Registration Dossier
Registration Dossier
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EC number: 209-097-6 | CAS number: 555-43-1
Biodegradation in water: screening tests
Administrative data
Link to relevant study record(s)
Description of key information
Readily biodegradable: 64% in 28 days (ISO 10708)
Key value for chemical safety assessment
Additional information
No standard experimental data evaluating the potential for ready biodegradability of glycerol tristearate (CAS No. 555-43-1) are available. Therefore, a ready biodegradability study from a structurally related analogue substance, castor oil hydrogenated (CAS No. 8001-78-3) is used as read-across in accordance with Regulation (EC) No. 1907/2006, Annex XI, 1.5. Castor oil hydrogenated is a UVCB substance, but both substances are esters formed from the esterification of C18 (hydroxylated in the case of CAS No. 8001-78-3) fatty acids and glycerol. Glycerol tristearate and castor oil hydrogenated are triglycerides (the three hydroxyl functional groups of the glycerol molecule are esterified with fatty acids). Therefore, considering that they share the same fatty acid C-chain length (C18), similar degrees of biodegradation are to be expected for these substances.
One study evaluating the potential for ready biodegradability of castor oil hydrogenated (CAS No. 8001-78-3) is available (Richterich and Mühlberg, 2001). The test was conducted according to ISO 10708. Activated sludge was exposed for 28 days to the test substance and biodegradation followed by measuring O2 consumption in the test vessels. After 28 days, the test substance reached 64% biodegradation. As the substance is an UVCB substance and thus consist of constituents with different degrees of esterification, sequential (instead of concurrent) biodegradation is expected to take place. Thus, referring to Annex I of the OECD Guideline for Testing of Chemicals ‘Revised introduction to the OECD guidelines for testing of chemicals, section 3’ (OECD, March 2006), the 10-day window criterion can be disregarded in this case and the substance considered as readily biodegradable. Additionally, biodegradation data on glycerol tristearate is available from a publication (Freitag et al., 1985). The test substance (0.05 mg/L) was incubated in activated sludge from a municipal sewage treatment plant for 5 days. Degradation was followed as the distribution of the substance between water and sludge and its conversion and degradation to CO2. After the exposure period, 24% biodegradation was reported.
Based on the above mentioned results, glycerol tristearate can be considered as readily biodegradable.
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