Student Research: Chang-Fu Wu
Most current instruments used for personal sampling can not accurately detect mixtures of compounds in real time. This dissertation presents a novel way of using open-path Fourier transform infrared (OP-FTIR) spectroscopy to overcome this problem for evaluating personal exposures. For conditions in which workers stayed at fixed workstations, a bi-beam sampling strategy was evaluated. A series of experiments with 6 human subjects performing two tasks at two workstations was conducted inside a chamber. The results show that the locations, tasks, and subjects are not significant factors when using the bi-beam strategy to estimate personal exposure at the nose height. Our model also fitted the experimental data reasonably well (R2=0.87). The gamma model was applied to estimate the mixing conditions and the range of the slope coefficient of the linear exposure model. For conditions in which workers moved freely, a Computed Tomography (CT) reconstruction approach was applied. This approach was assessed first with computer simulations which showed the average of the estimated exposures was close to the average of the true exposures. The concordance correlation factor (CCF) between the estimated and true exposures in these situations also was reasonably good (0.50 ~ 0.58). Experimental data were collected inside a ventilation chamber with a remote controlled robot as a surrogate for a real human to verify the simulation results. A personal sampling device measured for the true exposure on the robot. The estimated personal exposures were calculated from both the area sampling array data and from the CT-FTIR measurements along with the information about the robots' locations in real time. The location information was obtained by applying image analysis on recorded digital videotapes. The average slopes of the regression lines between the true and estimated exposures was 0.76 with 95% CI overlapping 1. The CCF value between the true and CT-FTIR estimated exposures was 0.52, which was similar to what we found in the simulation studies. The results from the simulation and experimental studies in this dissertation suggest that it is possible to estimate personal exposures for mobile subjects with the OP-FTIR or an area sampling array.