Sodium bis[4-hydroxy-3-[(2-hydroxy-1-naphthyl)azo]benzenesulphonamidato(2-)]cobaltate(1-)

Endpoint summary

Description of key information

LLNA: not sensitizing (Harlan CCR, 2015)

Key value for chemical safety assessment

Skin sensitisation

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not sensitising)

Additional information:

In this study the test item Eukesolar Rubine EB Liquid - dried was assessed for its skin sensitising potential using the Local Lymph Node Assay (LLNA) in mice according to OECD 429 guideline and GLP (Harlan CCR, 2015). Test item suspensions at different concentrations were prepared in the vehicle DMF (dimethylformamide). The local lymph node assay is recommended by international test guidelines (e.g., OECD) as an animal test for predicting skin sensitisation in humans and provides a rational basis for risk assessment. The basic principle underlying the LLNA is that sensitisers induce a primary proliferation of lymphocytes in the lymph node draining the application site. The ratio of proliferation in test item treated groups compared to that in vehicle controls is termed the Stimulation Index (S.I.). Radioactive labeling is used to measure cell proliferations. For this purpose a local lymph node assay was performed using test item concentrations of 1, 2, and 5% (w/w). The highest concentration tested was the highest concentration that could be achieved whilst avoiding systemic toxicity and excessive local skin irritation (as determined by a pre-experiment). The animals showed neither any signs of systemic toxicity during the course of the study nor were any cases of mortality observed. A possible erythema of the ear skin could not be assessed in all dose groups due to the inherent colour of the test item. A statistically significant increase in ear weights was not observed in any treated group in comparison to the vehicle control group. Furthermore, for BALB/c mice, a cut-off value of 1.1 for the ear weight index was reported for a positive response regarding ear skin irritation. None of the indices determined for the test item treated groups reached or exceeded this threshold. A test item is regarded as a sensitiser in the LLNA if exposure to one or more test item concentration results in a 3-fold or greater increase in incorporation of 3HTdR compared with concurrent controls, as indicated by the Stimulation Index (S.I.). The estimated test item concentration required to produce a S.I. of 3 is referred to as the EC3 value. In this study Stimulation Indices (S.I.) of 1.27, 2.01 and 2.22 were determined with the test item at concentrations of 1, 2, and 5% (w/w) in DMF, respectively. A clear dose response was observed. An outlier was identified in both statistical outlier tests in the group treated with 1% test item concentration (DPM value determined for animal number 9). Another outlier was identified in the Grubb`s test only (DPM value determined for animal number 16). However, as exclusion of these outliers did not change the overall test result, the values in question were not excluded from any subsequent calculations. A statistically significant or biologically relevant increase in DPM values was not observed in any treated group in comparison to the vehicle control group. A statistically significant increase in lymph node weights was observed in the low dose group in comparison to the vehicle control group. This increase is most likely attributed to the data not being normally distributed. A statistically significant but biologically not relevant increase in lymph node cell count was observed in the mid and highest dose group in comparison to the vehicle control group. However the cut-off value of 1.55 for a positive response regarding the lymph node cell count index reported for BALB/c mice was not reached or exceeded in any dose group. Furthermore, stimulation indices of all dose groups were well below the threshold value of 3 for a positive response.

The test item Eukesolar Rubine EB Liquid - dried was thus not a skin sensitiser under the test conditions of this study.

Justification for classification or non-classification

Based on the results of the LLNA, no classification is required.