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Biodegradation in water: screening tests

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Description of key information

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

No study on ready biodegradability is available for fatty acids, C8-16. Therefore, read across from the key studies of the most relevant aliphatic fatty acids was performed. According to the Substance Identity Profile lauric acid and myristic acid are the most representative structures for fatty acids, C8-16.
Therefore the data for lauric acid (C12, CAS 143-07-7) as well as QSAR predictions on ready biodegradability of myristic acid (C14, CAS 544-63-8) were considered to deduce the biodegradability of fatty acids, C8-16.

Two biodegradability tests are available for lauric acid demonstrating ready biodegradability. Richterich and Mühlenberg (2001) conducted a closed bottle test according to OECD 301D. Under the test conditions, 86% oxygen consumption at a test concentration of 2 mg/L and 62% at 5 mg/L were observed. The 10-day window was met. In the short summary of Geisel and Berger (1998), the biodegradability was tested according to EU Method C.4 –E. The test also showed lauric acid to be readily biodegradable (85% within 30d at 2 mg/L of test substance and > 55% at 5 mg/L of test substance, passing 10-day window). The substance, lauric acid, is thus readily biodegradability.

Results of the QSAR model BIOWIN v.4.10 (EPI Suite, 2012) predicts ready biodegradability for myristic acid. This method is based on the application of Bayesian analysis to ready biodegradation data for chemicals, derived collectively from all six OECD301 test methods plus OECD310.

Overall, fatty acids, C8-16 is regarded as readily biodegradable. This judgment is consistent with the hazard assessment presented in the OECD SIDS (2009) for the category “Aliphatic Acids Category” where aliphatic fatty acids with a carbon chain length in the range of C8 – C22 were judged to be readily biodegradable.