conclusion the results of the three individual in vitro assays need to be taken together as they reflect the three key events in the adverse outcome pathway (AOP) leading to skin sensitisation. For this reason, a weight of evidence approach is applied for the test battery stating that: 'any two of the three tests determine the overall results, i.e. any two positive results drive the prediction of a sensitiser, while any two negative results drive the prediction of a test substance to be a non-sensitiser'.

Ethyl hexanoate is not peptide reactive, does not activate keratinocytes, however activates dendritic cells. Taking together and applying the evaluation criteria described above, ethyl hexanoate is predicted not to be a skin sensitiser. Due to the read-across strategy it can be concluded that ethyl octanoate is also not a sensitiser. The supporting human maximisation studies on ethyl octanoate confirm the conclusion that ethyl octanoate is not a skin sensitiser.

Respiratory sensitisation

Endpoint conclusion

Endpoint conclusion:

no study available

Justification for classification or non-classification

Regarding the classification of the substance for skin sensitisation the results of the three individual assays of the in vitro skin sensitisation test battery need to be taken together as they reflect three key events in the adverse outcome pathway leading to skin sensitisation. For this reason, a weight of evidence approach is applied for the test battery stating that: 'any two of the three tests determine the overall results, i.e. any two positive results drive the prediction of a sensitiser, while any two negative results drive the prediction of a test substance to be a non-sensitiser'.

Due to the RA strategy it can be stated that ethyl octanoate is not peptide reactive, does not activate keratinocytes, however activates dendritic cells. Applying the evaluation criteria described above, the test substance is predicted not to be a skin sensitiser.

The supporting human maximisation studies on ethyl octanoate confirm the conclusion that ethyl octanoate is not a skin sensitiser.