Exposure of engineered nano-sized and respirable particles at different workplaces
|Keywords:||暴露評估;氣膠採樣;奈米微粒;可呼吸性微粒;旋轉腔體試驗;exposure assessment;aerosol sampling;nanoparticle;respirable particle;rotating drum test|
|Abstract:||本研究在三個不同工程奈米微粒相關的作業場所進行工程奈米微粒及可呼吸性微粒暴露量測，包括奈米二氧化矽氧化樹酯封裝材料製造廠的粉體混料區及奈米碳黑和奈米碳酸鈣粉體製造廠的粉體包裝區。結果顯示奈米微粒質量濃度在碳黑粉體製造廠為最高，主要原因柴油堆高機的廢氣中含有大量的奈米微粒。在奈米二氧化矽氧化樹酯封裝材料製造廠所測到的可呼吸性微粒質量濃度達1963±1051 □g/m3，比奈米碳黑及奈米碳酸鈣的159±52及154±74□□g/m3高很多，主要原因在於此工作場所逸散出的奈米微粒較多，且作業空間未使用有效的通風系統。此外在這三個作業場所中所量測到的質量中間氣動粒徑為4.6~6.1 □m，屬於超微米範圍而不是奈米尺度，此結果可由化學分析和旋轉腔體分散方法得到驗證。對於奈米微粒數目濃度而言，本研究發現只有在奈米粉體處理過程中或是柴油堆高機的廢氣才會導致作業場所中的奈米微粒數目濃度升高，在其餘時間其濃度皆維持在背景值附近。由穿透式電子顯微鏡的分析可知奈米微粒確實存在，然而現場量測及粉體分散之結果均顯示，奈米微粒的數目濃度雖高於微米級微粒，但由於奈米微粒聚集成微米級微粒之故，致使其質量濃度很低。因此本研究建議對於奈米粉體的作業場所的暴露評估，應同時兼顧奈米及可呼吸性微粒的數目及質量濃度。|
In this study, engineered nanoparticle (ENP) and respirable particles exposure measurements were conducted at three different ENP-related workplaces, including the mixing area of nano-SiO2 epoxy molding compound plant, two bagging areas of the nano-CaCO3 and nano-carbon black (nano-CB) manufacturing plants. Results show that NP mass concentration at the nano-CB manufacturing plant was the highest due to diesel forklift exhaust. The highest respirable particle mass (RPM) concentration was observed to be 1591±1051 □g/m3 at the nano-SiO2 epoxy molding compound plant, which was much higher than 159±52 and 154±74□□g/m3 at the bagging areas of the nano-CB and nano-CaCO3, respectively, due to higher NP emission rate and ineffective ventilation system at this location. The mass median aerodynamic diameters (MMADs) at these workplaces were supermicron rather than nano-sized, which was also confirmed by chemical analysis of the collected particles and the results of the rotating drum testing. The NP number concentration maintained at background level unless there were material handling activities or if the diesel forklifts were used in the workplaces. The TEM analysis showed that nano-sized particles indeed existed. However both the field exposure data and results of rotation drum test showed that although nanoparticle concentration was much higher than that of supermicron particles, its mass concentration was much lower due to agglomeration of nanoparticle into micron-sized particles. Therefore, it is suggested that both number and mass concentrations of nano-sized and respirable particles be considered when assessing the exposure of nanopowder-related workplaces.
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