多重污染源簡易暴露評估方法之研究

Abstract

政策環評和個案環評的決策過程，皆會將健康衝擊的評估結果納入考量，但對於空間尺度介於國家、區域與場址之間，或是同時評估多排放源的問題，現有的健康風險方法並無法有效率處理。因此，本研究擬以現有固定污染源實地風險評估方法為基礎，發展一套適用於評估不同空間尺度下之固定污染源健康衝擊的簡易評估方法。 本研究的第一部份，在於多重污染源簡易暴露評估方法之建立。本研究所建立之固定污染源實地風險簡易評估方法分成整體衝擊性評估及實地性評估兩個階段，整體衝擊性評估係依行業別自TEDS資料庫篩選出203個散布在台灣本島各縣市的固定污染源，先利用大氣擴散模式（AREMOD）模擬上述排放源之大氣擴散結果，再利用不確定性分析工具與環境多介質模式，結合大氣擴散結果與各類環境參數獲得各類環境介質累積機率濃度分佈；實地性評估的部分則是結合固定污染源的排氣量、排放濃度以及所在位置，轉換成衝擊率（impact ratio）、實地轉換因子-（site-specific transfer factor）、實地衝擊因子(site-specific impact factor)進行實地暴露量的估算。透過以上兩個步驟，即可有效簡化原本繁複的評估流程，又能獲得考量不確定性分佈的暴露評估結果，可用以評估台灣各地區的固定污染源。 本研究的第二部份，係以所建立之簡易評估方法進行現有的戴奧辛列管排放源之實地暴露評估；其目的係驗證此方法用於多污染源及跨區域問題時之適用性。案例模擬的部份總計涵蓋電力業、鋼鐵業、水泥業、金屬二次冶煉業及各型焚化爐在內的323個列管排放源，其分布縣市亦包含台灣本島所有行政區，是以評估結果亦可做為我國戴奧辛背景健康衝擊的參考。結果發現，在本研究所假設的排氣量（依據TEDS資料庫）及排放濃度（依現行管制標準）下，並假設其影響範圍為25km× 25 km，評估結果以電力業之整體實地暴露量最高，鋼鐵業次之，兩者分別佔整體暴露量的57%以及25%；健康衝擊相對較小的是廢棄物處理業，其總暴露量僅佔整體約3%。若就單一排放源的評估結果來看，不同的累積機率分佈下則有不同的排序差異所貢獻最高實地暴露量的排放源，然而，不論是以何種累積機率分佈，單一污染源皆以電力業下之中部火力發電廠之暴露量最高，其95%累積機率實地暴露量達4.61E-10 mg/kg-day，佔了總暴露量的28%。另依地區來看，臺中縣、彰化縣、高雄縣不論是在實地風險亦或族群風險都是偏高的。以上結果顯示，電力業的管制標準是我國現階段降低戴奧辛排放量應被優先檢討的；若有新設列管戴奧辛排放源，應避免設置在臺中縣、彰化縣、高雄縣，除了因為其係屬背景風險偏高的區域外，更重要的是上述行政區本來就是為實地衝擊特性偏高的地區。 然而，本研究並無針對不同地區的大氣擴散特性進行個別考量，在實地性的假設上亦建立在空間均質分佈的前提下，對於具極端特性的排放源之評估結果是無法有效呈現的。即便如此，本研究所建立之多重污染源簡化評估方法對於大量評估排放源的健康衝擊仍是可行的，未來亦可應用固定污染源排放其他種類污染物之評估中。

The health impact assessment will be considered both in the decision-making process of the strategic environmental assessment（SEA）and environmental impact assessment (EIA). However, when assessing the spatial scale among country, region and site, or multiple emissions, the existing health risk assessment method can not evaluate efficiently. Therefore, on the basis of existing site-specific risk assessment for stationary emission sources, this study intends to develop a new simplified exposure assessment method to evaluate multiple emissions under different scales. There are two phases in the simplified exposure assessment methods for multiple emissions. The first phase was to establish overall impact properties of emissions in Taiwan. The combination of atmospheric dispersion results from 203 emissions simulated by AREMOD, environmental parameters, environmental multimedia transport and transformation model and uncertainty analysis tools to get the cumulative probability distribution of 15 environmental media. The second phase is the site-specific exposure assessment, combing the emission rates, emission concentrations, and the location properties of the stationary emissions, and transferring to impact ratio, site-specific transfer factor and site-specific impact factor. Through the above steps, we can effectively simplify the original complicated evaluation process and consider the uncertainty of exposure assessment as well as. Case study is to assess existing dioxin emission sources in Taiwan. The purpose of this case is to verify the simplified method for multiple sources and cross-regional issues. There are 323 dioxin emission sources are simulated in this study, including the power industry, steel industry, cement industry, metal smelting industry and various types of incinerators. The results show that the power industry contributed the highest exposure, followed by iron and steel industry, which are 57% and 25%, respectively; the health impact of waste disposal industry is relatively small. From the view of region, Taichung County, Changhua County, Kaohsiung County, whether in the field or will risk groups are relatively high . These results indicate that control standards of the power industry should be reviewed priority to reduce dioxin emissions. In addition, new dioxin emission sources should be avoided to set in Taichung County, Changhua County, and Kaohsiung County, except for they are highly background risk areas, most important, the impact of administrative characteristics of the field has always been high for the region. However, there are some limits of this simplified exposure method, such as the assumption in the impact range is built on the premise of homogeneous distribution, emission sources with extreme properties of the assessment results can not be presented effectively. Even so, the simplified exposure assessment for multiple emissions is feasible and can be applied to assess the health impact of other types of pollutants from stationary emission sources in the future.