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EC number: 941-496-7
CAS number: 1689576-89-3
Treated animals showed a very low degree of change in irrtation scores
over the induction period.
Animals treated with low, mid or high induction concentrations exhibited
equivocal responses to high challenge concentrations of the test
material. Only one definitive response (score of 1) was seen at a low
induction dose to the mid-high challenge concentration.
No skin sensitization data exist for the target substance 44MDI/1,3-BD/TPG/PG. This endpoint is satisfied by weight of evidence and read across from six valid skin sensitization studies performed with 4,4’-MDI, 2,2’-MDI, 4,4’-MDI homopolymer, and 4,4’-MDI/DPG, all belonging to the MDI category. All of the available studies are assigned Klimisch ratings of either 1 or 2.
All substances of the MDI category share similar chemical features namely that they a) all contain a significant amount of mMDI, and b) contain at least two NCO functional groups per molecule which are bound to an aromatic ring, and this ring is connected to a second aromatic ring by a methylene group. It is the NCO value (driven by the low molecular weight bioaccessible groups on monomeric MDI and three-ring oligomer) which is responsible for chemical and physiological reactivity and subsequent toxicological profile. As mentioned above, all substances of the MDI category contain a high content of monomeric MDI. This is key to the hypothesised MoA for all substances of the MDI category.
Since it has been demonstrated that NCO value (as attenuated by solubility) is responsible for toxicity and the higher molecular weight, low solubility components do not contribute to the observed toxicity, it is reasonable to assume that their presence in these mixtures diminishes the overall toxicity causing variation in effect. However, as all substances contain sufficient bioaccessible MDI constituents to elicit effects, a worst-case approach is adopted in which the most bioaccessible substances are read across to all substances of the MDI category. Accordingly, the harmonized CLP classification (Category 1, H317) for 4,4’-MDI is adopted for all substances of the MDI category, including 44MDI/1,3-BD/TPG/PG.
For more details see category justification document attached in IUCLID section 13.
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