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Description of key information

No specific toxicokinetic studies are available and none are required according to the REACH Regulation. Based on physicochemical data, toxicity data and theoretical assessment, the basic toxicokinetics of 2-Oxepanone, polymer with 1,6-hexanediol can be adequately characterised. The substance is likely to be rapidly and extensively absorbed following oral or inhalation exposure, absorption following dermal exposure is likely to be less extensive and more gradual. Rapid and extensive distribution is predicted. Extensive metabolism of the substance is predicted, indicating that excretion is rapid and bioaccumulation is unlikely.

Key value for chemical safety assessment

Bioaccumulation potential:
no bioaccumulation potential
Absorption rate - oral (%):
50
Absorption rate - dermal (%):
50
Absorption rate - inhalation (%):
100

Additional information

No specific studies are required. According to Column 1 of Annex VIII of the REACH regulation, assessment of the toxicokinetic behaviour of the substance (to the extent that can be derived from the relevant available information) is required and this is provided. An adequate assessment of the basic toxicokinetics of the substance can be made from the existing toxicity data and theoretical considerations, without the need for specific testing.

Absorption

Data indicate that 2-Oxepanone, polymer with 1,6 hexanediol is hydrolytically stable at physiological temperature and pH; therefore no degradation is assumed in the gastrointestinal tract. Oral absorption is predicted for the lower molecular weight components of the substance (hexanediol; hexanediol + 1-3 ECL) based on the water solubility and moderate Log Pow values; however oral absorption of hexanediol + 3 ECL may be limited. The molecular weights and low water solubility of the other components (hexanediol + 4-7 ECL) mean that oral absorption is not predicted.An assumption of 50 % oral absorption may be made for the purposes of risk assessment, according to REACH guidance. The physicochemical properties of 2-Oxepanone, polymer with 1,6 hexanediol favour dermal absorption for the lower molecular weight components; dermal absorption of the high molecular weight components is likely to be low. The low vapour pressure of 2-Oxepanone, polymer with 1,6 hexanediol means that substance coming into contact with the skin will not be significantly lost through volatilisation. Dermal absorption is therefore predicted, but is likely to be less rapid and extensive than oral absorption. In the absence of specific data, a default, conservative dermal absorption value of 50% may be assumed for 2-Oxepanone, polymer with 1,6 hexanediol, according to REACH guidance and on the basis that dermal absorption will not exceed oral absorption (i.e. the same extent as oral absorption). 2-Oxepanone, polymer with 1,6 hexanediol is non-volatile; therefore inhalation exposure is not predicted unless the substance is used in situations in which liquid aerosols may be generated (e.g. by spraying). If inhalation exposure were to occur, absorption is potentially extensive. A default assumption of 100% inhalation absorption may be made, if required, for the purposes of risk assessment.

Distribution

Based on its water solubility, the systemic distribution of absorbed 2-Oxepanone, polymer with 1,6 hexanediol low molecular weight components and its predicted metabolites is likely to be rapid and extensive following oral, dermal or inhalation exposure.

Metabolism

OECD QSAR Toolbox predicts metabolism via hydrolysis of the ester groups, with the initial liberation of 1,6-hexanediol and 6-hydroxyhexanoic acid. Additional metabolism may occur through sequential oxidation of the terminal alcohol groups to form the corresponding aldehydes and carboxylic acids.  6-hydroxyhexanoic acid may be further metabolised by oxidation to adipic acid; 1,6-hexanediol is likely to be further metabolised by sequential oxidation to 6-hydroxyhexanoic acid and adipic acid. Adipic acid is known to be incorporated into normal metabolism through β-oxidation.

Excretion

The predicted metabolites of 2-Oxepanone, polymer with 1,6 hexanediol are of low molecular weight and high water solubility and are therefore likely to be subject to rapid urinary excretion. 6-hydroxyhexanoic acid and adipic acid are likely to be excreted in urine; the incorporation of adipic acid into normal metabolism has been shown to result in excretion as carbon dioxide, urea, glutamic acid, lactic acid and citric acid. 

Bioaccumulation potential

Based on the likely metabolic pathway and rapid excretion of metabolites, bioaccumulation is not predicted for 2-Oxepanone, polymer with 1,6 hexanediol.

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