Fatty acids, C18-unsatd., dimers, polymers with 2-ethylhexanol and neopentyl glycol

Biodegradation in water: screening tests

Description of key information

Readily biodegradable: >60% in 28 days (OECD 301F); read across

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Additional information

Data on the biodegradability of the target substance Fatty acids, C18-unsatd., dimers, polymers with 2-ethylhexanol and neopentyl glycol (CAS 68552-19-2) are not available. The assessment was therefore based on studies conducted with two analogue substances as part of a read across approach, which is in accordance with Regulation (EC) No 1907/2006, Annex XI, 1.5. The first analogue substance, Fatty acids, C18-unsatd., dimers, mixed esters with oleic acid and trimethylolpropane (CAS 147256-33-5), is a triester with unsaturated fatty acids up to a chain length of C36. The read across was chosen as a worst case approach covering unsaturated long fatty acid chains. The second source substance, Fatty acids, C18-unsatd., dimers, 2-ethylhexyl esters (CAS 68334-05-4), is an ester of2-ethylhexanol withdimerized unsaturated C18 fatty acid chain.

 

The ready biodegradability of the source substance Fatty acids, C18-unsatd., dimers, mixed esters with oleic acid and trimethylolpropane (CAS 147256-33-5) was tested according to OECD guideline 301F (GLP) under aerobic conditions using non-adapted effluent as inoculum. The inoculum was obtained from a STP predominately treating domestic sewage. Based on O2 consumption a mean degradation of 85% was observed after 28 days.

The biodegradability of the second source substance Fatty acids, C18-unsatd., dimers, 2-ethylhexyl esters (CAS 68334-05-4) was tested in a GLP study conducted according to OECD guideline 301B (CO2 evolution test) using activated sludge from a sewage treatment plant treating predominantly domestic sewage. The CO2 evolution of the inoculum was recorded 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 degradation rate did not meet the "10-day window" criteria. As Fatty acids, C18-unsatd., dimers, 2-ethylhexyl esters is an UVCB substance and thus consist of constituents with different chain-lengths, sequential (instead of concurrent) biodegradation takes place. According 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 criterion is not applicable for UVCB substances. Based on the determined degradation rate of > 60% within 28 days Fatty acids, C18-unsatd., dimers, 2-ethylhexyl esters can be considered as readily biodegradable.

Based on the results from suitable source substances (in accordance to Regulation (EC) No 1907/2006 Annex XI, 1.5), Fatty acids, C18-unsatd., dimers, polymers with 2-ethylhexanol and neopentyl glycol (CAS 68552-19-2) is considered as readily biodegradable.