六輕工業區鄰近地區空氣污染及居民健康風險評估

Abstract

六輕工業區於1991年於雲林縣麥寮鄉開始設立，先後完成四期之擴建及營運，於2007年6月全部完工營運，本研究係蒐集六輕工業區附近之環境資料，進行環境資料的整合，以了解空氣污染物濃度之長期變化、季節變化及日變化，及氣象因子與濃度之關係，並評估工業區鄰近地區居民暴露揮發性有機物（VOCs）之健康風險，此外，使用空氣擴散模式（The Industrial Source Complex Short Term Version 3rd edition）進行污染物濃度的模擬。為了解六輕工業區內各期工廠營運與環境品質變化之情形，本研究取得工廠興建、營運及排放客觀資料作為分析的標準，以各廠之建廠、試車及營運時間作為切割，將六輕工業區對環境的影響區分為四個階段。根據行政院環保署空氣品質監測網蒐集雲林縣台西、崙背及斗六三測站與彰化縣二林、嘉義縣新港等共五站1993年9月至2007年12月空氣品質監測資料，及台西光化學測站2007年3月至2008年12月資料，利用VOCs濃度之時平均和年平均值，進行急性（HIA）、慢性（HIC）健康性應以及非致癌風險、致癌風險之風險評估，彙整並以統計軟體SAS v9.1進行分析，此外，蒐集廠址原物料及排放等資料，且運用模式以了解污染物空間分佈情形。研究發現六輕工業區於2000年8月第一期完工營運後，雲林縣空氣品質已發生變化，全縣臭氧（O3）濃度逐年升高；台西及崙背一帶二氧化硫（SO2）濃度漸增，且由長期氣象資料統計顯示，台西站一年中秋冬季節（10月~3月）最常處於下風處，夏季（6 ~ 8月）最少處於下風處，總揮發性有機碳氫化合物（TVOC）於下風時段濃度高達200 ppb以上，此外，當風速小於5 m/s時，TVOC濃度亦高達200 ppb以上。利用2007年3月到2008年12月台西光化學測站的15種揮發性有機物濃度及台西一般空氣品質監測站4種空氣污染物濃度，進行居住於台西站附近居民之非致癌風險評估，若以95%分位數之年平均濃度計算慢性總危害指數(HIc)，其值為1.0000，大於一般可接受之風險值；致癌風險評估利用苯平均濃度與美國加州環保署（Cal EPA）及美國聯邦環保署（US EPA）的單位致癌風險值估算，該地區居民終生的致癌風險約為2.88E-6（US EPA）或3.80E-5（Cal EPA）。空氣擴散模式結果顯示出六輕工業區之排放最大著地點濃度位於麥寮鄉、台西鄉及四湖鄉。結合現有空氣監測資料及廠址資料，能夠釐清歷年來六輕工業區附近空氣污染之變化情形，並利用ISC模式以了解此廠址所排放之污染物的最大著地點濃度位置，此外，本研究利用現有資料做非致癌及致癌風險評估，故可提供一完整的系統資訊，以幫助了解此石化工業區對環境及居民的衝擊。

The No. 6 Naphtha Cracking Complex started construction in Yun-Lin County in 1991, completed the construction of all 66 plants, including oil refineries, chemical manufacturing plants, and coal power plants in 2007, and begun fully operation afterwards. The objectives of this study were to define the changes of air quality and to estimate health risks among the residents around the No. 6 Naphtha Cracking Complex. We obtaining air quality data of PM10, CO, ozone, NOx, and SO2 during 1993-2007 from five Taiwan EPA operated monitoring stations, air concentration data of 56 VOCs during 2007-2008 from a PAMS station in Tai-Si, applying the hourly and annual VOC concentrations to calculate acute hazard index, chronic hazard index, non-carcinogen risks and cancer risks using the reference concentrations and unit risk values from the US and the California EPA. Besides, we evaluate the potential concentration of SOx and VOC in the peripheral regions using air dispersion model (Industrial Source Complex Short Term, ISCST3). Our analyses found that ozone, PM10, and SO2 concentrations increased significantly since the first operation period in the exposed areas of the petrochemical complex. The weather data showed that October to March being the most likely downwind months to the petrochemical complex and June to August being the least likely downwind months in a year. TVOC concentrations could reach above 200 ppb in the downwind areas of the petrochemical complex. The simulated annual average concentrations of SOx and VOC by ISC model were highest at Mai-Liao, Tai-Si and Sih-Hu townships. The estimated chronic hazard index (HIc) who lives near Tai-Si station were 1.0000 using 95% quantile of the estimated concentration and life-time cancer risks of residents exposing to annual concentration of benzene were 2.88E-6 (US EPA) or 3.80E-5 (Cal EPA). Our findings indicated air pollution surrounding the No. 6 Naphtha Cracking Complex might cause excess health risks to residents in surrounding communities.