Registration Dossier
Registration Dossier
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EC number: 938-708-5 | CAS number: -
Endpoint summary
Administrative data
Link to relevant study record(s)
Description of key information
Key value for chemical safety assessment
- Bioaccumulation potential:
- no bioaccumulation potential
Additional information
The following remarks on the toxicokinetics of Desmodur RC (TDI Trimer) are based on physico-chemical properties of the compound and on toxicological data. Experimental toxicokinetic studies were not performed.
Desmodur RC is a white organic solid with a very low vapour pressure under normal ambient conditions (0.0011 Pa at 20°C), therefore inhalation exposure to the vapour is expected to be negligible. Acute inhalation of a liquid aerosol (dust) of Desmodur RC (25% in ethyl acetate) inhalable to rats revealed no signs of systemic toxicity at the maximum attainable concentration of 1839 mg/m3 air (Pauluhn, 2011). Even subacute (4-week) inhalation of Desmodur RC (25% in ethyl acetate) liquid aerosol to rats revealed no signs of systemic toxicity (Pauluhn, 2012). Due to the lack of systemic toxicity there is no proof of systemic availability after inhalation exposure.
At ambient temperature Desmodur RC undergoes a complete hydrolysis reaction in demineralized water within 24 hours and remains as hydrolysis product in form of an undissolved solid residue (Neuland, 2012). Due to hydrolytic instability of Desmodur RC in aqueous solutions neither water solubility nor log Pow value were determinable. Under physiological conditions it is expected that Desmodur RC decomposes in the GI tract mainly into oligomeric and polymeric ureas. Therefore intestinal absorption of Desmodur RC subsequent to oral ingestion may be limited. This assumption is confirmed by the data on acute oral toxicity in rats (LD50 ≥ 5000 mg/kg bw). In this study a dose of 2000 mg/kg bw was tolerated without mortalities, clinical signs, effects on weight gain or gross pathological findings (Gillissen, 2010).
An acute skin irritation study on rabbits revealed no systemic intolerance reactions after application of 0.5 g Desmodur RC moistened with corn oil (Gmelin, 2010). In this study a slight dermal irritation was seen. On the other hand, Desmodur RC proved as a moderate skin sensitizer in a local lymph node assay (LLNA) in mice (Vohr, 2011), therefore at least some dermal bioavailability after dermal contact is expected.
Based on the results of three in vitro genotoxicity tests (negative with and without metabolicactivation in an Ames test (Sutter and Köppe, 2011), in a HGPRT test (Hall, 2011) as well as in a chromosome aberration test (Nebelung, 2011) it is concluded that DNA-reactive metabolites of Desmodur RC will most probably not be generated in mammals in the course of hepatic biotransformation.
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