Studies on poisoning. IV. Toluene concentration in air and urinary hippuric acid measured by paperchromatography and mass screening examination method.

For the elucidation of the relationship between the toluene concentration in the air and the amount of hippuric acid excreted in the urine as a metabolite after the work in the workshop where they use toluene, we have succeeded in measuring minute quantities of urinary hippuric acid by a modified method of Gaffney's paperchromatography and also by a simple mass screening examination method devised by us, and obtained the following results. 1. The average concentration of hippuric acid in the urine collected at 2 p. m. from healthy individuals proved to be 184 μg/ ml, and the amount of its excretion was 174 μg/ min. 2. After the three-hour inhalation of toluene whose concentration in the air ranged 20, 50, and 160 ppm, the average concentration of hippuric acid in the urine was found to be 190,863 and 1,930 μg/ml, and the avarage increment of hippuric acid, 33.2, 193.9, and 1060 μg/min respectively. From this results we have found that there is a linear relationship between the toluene concentration in the air on one hand and the concentration of urinary hippuric acid and the increasing amount of its excretion on the other. Thus it has become possible to calculate the toluene concentration in the air even in the workshop where the workers are exposed to toluene discontinuously from the curves of the linear relationships just mentioned. 3. For the control of health in the workshop where they use toluene (such as auto-tricycle factory) we have devised a simple mass screening examination method for the detection of urinary hippuric acid, in which urinary hippuric acid is extracted with ether alcohol, and the coloration of its spots on filter paper is conducted with aroylglycine reagent (DAB and acetic anhydride mixture) in order to find out those excreting 1,000 μg/ml (the maximum allowable concentration) or over.