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Environmental fate & pathways

Biodegradation in soil

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Description of key information

Significant technical difficulties were encountered during method development for a recent study of adsorption/desorption (OECD 106, Wildlife, 2015) of the structurally analogous alcohol, decan-1-ol (CAS 112-30-1), using natural standard soils, in that it was not possible to detect sufficient substance and establish equilibrium in non-sterilised soil samples. During method development in preparation for this study, the laboratory reported that after equilibration with soils for 15-minute to 24-hour periods, decan-1-ol dosed into the test vessels was partly or completely transformed into a more polar product, which was clearly distinguishable from the starting material as clear and well separated peaks in the chromatograms. The rate of transformation depends on the soil type. Only after a very short (5-minute) equilibration the parent material remained intact (personal communication, 8 January 2015 from Wildlife International laboratory). Half-lives were not explicitly derived, but chromatograms presented would indicate the half-life of decan-1-ol in the soil test samples was approximately 30 min - 1 hour (silt loam soil); 1 - 2 hours (loamy sand), and 15 - 30 minutes (clay loam). Following sterilisation of the soil samples by autoclaving, the substance remained adequately stable for a 2-hour period, therefore the instability can be attributed to biodegradation of the substance by soil microbiota. The polar degradation product is most likely the corresponding carboxylic acid, though it was not definitively identified. The chromatograms show that decan-1-ol was effectively fully removed in all four soil types by the 24 h time point (in the case of 2 of the soil types, within 2 hours). Similar degradation can be expected for (Z)-octadec-9-enol.

Key value for chemical safety assessment

Half-life in soil:
2 h

Additional information

In accordance with Column 2 of REACH Annex IX, the full soil simulation test (required in Section 9.2.1.3) does not need to be conducted as the substance is readily biodegradable. Furthermore a close structural analogue, decan-1 -ol (CAS 112-30-1), has been shown to be very rapidly degraded in non sterilised standard soils as part of method development for the soil adsorption study.

Discussion of trends in the Category of C6-24 linear and essentially-linear aliphatic alcohols

The data available regarding persistence in soil are limited. A commercial multi-constituent substance (CAS 68155-00-0 (C14-18 and C16-18 unsaturated) and CAS 68002-94-8 (C16-18 and C18 unsaturated)) was found to be readily biodegradable in a reliable OECD 301D study using a non-standard inoculum; garden soil microorganisms (Borner, 1999). A recent and reliable study of adsorption and desorption using the batch equilibrium method (in compliance with OECD 106 and GLP) has been conducted with decan-1-ol (CAS 112-30-1).