煞車來令業石綿作業環境輔導改善

Asbestos Exposure Assessment and Workplace Improvement in the Brake Lining Industry

我國勞工暴露於石綿危害之行業以石綿水泥瓦製造業和煞車來令製造業兩個行業為主，前者之勞工八小時時量平均暴露濃度似已低於我國現行標準：1 f／cm3，後者在民國 84 年時仍約有 20%之環測樣品高於 1 f／cm3。故本研究主要目的在輔導煞車來令業者改善勞工石綿暴露之危害，藉由作業環境測定和現場調查掌握其石綿作業場所主要污染源及製程，再參考國內外局部排氣工程資料及作業管理方法研擬改善建議，並尋求協力廠商完成改善。最後彙整 12 家受訪廠不同製程的局部排氣缺失、環測資料，提出局部通風設計及安全衛生對策供業者參考。研究發現，投、卸料作業環境的石綿濃度最高，進行改善的工廠其樣品平均濃度由改善前的 1.66 f／cm3降至 0.71 f／cm3，濃度約降低 57%；同時樣品超過 8 小時時量平均容許濃度的廠家則由 5 家減少為 1 家。石綿濃度次高的為初胚作業，平均濃度為 0.46 f／cm3，其中有 1 家工廠的樣品超過 8 小時時量平均容許濃度。就製程單元的改善成效而言，投料氣罩外石綿濃度由 0.94 f／cm3降至 0.49 f／cm3，降幅達 48%；卸料部分則由 1.83 f／cm3降至 0.75 f／cm3，降幅達 59%。當增加作業環境清潔工作頻率，則可將區域濃度由平均之 0.50 f／cm3降低為 0.33 f／cm3，降幅為 34%。87年度實際工程改善前，投卸料作業之樣品原約有 75%高於 1 f／cm3，17%介於 0.5〜1 f／cm3，而改善後分別為 14%和 50%。這樣的改善成果若以美國 ACGIH 對白石綿之管制濃度為 0.5 f／cm3為參考標準，我國仍須加以努力。

The workers of asbestos cement board (ACB) and brake lining (BL) manufacturing industries are the major asbestos exposure groups. The eight-hour time-weighted average of asbestos were below the permissible exposure limit (PEL), 1 f/cc, in ACB factories while nearly 20% of air sampling data of BL factories were found to be over the PEL accordingly to a study published in 1995. This study aims to investigate the occupational asbestos exposure of BL factories. Walk- through survey, work place monitoring, job analysis and engineering control were conducted at 12 factories on-site. Practical local ventilation designs and good safety and health practices were also designed to disseminate the technological solutions to other BL factories. Workplace monitoring results indicated that loading and unloading processes had the highest exposure, and the average airborne concentrations before and after implementation of the improvement plan were 1.66 and 0.71 f/cc, respectively. Among the factories implemented the engineering control schemes, the percentage of worker exposures over PEL decreased from 66% to 17% in loading and unloading areas. The shaping process had the second highest exposure with an average of 0.46 f/cc with one factory exceeding the PEL. By improving poor ventilation equipment, asbestos emissions were also decreased by 48% from 0.94 to 0.49 f/cc for loading process and decreased by 59% from 1.83 to 0.75 f/cc for unloading processing. Meanwhile, workers’ exposures were also reduced by 54%. Sound hygiene practices reduced area exposure concentrations by 34% from 0.50 to 0.33 f/cc. For both loading and unloading processes, 75% and 17% of personal exposure samples were over 1 PEL and between 0.5 and 1 PEL. The percentages were improved to 14% and 50% with improved working condition according to this study. Despite the fact that significant improvement has been achieved, more efforts are needed to improve the work environment of brake lining manufacturing industries since ACGIH recently lowered the threshold limit value of chrystotile from 0.5 f/cc to 0.1 f/cc.