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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

Several non-guideline tests are available that investigate the biodegradability of the test substance under aerobic conditions. The outcome of the tests is indicative for rapid biodegradation in fresh water. Kohei (1985) finds 61-69% degradation (as BOD or DOC) over a priod of 80 hours, MITI (1979) reported 98% degradation (as TOC) over 14 days, Howard (1981) >94.5% (decrease of radioactivity) over 7 days and Freitag (1985) 65.4% (CO2 evolution) over 5 days at a concentration of 0.05 mg/L test substance.
In seawater the test substance degrades 10-80% (DOC removal) over a period of 8-28 days (Shimp 1987), but the test is performed without adding a specific inoculum to the water. Two tests with similarities to simulation testing are available (Junker 2009) that indicate that in a water sediment system the test substance degrades > 74.4% over a 8-day period. These studies are considered to be the key studies.
Several studies indicating that the test substance is completely biodegradable under anaerobic conditions are available (Birch, 1989; Uma, 2007;Nottingham, 1969; Kameya, 1995). The key study for anaerobic degradation (Birch, 1989) is performed according to the methods as described under OECD 311.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

Based on the large number of studies indicating a rapid and almost complete biodegrdataion, it can be concluded that the test substance is readily biodegradable. Although most tests do not provide information on the passing of the 10-day window, this is considered to be passed, because the overall test duration is in most tests shorter than 10 days.