Registration Dossier

Environmental fate & pathways

Biodegradation in soil

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Description of key information

The half-life of the parent compound in sediment has not been measured, but an approximate value can be generated from the biodegradation half-life in water or sewage sludge. The half-life in water  (Zahn-Wellens test) is approximately 60 days, and in sediment it is assumed to be similar. However, soil is different from water and sediment, it has periods of dryness and wetness, and it is more aerated. This means that the bio-degradation  half-live could be longer. We have chosen the value 120 days  which is twice as long as in sewage sludge; however, this value has to be considered as a guess.

Key value for chemical safety assessment

Half-life in soil:
120 d
at the temperature of:
298.15 K

Additional information

No data are available on the biodegradation half-life in soil. But there are data on the biodegradation in water as determined by the Modified Sturm test and the Zahn-Wellens test. Extrapolation from water to soil is difficult, but even if degradation takes longer in soil than in water, it has no major influence on the most important property of TGIC, its Mutagenicity. However, hydrolysis in water and air is fast (half-life = 6.6 days), and thus, detoxification of TGIC occurs long before it is biologically degraded. In the case of TGIC, the most important path is detoxification, while biodegradation of the detoxified molecule is secondary.

Therefore, the assumption that the half -life of biodegradation in soil is 120 days is in fact of minor importance.