| Aerosol-related health effects are strongly related to particle deposition in the human respiratory system, which is strongly dependent on particle size. Research on regional deposition has led to the definition of the inhalable, thoracic, and respirable fractions, which are now listed as exposure standards criteria for workplace aerosol standards. With the knowledge of the full particle size distribution, it then becomes possible to determine the aerosol contained not only within these fractions but also within any other fraction than may be defined based on measurements of regional deposition in humans for specific conditions. This is especially useful in assessing the workplace aerosol exposure. Therefore, the broad objective of this study was to explore improved ways to measure the particle size distribution in aerosol exposure environments and so to investigate the potential effects of the particle size distribution on the sampling performances of a number of personal aerosol samplers.; Five major objectives were achieved, including: (a) a calm air chamber with the ability to deliver constant aerosol for sampler testing, (b) a modified-Marple cascade impactor with a top foam stage to provide a clear-defined aspiration efficiency based on scientific theories to collect aerosols in environments, and later extended into a family of cascade impactor versions with different numbers of impaction stages, (c) an algorithm was developed in Microsoft EXCEL for interpreting the results from the modified-Marple family of samplers, (d) performance evaluation for the family of the modified-Marple and personal aerosol samplers (IOM, Baby-IOM, CIS, and Button) in laboratory environment and in actual workplaces. The modified-Marple cascade impactor was shown to provide information about particle size distribution with acceptable accuracy for both laboratory environment and actual workplaces. Yet, for the personal aerosol samplers, there exist some discrepancies between the laboratory experiments and the workplace measurements which could be the results of environmental factors outside of control and how the performance was defined and evaluated. These results reinforce the view that acquiring the information about the environment before conducting measurement is essential to a valid aerosol exposure assessment. More work is needed to resolve remaining issues derived from the processes of analyzing or interpreting the sampling results. |
