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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

Two OECD 301B studies have been conducted on this substance.  One of the guideline studies utilized pre-adapted inoculum following the guidelines for enhanced studies for the purposes of PBT assessment.

Key value for chemical safety assessment

Biodegradation in water:
inherently biodegradable

Additional information

Sucrose acetate isobutyrate has a very low water solubility and is therefore a difficult substance to test for a number of environmental endpoints including ready biodegradation. An initial study was performed to assess the ready biodegradability of the test item in an aerobic aqueous medium following the OECD 301B, Ready Biodegradability; C02 Evolution Test. Due to the low water solubility of the test substance, the test item was adsorbed onto granular silica gel prior to dispersion in the test medium to aid dispersion of the test item in the test medium and to increase the surface area of the test item exposed to the test organisms. In this study the test item attained 48% degradation after 28 days and therefore cannot be considered to be readily biodegradable under the strict terms and conditions of OECD Guideline No 301 B.

A second study was performed to determine the potential for ultimate biodegradation of sucrose acetate isobutyrate in water by the carbon dioxide evolution method following OECD Test Guideline 301B using the enhanced technique of a low-level pre-adapted system similar to what is described in Chapter R.7B of the REACH guidance regarding enhanced ready biodegradation studies. A half and half mixture of inoculum from an initial ready biodegradation study (adapted) was combined with fresh un-adapted inoculum to initiate this study. All other aspects of the study met the criteria of the OECD 301B guideline method. In this study the test item attained 63.06% degradation after 28 days. The result showing greater than 60% ultimate biodegradation (CO2 evolution) in the 28 day test demonstrates a lack of persistence in a PBT assessment.