DETERMINATION OF URINARY 2-MERCAPTOBENZOTHIAZOLE (2-MBT), THE MAIN METABOLITE OF 2-(THIOCYANOMETHYLTHIO)BENZOTHIAZOLE (TCMTB) IN HUMANS ANDRATS

A method for biological monitoring of urinary 2-(thiocyanomethylthio)b enzothiazole (TCMTB), a wood preservative and an industrial chemical, was developed. Three different doses of TCMTB in olive oil were given to male rats by gavage for 3 weeks. Urine was collected daily and the metabolites were analysed as thioethers by derivatization with pentafl uorobenzyl-bromide by gas chromatography-mass spectrometry. The parent chemical was not detected in urine samples, but two metabolites of TC MTB were identified. 2-Mercaptobenzothiazole (2-MBT) was the main meta bolite, and its excretion varied according to the dose. The second met abolite was 2-(mercaptomethylthio)benzothiazole. The amount of 2-MBT e xcreted in rat urine was 66 +/- 12% (SD), 51 +/- 20% and 44 +/- 9% for TCMTB doses of 15, 75 and 150 mg/kg, respectively. Two doses, 75 and 150 mg/kg, caused diuresis in rats during the 1 week of dosing. During the 3-week TCMTB treatment, rat liver microsomal CYP enzyme profile w as not significantly changed. Urine samples of sawmill workers exposed to TCMTB were collected after their work shifts for exposure assessme nt. TCMTB could not be detected in the urine samples of exposed worker s. Most concentrations of 2-MBT were below the limit of the detection, 0.12 mu mol/l, the concentrations were 0.12-0.15 mu mol/l only in few cases. The determination of 2-MBT in urine, when a sample is taken im mediately after a work shift, is a suitable indicator of workers' expo sure to TCMTB.