Octanoic acid, zinc salt, basic

Endpoint summary

Description of key information

No skin sensitisation study with Octanoic acid, zinc salt, basic is available, thus the skin sensitisation potential will be addressed with existing data on the moieties liberated upon dissolution zinc and octanoic acid, supported by human data on structurally similar zinc salts of fatty acids.

Octanoic acid, zinc salt, basic is not expected to show signs of dermal sensitisation, since the two moieties zinc and octanoic acid have not shown any skin sensitisation potential in experimental testing. Furthermore, human data on structurally similar zinc salts of fatty acids do not indicate sensitising potential as well.

Key value for chemical safety assessment

Skin sensitisation

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not sensitising)

Additional information:

Octanoic acid, zinc salt, basic

Octanoic acid, zinc salt, basic is not expected to show signs of dermal sensitisation, since the twoassessment entitieszinc and octanoic acid have not shown any skin sensitisation potential in experimental testing. Furthermore, human data on structurally similar zinc salts of fatty acids do not indicate sensitising potential as well. Thus, octanoic acid, zinc salt, basic is not to be classified according to regulation (EC) 1272/2008 as skin sensitising.

Read-across approach and conclusion are in line with the EU risk assessment carried out on the structurally similar substance Fatty acids, C16-18, zinc salts (i.e. zinc stearate) within the framework of EU Existing Chemicals Regulation 793/93 (EU RAR Zinc stearate (CAS# 91051-01-3, CAS# 557-05-1) Part II–Human Health. EUR 21168 EN (http://echa.europa.eu/documents/10162/08799aec-42c5-44e0-9969-baa022c66db1): “Animal data on skin sensitisation are not available for zinc distearate. However, based on the accepted derogation and the fact that zinc oxide is not a skin sensitiser, it is consequently concluded that zinc distearate is not likely to be skin sensitising, and therefore does not need to be classified/labelled. This is supported by the fact that the use of zinc distearate in pharmaceutical and cosmetic products is without reported skin sensitisation effects.”

Further testing is not required.

Please refer to the respective assessment entity section for data on the moieties zinc and octanoic acid. In brief:

Zinc

The skin sensitising potential of zinc oxide (purity 99.69%) was investigated in female Dunkin Hartley guinea pigs in two well-performed maximisation tests, conducted according to Directive 96/54/EC B.6 and OECD guideline 406. Based on the results of a preliminary study, in the main studies experimental animals (10 in each test) were intradermally injected with a 20% concentration and epidermally exposed to a 50% concentration (i. e. the highest practically feasible concentration). Control animals (5 in each test) were similarly treated, but with vehicle (water) alone. Approximately 24 hours before the epidermal induction exposure all animals were treated with 10% SDS. Two weeks after the epidermal application all animals were challenged with a 50% test substance concentration and the vehicle. In the first study, in response to the 50% test substance concentration skin reactions of grade 1 were observed in 4/10 experimental animals 24 hours after the challenge (40% sensitisation rate), while no skin reactions were evident in the controls. In contrast, in the second study no skin reactions were evident in the experimental animals (0% sensitisation rate), while a skin reaction grade 1 was seen in one control animal. The skin reaction observed in one control animal is probably a sign of non specific irritation (Van Huygevoort, 1999b1, 1999b2).

In a third well-performed maximisation test, conducted according to the same guidelines and with the same experimental design, another analytical grade zinc oxide was tested (Zincweiß Pharma A; purity 99.9%). The only difference with the studies described above was the intradermal induction concentration, which was 2% as for Zincweiß Pharma A this was considered the highest concentration that could reproducibly be injected. In this test no skin reactions were evident in both experimental and control animals, hence a 0% sensitisation rate for Zincweiß Pharma A. White staining of the treated skin by the test substance was observed in some animals 24 and 48 hours after challenge (Van Huygevoort, 1999a).

Human data:

In a human patch test performed with 100 selected leg-ulcer patients, 11/100 patients gave an allergic reaction with zinc ointment (60% ZnO and 40% sesame oil). However, 14/81 patients gave a positive response when treated with sesame oil alone. This study does not give any indication for a skin sensitizing potential of zinc oxide in humans (Malten and Kuiper, 1974).

The effect of zinc oxide on contact allergy to colophony was investigated. With 14 patients with earlier history of moderate patch test reactions to colophony (a patch test) with 10% ZnO (2.3 mg Zinc/cm²) with and without colophony was performed. No positive response was observed in the 14 patients when only a 10% solution of zinc oxide was used. The addition of zinc oxide to colophony decreased the allergic reaction induced by colophony (Söderberg et al., 1990).

 

Octanoic acid

Octanoic acid is a naturally occurring saturated C8- fatty acid, which is present in milk of various mammals and also in coconut oil and palm kernel oil. Based on this, the following endpoint is covered by publicly available data on fatty acids with the same or similar structure.

The non-sensitising properties of fatty acids were demonstrated in a skin sensitisation study in 28 volunteers. “Five 48-hour covered applications of 1% decanoic acid (C10) in petrolatum were made over a 10 day period. The results were negative since none gave positive reactions when challenged 10-14 days after the induction phase with a final 48-hour closed patch test using 1% in petrolatum (IUCLID, 2000a)” (HERA, 2002).

Further, KeratinoSens is one of the validated alternative methods for testing sensitisation in vitro. Octanoic acid and various other substances were used throughout the validation process of this system. The already known non-sensitising properties of octanoic acid determined in in vivo-experiments were proved once again in the KeratinoSens assay (Emter, R. et al.; 2010).

Structurally similar zinc salts of fatty acids

In studies in humans, two eye shadow formulations, each containing 10% Fatty acids, C16-18, zinc salts, were tested in the Schwartz-Peck Prophetic Patch assay and the Draize-Shelanski Repeated Insult Patch Assay. Both tests resulted in “virtually 0 reactions”. One of the formulations was applied twice daily for 28 days to 52 females. No “irritation or sensitisation” was noted when examined up to four weeks after application (CIR, 1982). Also a test on human volunteers twice a day for 28 days treated with a cosmetic formulation (eye shadow product) containing Fatty acids, C26-28, zinc salts, gave no indication on a sensitising activity. Reliable, adequate and relevant animal and human data on slightly soluble zinc oxide indicated no skin sensitising potential.

 

Respiratory sensitisation

Endpoint conclusion

Endpoint conclusion:

no study available

Justification for classification or non-classification

Octanoic acid, zinc salt, basic is not expected to show signs of dermal sensitisation, since the two moieties zinc and octanoic acid have not shown any skin sensitisation potential in experimental testing. In addition, human data on structural similar zinc salts of fatty acids also do not indicate sensitising potential. Thus, Octanoic acid, zinc salt, basic is not to be classified according to regulation (EC) 1272/2008 and its subsequent amendments as skin sensitising.