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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

Readily biodegradable: 73% (BOD) after 28 d (OECD 301C)

Key value for chemical safety assessment

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Since no studies investigating the ready biodegradability of ethane-1,2-diyl palmitate (CAS 624-03-3) are available for this endpoint, in accordance to Regulation (EC) No. 1907/2006 Annex XI, 1.5 a read across to structurally related category members ethylene distearate (CAS 627-83-8) and fatty acids, C16-18, esters with ethylene glycol (CAS 91031-31-1) was conducted. The read-across substances are characterized by the same alcohol component (ethylene glycol) diesterified with similar fatty acid (palmitic acid and/or stearic 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 first study (Ministry of Economy, Trade and Industry, Japan, 1998) was conducted with ethylene distearate according to the OECD Guideline 301C (GLP) under aerobic conditions using a mixture of activated sludge from sewage treatment plants, freshwater from rivers and lakes, marine water and marine sediment as inoculum. A mean biodegradation of 73% was observed after 28 d. Since the substance reached the pass level for OECD 301C (biodegradation is > 60% after 28 d, no 10-day window required) the test substances is stated to be readily biodegradable according to the OECD criteria. This result is supported by a second GLP-Guideline study with ethylene distearate according to OECD 301B using non-adapted activated sludge as inoculum (Mead, 1996). 70% biodegradation and the fulfilment of the 10-day window criterion classify the substance to be readily biodegradable. Testing with the read-across substance fatty acids, C16-18, esters with ethylene glycol according to ISO 10708 (GLP) resulted in a biodegradation of 61% after 28 d and 85% after 56 d, respectively (Richterich, 1998). This study was conducted using sewage from a municipal wastewater treatment plant as inoculum. For substances with different chain lengths the 10-day window should not be used for the interpretation of results. It is possible that a sequential biodegradation occurred which might have resulted in a prolonged lag-Phase and therefore a slower biodegradation period, although the test substance was biodegraded in a large amount after the test duration. In this case the pass level can be applied after 28 days and therefore the test substance is considered to be readily biodegradable. Based on the results from structurally related read-across substances (in accordance to Regulation (EC) No 1907/2006 Annex XI, 1.5) it can be concluded that ethane-1,2-diyl palmitate is readily biodegradable according to the OECD criteria. References: 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.