9-Octadecenedioic acid

Endpoint summary

Key value for chemical safety assessment

Skin sensitisation

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not sensitising)

Additional information:

Justification for read-across

There are not sufficient data available on the skin sensitisation potential of Octadec-9-enedioic acid (EC 802-22-7) to meet the requirements of Regulation (EC) No. 1907/2006. The assessment was therefore based on studies conducted with the target substance and the analogue substance (Z)-9-Octadecen-1,18-dioic acid (CAS 20701-68-2) as part of a read-across approach, which is in accordance with Regulation (EC) No. 1907/2006, Annex XI, 1.5.

For each specific endpoint the source substance structurally closest to the target substance is chosen for read-across, with due regard to the requirements of adequacy and reliability of the available data. Structural similarities and similarities in properties and/or activities of the source and target substance are the basis of read-across. Based on their chemical structure, both the target substance (Octadec-9-enedioic acid, EC 802-22-7) and the source substance ((Z)-9-Octadecen-1,18-dioic acid, CAS 20701-68-2), belong to the family of linear monounsaturated dicarboxylic acids. While the target substance contains a cis- and trans-isomer, the source substance consists of the cis-isomer. A detailed justification for the analogue read-across approach is provided in the technical dossier (see IUCLID Section 13).

Skin sensitisation

 

In vitro data

EC 802-122-7

A skin sensitisation test was performed with Octadec-9-enedioic acid using the direct peptide reactivity assay according to OECD guideline 442C, although the guideline was not mentioned in the study report (Bazin, 2015). The test addresses the first key event (molecular initiating event) in the development of skin sensitisation, which is protein reactivity. The reactivity of the test substance towards synthetic proteins with cysteine and lysine is measured as cysteine and lysine peptide depletion. A 100 mM solution of the test substance in acetonitrile/DMSO was prepared with a 1/10 ration of cysteine and a 1/50 ratio of lysine. Vehicle controls were prepared with vehicle (acetonitrile/DMSO and acetonitrile) and peptide, while interference controls were prepared with test substance and without peptide. The positive controls were 3-methylcatechol and benzoquinone. The samples (in triplicate) were incubated for 24 h at room temperature in the dark, and then analysed by HPLC-MS/MS. The vehicle and positive controls were shown to be valid and the positive control fell within the historical control value ranges. The standard calibration curve was shown to be valid for lysine and cysteine. The test substance had a mean depletion score of 1.36%, indicating no or minimal reactivity according to the DPRA prediction model. Therefore, the test substance was considered to be negative for skin sensitisation under the conditions of the test. 

An in vitro skin sensitisation test was performed with Octadec-9-enedioic acid using the ARE-Nrf2 luciferase test method according to OECD guideline 442D and under GLP conditions (Ostinet, 2015). The test covers the second key event in the development of skin sensitisation, which takes place in the keratinocytes. On Day 1, keratinocytes (KeratinoSens™) were seeded onto 96-well plates in maintenance medium (DMEM, non-heat inactivated FCS and 0.05% geneticin) and incubated for 24 h at 37 °C and 5% CO₂. On Day 2, the cells were exposed to test substance at concentrations of 0.2 – 400 µg/mL and incubated for 48 h at 37 °C and 5% CO₂. Following the exposure period, on Day 4, the cells were washed with PBS and incubated for at least 15 min with luciferase. The luciferase activity was then measured with an integration time of 2 sec using a luminometer. In parallel, the cytotoxicity was measured on Day 4. The cells were washed with PBS and staining solution (MTT) was added to each well. The plates were incubated for 4 h at 37 °C and 5% CO₂. After the incubation, the MTT solution was removed and the cells treated with 10% SDS overnight in the dark at 37 °C and 5% CO₂. The following day, the absorbance was measured at 540 nm. Two independent repetitions were performed, each in triplicate (induction) or as a single measurement (cytotoxicity). The vehicle and positive control were shown to be valid. The mean induction value (I_max) was 1.38 for the test substance and 8.96 for the positive control, respectively. The mean viability (IC₇₀) was 15.70 (geometric mean) for the test substance and the EC_1.5was 6.3 for the positive control. Because the I_max< 1.5 and EC_1.5< IC₇₀, the test substance was considered to be negative for skin sensitisation under the conditions of the test.

