評述職業暴露有害物質容許濃度標準之建立與風險量化

Comment on Setting up Occupational Exposure Level in Relation to Risk Assessment

最近有應用風險評估方法於職業場所化學暴露之呼籲，且政府相關單位成立勞工作業環境空氣中有害物容許濃度建議值審議委員會在廣泛徵求意見。故參考相關文獻與記載，提出此報告，討論工業衛生人員習慣使用的職場暴露容許濃度與風險評估的關係。認為職業暴露容許濃度標準源自劑量──效應曲線上的 NOAEL，在保護幾乎所有工作者的考慮下，使用安全係數法衍生而成；有經驗的職業衛生人員，將暴露值比上容許濃度值得到危害指數，然後決定行動的需要性，其構成與應用之中，已經具有風險評估與風險管理此兩要素的存在。前者在構成職業暴露容許濃度的過程中，客觀分析某化合物的劑量效應曲線亦是時下所談風險評估步驟中重要的風險分析，後者利用容許濃度標準判斷可接受的暴露水準則是具有主觀成分的風險管理。這樣形成的職業暴露容許濃度標準與應用，對有經驗的職業衛生人員而言，具有歷史性長遠可信的績效：可保護幾乎所有的工作者，但是如果必要回答「在此容許濃度標準之下，尚有多少量殘餘的風險？」這類問題，則需要進一步分析。要量化殘餘風險必須仰賴可靠的劑量效應數據，使用風險評估模式，除非很吻合模式成立的條件設定與限制，否則應用結果還是居於〝相信〞而非〝知識〞 。

Applying risk assessment on occupational exposure to chemicals is the overwhelmed suggestion recently. This report is intended to explore occupational exposure level (OEL) in terms of risk assessment. In fact, occupational exposure level, during its process of being constituted as well as its application, involves the essence of risk assessment and risk management. OEL, being claimed to prevent nearly all workers from adverse health effects, takes account of the risk analysis of dose－response curve, an important step in risk assessment, and introduces safety factor throughout its setup. In practice, occupational hygienists are used to calculate hazard index, the ratio of exposure level versus OEL, and rely on it to take action. This is due to the fact that hygienists appreciate the historically proved appraisal on OEL protecting nearly all workers, though it does not quantify the residual risk. If answering the residual risk under OEL is necessitated, quantifying risk approach based on reliable dose－response data and models is required. However, models employed by this approach usually underlie hypothesis as well as limitations. As a result, the estimated risk to the risk managers is also believable rather than knowledgeable, when the managers implement of risk management.