3-Isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate, oligomers, 2-Hydroxy-1(2)- methylethyl carbamate blocked

Endpoint summary

Description of key information

LLNA: not sensitizing

Key value for chemical safety assessment

Skin sensitisation

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not sensitising)

Additional information:

The skin sensitizing potential of the test substance was assessed by using the radioactive Murine Local Lymph Node Assay. The assay simulates the induction phase for skin sensitization in mice. It determines the response of cells in the auricular lymph nodes to repeated application of the test substance to the dorsal skin of the ears. 

Groups of 5 female CBA/CaOlaHsd mice each were treated with 10%, 25% and 50% (w/w) preparations of the test substance in methyl ethyl ketone (MEK) or with the vehicle alone.
The study consisted of 3 test groups and 1 control group. Each test animal was treated with 25 µL per ear of the appropriate test-substance preparation applied to the dorsal surfaces of both ears on three consecutive days. The control group was treated with 25 µL per ear of the vehicle alone. 

Three days after the last application, 20 µCi³H-thymidine in 250 µL sterile saline were injected into the tail vein of the mice. About 5 hours after the³H-thymidine injection, the mice were sacrificed and the auricular lymph nodes were removed. Lymph node response was evaluated by measuring³H-thymidine incorporation (indicator of cell proliferation). Cell counts and weights of each animal’s pooled lymph nodes were also determined. In addition, a 0.8cm diameter sample was punched out of the apical part of each ear and for each animal the weight of the pooled punches was determined to obtain an indication of possible skin irritation. 

No signs of systemic toxicity were noticed in all animals during general observation.

When applied as 10%, 25% and 50% preparation in MEK, the test substance did not induce a biologically relevant (no increase above the cut-off Stimulation Index of 3) or statistically significant increase of³H-thymidine incorporation into the cells from the auricular lymph nodes. 

Concomitantly, all concentrations did not induce a biologically relevant (no increase to 1.5-fold or above of control value = stimulation index (SI) ≥ 1.5) or statistically significant response in the auricular lymph node cell counts.

Statistically significant increases in lymph node weights were noted at the 25% and 50% concentration but were considered not to be biologically relevant, as the corresponding S.I.s for³H-thymidine incorporation and cell counts did not reach or exceed the cut-off values. 

The 50% test-substance concentration caused a statistically significant but not biologically relevant increase (SI > 1.25) in ear weights demonstrating the absence of relevant ear skin irritation. Slight test compound residues were noted in all animals at the 50% concentration during the observation period. 

Thus, it is concluded that the test substance does not exhibit a skin sensitizing potential in the Murine Local Lymph Node Assay under the test conditions chosen.

Respiratory sensitisation

Endpoint conclusion

Endpoint conclusion:

no study available

Justification for classification or non-classification

Based on the available data, the test substance is not classified with regard to sensitization according to Directive 67/548/EEC (DSD) and Regulation (EC) No 1272/2008 (CLP), respectively.