9-Octadecenedioic acid

Endpoint summary

Description of key information

Skin, rabbit: not irritating
Eye, in vitro: Cat. 2, H319

Key value for chemical safety assessment

Skin irritation / corrosion

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not irritating)

Eye irritation

Endpoint conclusion

Endpoint conclusion:

adverse effect observed (irritating)

Respiratory irritation

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

Justification for read-across

There are in vitro data available on the skin and eye irritation potential of Octadec-9-enedioic acid (EC 802-22-7). However, as the skin irritation data do not allow a thorough hazard assessment, read across to available data of a structural analogue substance was conducted. Therefore, assessment is 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 acis- andtrans-isomer, the source substance consists of thecis-isomer. A detailed justification for the analogue read-across approach is provided in the technical dossier (see IUCLID Section 13).

Skin irritation

In vitro data

EC 802-122-7
An in vitro skin irritation study was performed with Octadec-9-enedioic acid according to OECD guideline 439 and under GLP conditions (Ostinet, 2013). The Skin Ethic™ RHE (reconstructed three-dimensional human epidermis) model was used. 16 ± 2 mg of the undiluted test substance was applied to the tissue samples, which were moistened with 10 µLPBS to ensure good contact with the test substance. Concurrent control tissues treated with Dulbecco's PBS served as negative controls, while the positive controls were exposed to 5% SDS. All tests were performed in triplicates. The tissue samples were exposed to the test substance for 42 min at room temperature and rinsed with PBS before post-treatment incubation for 42 h at 37 °C and 5% CO2. To determine changes in cell viability, MTT reduction assays were performed after the incubation and post-treatment period. Tissue samples were incubated in 0.3 mL maintenance medium at 1 mg/mL MTT, for 3 h at 37 °C and 5% CO2. Then, tissues were washed in 1-2 mL PBS and extraction of the formazan product was carried out in 1.5 mL isopropanol. The optical density was measured at 570 nm wave length in triplicates. The solvent and positive controls were shown to be valid, with a cell viability of 100% and 1.7%, respectively. The test substance had a cell viability of 76.5%, indicating that the test substance is not a skin irritant according to the criteria defined in OECD Guideline 439.

In vivo data

CAS 20701-68-2

The skin irritation potential of (Z)-9-octadecen-1,18-dioic acid was assessed in a study conducted according to OECD guideline 404 and under GLP conditions (Pels Rijcken, 1996). 0.5 g of the test substance (moistened with water) was applied for 4 h to the shaved skin of 3 New Zealand White rabbits, under semiocclusive conditions. The scoring of skin reactions (erythema and edema) was performed 1, 24, 48 and 72 h after exposure and removal of the dressing. At the 1-h reading time point, very slight to well defined erythema (score 1-2) were observed in 3/3 rabbits and very slight edema (score 1) were noted in 2/3 rabbits. At the 24-h reading time point, 3/3 animals had very slight erythema, while the edema had cleared completely. All skin irritation effects had cleared within 48 h after patch removal. The mean scores for erythema over 24, 48, and 72 h were 0.33, 0.33 and 0.33. All edema scores were 0 for all 3 animals. No signs of systemic toxicity were seen. Therefore, the test substance is considered to be non-irritating to the skin.

Human data

EC 802-122-7

The skin irritation potential of Octadec-9-enedioic acid was assessed in a single exposure patch test, performed under Good Clinical Practice conditions and defined as non-interventional clinical research according to the French law 2004-806 of 09/08/2004 relating to the policy of public health (Magne, 2015). 11 human volunteers (4 males, 7 females) in the age range 18 – 70 years old were enrolled in the study. A 30% dilution of the test substance in glycerine was applied to the skin on the upper back of the volunteers for 48 ± 4 h. 20 µL test substance was applied under occlusive conditions by using a Finn Chamber. A negative control cup containing distilled water was applied in parallel with the test cup. The skin irritation effects (erythema, edema, vesicles, cutaneous dryness, papula, bulla, scabs, soap effect (shiny skin), pruritus) were assessed 15-30 min after patch removal and scored according to the Draize scoring system. In addition, the subjective experience of the volunteers was recorded. The test material did not induce skin irritation in any of the 11 subjects. 

