Pharmacokinetics of benzene in a human after exposure at about the permissible limit.

This limited range of experimental human exposure indicates that: 1. In the single experimental subject, the amount of benzene retained in the body 10 hours and more after exposure depends on the multiple of the concentration and duration of exposure. 2. At concentrations about the threshold limit value, the presence of other hydrocarbons does not affect the retention or elimination of benzene. 3. The amount of benzene retained in the body for 10 or more hours is dependent on the energy expenditure of the subject during exposure. There is reason to think that elimination after exposure is similarly affected. 4. While the principal route for elimination of benzene is the metabolite, conjugated phenol, in urine, the proportion eliminated in breath depends on the duration of exposure in the 1- to 8-hour range. 5. Three or four distinct compartments for retaining benzene are apparent and these may be identified with specific groups of organs in the body. 6. Mathematical modelling of the system can provide a reasonably accurate representation of benzene behavior in the body, and should enable dosage to individual or groups of organs to be estimated after occupational exposure. 7. Diurnal variation in the elimination of benzene after exposure may introduce a factor of uncertainty of about two into the prediction of exposure from biological monitoring. 8. Patterns of retention and elimination of toluene are very similar to those of benzene, though the principal metabolite in urine is different, and there may be a limit to the maximum amount that can be excreted by that route due to the relatively low solubility of hippuric acid in aqueous solutions.