Abstract
The recent reduction of the threshold limit value of the American Conference of Governmental Industrial Hygienists for toluene to 50 ppm called for a redefinition of the corresponding biological exposure indices (BEIs). The simulation model used in this study consists of seven compartments representing the different tissues. All simulations were done for a standard man (170 cm, 70 kg) exposed in standard working conditions (8 hours/day with a 1-hour break, 5 days/week). The comparison of the simulation results for several biological indicators with measurements in workers showed good agreement. The effects of confounding factors, such as exposure fluctuation, physical work load after exposure, and air contamination at the sampling site were also simulated. According to fluctuations of the exposure level within the exposure day, there were big differences in the venous blood toluene concentrations at the end of shift, but no difference in the venous blood toluene concentrations the next morning. The exercise of 100 W for 1 and 2 hours after work did not have a large effect on the venous blood toluene concentration the next morning. In conclusion, the simulation results show that toluene in venous blood sampled in the morning can be a reliable determinant to monitor toluene exposure. The BEI should be in the range of 0.07 to 0.09 mg/L.