| 摘要: | 本研究目的為評估金屬加工作業環境中，勞工之可呼吸性微粒(< 4 μm)質量濃度(PM4)、水溶性金屬成分及奈米微粒(<100 nm)數量濃度(NUF)與粒徑分布等暴露特性，並鑑別其主要來源製程。研究對象包括精密金屬加工廠、汽車零件製造廠、金屬氬銲廠及銑床加工廠。方法乃使用鋁製旋風分離器採集個人可呼吸性微粒，再以感應耦合電漿質譜儀(ICP-MS)檢測其中之10種水溶性金屬種類及濃度，並搭配掃描式電移動度分徑儀(SMPS+C)量測作業環境中奈米微粒數量濃度粒徑分布。本研究四間金屬加工廠勞工之PM4介於0.01至0.27 mg/m3間，遠低於法規之厭惡性可呼吸性粉塵濃度標準。此外，廠內作業環境NUF介於2.03 × 104 至1.19 × 106 個/cm3間，相當或顯著高於一般大氣與國外相關製程之濃度，且波峰粒徑多介於10至50 nm間。所有製程中之NUF與PM4間並無相關性，但物理性機械製程中之兩者間則有弱度負相關。勞工可呼吸性微粒中所含之水溶性金屬則隨製程而異；其中以金屬研磨、切斷及銲接作業所產生的微粒，其水溶性金屬濃度高於其他製程，當中又以K、Mn、Cu及Cd濃度為最高。作業環境中奈米微粒數量濃度粒徑分布易受到高污染製程、勞工作業方式、控制設備使用與否及效能、及通風狀況等影響，因此不易釐清“背景值”之影響，導致探討特定製程微粒特性之困難度增加。有鑑於此，建議未來相關之暴露評估研究不宜使用可呼吸性微粒質量濃度推估奈米微粒數量濃度，且建議使用奈米微粒個人暴露採樣方法，以獲得貼近勞工之暴露實況。
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. |
