Urinary excretion of hippuric acid and o-cresol after laboratory exposure of humans to toluene.

The urinary excretion of hippuric acid and o-cresol was studied after respiratory exposure of human volunteers to approximately 80 ppm (306 mg/m3 +/- SD 13) of toluene for 2 h under different work loads (0, 50, 100, 150 W, respectively, during 30-min periods). The diet before and after exposure varied. An isotachophoresis method for the determination of hippuric acid is described. The correlation between the total urinary excretion, excretion rate and concentration of hippuric acid, and the respiratory uptake of toluene was poor or non-existing. The same was true for the excretion of o-cresol, which 4 h after exposure was concluded amounted to 0.03-0.26% of the toluene uptake. Thus, after a short-time exposure neither metabolite proved to be a reliable measure of individual toluene uptake at varying workloads or food intake in combination with low exposure levels.