以熱暴露腔之均勻性探討其應用在評估勞工熱危害之影響

Skin Absorption and Biological Monitoring of Occupational Exposure to N,N-Dimethylformamide

本研究主要目的在評估一熱暴露腔之各環境參數在控制範圍下之均勻性，並探討以此熱暴露腔在不同環境參數組合下，應用於評估勞工熱危害之有效性。所探討之熱暴露腔內含四組電阻式溫度加熱器、三組超音波霧化器及四個紅外線熱源，並藉一輸送單元（含前置三組風扇、後置六組風扇及一迴風管道）之設置，使腔內之乾球溫度、黑球溫度、濕度及風速均勻分佈至熱暴露腔中。研究結果發現在測試段中，乾球溫度在 25.77～43.12℃、黑球溫度在 29.24～44.41℃、濕度在 1.71～3.25kPa 及風速在 0.91～1.70m/s 情形下，其變異係數均小於 10%，因此可知熱暴露腔對前述環境參數均勻性具良好的控制能力。但需注意的是，當本熱暴露腔環境風速為0.25m/s時，其變異係數則高達50%，究其原因本熱暴露腔對低風速之控制不足所致。唯本研究根據前述環境參數之變異情形，以蒙地卡羅模擬法探討各環境參數之變異性，對勞工熱危害評估之影響，結果發現在前述環境參數之測試範圍內，各環境變異對容許暴露時間之推估均未有重大影響，其推估值之 95%信賴區間均在 3 分鐘之內。因此，本研究推論所設計之熱暴露腔雖在低風速下有較大之變異，但仍足以用來評估勞工之熱危害。

N,N-dimethylformamide (DMF) has been considered as one of most readily skin-absorbed chemicals in literature. The previous reports regarding skin absorption of DMF were, however, conducted in a wellcontrolled condition in the laboratory using human volunteers. The skin absorption estimation of DMF exposure in actual occupational environment is still lacking. The aim of this study was to investigate the relations of urinary DMF biomarkers to the DMF exposures via inhalation and skin in the occupational settings. Seventy-five employees in four DMF-related factories were recruited in this study. Environmental monitoring included breathing-zone sampling and dermal sampling on forearms and hands for each participant. Individual-based biological monitoring included the pre- and post-shift urine measurements with respect to biological monitoring of urinary levels of DMF and N-methylformamide (NMF). We found that 1. Significant differences of DMF concentrations in air and skin were found among different manufacturing processes. Among them, synthetic leather industry was found with the highest DMF exposure. 2. Contrasting to unremarkable skin exposure in hands and forearms in the manufacturing processes of copper-laminate circuit board and synthetic acrylic fiber, the skin exposures in synthetic leather industry were considerably significant. 3. The urinary biomarkers of DMF exposure in this study were significantly associated with both the exposure via inhalation and that via skin. The contribution of skin exposure in hand to urinary biomarkers remained significant even after adjusting the contribution of inhalation exposure. This study affirmed that the skin exposure for those workers who are occupationally exposed to DMF is an important issue in control.