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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

The substance is readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

The ready biodegradability of the Sulfonium compound mixture was tested in two GLP guideline studies according to OECD 301 B (Ready Biodegradability: CO2 Evolution Test) [BASF AG, 2003; BASF SE, 2013]. The biodegradation rate was determined by measuring the CO2 evolution of non-adapted domestic activated sludge at the test substance concentration of 20 mg/L and 38 mg/L, respectively.

The substance is a mixture of similar Sulfonium compounds. Degradation of mixtures is characterized by multiphase kinetics. In such cases the 10-day time-window criterion is not scientifically justified. It is recommended that mixtures of similar compounds, which exceed the pass level within the standard test duration of 28 days are considered as “readily biodegradable”, independent from the 10-day time-window criterion [UN/SCEGHS/16/INF.17].

For the described mixture the result of the two biodegradation tests differs considerable. One test results in a biodegradation rate of less than 10% [BASF SE, 2013], whereas the degradation rate in the other study exceeds the pass level of 60% [BASF AG, 2003]. Based on the stringent test conditions of ready biodegradability tests, the guidance documents declare: “Realising that ready biodegradability tests may sometime fail because of the stringent test conditions, in general, and the differences among the individual tests in terms of their stringency, consistent positive test results from test(s) should generally supersede negative test results” [ECHA Guidance on information requirements and chemical safety assessment Chapter R. 7b, 2012].

Hence, it can be concluded from the available data, that the substance is “ready biodegradable”.