- 學位論文
以區域風險評估之方法探討風險轉移及風險降低策略之有效性
A regional risk assessment approach to evaluate the transfer of risk and the effectiveness of risk reduction
摘要
傳統的健康風險評估主要著重在評估單一污染源的影響，每一個單一污染源可能均符合法規或管制標準；然而，在國家尺度或區域尺度的風險評估架構下，風險的來源在於受體經由不同的暴露途徑而接觸到污染物質，而造成暴露的方式則可分為直接的與間接的，直接的暴露為受當地污染排放影響或鄰近污染排放跨區域傳輸的影響，間接的暴露為透過農產品運銷而接觸到其他區域所排放的污染物質。在現階段的風險評估中，間接暴露的影響是極少被提及的，這可能造成忽略了部分的風險危害。 本研究考量多重污染源所造成的累積性效應，以建立大尺度的區域風險評估方法為目的，將跨區域影響之因素納入評估流程，並採用敏感度分析的概念，建立不同區域與產業之排放量，對不同區域受體所產生風險的關係，作為判定風險減量效率之依據。利用各縣市間農產品的運銷量進行受體暴露量的修正，建立跨區域風險傳輸模型。結果顯示考量農產運銷對風險結果的排序有很大的影響，同時呈現出各縣市不同的風險來源，不再只是鄰近的污染源所造成，更有可能透過農產運銷的方式將風險轉移。利用風險轉移率來計算考量農產運銷後的風險變化，對於風險轉移率大於1的地區，代表因透過農產運銷將受污染之農產品輸入進來，提高暴露機會而增加了風險，顯示若在傳統的風險評估架構下，其風險是被低估的，因此考量跨區域風險傳輸是必要的。 將總排放量與風險評估結果進行比較，發現不論是否考量農產運銷的影響，排放量的高低與造成各縣市風險高低的排序，並沒有存在一致性，即高排放量的地區並不一定使當地成為高風險地區。因此，本研究利用敏感度分析的概念，分別將各縣市總排放量和產業總排放量作為分析之變數，計算風險減量之敏感度和彈性，探討不同地區不同產業類別的排放減量對各縣市風險減量的有效程度，並將其整合成風險減量效率的分數，以反映整體風險減量的效果；結果顯示，電子零組件製造業和飲料製造業的分數高於其他產業，在縣市別的部分以雲林、苗栗和彰化的分數高於其他縣市。 應用本研究之分析方法，可以找出對特定地區風險減量有效的管制對象，針對高風險敏感度和高風險彈性的地區進行排放管制，所得到的效果是最大的；另一方面其也反映了產生風險的潛勢，若未來在選擇新設場址時，高風險敏感度和高風險彈性的地區是不適宜的，因其造成的影響較大且較廣；而就產業別而言，高風險敏感度和高風險彈性的產業必須加強管制，因其增加一部分排放量，則可能影響到許多縣市。同時可藉由此研究可判別出不同的區域，其風險來源主要為當地貢獻或是由其他地區轉移而來，提供資訊給管理者作為決定加強排放管制對象的依據。
並列摘要
The conventional health risk assessment is the process used to estimate the health effect of a certain emission source. Each source may meet the emission control standards. However, at national or regional scales, receptors expose to contaminants from all emission sources. Local emission sources are a dominant and direct factor for health risk. Emission sources directly affect contaminant inhalation and food intake via local agricultural products. Moreover, the transportation of agricultural products is an indirect factor causing the transfer of risk between different areas through ingestion of agricultural products obtained from other areas. This indirect exposure pathway is rarely included in the conventional health risk assessment. The objective of this study is to reveal the effect of assessment including the transportation of agricultural products, evaluating the results of exposure to local and non-local food as a spatial attribute. Furthermore, human health risk results from the quantity of emissions, the location and geography of emission sources, and the transportation of food. Because of the complexity of risk, the other aim of this research is to assess the health risk caused by total emission sources, to identify the spatial distribution of risk, and to estimate the effectiveness of risk reduction. The results show that the transportation of agricultural products is the major and indirect factor causing the transfer of risk. Local receptors may ingest food which contaminated by other emission sources and transported to local market. The risk transfer ratio was developed to reveal the effect of including the transportation factor of agricultural products in each area. If the ratio is greater than 1, the risks increase as a result of importing agricultural products, i.e., people ingest contaminated food from other counties. Assessments that do not include the transportation of agricultural products may not represent the overall real situation. In this study, an adjusted method incorporating transportation of agricultural products has been developed for assessing transfer of risks. This approach is valuable for assessing the overall health risks because it describes indirect impacts on site-specific health risks and the proportion of health risks derived from other locations. Moreover, high emissions in a county do not correspond to high risk. Hence, there is an urgent need to develop an evaluation method to effectively reduce risk. To understand how risk evaluation is dependent on the variability of emissions, sensitivity and elasticity analysis were adopted in this study, and designed a risk score to rank the efficiency of risk reduction. The results indicate that highest risk scores with respect to the emissions reduction of each industry sector are electronic parts and components and beverage. The highest risk scores with respect to the emissions reduction of each area are Changhua and Yunlin. This indicates that emissions reduction in these industry sectors or areas would more efficiently reduce the risks. The findings of this study illustrate the need to evaluate the efficiency of risk reduction. The government and decision-makers can be proactive in targeting industry sectors and areas when establishing environmental policy and managing health risk. Moreover, risk scores can identify the reduction potential of each sector or area. This method can provide more holistic information for risk management and prevents the development of increased risk.
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