本研究使用兩套不同先進國家開發之多介質模式,California Environmental Protection Agency, Department of Toxic Substances Control (CalTOX)與European Union System for the Evaluation of Substances (EUSES),探討桃園地區居民將自來水作為各種用途後(飲用水、游泳用水、飼養家畜或魚再食用以及農作物澆灌等),在攝入途徑可能造成之終生總致癌風險與總非致癌風險。 對4種毒理資料較完善之重金屬(砷、鉛、總鉻及鎘)提出討論,假設以桃園地區淨水場對重金屬之方法偵測極限的二分之一數值作為淨水廠濃度模擬之基準值,並設定年齡分層(0-5歲、6-18歲、19-64歲及65歲以上)、性別及3種暴露量設定(5、50與95百分位值)進行討論。 淨水廠濃度模擬攝入途徑整體總致癌風險結果(包含性別差異、4種年齡分層及3種暴露量設定),CalTOX模擬砷為5.72×10-6~4.28×10-5;鉛為3.53×10-8~2.65×10-7;總鉻為5.20×10-7~3.89×10-6;鎘為5.20×10-6~3.89×10-5。EUSES模擬砷為1.50×10-5~1.18×10-4;鉛為9.27×10-8~7.26×10-7;總鉻為1.37×10-6~1.07×10-5;鎘為1.39×10-5~1.09×10-4。整體而言, 砷、總鉻及鎘3種重金屬在部分暴露量條件設定下,超過美國環保署致癌風險建議值10-6。針對超過建議值的重金屬,根據美國環保署與加州環保署提出之飲用水中暴露終生無危害濃度,鎘在0.005 mg/L濃度下暴露終生並不會產生致癌性,砷估算致癌風險10-4對應之濃度為0.002 mg/L;六價鉻估算致癌風險10-6對應之濃度為0.02 ppb。因此,本研究採保守估算結果,以致於估算結果高於建議值。 非致癌風險部分,CalTOX整體模擬結果顯示,砷重金屬為0.01~0.10;總鉻重金屬為0.0003~0.0026;鎘重金屬為0.001~0.005。EUSES模擬結果,砷重金屬為0.033~0.262;總鉻重金屬為0.001~0.007;鎘重金屬為0.002~0.015,兩套模式模擬結果均低於美國環保署非致癌風險建議值1。 本研究為求得保守風險估算結果,採過量的毒理資料計算(六價鉻替代總鉻;鎘吸入致癌因子與鎘口服致癌因子相等)造成致癌風險相對被高估,亦可能受敏感性參數缺乏,如:每日飲水量,導致性別與年齡分層差異變化性不高。 本研究建議未來應加強本土環境及暴露參數建立,於法規標準制定過程中亦可採用多種風險計算模式,將風險估算結果納入參考。
This study aims to assess lifetime health risk associated with concentrations of heavy metals (arsenic, lead, total chromium and cadmium) in tap water using multimedia exposure models - the CalTOX proposed by California Environmental Protection Agency, and European Union System for the Evaluation of Substances (EUSES) proposed by European Commission for population residing in Taoyuan county. Lifetime cancer risk and hazard quotients were conducted for various age (0-5 years, 6-18 years, 19-64 years and more than 65 years old) and sex stratifications. Exposure scenarios of heavy metals were also evaluated for their measurements at 5, 50 and 95 percentiles. The CalTOX estimated lifetime cancer risk were 5.72×10-6-4.28×10-5 for arsenic, 3.53×10-8-2.65×10-7 for lead, 5.20×10-7-3.89×10-6 for total chromium, and 5.20×10-6-3.89×10-5 for cadmium in ingestion pathway. The EUSES estimated lifetime cancer risk were 1.50×10-5-1.18×10-4 for arsenic, 9.27×10-8-7.26×10-7 for lead, 1.37×10-6-1.07×10-5 for total chromium, and 1.39×10-5-1.09×10- 4 for cadmium in ingestion pathway. The CalTOX estimated hazard quotients were 0.01-0.10 for arsenic, 0.0003-0.0026 for total chromium, and 0.01-0.04 for cadmium in drinking water pathway. The EUSES estimated hazard quotients were 0.033-0.262 for arsenic, 0.001-0.007 for total chromium, and 0.001-0.005 for cadmium in ingestion pathway. This study suggested that establishments for local environmental and population exposure parameters would enhance the accurateness and precisions of health risk associated with environmental toxicants in Taiwan.