Calcium distearate

Endpoint summary

Key value for chemical safety assessment

Skin sensitisation

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not sensitising)

Additional information:

The substances in the category are considered to be similar on the basis that they have common structures of a calcium ion varying only by the length of the fatty acid chain and the presence of unsaturated and/or hydroxyl functional groups. As a result it is expected that the substances will have similar, predictable properties. REACH Annex V, Entry 9, groups fatty acids and their potassium, sodium, calcium and magnesium salts, including C6 to C24, predominantly even-numbered, unbranched, saturated or unsaturated aliphatic monocarboxylic acids. Provided that they are obtained from natural sources and are not chemically modified, the substances included in REACH Annex V, Entry 9 are exempt from registration, unless they are classified as dangerous (except for flammability, skin irritation or eye irritation) or they meet the criteria for PBT/vPvB substances. The metal fatty acid substances in the category are therefore not expected to be hazardous. Due to the close structural similarity and the narrow range of carbon chain numbers covered in this category, the sensitisation properties are expected to be predictable across the category.

Since REACH Annex V groups together calcium, potassium, sodium and magnesium salts of C6 to C24 fatty acids as being potentially exempt from registration, these metal cations are therefore not considered to contribute to any health hazard. On this basis, relevant published or proprietary data on any potassium, sodium or magnesium salt within the fatty acid category range of C14 to C22 can be used to read across to the calcium salts of C14-C22 fatty acid category.

Lithium salts of fatty acids are not included in REACH Annex V as being potentially exempt from registration. For these salts it is expected that the lithium cation would be the species with the potentially higher toxicity profile when compared to calcium, potassium, sodium, and magnesium cations. However, the substance fatty acids C18 (unsaturated) lithium salts contains a fatty acid anion that falls within the C14-C22 category. Experimental data for the mammalian toxicity Annex VIII endpoints have been generated on this substance and the results obtained are relevant to read across to the calcium salts of C14-C22 fatty acids either in a weight of evidence approach or as key studies due to the structural similarity and its position within the category fatty acid range.

Neither the fatty acids themselves nor the calcium fatty acid salts in the category are expected to be skin sensitisers. There are a number of published reviews that consider the sensitisation potential of both the acids and the salts. Additionally, data on this endpoint can be extrapolated from available information on related fatty acid substances using other metal cations such as lithium. CIR (1987) reports on the sensitisation potential of stearic and oleic acids formulated into cosmetic creams at 1-5% concentrations using maximisation tests in guinea pigs. The results indicated that these substances were not sensitisers.

Human volunteer studies following a number of protocols including maximisation, Repeated Insult Patch Test (RIPT) and modified RIPT (Draize and Shelanski method) under open, semi-occlusive and occlusive conditions have been conducted on a wider range of fatty acids in the C12 to C18 chain lengths formulated at concentrations between 1 and 13% (CIR 1987). No primary or cumulative irritation or sensitisation was reported, although there were some individuals that reacted to a few, isolated, induction patches. Slight, if any, reactions were observed after challenge patching at original or adjacent sites. The intensity of observed reactions to the formulations was not directly related to the concentrations of the fatty acid ingredients.

A key Local Lymph Node Assay on C18 (unsaturated) lithium salts was conducted in mice according to OECD Guideline 429. The test material was considered to be a non-sensitiser under the conditions of the test with the highest Stimulation Index of 1.68 at 10% concentration in ethanol/distilled water.The result from this lithium salt is considered relevant to read across to the calcium fatty acid salts in the category since the only difference is the lithium cation (see introduction to this section).

A number of additional supporting studies on the skin sensitisation potential of lithium 12 -hydroxystearate in a grease base using the Magnusson and Kligman maximisation test have been considered. In all cases the results were negative. A published sensitisation study using a lithium complex grease containing 8.8% lithium 12 -hydroxystearate according to the Buehler method also showed no evidence of sensitisation.

On the basis of the category justification and the preamble to this endpoint, it is justifiable to read across the negative results from the fatty acids C18 (unsaturated) lithium salts study, the results from sensitisation studies on lithium 12-hydroxystearate, together with the published data on the lack of sensitisation potential for the fatty acids and simple metal salts of fatty acids to the calcium fatty acid salts category.

Reference

CIR (Cosmetics Ingredients Review) (1987) Final report on the safety assessment of oleic acid, lauric acid, palmitic acid, myristic acid and stearic acid. Journal of American Toxicologists, vol. 6, issue 3, pp. 321-401

Migrated from Short description of key information:
Local Lymph Node Assay: Stimulation Index <3 at the highest concentration tested.

Justification for selection of skin sensitisation endpoint:
This substance is a representative fatty acid salt that can be read across to the calcium salts of C14-C22 fatty acids category

Respiratory sensitisation

Endpoint conclusion

Endpoint conclusion:

no study available

Justification for classification or non-classification

No classification required. Stimulation Index <3 in a LLNA