Cyclohexanethiol

Endpoint summary

Key value for chemical safety assessment

Skin sensitisation

Endpoint conclusion

Endpoint conclusion:

adverse effect observed (sensitising)

Additional information:

A skin sensitisation study was conducted with cyclohexylmercaptan according to OECD 429 and in compliance with GLP. Test concentrations of 25, 50 and 100% in acetone/olive oil 4:1 were applied, resulting in stimulation indices (SI) of 13.61, 17.65 and 18.27. On the basis of these results it was concluded that cyclohexylmercaptan is a skin sensitiser.

The EC3 value was not reported in the study and the selected test concentrations were such that it is not possible to determine the value using linear interpolation between the two points immediately above and below SI = 3. For the purposes of classification according to the 2nd Adaptation to Technical Progress of Regulation (EC) No 1272/2008 it is therefore not possible to distinguish between sub-categories 1A and 1B for skin sensitisation based on this study alone. However, LLNA studies have been conducted on a number of other mercaptan substances including linear, branched and cyclic structures in the carbon number range C3 -C12. The results of these studies indicated that the substances required classification in category 1B with only one exception (n-dodecylmercaptan, linear C12), which met the criteria for classification in category 1A based on an EC3 value between 0.8 and 1.6%.

Migrated from Short description of key information:
In the key skin sensitisation study (Harlan, 2010), conducted according to OECD 429 (local lymph node assay) cyclohexylmercaptan was determined to be sensitising to skin based on stimulation indices of 13.61, 17.65 and 18.27 at test concentrations of 25, 50 and 100% in acetone/olive oil 4:1, respectively. The EC3 value was not reported.

Justification for selection of skin sensitisation endpoint:
The selected study is the only available skin sensitisation study for the registered substance. It was conducted according to an appropriate OECD test guideline and in compliance with GLP.

Respiratory sensitisation

Endpoint conclusion

Endpoint conclusion:

no study available

Justification for classification or non-classification

Based on the available in vivo skin sensitisation study, cyclohexylmercaptan is classified as a skin sensitiser. Weight of evidence from Local Lymph Node Assay studies performed with a range of linear, branched and cyclic mercaptans with carbon number in the range C3 -C12 indicates that classification in Category 1B is appropriate, with hazard statement H317 "May cause an allergic skin reaction", according to the criteria of Regulation (EC) No 1272/2008 and Regulation (EU) No 286/2011.