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Environmental fate & pathways

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Hasson & Agrup (1993) reported a negligible dissipation of MBTS in the buffer solution of pH6.5. Increased dissipation of MBTS with metabolites like MBT (149-30-4), BT (95-16-9) and BTon (934-34-9) was observed under increased temperature and pH (e.g. 6.7 % dissipation of MBTS at pH 9.8 and 58 °C in 65 hours) and decreased particle size present in the aqueous solution. In conclusion, MBTS is considered as hydrolytically stable under environmental relevant pH and temperatures with the presence of atmospheric oxygen in aqueous solution. The UV spectrum of MBTS indicates that photodegradation under environmental conditions is possible. A half-life of 3 hours of MBTS due to direct phototransformation in water at midday in August was obtained (Monsanto, 1980). The indirect atmospheric oxidation rate by reaction with OH-radicals was estimated by using AOPWIN v1.92 to be 3.15 *10-10 cm3 molecule-1 s-1 and half-life thus 1.22 h (Currenta, 2010). The estimated half-life in air of MBTS is much shorter than 48 hours and hence no potential for long-range transport of MBTS in air is expected. The main abiotic degradation products of MBTS and its reductive product MBT are BT (CAS: 95-16-9) and BTon (CAS: 934-34-9). In the EU-Risk Assessment, BT and BTon are reported as persistent under environmental conditions. Another described metabolite from MBT is MeSBT, which is also reported as resistant both to biodegradation and photolysis.