 

Eye irritation

In vitro data

EC 802-122-7

An in vitro Bovine Corneal Opacity and Permeability Test was performed with Octadec-9-enedioic acid according to OECD guideline 437 and under GLP conditions (Maillet, 2014). Eyes were sourced from cattle less than 12 months old, and the eyes were transported in buffered Hanks´ medium at room temperature with 0.2% penicillin/streptomycin and used within 4 h after harvesting. Excised corneas were quality checked before being mounted in cornea holders incubated in a water bath at 32 °C. 750 mg of the test substance was applied to 3 corneas for 4 h at 32 °C. 0.9% (w/v) sodium chloride in distilled water served as the negative control, while 20% (w/w) imidazole solution in NaCl (to 0.9%) served as the positive control. After treatment, all corneas were washed twice with EMEM containing phenol red and once with EMEM without phenol red. The corneal opacity was determined using an opacitometer, while the corneal permeability was determined by UV/VIS spectrophotometry at 490 nm. The mean opacity values for the negative control, test substance and positive control were 3.3, 26.1 and 138.7, respectively. The permeability values for the test substance and positive control relative to the negative control (blank sample) were 0.048 and 3.808, respectively. The in vitro irritancy score (IVIS, which indicates either classification as an eye corrosive or non-classification according to the conditions of the test), for the test substance and positive control relative to the negative control (blank sample) were 27.4 and 195.8, respectively. The results indicate that the test substance did not cause corrosive effects to the eye. The result did suggest the test substance may be irritating to the eye. However, based on the criteria defined in OECD Guideline 437, no classification for eye irritation can be applied based on this test alone.

An in vitro study was performed using Octadec-9-enedioic acid according to the non-validated SkinEthic Human reconstructed corneal epithelium model (Maillet, 2015). The method was compatible with the 'Pre-validation of a new in vitro reconstructed human cornea model to assess the eye irritating potential of chemicals' (Van Goethem et al., 2006) and 'Three-dimensional construct of the human corneal epithelium for in vitro toxicology' (Nguyen et al., 2003). Prior to treatment, the 6-day old tissues were transferred into the wells of the treatment plates containing 0.5 mL maintenance medium and incubated overnight. Afterwards, duplicate tissues were treated with 30 mg of the test item for 10 min, 1 and 3 h. Tissues were treated with 30 µL 0.9% (w/v) sodium chloride in sterile water to serve as negative controls, while tissues treated with 30 µL of 1.5% SDS served as positive control (controls were also tested in duplicate). The plates were incubated at 37 °C, 5% CO2 and 95% humidity during the exposure time. At the end of the treatment period, each tissue was removed from the well and rinsed with pre-warmed PBS for 30 min. To determine effects on cell viability, MTT reduction assays were performed immediately after the incubation period. The tissues were incubated in a 500 µL freshly prepared 0.5 mg/mL MTT solution for 1 h at 37 °C and 5% CO2. The tissue was transferred to a 24-well plate containing 1 mL isopropanol to extract the formazan crystals. For each tissue sample the optical density was measured at 570 nm wave length. The T50 contact time point causing 50% cytotoxicity was determined as a measure of relative cell viability. The T50 for the negative control was > 180 min and for the positive control 26.2 min, showing that both controls were valid. The T50 value for the test substance was 34.6 min. Therefore, the test item was considered to be ‘moderately irritating’ under the conditions of this test. The results were not taken into consideration for the classification of the substance as the test system is not a validated method for assessment of eye irritation.

 

Overall conclusion for skin and eye irritation

The available in vitro and in vivo data on the target and source substance did not indicate skin irritating properties. Therefore, the target substance Octadec-9-enedioic acid is not considered to be a skin irritant.

The available in vitro data on the target substance indicated that the target substance has eye irritating properties. Considering all the data, Octadec-9-enedioic acid should be classified for causing eye irritation (category 2).

Justification for selection of skin irritation / corrosion endpoint:
Hazard assessment is conducted with data on the target substance and by means of read-across from a structural analogue. The selected study is the most adequate and reliable study based on the identified similarities in structure and intrinsic properties between the source and target substance and overall quality assessment (refer to the endpoint discussion for further details).

Justification for selection of eye irritation endpoint:
The selected study is the most adequate and reliable study based on overall quality assessment (refer to the endpoint discussion for further details).

Effects on eye irritation: irritating

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 information available on reference source substance(s) to avoid unnecessary animal testing, in addition to the in vitro data available on the target substance. Additionally, once the analogue read-across concept is applied, substances will be classified and labelled based on the available data.

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

The data on eye irritation/ corrosion do not meet the classification criteria according to Regulation (EC) 1272/2008, however, a classification was applied based on the available data. Octadec-9-enedioic acid (EC 802-122-7) is classified for eye irritation, category 2 (H319).