Effect of simultaneous exposure to methanol and toluene vapor on their metabolites in rats

Abstract

Wistar male rats were exposed to methanol and toluene vapors by inhalation individually and simultaneously. Blood was sampled from the tail of the rats at 0, 1.5 and 3 h after a 6-h exposure and the methanol and/or toluene concentrations were measured by the headspace-gas chromatography-mass spectrometry (GC/MS). Major metabolites of methanol and toluene, that is, formic acid and hippuric acid in urine were measured at 0, 18 and 42 h after the end of the exposure. The toluene concentration in blood in the simultaneous exposure group was lower than that in the toluene exposure one. The biological half time of toluene in blood in the simultaneous exposure group was shorter than that in the single exposure one. The excretion rate of hippuric acid in urine in the simultaneous exposure group was significantly lower than that in the toluene exposure one when both the methanol and toluene concentrations were 300 ppm. These results suggest that the metabolic rate of toluene was enhanced by methanol. On the other hand, the biological half time of methanol in blood and the formic acid concentration in urine were not significantly different in the single and simultaneous exposure groups, although the methanol concentration in blood in the simultaneous exposure group was lower than that in the methanol exposure one.