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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

Additional information

SMBT is an organic salt of strong base NaOH and weak acid of MBT and it is solely marketed as aqueous solution. The presence of MBT determines the hazard profile of SMBT aqueous solution; and hence the environmental fate and behavior of MBT is used as read-across approach to support the risk assessment of SMBT.