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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

Following the OECD Guideline 301C (MITI Test (I)) a degradation of 2.5% within 14 days was observed. Therefore 2-mercaptobenzothiazole is classified as not readily biodegradable (MITI 1992). On the other hand the inherent biodegradability of MBT was tested with acclimated bacterial inoculum andonly 2% biodegradation of MBT was observed during 35 days of exposure (Monsanto, 1979); and hence MBT can be concluded as not inherently biodegradable. In the EU-Risk Assessment for CBS (CAS: 95-33-0), information regarding the biodegradability of the main metabolites of MBT, such as MBTS, BT, BTon, and MeSBT, is also summarized and discussed. The described metabolites are also not readily biodegradable. Only when the inoculi were adapted under special conditions, certain level of degradation of BT, BTon, and MeSBT was observed. Such processes are expected in biological treatment plant, but not in the environment.

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed

Additional information

ZMBT is an organic complex with where the relation of Zn to Sulfur bridge is considered to be ionic.

The dissolution of MBT determines the hazard profile of ZMBT aqueous solution; and hence the environmental fate and behavior of MBT is used as read-across approach to support the risk assessment of ZMBT. The read-across is justified as ZMBT has an ionic structure where MBT is contained.