Cyclohexanol, 4-(1,1-dimethylethyl)-, trans-

Endpoint summary

Description of key information

Skin sensitisation: not sensitising (EU method B.6; OECD 429; GLP compliant).

Key value for chemical safety assessment

Skin sensitisation

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not sensitising)

Additional information:

Skin sensitisation

The potential for skin sensitization was evaluated in a weight-of-evidence-approach. For this purpose three studies were used. One animal study (2008, EU method B.6; GLP compliant) is considered to be reliable without restrictions for this kind of substance. According to the results of this test, the substance does not have a sensitising potential. Furthermore, one animal study (2009, OECD 429; GLP compliant) is considered to be reliable with restrictions and again shows that the substance does not have a sensitising potential. However, a third reference (2009; OECD 429; GLP compliant) reliable with restrictions stated results, which indicated that the test substance is considered to be a skin sensitiser.

 

Given that the substance lacks any significant capacity to cause skin irritation (please refer to Section 7.3.1 Skin irritation / corrosion, skin reactions seen in sensitisation testing ought, most probably, to indicate the presence of allergenic hazard. However, two well conducted predictive assays which used high purity test samples (98% or greater), a GPMT (reference 2008)) and a LLNA (reference 2009)), were both convincingly negative. This conclusion was supported by a predictive human sensitisation test (please refer to Section 7.10.4 Sensitisation data (humans)). Furthermore, the chemical structure of the test substance, is not one likely to be associated with the reactive chemistry of skin sensitisation (Roberts et al. (2007))*.

 

Set against this, the other LLNA (reference 2009), conducted with a less pure sample and in a different vehicle, gave a weakly positive result. Added to this was the (unconfirmed) identification of a pre-sensitised individual in the HRIPT (please refer to Section 7.10.4 Sensitisation data (2009). It is possible that this individual was already sensitised to one of a number of related chemicals, e.g. p-tertbutylphenol, p-tert-butylcatechol etc., but it must be borne in mind that the chemistry of benzene and cyclohexane differs and that the understanding of cross reaction chemistry remains somewhat limited.

 

Search of the clinical literature does not yield any evidence of skin sensitisation to the test substance (e.g. Rietschel and Fowler (2008)**; Johansen et al. (2011)*** ), neither does a search of the internet via Google for “tertiary butyl cyclohexanol allergy”. Although the search is therefore consistent with a lack of skin sensitising activity associated with the test item, it must be recognised that this only represents an absence of evidence.

 

Based on the weight of available evidence, the test substance should not be classified as a skin sensitiser.

 

For more information please refer to the expert statement attached.

 

* (Roberts et al. (2007) Electrophilic chemistry related to skin sensitisation. Reaction mechanistic applicability domain classification for a published data set of 106 chemicals tested in the mouse local lymph node assay. Chemical . Research. Toxicology. 20, 44-60)

** Rietschel and Fowler (2008) Fisher’s Contact Dermatitis, 6th edition. BC Decker, Hamilton.

*** Johansen et al. (2011) Contact Dermatitis, 5th edition. Springer, Heidelberg

Justification for classification or non-classification

Classification, Labelling, and Packaging Regulation (EC) No 1272/2008

The available experimental test data are reliable and suitable for classification purposes under Regulation (EC) No 1272/2008.

 

Skin sensitisation

Based on a weight-of-evidence approach, the test item should not be classified as a skin sensitiser according to Regulation (EC) No 1272/2008 (CLP), as amended for the seventeenth time in Regulation (EU) No 2021/849.

 

Respiratory sensitisation

During long-year industrial practice no cases of hypersensitivity were observed till now by workers exposed exclusively to the test item. Thus, no classification as respiratory sensitiser according to regulation (EC) 1272/2008 is required up to now.