Exposure Assessment of Respirable Particulate Matter and Nanoparticle Number Concentrations in Selected Metal Processing Plants

• Main Authors: Wei-Lun Chang, 張維倫
• Other Authors: Li-Hao Young
• Format: Others
• Language: zh-TW
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/05602472009951202359

碩士 === 中國醫藥大學 === 職業安全與衛生學系碩士班 === 99 === This study aims to determine workers’ personal exposure to respirable particles (< 4 μm) and their associated water-soluble metals, characterize the number size distributions of ambient nanoparticles (<100 nm), and subsequently identify influential their emission sources in selected metal processing plants. The selected workplaces include one precision metal processing plant, one automotive body-parts processing plant, one metal welding plant and one metal milling plant. Respirable dust aluminum cyclones were used to collect respirable particles, a sequential mobility particle sizer (SMPS+C) for number size distribution measurements, and an ICP-MS for water-soluble metals analysis. The results show that the workers’ respirable particle concentrations (PM4) were between 0.01 to 0.27 mg/m3, which are well below the regulatory standard. The workplace nanoparticle number concentrations are between 2.03 × 104 to 1.19× 106 particles/cm3, equivalent or significantly higher than that in similar processes reported in earlier studies and typical ambient concentrations, with mode diameters in the size range of 10 to 50 nm. The PM4 and NUF showed negligible correlation among all the processes, except the mechanical processes in which a weak negative correlation was observed. The concentrations of water-soluble metals varied with the metal production processes; nevertheless, higher concentrations of K, Mn, Cu and Cd were associated with grinding, cutting and welding. The number size distributions of nanoparticles are easily affected by nearby strong emission sources, workers’ operation procedures, emission control devices, and ventilation. As a result, it is difficult to elucidate the so-called “background” level and hence process-specific particle emission characteristics. With that in mind, future exposure assessment studies are recommended not to use respirable particles as a surrogate for nanoparticles, and to focus on personal exposure to workplace nanoparticles.