職業暴露環境中金屬粉塵採樣技術：濾紙種類對殘留率之影響

Sampling Techniques for Metal Dust in Occupational Exposure Environments: The Effect of Filter Membrane Types on Wall Residue Ratio

勞工作業環境中，使用傳統濾紙匣採樣器進行空氣中金屬粉塵採樣時，因內壁損失，導致採樣樣品濃度被低估。為避免此類採樣誤差，美國NIOSH 7306方法建議使用囊式濾紙採樣器進行採樣，該方法在採樣過程中可將所有金屬粉塵收集在膠囊內，從而解決傳統採樣方法因內壁殘留導致分析結果偏低的問題。
本研究採用實驗室模擬（鋅粉）與現場實測（鉛蓄電池製造廠及金屬加工廠），同步比較傳統混合纖維素酯濾紙（Mixed Cellulose Ester Membrane Filter，MCE，簡稱MCE濾紙）與新型纖維素內膠囊濾紙（Cellulosic Internal Capsule，CIC，簡稱CIC濾紙）對鋅、鐵、鉻3種金屬粉塵殘留率的影響。透過電感耦合電漿體原子發射光譜法（Inductively Coupled Plasma Atomic Emission Spectroscopy，ICP-AES）進行定量分析，並以成對樣本中位數差異檢定（Wilcoxon Signed-Rank Test）與多樣本中位數差異檢定（Kruskal-Wallis Test）統計差異顯著性（α=0.05），為我國金屬粉塵採樣方法修訂提供實證依據。
研究結果顯示，在實驗室暴露腔採集的24對鋅粉塵成對樣品中，CIC濾紙在總粉塵與可呼吸性粉塵的平均殘留率（分別為0.74%和1.24%）均顯著低於MCE濾紙（7.77%和5.72%），且差異具有統計學意義；在鉛蓄電池製造及鋼鐵業共4家工廠的現場環境中，對鋅、鐵、鉻等3種元素進行總粉塵與可呼吸性粉塵的成對採樣（每廠各6對），MCE濾紙樣本的平均殘留率也顯著高於CIC濾紙樣本，各廠多數成對樣品均呈現統計學上的顯著差異。
CIC濾紙能有效降低採樣匣內壁殘留，提升樣品完整性，建議納入我國金屬粉塵標準採樣方法。然而，在低濃度環境下，需要調整採樣時間等參數，以避免殘留率偏差。後續研究可探討採樣流速與粉塵粒徑分布對殘留機制的影響，以進一步優化監測規範。

In occupational settings, conventional filter cassette samplers used for airborne metal dust sampling result in underestimation of sample concentrations due to wall residues. To mitigate this bias, NIOSH Method 7306 recommends using cellulosic internal capsule (CIC) samplers, which retain all dust within the capsule, thereby eliminating wall residue-induced analytical bias.
We conducted laboratory tests using zinc dust and field sampling at lead-acid battery manufacturing and metal processing plants to compare wall residue ratios of Zn, Fe, and Cr between MCE membrane and CIC samplers. We performed quantitative analysis via ICP-AES and conducted statistical testing (Wilcoxon and Kruskal-Wallis tests,α= 0.05). This study provides empirical evidence for optimizing metal dust sampling protocols in Taiwan.
Results indicate that for 24 paired zinc dust samples in laboratory exposure chambers, the CIC filter membrane exhibited significantly lower wall residue ratios (0.74% for total dust; 1.24% for respirable dust) than those of MCE filter membrane (7.77% and 5.72%, respectively). Field studies across 4 factories (6 paired samples per site) consistently showed higher wall residue ratios in MCE filter membrane samples for Zn, Fe, and Cr, with statistical significance in most comparisons.
CIC filter membranes effectively reduce sampler wall residue and enhance sample integrity, warranting inclusion in Taiwan's standard metal dust sampling protocols. However, parameter adjustments (e.g., sampling duration) are necessary in low-concentration environments to minimize residue bias. Future work should investigate flow rate and particle size distribution effects on residue mechanisms to refine monitoring standards.