reaction mass of: pentasodium bis[6-anilino-3,5'-disulfonatonaphthalene-2-azobenzene-1,2'-diolato]cobaltate(III);tetrasodium [6-anilino-3,5'-disulfonatonaphthalene-2-azobenzene-1,2'-diolato][6-anilino-5'-sulfamoyl-3-sulfonatonaphthalene-2-azobenzene-1,2'-diolato]cobaltate(III);trisodium bis[6-anilino-5'-sulfamoyl-3-sulfonatonaphthalene-2-azobenzene-1,2'-diolato]cobaltate(III)

Endpoint summary

Description of key information

Skin sensitizer

Key value for chemical safety assessment

Skin sensitisation

Endpoint conclusion

Endpoint conclusion:

adverse effect observed (sensitising)

Additional information:

In order to assess the cutaneous allergenic potential of test substance, the GPMT and the Buhler assay were performed in accordance with OECD Guideline 406 (1992) and the method B.6 of EEC-Directive 96/54 EEC.

GUINEA PIG MAXIMISATION TEST (GPMT, OECD TG 406)

The test was performed in 15 (10 test and 5 control) male albino guinea pigs. The intradermal induction of sensitization In the test group was performed in the nuchal region with a 20 % dilution of the test item in PEG 300 and in an emulsion of Freund's Complete Adjuvant (FCA) / physiological saline. The epidermal Induction of sensitization was conducted for 48 hours under occlusion with the test item at 50 % in PEG 300 one week after the intradermal induction. The animals of the control group were intradermally induced with PEG 300 and FCA/physiological saline and epidermally induced with PEG 300 under occlusion. Two weeks after epidermal induction the control and test animals were challenged by epidermal application of the test item at 15 % in PEG 300 and PEG 300 alone under occlusive dressing. Cutaneous reactions were evaluated at 24 and 48 hours after removal of the dressing.

10 animals (at the 24-hour reading) and 8 (at the 48-hour reading) out of 10 test animals showed showed positive reactions after the challenge treatment with test item at 15% (w/w) in PEG 300. No skin effect was observed in the control group.

BUEHLER ASSAY (OECD TG 406)

20 male albino guinea pigs of the test group were treated topically with test item at 50 % in PEG 300 once a week for a 3 week induction phase. Two weeks after the final induction application the animals were challenged with the test item concentration of 25 % in PEG 300. 10 animals of the control group were not treated during the induction. They were treated once at challenge with test item at 25 % in PEG 300. None of the control and test animals were observed with skin reactions after the challenge treatment with the highest tested non-irritating concentration of test substance at 25 % in PEG 300. The highest tested non-irritating concentration used for challenge was 25 % in PEG 300.

None of the control and test animals were observed with skin reactions after the challenge treatment with the highest tested non-irritating concentration of test item at 25 % in PEG 300.

Respiratory sensitisation

Endpoint conclusion

Endpoint conclusion:

no study available

Justification for classification or non-classification

In the CLP Regulation (EC 1272/2008) a skin sensitizer is defined as “a substance that will lead to an allergic response following skin contact”. A substance classified as skin sensitiser (Category 1) may be allocated to one of the two sub-categories 1A or 1B in accordance with the criteria given in Annex I, Part 3, Table 3.4.2.. If classification is based on results obtained from studies conducted in experimental animals, the test results from the LLNA, GPMT and the Buehler assay can be used directly for classification. Guidance values are presented in the CLP Regulation (EC 1272/2008) in Annex I, Part 3, Table 3.4.3 for classification in sub-category 1A and in Annex I, Part 3, Table 3.4.4 for classification in sub-category 1B.

Based on the results from the GPMT performed, the substance induces a sensitisation rate of 80 -100 % after the challenge epidermal application of the test item at 15 % in PEG. This result meets the classification criterion for Skin sens. Cat. 1B “≥ 30 % responding at > 1 % intradermal induction dose”. On the contrary, results from the Buhler assay shown no skin reactions after the challenge treatment with the test item at 25 % in PEG 300. Even if the two different tests were both performed according to the OECD Guideline 406, clearly the two results are opposing.

Considering that:

- no significant deviations from the standardised followed methods that could lead to a lower reliability of the studies can be found;

- it should be recognised that there is often a degree of uncertainty associated with the derivation of allergenic potencies from both the GPMT and the Buhler, as also the “Guidance on the Application of the CLP Criteria – Version 5.0, July 2017” reported it should be considered a worst case approach;

- the substance is listed in the Annex VI of the CLP Regulation (EC 1272/2008)

the substance should be classified as Skin sens. Cat. 1B.