 

In vivo data

CAS 20701-68-2

A Guinea pig maximisation test was performed with (Z)-9-octadecen-1,18-dioic acid under GLP conditions and using a protocol similar to OECD guideline 406 (Pels Rijcken, 1996). 10 test and 5 control Himalayan guinea pigs were induced intradermally with 50% test substance in propylene glycol on both sides of the spine with and without Freud's complete adjuvant. On Day 8, a 48-h epicutaneous induction treatment with 10% test substance was performed under semi-occlusive conditions. On Day 21, the challenge treatment was performed by topical application of 5% test substance on the flank of all animals for 24 h, under semi-occlusive conditions. Skin reactions were evaluated 24 and 48 h after the challenge application. 48 hours after intradermal induction, very slight to well-defined erythema was noted at all of the sites injected with FCA/water in 10/10 treated and 5/5 control animals. Necrosis was observed at all the water/test substance and FCA/test substance injection sites in 10/10 treated and 5/5 control animals. The authors concluded that the vehicle, propylene glycol, caused the irritation as the same effects were noted in the preliminary study. Following epidermal induction, very slight erythema was observed in 2/10 treated animals. 24 and 48 hours after the challenge ended, no sensitisation reactions were observed in the treated animals. No skin irritation was noted in any of the treated and control animals. There was no mortality during the study period, and no signs of toxicity or treatment-related effects on body weight were observed. The results of the reliability check carried out at regular intervals were positive, confirming the reliability of the assay. Based on the results, the test substance had no sensitising effect in guinea pigs under the experimental conditions of the study.

 

Human data

EC 802-122-7

The sensitizing potential of Octadec-9-enedioic acid was assessed in a Repeated insult patch test with challenge (epicutaneous test) performed in 104 human volunteers (23 males, 84 females) (Olsavszky, 2015). During the induction phase, volunteers were exposed a total of nine times at an average of 3 times/week during 3 weeks. An occlusive patch (Finn chamber) with 20 µL of 30% test substance in glycerine was applied to the scapular area for 48 h (72 h if a patch was applied on a Friday). An occlusive patch containing 20 µL distilled water was applied adjacent to the treatment patch. The challenge was performed approximately two weeks after the last induction. One challenge patch was applied to the induction site and one challenge patch was applied to a new site and remained in place for 48 h. The sensitisation reaction at the challenge sites was assessed 0 and 48 h after patch removal. No volunteers exhibited skin irritation during the induction phase. Following the challenge treatment, none of the subjects showed skin irritation reactions. The test material did not induce skin sensitisation in any of the 104 subjects. 

 

Overall conclusion for skin sensitisation

A weight-of-evidence approach was applied to assess the skin sensitising potential of the target substance Octadec-9-enedioic acid. Two in vitro studies did not indicate a skin sensitising potential of the target substance, while a human repeated insult patch test was negative for skin sensitisation. The GPMT study performed with the source substance was negative. Taking into account the available information, Octadec-9-enedioic acid is not considered to be skin sensitising.

Migrated from Short description of key information:
Skin sensitisation (GPMT, in vitro DPRA, in vitro luciferase test, human RIPT): not sensitising

Justification for selection of skin sensitisation endpoint:
No study was selected, as a weight-of-evidence approach was applied.

Respiratory sensitisation

Endpoint conclusion

Endpoint conclusion:

no study available

Justification for classification or non-classification

According to Article 13 of Regulation (EC) No. 1907/2006 "General Requirements for Generation of Information on Intrinsic Properties of substances", information on intrinsic properties of substances may be generated by means other than tests e.g. from information from structurally related substances (grouping or read-across), provided that conditions set out in Annex XI are met. Annex XI, "General rules for adaptation of this standard testing regime set out in Annexes VII to X” states that “substances whose physicochemical, toxicological and ecotoxicological properties are likely to be similar or follow a regular pattern as a result of structural similarity may be considered as a group, or ‘category’ of substances. This avoids the need to test every substance for every endpoint". Since the analogue concept is applied to Octadec-9-enedioic acid (EC 802-122-7), data will be generated from reference source substance(s), in addition to the data on the target substance, to avoid unnecessary animal testing. Additionally, once the analogue read-across concept is applied, substances will be classified and labelled on this basis.

Therefore, based on the analogue read-across approach and data on the target substance, the available data on skin sensitisation do not meet the classification criteria according to Regulation (EC) 1272/2008, and are therefore conclusive but not sufficient for classification.