tert-butylphenyldiphenyl phosphate (tBuTPP)

Endpoint summary

Key value for chemical safety assessment

Skin sensitisation

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not sensitising)

Additional information:

The supporting study is a mouse Local Lymph Node Assay. Under the conditions of the study, Stimulation Indices (SI) of 3.36, 4.00, and 3.24 were calculated for 25%, 50%, and 100% Phosflex 71B, respectively. Considering the SI threshold value of 3 as stated in Annex I of 1272/2008/EC and Annex VI of 67/548/EEC, the substance needs to be classified as a sensitizer.

In the LLNA test, the SI was >3 in all concentrations tested, however, no dose-response relationship was observed. The LLNA test is designed to study the induction phase of skin sensitization and usually provides quantitative data suitable for dose-response assessment. Furthermore, according to OECD guideline 429, the decision process with regard to a positive response includes a stimulation index ≥ 3, together with consideration of dose-response and, where appropriate, statistical significance.

It is not clear why no dose-response was observed in this study. A potential cause may be that the substance reached a maximum saturation in the skin, which is supported by the expectation based on the log Kow of this read-across substance (4.85) that uptake into the stratum corneum will be high, but the rate of penetration may be limited by the value of transfer between the stratum corneum and the epidermis. Therefore, a new study should be performed with lower concentrations to enable the calculation of an EC3 value.

 

To verify the potential sensitizig effects in humans, a Human Patch test was performed. This study was regarded as the key study. This test was initiated because there was a doubt about the validity of the test in relation to humans, as no major incidences have been recorded at the production site nor from downstream users regarding sensitization. The substance is being produced over 40 years in US production facilities.

The result of the Patch test was clearly negative, and this result in combination with the fact that there is no human epidemiological data that shows that the substance causes sensitization, it was concluded that it does not need to be classified for sensitization classification of the substance under CLP.

Migrated from Short description of key information:
A Mouse Local Lymph Node Assay (LLNA) (according to OECD 429) resulted in the conclusion that the substance is sensitising , A Patch test on humans however indicated that the substance is non-sensitizing, case study production facility, no incidences of sensitization known.

Respiratory sensitisation

Endpoint conclusion

Endpoint conclusion:

no study available

Justification for classification or non-classification

Based on the outcome of the Human Patch test in combination with worker information from the production facility, it was not deemed necessary to classify the substance for sensitization.