Castor oil, dehydrated

Endpoint summary

Key value for chemical safety assessment

Skin sensitisation

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not sensitising)

Additional information:

A series of in vitro studies were conducted with castor oil, dehydrated to determine whether this substance has the potential to be sensitising. Chemical reactivity has been shown to be well associated with allergenic potency (Gerberick et al., 2007). Within this context, measuring the amount of proteins with nucleophilic side chains such as cysteine or lysine residues after incubation with putative allergens may serve as surrogate markers. Due to the complexity of the skin sensitisation process a single in vitro assay is not sufficient to adequately assess this toxicological endpoint. Therefore, a combination of several methods addressing the major steps of the sensitisation process: protein reactivity, activation of keratinocytes and activation of dendritic cells has been proposed (Kolle, S, N 2013).

In the Direct Peptide Reactivity Assay (DPRA), the reactivity of the test substance towards synthetic cysteine (C)- or lysine (K)-containing peptides was evaluated (Kolle, 2013a). For this purpose, the substance was incubated with synthetic peptides for 24 h at room temperature and the remaining non-depleted peptide concentration was determined by high performance liquid chromatography (HPLC) with gradient elution and UV-detection at 220 nm. The test substance was solved in propanol and incubated in ratios of 1:5 for C-peptide or 1:24 for K-peptide based on absolute mass. Additionally triplicates of the concurrent vehicle control (= NC) were incubated with the peptides. Further, a co-elution control was performed in order to detect possible interference of the test substance with the peptides. The samples consisted of the test substance, vehicle and the respective peptide buffer but without peptide. Moreover the samples were additionally analysed by measuring UV absorbance at 258 nm and the area ratio 220 / 258 was calculated as a measure of peak purity. The peptide depletion of test-substance incubated samples was compared to the peptide depletion of the NC samples and expressed as relative peptide depletion. For the test substance, the mean peptide depletion as average of C- and K-peptide depletion was calculated and used for evaluation of the chemical reactivity. Based on the observed results and applying the prediction model proposed in Gerberick et al. (2007), it was concluded that castor oil, dehydrated showed minimal chemical reactivity in the DPRA under the chosen test conditions (Kolle, S, N, 2013).

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The activation of keratinocytes in the genetically modified human HaCaT cell line LuSens using luminescence detections system was investigated (Kolle, 2013c). This assay employs the reporter gene for luciferase under the control of an antioxidant response element (ARE) and hence monitors Nrf-2 transcription factor activity. The endpoint measurement was the up-regulation of the luciferase activity after 48 hours incubation with the test substances. This up-regulation is an indicator for the activation of the Keap1/Nrf2-ARE signalling pathway. The cell line LuSens was treated with 6 test substance concentrations for 48 hours in at least two independent experiments with 3 triplicates each. Cells were lysed and luciferase induction was evaluated by measuring luminescence signal after substrate addition. In parallel a MTT assay was performed to assess the cytotoxicity of the test substance. A test substance was considered to have an ARE induction potential if the fold induction of luciferase activity was >1.5 and viability determined in the MTT assay was >70% at the test concentrations. After 48 hours of exposure to test substance, luciferase activity in LuSens cells was induced at concentrations affording at least 70% viability in two independent experiments. From this, it was concluded that the test substance has a keratinocyte activating potential.

In the dendritic cell activation test, the human pro-monocytic cell line U937 was used as surrogates for dendritic cells (Kolle, 2013b). As readout, the change in the expression of the cell membrane marker CD86 was measured by flow cytometry after 48 hours of exposure to castor oil, dehydrated. The test substance is predicted to activate dendritic cells when CD86 cell surface expression exceeds the threshold in relation to vehicle control in at least two independent assays. Under the test conditions, CD68 cells were not induced at test substance concentrations affording at least 70% viability, therefore the test was considered to be negative.

The above battery of in vitro tests, castor oil, dehydrated was not peptide reactive and does not activate dendritic cells. Castor oil does however, have the potential to activate keratinocytes. Thus following the application of the evaluation criteria i.e., any two of the three tests determine the overall results. Two positive test results indicates the prediction of a positive skin sensitiser. Any two negative results indicates the test substance to be a non-skin sensitiser. Therefore, castor oil, dehydrated is predicted to be a non skin sensitiser (Kolle, S, N 2013).

