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Description of key information

Butane-1,3 -diol is absorbed after oral application, no quantification is possible on basis of the available data. In vitro data reveal that the substance is also absorbed through the skin. No information on absorption after inhalative exposure is available.

In vitro and in vivo data indicate that butane-1,3 -diol is rapidly metabolised to the physiological substrates beta-hydroxybutyrate and acetoacetate by alcohol and aldehyde dehydrogenases. In vivo studies with dogs point to a low bioaccumulation potential: 95% of the substance were eliminated from the plasma within 5 h.

Key value for chemical safety assessment

Bioaccumulation potential:
no bioaccumulation potential

Additional information

There are several studies on the toxicokinetics of 1,3-butylene glycol in vitro and in vivo. One study investigates the metabolism of radiolabelled R- and S-1,3-butylene glycol in perfused rat livers: Desrochers et al. (1992) investigated the a) uptake of the diol, b) contribution of the diol to ketogenesis, c) contribution of the diol to total fatty acid plus sterol synthesis, and d) conversion of S-1,3-butylene glycol into the (non physiological) metabolite S-3-hydroxybutyrate. Both enantiomers were taken up by the isolated and perfused livers of fed or starved rats at the same rate. R-1,3-butylene glycol were mainly transformed to the physiological ketone bodies R-3-hydroxybutyrate and acetoacetate. Only 29 -38% of the S-enantiomer were converted into physiological ketone bodies. The S-enantiomer was further metabolised to S-3-hydroxybutyrate (no natural compound), lipids and carbon dioxide.

Metabolism of 1,3-butylene glycol to the physiological substrates beta-hydroxybutyrate and acetoacetate has been described by several other studies which were performed with non-radiolabelled 1,3-butylene glycol in vivo and in vitro (Mehlmann et al., 1971, 1975; Tate et al., 1971; Muenst et al., 1981; Tobin et al., 1978). These studies further suggest that alcohol and aldyhyde dehydrogenases and the NAD+ regeneration system are involved in the metabolism of 1,3-butylene glycol.

The test substance has probably a low potential for bioaccumulation. This can be concluded from the findings on the extensive metabolism of the test item to physiological ketone bodies. Further, the findings by Münst et al. (1981) support this conclusion: Based on the graphical presentation it can be concluded that > 95% of 1,3-butylene glycol are eliminated within 5 hours from the plasma of dogs.

Dermal absorption of 1,3-butylene glycol has been investigated by Hatanaka et al. (1994) in vitro. These in vitro data with rat skin revealed that 1,3-butylene glycol can penetrate the skin, skin penetration was similar to that of ethylene glyocol in vitro. Investigations on the dermal absorption of ethylene glycol in vivo in rats and mice (Frantz et al., 1996, Xenobiotica 26: 1195 -1220) showed that the dermal absorption can vary over a wide range (26% -84%) within 96 hours under occlusive test conditions. Therefore, it is concluded that dermal absorption of 1,3-butylene glycol is possible.

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