山梨医科大学雑誌　第6巻3号　137-149(1991)

Biological Monitoring of Exposure to Organic Solvent Vapors
II. Simulation Studies using a Physiological Pharmacokinetic
Model for m-Xylene

Takashi KANEKO, Kazushi ENDOH, and Akio SATO

Abstract: The relationship between external and internal doses of m-xylene and the effects of body weight, body fat content, sex, and physical activity on the pharmacokinetics of m-xylene were studied using a physiological simulation model.
1. At low exposure concentrations, equal time-weighted average (TWA) concentrations gave almost the same internal dose of m-xylene.
2. The m-xylene concentration in the blood increased continuously with increasing m-xylene concentration in inhaled air. By contrast, the excretion rate of m-methyl hippuric acid (m-MHA) in the urine approached a plateau with increasing m-xylene exposure concentration.
3. The larger the body size, the larger the amount of m-xylene absorbed. However, no significant change was found in m-xylene concentration in the blood with increase in body size. By contrast,the amounts of m-MHA excreted in the urine varied with body size: the larger the bedy size, the greater was the rate of urinary m-MHA excretion.
4. Both m-xylene concentration in the blood and the rate of urinary m-MHA excretion were higher in a slim than in an obese man during exposure, but this relationship was reversed in due course of time after exposure.
5. The physical activity (50 W) during exposure greatly increased the blood concentration of m-xylene as well as the rate of urinary m-MHA excretion.
6. The concentration of m-xylene in the blood during exposure was lower in women than in men, while the opposite was true starting about 10 hours after the end of exposure. The rate of m-MHA excretion in the urine was lower in women than in men both during and after exposure.

Key words: Physiologically based pharmacokinetic model, m-Xylene, m-Methyl hippuric acid, External and internal doses, Biological exposure monitoring




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