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Administrative data

Link to relevant study record(s)

Reference
Endpoint:
basic toxicokinetics in vitro / ex vivo
Type of information:
other: Assessment, based on physico-chemical properties of the compound and on toxicological data. Experimental toxicokinetic studies were not performed.
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
The assessment of the toxicokinetik of cyclohexane, 5-isocyanato-1-(isocyanatomethyl)-1,3,3-trimethyl-, homopolymer, caprolactam-blocked (IPDI homopolymer, caprolactam-blocked) is based on physico-chemical properties of the compound and on toxicological data. Experimental toxicokinetic studies were not performed.
Principles of method if other than guideline:
Assessment on toxicokinetics

The remarks on the toxicokinetics of cyclohexane, 5-isocyanato-1-(isocyanatomethyl)-1,3,3-trimethyl-, homopolymer, caprolactam-blocked (IPDI homopolymer, caprolactam-blocked) are based on physico-chemical properties of the compound and on toxicological data. Experimental toxicokinetic studies were not performed.

Description of key information

There were no studies available in which the toxicokinetic properties (absorption, distribution, metabolism, elimination) of cyclohexane, 5-isocyanato-1-(isocyanatomethyl)-1,3,3-trimethyl-, homopolymer, caprolactam-blocked (IPDI homopolymer, caprolactam-blocked) were investigated. Based on the molecular structure, molecular weight, water solubility, and octanol-water partition coefficient significant oral, inhalative and dermal absorption is not expected. In fact, the available data give no indications for systemic availability, since no systemic toxicity could be concluded from the animal studies at all.

Key value for chemical safety assessment

Additional information

Cyclohexane, 5-isocyanato-1-(isocyanatomethyl)-1,3,3-trimethyl-, homopolymer, caprolactam-blocked (CAS No. 127184-53-6); Information/Assumptions regarding toxicokinetics

The following remarks on the toxicokinetics of cyclohexane, 5-isocyanato-1-(isocyanatomethyl)-1,3,3-trimethyl-, homopolymer, caprolactam-blocked are based on physiochemical properties of the compound and on toxicological data. Experimental toxicokinetic studies were not performed.

Cyclohexane, 5-isocyanato-1-(isocyanatomethyl)-1,3,3-trimethyl-, homopolymer, caprolactam-blocked is a oudor- and colourless solid (powder) having a molecular weight of ca. 1000 g/mol. It has an extremely low vapour pressure (< 6 * 10-11hPa at 20°C; Dornhagen, 2012) and is practically insoluble in water (ca. 0.1 µg/l at 20 °C; Lange, 2012) under normal ambient conditions. The partition coefficient octanol/water was determined as log Kow = 8.6 - 9.6 at 23.3 °C (Goller, 2012) and calculated as log Kow = 15.22 indicating a lipophilic character of the substance. In a preliminary hydrolysis test, less than 10% of the substance was observed to hydrolyse at 50°C at pH 4,7 and 9 after 120 hours (Lange, 2012). In the molecular structure of cyclohexane, 5-isocyanato-1-(isocyanatomethyl)-1,3,3-trimethyl-, homopolymer, caprolactam-blocked no functional groups with relevant acidic or basic character can be found. Therefore, no significant dissociation is expected at physiological pH values and beyond. The site of blocking is known to be physically stable. Only at elevated temperatures of > 90 °C a de-blocking occurs and reactive groups are released.

Oral and GI absorption: Due to a very high hydrolysis half-life of cyclohexane, 5-isocyanato-1-(isocyanatomethyl)-1,3,3-trimethyl-, homopolymer, caprolactam-blocked it is not expected that the substance is significantly hydrolysed in the gastro-intestinal tract. Furthermore, due to the relatively high molecular weight and the very low water solubility of the substance oral absorption is not expected. In fact, the acute oral toxicity is very low with a LD50(rat) of > 10000 mg/kg bw (Hüls AG, 1986). Necropsy showed only partial hyperemia of small intestine mucosa and stomach mucosa in two animals. No other systemic signs could be observed.

Dermal absorption: Dermal penetration of cyclohexane, 5-isocyanato-1-(isocyanatomethyl)-1,3,3-trimethyl-, homopolymer, caprolactam-blocked could not be excluded based on a log Kow that shows a high lipophility. Otherwise, due to the high moelcular weight a significant dermal absorption is not expected. In fact, no signs of systemic toxicity were observed in an acute dermal irritation/corrosion study (Hüls AG, 1986). No indications for a dermal uptake could be concluded from two skin sensitization tests (Buehler test (Hüls AG, 1996) and guinea pig maximization test (RTC, 2000)), since no skin sensitization potential was detected.

Respiratory absorption: Due to the very low vapour pressure of the substance significant respiratory absorption via vapour is not expected. Furthermore, highly lipophilic compounds (log Kow > 4), particular those that are poorly soluble in water (1 mg/l or less), are expected to be poorly absorbed. In fact, there are no indications of systemic toxicity and systemic availability after inhalative exposure of the aerosol for 14 days. No treatment-related clinical abnormalities were observed after the first two days of exposure. Mortality did not occur (TNO, 2012).

Distribution: The physico-chemical information (high molecular weight, low vapour pressure, lipophilicity and low water solubility) indicates that cyclohexane, 5-isocyanato-1-(isocyanatomethyl)-1,3,3-trimethyl-, homopolymer, caprolactam-blocked could be distributed only to a low amount.

Accumulative potential: Bioaccumulation potential could not be excluded based on the physico-chemical data (e.g. log Pow). However, no indications of systemic availability could be concluded from the available animal studies, and therefore an accumulation potential for the substance seems to be questionable.

Excretion: No data are available regarding the excretion of absorbedcyclohexane, 5-isocyanato-1-(isocyanatomethyl)- 1,3,3- trimethyl-, homopolymer, caprolactam-blocked. Based on the results of several in vitro genotoxicity tests (LPT, 2012; all performed with and without metabolic activation) it is concluded that DNA-reactive metabolites of cyclohexane, 5-isocyanato-1-(isocyanatomethyl)-1,3,3-trimethyl-, homopolymer, caprolactam-blocked will not be generated in mammals in the course of hepatic biotransformation.