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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

Readily biodegradable: 79.9% after 28 d (OECD 310)

Key value for chemical safety assessment

Additional information

Since no studies investigating the ready biodegradability of fatty acids, C14-18 and C16-18-unsatd., esters with propylene glycol (CAS 84988-75-0) are available for this endpoint, in accordance to Regulation (EC) No. 1907/2006 Annex XI, 1.5 a read across to structurally related category member 1-methyl-1,2-ethanediyl diisooctadecanoate (CAS 68958-54-3) was conducted. The read-across substance is characterized by the same alcohol component (propylene glycol) diesterified with a longer fatty acid (isostearic acid) and can therefore be used for read-across as a worst case approach since the chain length is the determining factor for biodegradation. The first step of biodegradation is the enzyme-catalysed cleavage of the ester bond by lipase or esterase which are synthesized by a wide range of microorganisms (Boczar et al., 2001). The free fatty acids (C4 to C24 incl. C18 unsatd.) are known to be degraded rapidly and utilized as substrates by activated sludge microorganisms (Kangala & Medrzycka, 2008).

The study for CAS 68958-54-3 was conducted according to OECD 310 (GLP) under aerobic conditions using 10% mixed liquor supernatant from a municipal sewage treatment plant as inoculum and a test substance concentration of approx. 10 mg/L based on TOC (Philpotts, 1997). A mean biodegradation of 79.4% was observed after 28 d. Since the substance reached the pass level (biodegradation is > 60% within the 10-day window) the test substance is stated to be readily biodegradable according to the OECD criteria.

In conclusion, fatty acids, C14-18 and C16-18-unsatd., esters with propylene glycol can be considered to be readily biodegradable based on the result from the suitable read-across substance 1-methyl-1,2-ethanediyl diisooctadecanoate (in accordance to Regulation (EC) No 1907/2006 Annex XI, 1.5).


Boczar, A.A., Forney, L.J., Begley, W.M., Larson, R.J., Federle, T.W. (2001): Characterization and distribution of esterase activity in activated sludge. Water Research 35(17), 4208-4216.

Kangala, B.C., Medrzycka, K. (2008): Characterization of the fate of lipids in activated sludge. Journal of environmental sciences 20, 536-542.