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Administrative data

Link to relevant study record(s)

Description of key information

Absoption by the oral, dermal and inhalation routes is expected. Moreover, distribution through extracellular body fluids is likely. The formation of reactive metabolites is unlikely. Excretion will most likely occur via the urine. No bioaccumulation is expected.

Key value for chemical safety assessment

Bioaccumulation potential:
no bioaccumulation potential

Additional information

In line with chapter R.7 c (ECHA, 2012) the main toxicokinetic properties of N-Vinylcaprolactam (CAS No. 2235-00-9, 1-vinylhexahydro-2H-azepin-2-one) are assessed on the basis of its physico-chemical properties and with special regard to the results of the standard toxicity studies performed with this substance. Specific toxicokinetics or dermal absorption studies are not available for N‑Vinylcaprolactam.

 

1.        Relevant physico-chemical properties of N-Vinylcaprolactam

Molecular weight:    139.2 g/mol

logPow:                     1.2 (at 25 °C, pH 7.2)

Water solubility:        49.3 g/L (at 20 °C, pH 6.8)

Vapour pressure:     0.03 hPa (at 20 °C)

Boiling point:            250.4 °C (at 1013.25 hPa)

Hydrolysis:                As a tertiary aliphatic amine containing a keto-group, should be generally resistant towards hydrolysis.

Surface tension:       Based on chemical structure, no surface activity is predicted.

Particle size:             Substance is marketed or used in a non-solid or granular form.

 

2.        Absorption:

Based on its low molecular weight, moderate logPow and relatively high water solubility N‑Vinylcaprolactam is likely to be absorbed in the GI tract. The moderate logPow value of 1.2 (at 25°C, pH 7.2) indicates that the substance is lipophilic, i.e.in the range between -1 and 4, and will thus diffuse well across plasma membranes. In addition, gastro-intestinal absorption of N‑Vinylcaprolactam is considered to be triggered by passage through aqueous membrane pores or carriage with the bulk passage of water, which is favoured for small (molecular weight < 200 g/mol), water soluble substances. It is unclear whether an active transport for N-Vinylcaprolactam exists.

Overall, quantitative gastrointestinal absorption is expected for N-Vinylcaprolactam, based on its physicochemical properties.

 

With a logPow value between -1 and 4 and in view of the above considerations for the oral route of exposure, N-Vinylcaprolactam is considered to be absorbed directly across the respiratory tract epithelium by passive diffusion when its vapour or particles reach the alveolar regions of the lungs. However, based on the low volatility and the high boiling point exhibited by N-Vinylcaprolactam, generally only low amounts of the substance will be available for inhalation under ambient conditions.

 

With respect to the physicochemical properties (molecular weight, logPow and water solubility) and that N-Vinylcaprolactam is a skin sensitizer in the Local Lymph Node Assay, it is concluded that dermal absorption occurred.

 

This assessment is substantiated by signs of systemic toxicity noted in acute and repeated dose toxicity studies following oral, dermal and/or inhalation exposure.

 

3.        Distribution/Metabolism:

Distribution of N-Vinylcaprolactam to CNS could be demonstrated by the clinical signs (like slight convulsion and narcotic-like state) observed in an acute oral toxicity study in rats (BASF AG, 1963). The logPow >0 and the good water solubility of N-Vinylcaprolactam support this conclusion.

 

As the liver as the organ with the greatest metabolic capacity was affected by increased liver weights and increased gamma-glutamyl transferase activity in an oral repeated dose 90-day study (BASF AG, 1991), it could be concluded that N-Vinylcaprolactam will be metabolised in rats. This conclusion is supported by the fact that the clinical observations related to CNS in the acute oral toxicity study were reversible after 2-4 days p.a.

 

Generally, metabolism will render a xenobiotic molecule more polar and harmless, leading to fast and quantitative excretion. For N-Vinylcaprolactam, no conversion into a metabolite that was more cytotoxic or more genotoxic than the parent substance was noted when comparing in vitro test results with metabolic activation to in vitro test results without metobolic activation system (genetic toxicity tests). Based on this, a clear indication is given that the formation of reactive metabolites is unlikely.

 

4.        Excretion:

The low molecular weight (below 300 g/mol in the rat) and good water solubility of N‑Vinylcaprolactam lead to the conclusion that urinary excretion will be the most relevant route of excretion. This is considered to apply also to the potential polar metabolites of N‑Vinylcaprolactam. The log Pow indicates no potential for accumulation in the tissues.

 

Reference

- ECHA (2012). Guidance on information requirements and chemical safety assessment, chapter R.7c: Endpoint specific guidance. ECHA-12-6-23-EN.R.7.12 Guidance on Toxicokinetics.

- EFSA (2012). Guidance on dermal absorption. EFSA Journal: 10 (4), 2665.