The conclusion of not sensitising is supported by studies with other glycerides representative of the constituents of castor oil, dehydrated. When tested according to the guinea pig maximisation protocol, soybean (rich in C18:2) and palm oil (both C16-18 and C18-unsatd.) were not sensitising (IUCLID, 2000c; CIR, 2000). Coconut and fully hydrogenated coconut oil (C8-18 and C18-unsatd.) were not sensitizing in a guinea pig maximisation and a Buehler test, respectively (CIR, 1986).

In two studies, castor oil was applied via Finn chambers to human volunteers for 48 hours. Readings were conducted 30 minutes after removal of the chamber, then after 1, 4 and 5 days. In the first study with 49 patients, no positive reactions were noted (Fujimotoet al.,1997). In the second study with 346 patients, one positive reaction occurred but this was observed only at the second reading (Hino et al.,2000).

Patch testing with human volunteers conducted with soybean oil (rich in C18:2) as well as other glycerides with fatty acids chain lengths of C16-18 and C18-unsatd. (partially hydrogenated soybean oil, palm oil and partially hydrogenated palm oil) yielded no negative sensitising reactions (Bush et al., 1985;Cuthbert and Neilson, 1996; CIR, 2000). The same result was obtained with fully hydrogenated cottonseed oil (CIR, 2001).

Exposure via the inhalation route and consequent respiratory sensitisation is not expected given the physical state and low vapour pressure of the substance.

Overall, the weight of evidence from the different constituents suggests that castor oil, dehydrated will not be sensitising to the skin.

Migrated from Short description of key information:
Castor oil, dehydrated is not expected to be a skin sensitiser.

Justification for selection of skin sensitisation endpoint:
No one study was selected since the conclusion from all the studies demonstrates that the substance is not a skin sensitiser.

Respiratory sensitisation

Link to relevant study records

Reference

Endpoint:

respiratory sensitisation

Data waiving:

other justification

Justification for data waiving:

other:

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not sensitising)

Additional information:

As chemical respiratory sensitisers also elicit positive results in predictive tests for contact sensitisation, a negative outcome for dermal sensitisation is also predictive for non-respiratory sensitisation of the substance. The substance is a liquid with a low vapour pressure. Due to it physical state and physical chemical properties, it is unlikely that it will form inhalable dust, mist or fumes when handled and used. In case inhalable forms of the substance are created under particular conditions (e. g. spraying, elevated temperature/pressure), appropriate risk management measures such as closed systems, exhaust ventilation or wearing of respirators are implemented to control exposure. Under such conditions, the risk to humans following inhalation exposure can be considered minimal and further testing involving vertebrate animals may be omitted, in accordance with Annex XI (1.2) of the REACH regulation.

Migrated from Short description of key information:
Castor oil, dehydrated is not expected to be a respiratory sensitiser.

Justification for selection of respiratory sensitisation endpoint:
As chemical respiratory sensitisers also elicit positive results in predictive tests for contact sensitisation, a negative outcome for dermal sensitisation is also predictive for non-respiratory sensitisation of the substance. The substance is a liquid with a low vapour pressure. Due to it physical state and physical chemical properties, it is unlikely that it will form inhalable dust, mist or fumes when handled and used. In case inhalable forms of the substance are created under particular conditions (e. g. spraying, elevated temperature/pressure), appropriate risk management measures such as closed systems, exhaust ventilation or wearing of respirators are implemented to control exposure. Under such conditions, the risk to humans following inhalation exposure can be considered minimal and further testing involving vertebrate animals may be omitted, in accordance with Annex XI (1.2) of the REACH regulation.

Justification for classification or non-classification

The data available on human and animals for castor oil, dehydrated, tested as castor oil and zinc rincinoleate, no skin sensitisation potential is expected. Furthermore, as chemical respiratory sensitisers also elicit positive results in predictive tests for contact sensitisation, a negative outcome for dermal sensitisation is also predictive for non-respiratory sensitisation of the substance. The substance is a liquid with a low vapour pressure. Due to it physical state and physical chemical properties, it is unlikely that it will form inhalable dust, mist or fumes when handled and used. In case inhalable forms of the substance are created under particular conditions (e. g. spraying, elevated temperature/pressure), appropriate risk management measures such as closed systems, exhaust ventilation or wearing of respirators are implemented to control exposure. Under such conditions, the risk to humans following inhalation exposure can be considered minimal and further testing involving vertebrate animals may be omitted, in accordance with Annex XI (1.2) of the REACH regulation.

Based on the above information, the substance does require classification for sensitization according to Directive 67/548 EC or Regulation 1272/2008/EC.