Fatty acids, C18-unsatd., dimers, 2-ethylhexyl esters

Biodegradation in water: screening tests

Description of key information

Fatty acids, C18-unsatd., dimers, 2-ethylhexyl esters are readily biodegradable.

Additional information

Four studies investigating the ready biodegradability of Fatty acids, C18-unsatd., dimers, 2-ethylhexyl esters (CAS No. 68334-05-4) are available.

The key study (Weiss-Fuchs, U. and Ipser, A., 2007) is a GLP study conducted according to OECD guideline 301B (CO2 evolution test) using activated sludge from a treatment plant treating predominantly domestic sludge over 28 days. The test substance concentration tested was 15 mg/L carbon content (20 mg/L test substance). To aid dispersion it was not directly added to the medium but applied to a solid carrier (silica gel) due to the low water solubility of the test substance.

However despite being biodegraded in excess of 60% after 28 days (62.1%), the test did not meet the "10-day window" criteria. As Fatty acids, C18-unsatd., dimers, 2-ethylhexyl esters are an UVCB substance and thus consist of constituents with different chain-lengths, sequential (instead of concurrent) biodegradation takes place. Thus, referring to Annex I to 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 should not be considered for this UVCB substance and due to a degradation of > 60% within 28 days Fatty acids, C18-unsatd., dimers, 2-ethylhexyl esters can be regarded as readily biodegradable.

The two other reliable GLP studies reported biodegradation of 42% (according to OECD 310) and 12.7% (according to OECD 301B) and thus stated that the test substance is not readily biodegradable.

As a consistent positive test result supersedes negative test results Fatty acids, C18-unsatd., dimers, 2-ethylhexyl esters can be regarded as readily biodegradable.