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EC number: 613-645-3 | CAS number: 646505-36-4
The following remarks on toxicokinetics are based on the physico-chemical properties of Desmorapid 01 and on toxicological data. Experimental studies on toxicokinetics were not performed.
Desmorapid 01 is used as catalyst in the manufacture of polyurethanes. During the reaction of diisocyanates with polyols Desmorapid 01 is fully and tightly integrated into the polymeric matrix. Because of its complex composition Desmorapid 01 is considered a UVCB substance.
Desmorapid 01 can be chemically described as ‘butanoic acid, 3-oxo-, methylester, reaction products with N,N-dimethyl-1,3-propanediamine and propylene glycol ether with trimethylol propane (3:1) (CAS-No. 646505-36-4)’ or (different description of the same substance) ‘poly [oxy(methyl-1,2-ethanediyl)], a-hydro-w-hydroxy-, ether with 2-ethyl-2-(hydroxymethyl)-1,3-propanediol (3:1), 3-[[3-dimethylamino) propyl]imino]butanoate’ (CAS-No. 857285-61-1). The closely related CAS-No. 179733-18-7 describes the same substance and differs only in the manufacturing process where ethanol is distilled off while for the other two CAS-Nos. methanol is distilled off (see IUCLID section 1.1). Thus, toxicological data for all three CAS-Nos. are considered relevant for the substance to be registered and are taken into account for human health assessment.
Desmorapid 01 is a yellow liquid (Prüm, 2010) with a very low vapour pressure under normal ambient conditions (0.0041 Pa at 20°C, Fonseca, 2012). Inhalation exposure to the vapour is therefore not to be expected. Desmorapid 01 is not used in industrial spray processes.
Limited oral and dermal absorption can be assumed based on the high mean molecular weight of about 630 g/mole (see IUCLID section 1.1), however, the water solubility of 600 mg/L (see IUCLID section 4.8) and the mean log Pow of 2.8 (Neuland, 2013) are favourable for absorption. In fact, at least some of the substance seems to be bioavailable in rats after repeated ingestion of high doses. In a 28 day oral toxicity study (Eiben, 2011) the limit dose of 1000 mg/kg bw and day (gavage) induced slight systemic toxicity in liver and thymus, indicating bioavailability. The next lower dose of 300 mg/kg bw constitutes the NOAEL in this study. No indications of systemic availability were observed after acute oral (Bomhard, 1993) exposure of rats to 2000 mg/kg bw as there were no systemic toxicological effects reported. However, slight clinical signs as breathing sounds after acute oral administration, focal inflammation of the glandular stomach in some animals after repeated oral administration and partial skin reddening after dermal application indicate irritating properties of the substance.
The log Pow of 2.8 does not indicate a relevant bioaccumulation potential of Desmorapid 01.
In skin and eye irritation studies (Krötlinger, 1994 a, b) the substance was proven as moderate skin irritant and severe eye irritant. Acute dermal application of high doses to rats did not result in systemic toxicity (Gillissen, 2010). However, after overcoming the skin barrier, Desmorapid 01 is bioavailable as was shown in a skin sensitization study on Guinea pigs. Desmorapid 01 has to be considered as a moderate skin sensitizer in the Guinea pig maximization test (Vohr, 1993).
Based on the negative results of three in vitro genotoxicity tests performed with and without metabolic activation (Ames Test, Nern, 2011; HPRT Test, Hall, 2011; Micronucleus test, Sutter, 2011) it can be assumed that DNA-reactive metabolites of Desmorapid 01 will not be generated in mammals in the course of hepatic biotransformation.
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