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EC number: 205-736-8 | CAS number: 149-30-4
Phototransformation in water
Administrative data
Link to relevant study record(s)
Description of key information
The screening experiment for the sunlight direct photolysis of MBT in pure water gave a first-order rate constant of 0.0223 min-1 corresponding to a half-life of 31.1 minutes and for indirect photolysis in synthetic humic water gave a first-order rate constant of 0.0253 min-1 corresponding to a half-life of 27.4 minutes. The small difference between the rate constants of direct photolysis and indirect photolysis suggests that 2-mercaptdbenzothiazole is marginally susceptible to indirect photolysis (CMA, 1989).
Brownlee et al. (1992) identified the reaction products of photolysis as 2-benzothiazolone (BTon) and benzothiazole (BT) after irradiation of MBT solution in phosphate buffer with sunlight and similar results were obtained in the presence of dissolved organic matter. The authors also conclude that BT and BTon were stable products of MBT photolysis in aquatic environments.
Key value for chemical safety assessment
Additional information
2-Mercaptobenzothiazole was irradiated in pure water and synthetic humic water to differentiate between direct and indirect photo-processes (CMA, 1989). The similarity of these results is indicating that direct photolysis is more important than indirect degradation.
The values mentioned above refer to the top millimetres of a water body in summer, because of factors like cloudiness, shadowing effects of vegetation, absorption and scattering of light by suspended solids etc. The actual environmental lifetime is certainly longer.
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