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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

Readily biodegradable: 88% (O2 consumption) in 28 days; read-across

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

Since no reliable studies investigating the ready biodegradability of Reaction products resulting from the esterification of Sorbitol with C8-18 (even) and C18unsaturated fatty acids in the ratio 1:1 (EC 931-434-7) are available, in accordance to Regulation (EC) No. 1907/2006 Annex XI, 1.5, a read across to the structurally related category members Sorbitan stearate (CAS No. 1338-41-6) and Sorbitan oleate (CAS No. 1338-43-8) was conducted. All substances are UVCBs with partly overlapping compositions of Sorbitan fatty acid esters. Sorbitan stearate, which contains mono- and triesters of C16 and C18 fatty acids, is readily biodegradable. Generally, larger and branched molecules are considered as a worst case approach, since the chain length and substitutions are determining factors for biodegradation of fatty acid alcohol esters (Bozcar et al., 2001; Dias and Alexander, 1971). Sorbitan laurate, which contains mono- and diesters of fatty acids of the same length or shorter, is thus expected to be readily biodegradable as well. Since Sorbitan laurate additionally contains unsaturated C18:1 fatty acids, Sorbitan oleate (CAS No. 1338-43-8) was used as additional read-across, in order to demonstrate the ready biodegradation of the unsaturated C18 fatty acid chain. Furthermore, as can be seen in the data matrix of the category justification in Section 13, all reliable data in the category support the biodegradability assessment of each category member, by showing a consistent pattern of results.

The key study carried out with Sorbitan stearate (CAS No. 1338-41-6) was performed following the OECD Guideline 301 C and according to GLP (MoE, 1996). A mixed inoculum containing microorganisms from sewage plants and from natural waters was used. During the 28-day test period, biodegradation reached 88%, based on O2 consumption.

The key study carried out with Sorbitan oleate (CAS No. 1338-43-8) was performed following the OECD Guideline 301 B (van Dievoet, 2005). Non-adapted domestic activated sludge was used as inoculum. During the 28-day test period, biodegradation reached 84.5%, based on CO2 evolution.

One test result is available for Sorbitan laurate (CAS No. 1338-39-2). The study was conducted according to OECD Guideline 301 C. After the 14-day test period 56.9% biodegradation was reached, based on O2 consumption. Due to the shorter test duration and the lack of information on reference substance biodegradation or details on inoculum, the test was considered unreliable.

Thus, based on theabove mentioned results, and due to the structural and profile similarities of the substances, Reaction products resulting from the esterification of Sorbitol with C8-18 (even) and C18unsaturated fatty acids in the ratio 1:1 (EC 931-434-7) can be considered as readily biodegradable according to OECD criteria.