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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

OECD guideline-compliant studies have shown amides, C12-18 (even numbered) and C18-unsatd., N,N-bis(hydroxyethyl) and (in support of this assessment), the structurally similar amides, C8-18 and C18-unsatd., N,N-bis(hydroxyethyl) to be readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

Ready biodegradability of amides, C12-18 (even numbered) and C18-unsatd., N,N-bis(hydroxyethyl) was evaluated in the Closed Bottle Test according to OECD guideline 301 D. The test substance at 2 and 5 mg/L was incubated with sludge from a domestic waste water treatment plant and O2 consumption was followed over a period of 28 days. A total of 84% O2consumption was obtained at 2 mg/L and the plateau for ready biodegradability was reached within 14 days, at which point there was 10% degradation. At 5 mg/L, 71% O2consumption was obtained, although there was insufficient O2left in the flask at the end of the test. Amides, C12-18 (even numbered) and C18-unsatd., N,N-bis(hydroxyethyl) was therefore considered to be readily biodegradable (Werner and Berger 1996).

In another study, biodegradability of the structurally similar amides, C8-18 and C18-unsatd., N,N-bis(hydroxyethyl) was evaluated in the CO2-evolution test, conducted according to OECD guideline 301 B (Modified Sturm test). A solution of the test substance in a mineral medium, corresponding to 10-20 mg total organic carbon (TOC)/L, was inoculated with activated sludge (30 mg d. s. /L). The test vessels were aerated by the passage of CO2-free air and were incubated under aerobic conditions for 28 days. Degradation was assessed by determining the amount of CO2 produced and absorbed to sodium hydroxide via IC-measurement on days 3, 6, 10, 14, 21 and 28 of the study. The reference material used was sodium benzoate at a concentration of 20 mg TOC/L. The reference substance reached the pass levels for ready biodegradability within 3 days. The mean degradation extent of the test material was 92.5% within 28 days after acidification (mean value of three test vessels), (after acidification), which meets the criteria for ready biodegradation (Kronenberger-Schäfer K 2008).

The ready biodegradability of the structurally similar amides, C8-18 and C18-unsatd., N,N-bis(hydroxyethyl) was also evaluated according to the EU Method C.4-D in compliance with GLP. The test material (100 mg/L) and reference substance (acetic acid, sodium salt; 100 mg/L) was inoculated with activated sludge and kept in a closed respirometer flask and observed for degradation by measurement of the dissolved oxygen concentration over a 28 day period. The degradation of the test material and reference substance was 71.1% and 80%, respectively, after 28 days. Based on these results, amides, C8-18 and C18-unsatd., N,N-bis(hydroxyethyl) can be considered as readily biodegradable (Zielinski J 2005).