EFFECTS OF VARIATION IN EXPOSURE TO AIRBORNE ACETONE AND DIFFERENCE IN WORK LOAD ON ACETONE CONCENTRATIONS IN BLOOD, URINE, AND EXHALED AIR

Using a physiologically based pharmacokinetic (PBPK) model, the effect s of variation of exposure concentration of acetone on three biologica l indicators--acetone concentrations in blood, urine, and exhaled air- -were investigated. The effect or the difference in work load was also examined. It was confirmed that the model could be used to estimate a cetone concentrations during fluctuating exposure by comparing simulat ed acetone concentrations with the corresponding values observed in fi eld surveys. By inputting the exposure situations into the PBPK model, the variabilities of the biological indicators were simulated. The va riation of acetone exposure was expressed by seven 1-hour time-weighte d averages (CexpS). The arithmetic means of the CEXPS were 200 and 750 ppm. The geometric standard deviations (GSDs) were 1.5, 2.0, and 3.0, representing low, moderate, and high variations, respectively, Work l oads were set at 15 and 50 W. Consequently, there were 12 exposure sit uations. The acetone concentrations in Venous blood (C-B) and exhaled alveolar air (C-A) at 1 minute after the end of the work shift were se lected as biological indicators of exposure because they were predicte d to decrease rapidly at the end of exposure and become relatively sta ble after 1 minute. The acetone concentration in urine excreted during the last 2 hours of the work shift (C-U) was also used as a biologica l indicator. Simulation was repeated 100 times with randomly permuting CEXPS for each situation. The mean values of C-B, C-U, and C-A showed almost no variation regardless of the difference in the GSD of CEXPS. The coefficients of variation increased with the GSD of G(EXP)S but w ere less than 0.2. Consequently, these variables were acceptable as bi ological indicators of daily average exposure for the same work load. However, the difference in work load greatly changed the mean values o f C-B, C-U, and C-A, thus making it difficult to use these variables a s indicators of daily average exposure for different work loads.