Fatty acids, C16-18 and C18-unsatd., iso-Bu esters

Biodegradation in water: screening tests

Description of key information

Readily biodegradable: 99% (O2 consumption) in 30 days

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Additional information

Two ready biodegradation studies and one marine BODIS test are available for Fatty acids, C16-18 and C18 unsaturated, isobutyl esters (CAS No. 84988-79-4).

 

The key ready biodegradability study, conducted with Fatty acids, C16-18 and C18 unsaturated, isobutyl esters (CAS No. 84988-79-4), was performed according to OECD guideline 301 D (Richterich, 2001). Effluent from a domestic sewage treatment plant was used as inoculum. During the 30-day test period, biodegradation reached 99%, based on O2 consumption, and the 10-day window criterion was met. After 28 days, degradation was ca. 95%, as can be seen in the degradation curve, although this value is not reported. Additional analytical determinations indicated a nitrification of the nitrogen containing (1.4 mg/L NH4Cl) mineral test medium. Taking into account a total nitrogen oxidation (worst case max. oxygen demand 2.03 mg O2/L) to nitrate, at least 65% of the test substance was degraded within 32 days of test period.Since the substance is a UVCB and thus consists of saturated and unsaturated constituents with different chain lengths, sequential (instead of concurrent) biodegradation can take place, but all constituents can be considered as readily biodegradable. 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 the substance can be regarded as readily biodegradable.

 

The supporting ready biodegradability study, conducted with Fatty acids, C16-18 and C18 unsaturated, isobutyl esters (CAS No. 84988-79-4), was performed according to ISO/ DIS method 10708 (BODIS test) (Richterich, 2001). Domestic, non-adapted activated sludge was used as inoculum. During the 28-day test period, biodegradation reached 72%, based on O2 consumption. The 10-day window criterion, defined for mono-constituent substances, was met, although it would not be required since the substance is a UVCBs.

 

The supporting marine biodegradability study, conducted with Fatty acids, C16-18 and C18 unsaturated, isobutyl esters (CAS 84988-79-4), was performed following the guideline MARINE BODIS ISO/TC 147/SC 5/WG 4N 141 (Everiss, 1999). Only natural seawater, fortified with mineral nutrients, was used as source of microorganisms. During the 28-day test period, biodegradation reached 75%, based on O2 consumption.

 

In conclusion, Fatty acids, C16-18 and C18 unsaturated, isobutyl esters (CAS No. 84988-79-4) can be considered readily biodegradable according to OECD criteria.