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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

The substance was not readily biodegradable in OECD TG 301B tests.

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed

Additional information

Two biodegradation in water (screening tests) are available. In the key study, while some degradation was observed during the last week of the test (approximately 10 %), it was insufficient for the substance to be considered readily biodegradable.

In the key GLP study, conducted according to OECD Guideline 301B and EU Method C.4-C, the ready biodegradability of the test material was examined over a 28-day period by measuring CO₂ evolution during exposure to an inoculum of domestic activated sludge under aerobic conditions. The biodegradation of a reference substance, sodium benzoate, was also determined in the presence and absence of the test material.

The extent of biodegradation of the test material under the conditions of the study was about 10 % (mean of 3 determinations), whereas that of the reference substance was between 83 % (% theoretical CO₂ evolution) and 91 to 100 % (removal of dissolved organic carbon). The biodegradation of sodium benzoate in the presence of the test material confirms that inoculum bioactivity is not markedly inhibited by the test material.

The test material is not readily biodegradable over a 28-day period in this test since the pass level of 60 % ThCO₂ was not reached; however, some biodegradation occurred during the last week of the test.

In the supporting GLP study conducted according to OECD Guideline 301B and EU Method C.4-C, the ready biodegradability of the test material was examined over a 28-day period by measuring CO₂ evolution during exposure to an inoculum derived from activated sludge under aerobic conditions. Sodium benzoate was confirmed as a readily biodegraded reference compound when incubated alone with the inoculum. In control incubations, the test material was assessed to be non-inhibitory with respect to microbial degradation of sodium benzoate (a readily biodegradable reference compound).

The extent of biodegradation of the test material under the conditions of the study was 0 % (mean of duplicate test suspensions) over 28 days. The biodegradation of the reference substance, sodium benzoate, when incubated alone with the inoculum was 77 and 87 % (based on %ThCO₂) at 11 and 28 days, respectively. Biodegradation of sodium benzoate measured by removal of DOC was 93 to 100 % (measurements taken at 0 and 28 days). The test system was considered valid according to the guideline criteria.

Under the conditions of the test, the test material was not readily biodegradable.