[The relationship between external and internal doses of trichloroethylene. A simulation study using a physiological pharmacokinetic model].
The relationship between external dose and internal dose of trichloroethylene (Tri) was analyzed by using a physiological simulation model. The external dose of Tri was represented by the time-weighted average (TWA) concentration in inhaled air or by the product of exposure concentration and exposure duration, and the internal dose by the area under the curve (AUC) of Tri blood concentration or by the cumulative amount of total trichloro compounds (TTC) in urine. If TWA concentrations were equal, the internal doses were also equal irrespective of whether Tri exposure was continuous, intermittent, or random. Both AUC of Tri and cumulative amounts of urinary TTC increased linearly with increase of Tri concentration in inhaled air up to 100 ppm. The increase at exposure concentrations between 100 and 500 ppm was non-linear. At concentrations above 500 ppm where Tri metabolism was saturated, AUC increased linearly again but much more sharply than the increase at concentrations below 100 ppm. In contrast, the increase of cumulative amounts approached a plateau along with Tri exposure concentration. If the exposure concentration was below the level when saturation of Tri metabolism did not occur, equal products of Tri concentration and exposure duration resulted in almost the same internal dose. In general, however, the AUC of blood concentration in a high-concentration, short-duration exposure was larger than that of a low-concentration, long-duration exposure, whereas the cumulative amount of TTC was larger in the latter than in the former.