以生理觀點探討依WBGT規範高溫作業勞工作息標準之合理性研究

A Study on the Feasibility of Using the WBGT Index to Evaluate Heat Strain of Workers on the Physiological Basis

本研究嘗試利用本省南部某兩家鋼鐵廠合計91 位高溫作業勞工之生理測值，依熱蓄積與水份流失之生理觀點，探討以WBGT 規範高溫作業勞工工作休息時間合理性。結果發現無論就ACGIH 之恕限值或我國法令之作息標準，依WBGT 所規範之作息時間，就生理觀點而言，並無法適用於全部高溫作業環境；並且依生理觀點所推估之理論容許作息時間，與WBGT 之規範工作時間比值討論之，發現在每小時容許作息時間比例為25％時，無論ACGIH 或我國法令標準，均有保護過當之現象，而其嚴重情形有隨工作負荷要求之增加，而有下降之趨勢；至於在其他容許作息時間比例，本研究發現我國現有標準保護不足之情形，但在ACGIH 則僅重工作時有此現象。另本研究亦發現WBGT 與生理觀點之理論容許作息時間，僅在中度工作時存在相關模式（R2=0.24），至於在輕工作或重工作則相關性並不清楚，其可能與數據本身涵蓋範圍不足以描述關係模式，抑或其間實質上並不存在相關模式有關。因此，未來是否應進一步擴大測試範圍，以確認相關模式之存在情形，抑或應結合生理觀點以建立一合理之熱壓力預測模式，來取代現有之WBGT，實有其重要性。

In this study, physiological measurement data of 91 workers from two steel milling plants are used to access the feasibility of using the WBGT index to evaluate the resultant heat stains (including heat storage and dehydration ) of workers. The result shows that the both WBGT-based work/rest time regimen standards as suggested by ACGIH and regulated by Taiwan government are found to be not fully feasible from the aspect of point of heat strains. In general, over-protections are found at the regimen as allowing 25% work / 75% rest for both standards, and the degree of over-protections increased as work loading decreased. Under other work / rest time regimen situations, inadequate protections are found for all work-loading levels as estimated by using Taiwan governmental standard; however, only the heavy work-loading level is found inadequate as estimated by using ACGIH suggested standard. No correlation can be found between physiological-basis allowable exposure time and WBGT index under light and heavy work loading levels; however, a poor relationship (R2=0.24) is found at moderate work-loading level. It seems that the WBGT index is not able to fully reflect the strength of resultant heat strains, and thus the development of new heat stress indices would be necessary in the future.