人工暴露室を用いたTolueneの気中濃度と尿中馬尿酸排泄量の関係 : Thinner中毒第5報, 有機溶剤中毒第9報

Abstract

For elucidation of the relationship between the toluene concentration in the air and the amount of hippuric acid excreted in the urine as a metabolite, expermiments were carried out in an exposure chamber. We made use of two groups of volunteers as experimental subjects: one i.e. the three-hour exposure group which was exposed to 100 p.p.m. 200 p.p.m. toluene for three hours, and the other i.e. the seven-hour exposure group which was exposed for three hours in the morning and for four hours in the afternoon with one hour intermission in between. Results obtained are as follows. 1) Urinary excretion of hippuric acid during and after the exposure. In the case of seven-hour exposure group, the excretion increased rapidly from the beginning to two hours of exposure. Similar results were obtained in the three-hour exposure group. During one hour intermission a decrease was observed. In the afternoon, a similar excretion curve to that of the morning was obtained except that the urine collected at the beginning of the exposure showed a relatively high level. The maximum concentration of hippuric acid was observed in the urine immediately after leaving the exposure chamber or one hour later; and 18 hours later the concentration recovered to the normal level. 2) Relationships between toluene density in the air and the concentration, the amount of excretion per minute, and the total excreted amount of hippuric acid in the urine. Values of these three items as to the urinary hippuric acid were proportional to the toluene density in the exposure chamber, although there was a tendency that the ratios of these three items to the toluene density in the volunteers exposed to 200 p.p.m. toluene was a little less than those exposed to 100 p.p.m. The excretion rate of toluene in the urine as hippuric acid, calculated by Patty's equation, was 63-66 per cent in the three-hours exposure group and 74-82 per cent in the seven-hours exposure group. 3) Maximum allowable concentration (M.A.C.) or maximum allowable excretion per minute (M.A.E.) of the urinary hippuric acid. M.A.C. (mg/ml) corresponding to 200 p.p.m. of toluene was 3.74 (3.69) in the morning urine, 8.19 (7.84) in that of the afternoon, and 5.74 (5.54) throughout the working time. M.A.E. (mg/min) corresponding to 200 p.p.m. of toluene was 3.13 (3.06), 4.61 (4.51), and 3.77 (3.78) respectively. Screening level of the concentration (mg/ml) of urinary H.A. corresponding to 200 p.p.m. of toluene was 3.15 (2.83), 5.57 (5.83), and 5.14 (4.73) and that of excretion (mg/min) was 2.77 (2.67), 3.81 (3.55), and 3.05 (3.14), taken as minus value u2=1/(N-1)Σ^^N__(i=1)(xi-x^-)2. M.A.C. corresponding to 200 p.p.m. of toluene, corrected to the specific gravity of the urine at 1.024 according to Elkins, was 3.71 (3.63), 5.85 (5.89), and 5.99 (5.76), and the screening level 3.04 (3.04), 4.61 (4.99), and 4.80 (4.73). These values were calculated from interpolation along the line indicating the relation between the toluene concentration and the amount of the urinary hippuric acid, and those in parenthesis were obtained from the following calculation; Regression line was made from the hippuric acid concentration after inhalation of 100 p.p.m. and 195 p.p.m. toluene. Y-y^-=(Σ(x=x^-)(y-y^-))/(Σ(x-x^-)2)(X-x^-) where x^-=(100+195)/2p.p.m. y^-=1/2(Σ H.A. mg/ml at 100 p.p.m./N+Σ H.A. mg/ml 195 pp.m./N) N: number of cases calculated Using these regression line, we found that the amount of hippuric acid at 200 p.p.m. of toluene was assessed by extrepolation. Excretion per minute also by the similar method is indicated as values in the parenthesis. 4) Normal values of the urinary hippuric acid. Hippuric acid concentration, excretion per minute, and total excretion in the diurnal urine of healthy persons, was 0.27 mg/ml, 0. [the rest omitted]