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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

Readily biodegradable: 78% in 28 days (OECD 301C, Modified MITI Test)
75% in 28 days (ISO Draft (BOD Test for Insoluble Substances)
90.4% in 28 days (OECD 301B, CO2 Evolution Test)

Key value for chemical safety assessment

Additional information

As no experimental data evaluating the potential for ready biodegradability of Fatty acids, C12-16 (even numbered) and C18 unstd., methyl esters (CAS No. 1234694-02-0) are available, in accordance to Regulation (EC) No. 1907/2006, Annex XI, 1.5, read-across from structurally related category members, methyl laurate (CAS No. 111-82-0), methyl palmitate (CAS No. 112-39-0) and methyl oleate (CAS No. 112-62-9) is performed. All four substances are characterized as esters of methanol and C12 (CAS No. 111-82-0), C16 (CAS No. 112-39-0), C18 (CAS No.112-62-9) and C12-16 (even numbered) and C18 unsaturated (CAS No. 1234694-02-0) fatty acids. Therefore, as representatives of the C-chain lengths of the individual fatty acid components that can be found in Fatty acids, C12-16 (even numbered) and C18 unstd., methyl esters, the read-across substances are expected to give a valid indication of its biodegradation potential.

The test available for methyl laurate (CAS No. 111-82-0) was conducted according to OECD 301C under GLP-conditions (Japanese Ministry of Economy, Trade and Industry, 1995). A mixture of sewage, soil and natural water was used as inoculum. After 28 days, the test substance reached 78% biodegradation. Since the 10-d window concept does not apply to the MITI method, methyl laurate can be considered readily biodegradable according to OECD criteria. A study performed according to ISO Draft (BOD Test for Insoluble Substances), under GLP conditions is available for methyl palmitate (CAS No. 112-39-0). 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 75% biodegradation, fulfilling the 14-day window criterion in two of the three replicates (the third replicate reached only 35% degradation after 14 days). Nevertheless, biodegradation values in the third replicate differed more than 20% in comparison to the values in the other two throughout the test (observed in samples collected at 14, 18 and 28 days). Therefore, the results from the third replicate are considered invalid and disregarded for the final biodegradability assessment, and the substance can be considered as readily biodegradable. Finally, the test conducted with methyl oleate (CAS No. 112-62-9) was performed according to OECD 301B, under GLP conditions (King, 1994). Secondary effluent from a STP was used as source of inoculum. After an incubation period of 28 days at 20°C, the substance reached 90.4% biodegradation, fulfilling the 10-day window criterion (84.2% biodegradation was reached on day 11) and therefore it is readily biodegradable as well according to OECD criteria.

Based on the results obtained for the structurally related category members (in accordance with Regulation (EC) No. 1907/2006, Annex XI, 1.5) Fatty acids, C12-16 (even numbered) and C18 unstd., methyl esters can be considered as readily biodegradable.