每天打開水龍頭，看似清澈的飲用水，可能含有肉眼看不見的金屬。其中，銅不僅是人體必需的微量元素，也可能因管線腐蝕進入飲用水。究竟飲用水中的銅對健康有什麼影響？除了銅，還有哪些容易被忽略的金屬風險？就讓公共衛生專家胡景堯教授告訴你。
家中飲用水，可能藏著哪些重金屬風險？
銅是人體必需的微量元素，參與能量代謝、鐵的利用、結締組織形成、神經功能及抗氧化作用。人體主要透過腸道吸收，並由肝臟調節及膽汁排泄，維持體內銅的平衡。因此，銅是否對健康造成影響，取決於攝取量、銅的存在形態、攝取方式及個人體質等因素。[1–3]
一般人主要從食物攝取銅，飲用水通常只占少部分。然而，當飲用水中的銅濃度較高，尤其在空腹飲用時，可能引起噁心、嘔吐、腹痛或腹瀉等腸胃不適。至於嚴重肝臟損傷，則多見於高劑量暴露、長期顯著過量，或銅代謝與排泄異常者，不能僅因飲水中檢出低濃度銅，就推定已造成健康損傷。[2–4,6,7]
此外，嬰幼兒的銅代謝與排泄系統發育尚未完全，對高濃度銅暴露應更加謹慎；威爾森氏症等銅代謝異常患者，也屬於較需注意的族群。不過，目前健康嬰兒因飲水中的銅而發生慢性肝病的證據仍有限。[3,4,9,10]
飲用水中的銅不一定來自水源。在許多使用銅管的供水系統中，水流經建築物內的銅管、黃銅水龍頭、閥件及接頭時，若管線或零件受到腐蝕，就可能使銅釋出至水中。不過，天然地質、採礦或工業活動也可能影響水源，仍須透過檢測確認實際來源。[4,5,11]
影響銅釋出的因素不只有管線材質，水的酸鹼度、鹼度、溶氧及消毒劑等，也可能改變管線腐蝕的情況。銅在腐蝕過程中，可能以溶解態或細小顆粒進入水中，因此不能只憑水的外觀判斷是否含有銅。[5,11–14]
水在管線中停留的時間，也是影響銅濃度的重要因素。例如夜間或長時間未使用水龍頭時，銅可能從管線內壁逐漸釋出並累積在靜置水中，使最初流出的水含銅濃度高於充分放流後的水。因此，即使是同一個水龍頭，不同時間取得的水樣，也可能出現不同的檢測結果。[4,5]
此外，管線腐蝕程度還會受到水質及材料相容性影響。當不同金屬管材相互連接時，也可能增加局部腐蝕風險，因此管線材料的選擇、正確施工與水質控制同樣重要。[5,11]
除了銅管，水龍頭、閥件及接頭常用的黃銅，也可能是金屬釋出的來源。黃銅主要由銅與鋅組成，在特定水質條件下可能發生「脫鋅」腐蝕，使鋅選擇性溶出，留下多孔的富銅結構，造成材料結構劣化，並影響後續金屬釋出，但這不代表必然會大量釋出銅。[15,16]
更值得注意的是，部分含鉛黃銅零件，在腐蝕性水質、長時間停滯或顆粒脫落等情況下，也可能釋出鉛。與人體必需的銅、鋅不同，鉛並非人體必需元素，且具有累積性神經毒性，尤其可能影響兒童的神經發育，孕婦也需要特別留意。現代低鉛或無鉛零件雖能降低材料來源風險，仍需符合飲用水接觸材料規範。[16–19]
此外，部分管線或金屬零件也可能涉及鎳等其他金屬的釋出。因此，當飲用水中銅濃度異常升高時，不應只關注銅本身，也應進一步了解管線材質與腐蝕狀況，必要時評估鉛、鋅、鎳等其他金屬。不過，銅濃度升高並不代表其他金屬一定同時存在，仍須依實際檢測結果判斷。[5,11,16–19]
飲用水中的銅除了涉及健康風險，也可能是管線腐蝕的警訊。當檢測出現異常值時，應進一步確認污染來源及管線狀況。日常可在長時間未使用水龍頭後適當放流，飲用及烹調使用冷水，並定期清潔水龍頭起泡器。若金屬濃度持續異常，仍需透過專業檢測、腐蝕控制或材料更換等方式改善。[4,5,11]
由於飲用水中的金屬可能來自建築管線、水龍頭及接頭等設備，因此除了重視水源品質，更應留意家中實際飲用的水質。選擇符合水質需求、具有特定污染物去除能力的末端淨水設備，能為家庭飲水增加一道防護，讓日常飲水更安心。[4,5]
參考文獻
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