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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

An OECD guideline-compliant study has shown amides, C12-18 (even-numbered) and C18-unsatd., N-hydroxyethyl to be readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

An OECD guideline 301 D (Closed Bottle test) study was conducted to determine the biodegradability of amides, C12-18 (even-numbered) and C18 -unsatd., N-hydroxyethyl in an aerobic aqueous medium. The test (2 and 5 mg/L with 2 and 5 mg/L emulsifier, respectively) and reference (dodecylsulfate, 1.89 mg/L) substances were inoculated with the effluent of domestic sewage, kept in completely filled closed bottles and observed for degradation by measurement of the dissolved oxygen concentration over a 30 day period. Degradation of the test substance was determined to be 56-60%, 71 -82% and 74 -82% after 5, 15 and 30 days, respectively. Chemical Oxygen Demand (COD) of the test substance determined by DIN-method 38409 part H41-1 was 2.23 mg O2/mg test substance. The degradation of the reference substance was determined to be 51, 77 and >100% after 5, 15 and 30 days, respectively. The Theoretical Oxygen Demand (ThOD) of the reference substance was calculated on the basis of its structural formula to be 2.02 mg O2/mg dodecylsufate. In conclusion, amides, C12-18(even-numbered) and C18(unsatd.), N-hydroxyethyl undergoes 74-82% degradation within a 30 days period. Since the pass level (i.e., 60% ThOD) was reached, the substance can be considered as readily biodegradable (Richterich DIK, 2001).

In another study, the ready biodegradability of structurally similar amides, C8-18 (even numbered) and C18-unsatd., N-(hydroxyethyl) was assessed in an aerobic aqueous media according to OECD guideline 301 B. The test material was exposed to activated sewage sludge micro-organisms at a concentration of 20 mg C/L with culture medium in sealed culture vessels in the dark at 21ºC for 28 days. The degradation of the test material was assessed by the determination of carbon dioxide produced. Control solutions with inoculum and the standard material, sodium benzoate, were used for validation purposes. Amides, C8-18 (even numbered) and C18-unsatd., N-(hydroxyethyl) attained 72% degradation after 28 days and can be considered to be readily biodegradable (Mead C, 1996).