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Environmental fate & pathways

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2-mercaptobenzothiazole is stable to hydrolysis at pH 7 and ambient temperature, but it oxidizes rapidly in phosphate buffer at pH 6.5 with 60% conversion into MBTS within 2 hours and it also photolyzes rapidly in pure water with a half-life of 31.1 minutes. Only small difference was observed between the rate constants of direct photolysis in pure water and indirect photolysis in synthetic humic water suggesting that MBT is marginally susceptible to indirect photolysis. Brownlee et al. (1992) identified the photolysis products of MBT in water as 2 -benzothiazolone (BTon) and benzothiazole (BT). The indirect atmospheric oxidation rate by reaction with OH-radicals was estimated by using AOPWIN v1.92 to be 7.95 *10-11cm3/(molecule*sec) and half-life thus 9.5 h. The estimated half-life in air of MBT is much shorter than 24 hours and hence no potential for long-range transport of MBT in air is expected. The main abiotic degradation products of MBT and its oxidative product MBTS are BT (CAS: 95-16-9) and BTon (CAS: 934-34-9). In the EU-draft risk assessment, BT and BTon are reported as persistent under environmental conditions. Another described metabolite from MBT is MeSBT (615-22-5), which is also reported as resistant both to biodegradation and photolysis.