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This study used a full scale mockup of a concrete drilling simulator to simulate drilling processes in an exposure chamber. Six drilling conditions were selected with rotating speeds and drill bit sizes varied from 265 to 587 rpm and 16 to 32 mm, respectively. For each drilling condition, the emitted noise power spectrums were measured and dust exposure concentrations of the fractions of the total (C(tot)), inhalable (C(inh)), thoracic (C(tho)), and respirable (C(res)) were estimated. We find that neither the resultant dust exposure levels nor the noise levels can be explained simply by the involved drilling mechanical energy. By dividing the emitted noise power spectrums into the high and low frequency noise (i.e., W(H) and W(L)), we find that 86.3%, 85.6%, 81.5%, and 77.6% variations of C(tot), C(inh), C(tho), and C(res) could be explained by the combination of W(H) and W(L), respectively. We also find that the emissions of coarse particles and W(L) were possibly contributed by two mechanisms of the impact wear and brittle fracture wear, whereas fine particles and W(H) could be contributed by the mechanism of abrasive wear. Although the predictive models obtained from this study could not be directly used in other dust emission sources, the developed methodology would be beneficial to industries in the future for aerosol exposure assessment, particularly when conducting conventional personal aerosol samplings is not possible in the field.

This study reports a method for constructing a head model with a continuous airway passage beginning from the nostrils and continuing through the second generation of bronchi, using computerized tomographic (CT) images of facial features and airway passages from a healthy Taiwanese male adult. When combined with a manikin torso and connected to a cyclic breathing machine, the Taiwanese head model can simulate human breathing movement. This model enables investigation of important parameters of deposition efficiency without the inter- and intrasubject variability that often occurs in human studies. Being an assembly of numerous polymethyl methacrylate (PMMA) plastic slabs, the head model can be applied to study particle deposition at specified respiratory regions. The nasal geometry obtained in this study was compared with those obtained in other studies, which demonstrated this head model to be 36% smaller in nostril cross-sectional area than for European Americans. Additionally, this Taiwanese head model was found to be shorter in nasal cavity length, and the minimum cross-sectional area was only 50% compared to that of European Americans. This study also measured the nasal inhalation efficiency and deposition for particles ranging from 1.5 to 15 microm under various ventilation levels to test the feasibility of this head model. Future particle deposition studies using this Taiwanese head model can be compared with the currently available data, which are primarily based on Caucasian cast models or human subjects.

Abstract: Although airborne pollutants in urban buses have been studied in many cities globally, long-distance buses running mainly on highways have not been addressed in this regard. This study investigates the levels of volatile organic compounds (VOCs), carbon monoxide (CO), carbon dioxide (CO2) and particulate matter (PM) in the long-distance buses in Taiwan. Analytical results indicate that pollutants levels in long-distance buses are generally lower than those in urban buses. This finding is attributable to the driving speed and patterns of long-distance buses, as well as the meteorological and geographical features of the highway surroundings. The levels of benzene, toluene, ethylbenzene and xylene (BTEX) found in bus cabins exceed the proposed indoor VOC guidelines for aromatic compounds, and are likely attributable to the interior trim in the cabins. The overall average CO level is 2.3 ppm, with higher average level on local streets (2.9 ppm) than on highways (2.2 ppm). The average CO2 level is 1493 ppm, which is higher than the guideline for non-industrial occupied settings. The average PM level in this study is lower than those in urban buses and IAQ guidelines set by Taiwan EPA. However, the average PM10 and PM2.5 is higher than the level set by WHO. Besides the probable causes mentioned above, fewer passenger movements and less particle re-suspension from bus floor might also cause the lower PM levels. Measurements of particle size distribution reveal that more than 75% of particles are in submicron and smaller sizes. These particles may come from the infiltration from the outdoor air. This study concludes that air exchange rates in long-distance buses should be increased in order to reduce CO2 levels. Future research on long-distance buses should focus on the emission of VOCs from brand new buses, and the sources of submicron particles in bus cabins. [Copyright &y& Elsevier]

This study investigates the levels of particulate matter smaller than 2.5μm (PM2.5) and some selected volatile organic compounds (VOCs) at 12 photocopy centers in Taiwan from November 2004 to June 2005. The results of BTEXS (benzene, toluene, ethylbenzene, xylenes and styrene) measurements indicated that toluene had the highest concentration in all photocopy centers, while the concentration of the other four compounds varied among the 12 photocopy centers. The average background-corrected eight-hour PM2.5 in the 12 photocopy centers ranged from 10 to 83μgm−3 with an average of 40μgm−3. The 24-h indoor PM2.5 at the photocopy centers was estimated and at two photocopy centers exceeded 100μgm−3, the 24-h indoor PM2.5 guideline recommended by the Taiwan EPA. The ozone level and particle size distribution at another photocopy center were monitored and indicated that the ozone level increased when the photocopying started and the average ozone level at some photocopy centers during business hour may exceed the value (50ppb) recommended by the Taiwan EPA. The particle size distribution monitored during photocopying indicated that the emitted particles were much smaller than the original toner powders. Additionally, the number concentration of particles that were smaller than 0.5μm was found to increase during the first hour of photocopying and it increased as the particle size decreased. The ultrafine particle (UFP, <100nm) dominated the number concentration and the peak concentration appeared at sizes of under 50nm. A high number concentration of UFP was found with a peak value of 1E+8 particlescm−3 during photocopying. The decline of UFP concentration was observed after the first hour and the decline is likely attributable to the surface deposition of charged particles, which are charged primarily by the diffusion charging of corona devices in the photocopier. This study concludes that ozone and UFP concentrations in photocopy centers should be concerned in view of indoor air quality and human health. The corona devices in photocopiers and photocopier-emitted VOCs have the potential to initiate indoor air chemistry during photocopying and result in the formation of UFP. [Copyright &y& Elsevier]