Dibutyl terephthalate

Endpoint summary

Key value for chemical safety assessment

Skin sensitisation

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not sensitising)

Additional information:

The potential for dibutyl terephthalate to cause dermal sensitization was evaluated using data from a local lymph node assay (LLNA) conducted in mice according to OECD Guideline 429 and a repeat insult patch test conducted in humans according to sound scientific principles. In the LLNA, concentrations of 25%, 50% or 100% of the test material were applied to the dorsal surface of each ear of groups of 5 female mice for three consecutive days. Exposure to the undiluted material resulted in a stimulation index of > 3 while the 25% and 50% solutions resulted in a stimulation index of < 3. According to the protocol for this assay, a stimulation index > 3 indicates the test material is regarded as a sensitizer. There were no other clinical signs of toxicity in the study. In the repeat insult patch test, the test material was evaluated in a group of 208 male and female human volunteers ranging in age from 16 to 79 years. The test material was applied three (3) times per week for three (3) weeks under occlusion for twenty-four (24) hours to the upper back between the scapulae. Approximately two (2) weeks after the final induction patch application, a challenge patch was applied to a virgin site adjacent to the original induction patch site following the same procedure as described for induction. Except for a moderate response in a single individual on one occasion and a slight reaction after another induction, there was no evidence of dermal irritation or allergic contact sensitization in the other 207 subjects in this study. Dibutyl terephthalate was not classified as a skin sensitizer in humans in this study.

Migrated from Short description of key information:
A guideline LLNA in mice indicates the undiluted material has a potential for skin sensitization. However, adequate human data from a repeated insult patch test indicates no sensitization potential. Thus, the material is not rated as a skin sensitizer.

Justification for classification or non-classification

According to the GHS guidelines, positive effects seen in either humans or animals will normally justify classification. However, in making the decision to classify when there is conflict between the results, respondents are directed to assess the quality and reliability of the evidence from both sources. While evidence from animal studies is usually more reliable because it is obtained under controlled conditions, the repeat insult patch test with dibutyl terephthalate was conducted in a controlled experiment with 208 human volunteers for the purpose of hazard classification. Based on an absence of response in the repeat insult patch test, dibutyl terephthalate is not classified for “Skin Sensitization” or Skin Irritation” according to the GHS guidelines.