2,4,6-tri-tert-butylphenol

Endpoint summary

Key value for chemical safety assessment

Skin sensitisation

Endpoint conclusion

Endpoint conclusion:

adverse effect observed (sensitising)

Additional information:

An assessment of the potential for the test material to cause skin sensitisation was made in the mouse in a Local Lymph Node Assay (LLNA) study carried out in accordance with the standardised guidelines OECD 429, EU Method B.42 and US EPA OPPTS 870.2600 under GLP conditions. The study has been assigned a reliability score of 1 in line with the principles for assessing data quality as defined by Klimisch et al. (1997).

The test material concentrations selected for the main study were based on the results of a pre-screen test. In the main study, three experimental groups of five female CBA/J mice were treated with test material concentrations of 10, 25 or 50 % w/w on three consecutive days, by open application on the ears. Five vehicle control animals were similarly treated, but with vehicle alone (N,N-Dimethyl formamide).

Three days after the last exposure, all animals were injected with ³H-methyl thymidine and after five hours the draining (auricular) lymph nodes were excised and pooled for each animal.

After precipitating the DNA of the lymph node cells, radioactivity measurements were performed. The activity was expressed as the number of Disintegrations Per Minute (DPM) and a stimulation index (SI) was subsequently calculated for each group.

No irritation of the ears was observed in any of the animals examined. White staining of test material remnants on the dorsal surface of the ears of one animal treated at 10 % and all animals treated at 25 and 50 % did not hamper scoring for erythema.

 All auricular lymph nodes of the animals of the 10 % and control groups were considered normal in size. The auricular lymph nodes of two animals treated at 25 % and all animals treated at 50 % appeared larger in size. No macroscopic abnormalities of the surrounding area were noted for any of the animals.

Mean DPM/animal values for the experimental groups treated with test material concentrations 10, 25 and 50 % were 1155, 2289 and 3174 DPM, respectively. The mean DPM/animal value for the vehicle control group was 692 DPM. The SI values calculated for the material concentrations 10, 25 and 50 % were 1.7, 3.3 and 4.6, respectively.

These results indicate that the test material could elicit a SI ≥ 3. The data showed a dose-response and an EC3 value (the estimated test material concentration that will give a SI =3) of 22.2 % was calculated.

Under the conditions of this study, the test material is considered to be a sensitiser.

Migrated from Short description of key information:
The test material was determined to be a skin sensitiser in the LLNA.

Justification for selection of skin sensitisation endpoint:
Only one study available.

Respiratory sensitisation

Endpoint conclusion

Endpoint conclusion:

no study available

Justification for classification or non-classification

In accordance with the criteria for classification as defined in Annex I, Regulation (EC) No 1272/2008, the substance requires classification with respect to skin sensitisation as Category 1B (H317: May cause an allergic skin reaction).