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Environmental fate & pathways

Biodegradation in soil

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Description of key information

No tests are required due to ready biodegradability of category members Fatty Acids.

Key value for chemical safety assessment

Additional information

The category members Fatty Acids are readily biodegradable. In accordance with column 2 of EC 1907/2006 Annex IX 9.2.1.3 the soil simulation testing is not required for readily biodegradable substances.

For the sake of completeness available experimental results on degradation in soil are mentioned for the category member stearic acid (CAS No. 57-11-4).

Larson (1992a) reported a study on the biodegradation of stearic acid in sludge amended soils. Sludge amended soil (5.0 g) were incubated with 0.1 ppm and 1.0 ppm of radiolabeled test substance. Degradation was monitored by respired CO2 which was trapped by potassium hydroxide, counted by LSC and quantified by calculating against the initial amounts radiolabeled substance added. The determination of degradation was based on the recovery rate of 14-CO2. The overall degradation values were 59.48% and 40.93% for 0.1 ppm and 1.0 ppm, respectively after 134 days. The calculated rate constants were 0.057 day-1 and 0.013 day-1 for 0.1 ppm and 1.0 ppm, respectively. The corresponding half- lives were reported to be 12.2 days and 53.2 days.

Another study performed by Larson (1992b) according to the above mentioned study design supported theses findings. The tested concentration of 0.1 ppm revealed a cumulative degradation of 55.96% after 134 days. The half life and rate constant were not determined.

A Draft Assessment Report (DAR, 2008) published by the EFSA comprised degradation studies in soil with fatty acids potassium salts according to BBA IV 4-1 which support a fast degradation of fatty acids and their derivatives with DT50values of 1 to 3 days for Fatty Acids (C7-C29) (DAR, 2008).

 

Reference: Draft Assessment Report (DAR) for Fatty Acids (C7-C29) (Volume 3, Annex B, Part 4, B.8, August 2008)