- 學位論文
屏東地區飲用含有重金屬地下水之健康風險評估
Health Risk Assessmemt by Intake Heavy Metals in Groundwater in Pingtung Area
摘要
台灣地區自來水普及率達到90.7 %，為國民最主要的飲用水，但在屏東縣卻只有45.13 %，為台灣地區中自來水普及率最低的縣市。屏東地區無論灌溉、養殖、生活、工業等各標的用水均有利用地下水之情形，且取自地表水佔總用水量的24.27%，取自地下水者佔總用水量的70.52%，而屏東地區生活用水上主要大部分為地下水水源。一旦屏東地區居民長期飲用、使用含有重金屬的地下水，導致重金屬進入人體中，居民的健康風險有必要深入了解。 本研究以環保署全國環境水質監測資訊網中2003年到2008年共6年的屏東地區地下水水質監測數據為本次研究風險評估資料來源。其中地下水的重金屬砷、鎘、鉻、銅、鉛、鋅、錳項目進行健康風險評估。本研究風險評估採層次性方法之步驟，由第一層次至第三層次，第一層次採用最大重金屬濃度計算風險；第二層次採用重金屬濃度平均值95%的上信賴界限(以貝氏統計方法)執行風險計算；第三層次則是以重金屬濃度機率分布計算風險(以蒙特卡羅方法模擬)。 研究顯示屏東縣各鄉鎮地區地下水中重金屬濃度自2003 ~ 2008年都符合現行地下水之管制標準。屏東沿海地區重金屬平均濃度大抵高於內陸地區重金屬濃度。除了砷、鎘、錳重金屬外，其他沿海地區與內陸地區地下水各重金屬濃度無顯著差異。在重金屬之健康風險，不論致癌風險及非致癌風險皆以食入暴露途徑風險貢獻最大，皮膚接觸途徑風險貢獻較小。而重金屬暴露物種以砷、錳所佔風險比例最高。以致癌風險10-6作為是否危害的標準，評估結果所承受的風險皆高於此標準。但如果以人體尚可接受的風險10-4標準，僅有少數鄉鎮如崁頂鄉、林邊鄉在成人與兒童致癌風險高於此標準。非致癌風險以1作為是否危害的標準時，研究發現所承受的指數部分鄉鎮高於5以上，而在合理估計屏東地區38.1%鄉鎮高於此標準，但有61.9%鄉鎮風險則是低於標準。建議在高風險地區飲用地下水時加裝簡易去除設施則可以降低風險。
並列摘要
In Taiwan, drinking water is popularized up to 90.7% but in Pingtung County the popularization rate for drinking water is only 45.13%, which is the lowest one in Taiwan. In Pingtung area, groundwater is the most important water resources whether for irrigation, aquaculture, life, and industrial purpose are used groundwater. The water consumption from groundwater is 70.5% and from surface water is 24.3%. Therefore, once people living in Pingtung area use groundwater as drinking water the long-term consumption of groundwater containing heavy metals, leading to heavy metals accumulated in the body that is a concern for health risks. In this study, the data for health risk assessment was taken from EPA National Environmental Information Network (the groundwater monitor data) ranging from 2003 to 2008. The groundwater data has periodically measured the concentrations of heavy metals. The concentrations of arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), lead (Pb), zinc (Zn), and manganese (Mn) in groundwater were used to asses health risk in the study. The health risk assessment was carried out by tier method. Tier one the maximum concentrations of heavy metals were used to compute heath risk. In tier two the concentrations of heavy metal was taken mean 95% upper confidence limits (using Bayesian statistical method). In tier three the concentrations of heavy metals were used probabilistic distributions to calculate health risk with Monte Carlo simulation. The results show that the concentrations of heavy metals in groundwater met the current regulation standards in every township in Pingtung County from 2003 to 2008. In addition, most heavy metal concentrations in coastal areas are higher than the concentration in inland areas. The concentrations of arsenic, cadmium, and manganese showed significantly different between the two areas. The results of health risk assessment showed oral ingestion was most important exposure pathway both carcinogenic risk and non-carcinogenic risk. The skin exposure pathway had a minor contribution. The arsenic and manganese contributed the highest proportion of risk. Regarding carcinogenic risk, the results calculation in all scenarios were greater than 10-6 but a few townships such as Kanding Township, and Woodside Township the carcinogenic risk were greater than 10-4. Regarding non-carcinogenic risk, the results show a few townships were greater than 5 in the results from tier 1 and tier 3 calculations. Nevertheless, there were 38.1% of township was greater than 1 with tier calculation but it need notice that 61.9% of the area the risk less than 1 with tier two calculation. Therefore, in the relatively high risk area the point of use to remove heavy metals in groundwater was recommended to reduce health risk using drinking water.