Development of evaluation method on the health effects of multicomponent organic vapors using biological exposure indices

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Most organic sovents used in work environments are mixture of several solvents. This study addresses the influence of simultaneous exposure of organic vapors by inhalation on their metabolic disposition.Wister male rats (8 weeks old) were exposed to methanol, toluene, MEK and their mixtures. The exposure periods were 6 hours a day for 1day and 1 month. After the termination of the exposure, the rats were transferred into separate metabolic chambers and urine were collected individually at 18 and 42 hours after the exposure. Blood samples were also collected from tale of the rats temporary up to 3 hours after the exposure. Major metabolites of the solvents in urine and the solvent concentrations in blood were determined.For methanol-toluene system, compared with single exposure, simultaneous exposure resulted in larger amount of excreted hippuric acid and formic acid in urine during the exposure period. However, hippuric acid excretion rate in the simultaneous exposure group was significantly smaller than that in the toluene exposure group during 0-18 hours, and there was no significant difference observed during 18-42 hours. Biological half time (t<@D21/2@>D2) of toluene in blood in the simultaneous exposure group was 1.2 (]SY.+-。[) 0.1 hr hours, which was significantly shorter than that in the toluene exposure group (2.0 (]SY.+-。[) 0.4 hr). On the other hand, the half time of methanol in blood was not dignificantly different between both methanol (2.7 (]SY.+-。[) 0.4hr) and simultaneous exposure (2.6 (]SY.+-。[) 0.6hr) groups. The results suggest that methanol promotes toluene metabolic disposition, but toluene may not affect significant influence in the methanol metabolites. For MEK-toluene system, the biological half time of toluene in blood for simultaneous exposure group was longer than that for toluene exposure group, suggesting that the the metabolic disposition of toluene was inhibited by MEK.