| This dissertation presents a number of concepts that are drawn together because of their important contribution to the understanding of exposure to indoor air pollutants and the potential for reducing exposure through application of technological controls. Two classes of indoor air pollutants that are generated by human occupants are considered: environmental tobacco smoke (ETS), and airborne particles carrying bacteria or viruses that are released from persons with certain infectious diseases, such as tuberculosis (TB). This dissertation specifically develops and applies an innovative method for apportioning exposure from previously gathered personal monitoring and emission factor data; a powerful set of tools to quantitatively investigate residential ETS-particle exposures and to evaluate the effectiveness of practical control measures; and new experiments on the effectiveness of technological controls for infectious disease control.;In the first part of the dissertation, a new method was developed and applied to estimate the contribution of ETS to exposures to selected toxic air contaminants (TACs). We used previously published data on personal exposure to volatile organic compounds and measurements of ETS emission factors. We randomly sampled the available monitoring data to derive unexposed and passive exposure distributions and iteratively refined an estimate of the ETS-only distribution based on the differences between the unexposed and passive distributions. Emission factors were then employed to infer the ETS-caused exposure to eleven other compounds based on exposure measurements for m,p-xylene, o-xylene, benzene, and styrene. Results showed that ETS contributed a small, but nonnegligible fraction of total exposure for a majority of the studied compounds.;The second portion of the dissertation explored the impact of practical technology-based controls for reducing residential exposures to ETS particles. We used two material balance models, a newly developed analytical model and a previously published multizone aerosol dynamics model, to predict ETS-particle concentrations in multizone indoor environments under different building system configurations. To more directly explore the effects of exposure conditions on health risk, we applied a lung deposition model to predict the mass of ETS particles deposited in the lungs of a nonsmoker exposed in either the smoking or the nonsmoking rooms. We conducted validation experiments to substantiate the model predictions of ETS-particle concentrations. Comparisons between the experimental data and model predictions showed generally good agreement, but that the model predictions were sensitive to the assumed particle emissions. We used the concentration models to investigate the behavior of ETS particles in typical residences. ETS exposures were reduced 10-95% by such control measures as segregating nonsmokers from smokers with closed doors or on different floors of the house, turning on exhaust fans, and using portable air filters.;In the final section of the dissertation, the effectiveness of in-room air filtration, in conjunction with dilution ventilation, was experimentally evaluated for controlling TB exposure in high risk settings. We assessed the effectiveness of in-room air filtration plus ventilation by comparing particle concentrations measured with and without device operation. The seven commercial filters we evaluated typically reduced room-average concentrations by 30-90%, relative to a scenario with 2 air-changes per hour of ventilation (outside air) only. Both the airflow configuration of the filter and its placement within the room were important, influencing room airflow patterns and the spatial distribution of concentrations. Air filters containing highly-efficient (HEPA) filter media were as effective as air filters containing nonHEPA filter media. (Abstract shortened by UMI.)... |
