(R)-(-)-butane-1,3-diol

Endpoint summary

Description of key information

The ready biodegradability of the source substance (R/S)-1,3-butanediol was studied in a Modified Sturm Test following OECD 301B. The test substance was degraded to 81% (CO2/ThCO2) after 29 days. The 10-days window was met. The source substance 1,3-butanediol is readily biodegradable according to OECD criteria.

 

It is considered appropriate and scientifically justifiable to use the available ready biodegradability data for the source substance to address the ready biodegradability endpoint for the target substance. In this regard, based on the results of a key GLP-compliant study that was conducted according to OECD guideline 301 B / EU Method C.4-C, the target substance can be concluded to be readily biodegradable.

HYPOTHESIS FOR THE ANALOGUE APPROACH

Data for butane-1,3-diol (CAS No. 107-88-0) is used to address the ready biodegradability data requirement for (R)-(-)-butane-1,3-diol (CAS No. 6290-03-5) in an analogue read-across approach. The basis for this read-across approach is the extreme structural similarity of the source and target substances, in that the source substance is a racemic mixture of a pair of enantiomers, whereas the target substance is solely the R-enantiomer of that source pair. Two compounds that are enantiomers of each other have the same physical properties, except for the direction in which they rotate polarized light and how they interact with different optical isomers of other compounds (ECHA, 2008). Passive absorption of a substance into a test species and distribution through its tissues are governed by the physical-chemical properties of the substance, particularly its molecular size, log P, and water solubility (ECHA, 2014), and are therefore expected to be exactly the same for both enantiomers. The R-enantiomer half of the source substance and all of the target substance have been shown to metabolise in a mammalian system to a physiological ketone body, whereas the S-enantiomer of that ketone body derived from the other half of the source substance has been shown to metabolise into a compound that is not naturally present, but which can still be utilized by a less direct pathway (Desrochers et al., 1992). On the premise that the mixed microbial inoculum used in biodegradation studies will possess a considerably broader range of enzymes than a mammalian system, the minor difference in the rates of metabolism of the two enantiomers observed by Desrochers et al. (1992) is not expected to exist in their biodegradation rates, and the experimentally determined “readily biodegradable” result for the source substance is therefore directly applicable to the target substance.

 

The biodegradation in water - simulation testing on ultimate degradation in surface water and sediment simulation testing studies do not need to be conducted because the substance is readily biodegradable (study scientifically not necessary). Identification of degradation products does not need to be conducted because the substance is readily biodegradable - [study scientifically not necessary]

The biodegradation in soil: simulation testing study does not need to be conducted because the substance is readily biodegradable (study scientifically not necessary). Identification of degradation products does not need to be conducted because the substance is readily biodegradable - [study scientifically not necessary].