耐火材料業勞工游離二氧化矽暴露特徵

Characteristics of Free Silica Exposures for Workers in the Refractory Material Manufacturing Industry

本研究針對南台灣地區之兩家耐火材料工廠，進行不同製程勞工（共計 58 人次）之可呼吸性粉塵採樣，以評估勞工之粉塵及游離二氧化矽（free silica）暴露情形。結果顯示，兩家耐火材料業之呼吸性粉塵暴露濃度介於 0.03～13.70 mg/m3 ，而游離二氧化矽之濃度則介於低於偵測下限至 127.85 µg/m3 ，其中以混合區及包裝區較高，而原料倉庫區為最低。在考量耐火材料業之游離二氧化矽之重量百分比情形下，可發現其屬第一種（free silica ≥ 10%）及第二種粉塵（free silica < 10%）粉塵之不合格率分別為100%及81.2%；唯若以厭惡性粉塵來評估之，則均未發現不合格之情形。由此可知free silica 之定量對耐火材料業勞工之暴露評估扮演極重要之角色。有鑑於空氣樣本 free silica 之分析過程相當繁複，因此本研究亦嘗試探討是否可採用作業場所之地板粉塵或堆積原物料之大體積樣本（bulk sample）之free silica含量取代之。結果發現以地板粉塵或堆積原物料之free silica重量百分濃度，直接推估空氣樣本濃度並不可行。另本研究亦發現作業環境空氣中粉塵之粒徑分布與游離二氧化矽粒徑分布具明顯差異，因此如欲考量以傳統之大體積空氣樣本（bulk air sample）之free silica含量推估可呼吸性粉塵之含量，則需留意所採用之採樣器之粉塵捕集性能需符合可呼吸性粉塵之採樣準則。

In this study, sampling was conducted on two refractory material manufacturing plants located in southern Taiwan. A total of 58 personal dust samples were collected to assess workers’ dust and free silica exposures. Results show the respirable dust and free silica personal exposure concentrations ranged from 0.03~13.70 mg/m3 and ND~127.85 μg/m3, respectively. Among them, workers at both the mixing and packaging areas were found with higher exposure levels than those at the warehouse. As samples classified based on their free silica content, 100% and 81.2% samples are found above current permissible exposure limits (PELs) for Type I dust (i.e., free silica ≥ 10%) and Type II dust (i.e., free silica < 10%), respectively. On the other hand, no sample was found above for samples containing no free silica (i.e., Type IV dust). Above results clearly indicate the importance of free silica content on assessing worker's dust exposure. In addition, this study also suggests that free silica content that found in the raw material or the floor dust were not representative to that containing in the workplace atmosphere. Moreover, significant differences were found between the size distribution of dust contents and free silica contents for samples collected from each individual workplace. Results of this study suggest that the use of free silica content containing in bulk air sample to estimate the free silica content in respirable sample, the performance of the bulk air sampler is required to comply with the respirable dust sampling criterion.