根據非營利的環保團體「環境工作小組」於19日發表的報告指出，檢測美國35個城市的自來水，其中有31個城市的水中測出六價鉻(hexavalent chromium)。其中以奧克拉荷馬州諾曼市、夏威夷檀香山以及加州河濱市的濃度最高。
此項致癌物因2000年茱莉亞羅勃茲主演電影「永不妥協」而為大眾所熟知。
這部電影取材自加州辛克利鎮(Hinkley)罹癌居民，控告「太平洋煤氣與電力公司」造成自來水六價鉻汙染一事，於1996年贏得3.33億美元和解金的故事。
「環境工作小組」說，「儘管有越來越多污染物質毒性反應的證據，其中還包括美國環保署的毒理學審查將它分類為『從飲用水攝入，很可能對人類具有致癌作用』，環保署卻仍然未對自來水的六價鉻設立標準，也沒有要求水公司檢測。」
「環境工作小組」報告表示，六價鉻來自鋼鐵廠、紙漿廠、電鍍廠以及揉皮廠，並可透過遭受侵蝕的土壤和岩石汙染水源。
「全國毒物計畫」(NTP)發現，飲用水中的六價鉻在實驗動物身上具有明確致癌證據，會增加罹患腸胃道罕見腫瘤的風險。
針對此類研究，去年加州官員提案，為公眾健康目標，欲建立飲用水的鉻含量標準為0.06ppb。
此次「環境工作小組」檢測出25個城市的飲用水六價鉻含量超過加州提案的標準。
擁有9萬人口的奧克拉荷馬州諾曼市，其水中六價鉻含量超過加州提案的安全值200倍以上。奧克拉荷馬大學位於諾曼市。
「環境工作小組」在報告中說，「42個州至少有7400萬美國人飲用鉻汙染的自來水，其中大半都是致癌的六價鉻形式。由於暴露的範圍和潛在風險的影響程度，環保署應迅速採取行動，建立該物質在自來水中的標準，並要求自來水公司測試。」
美國環保署署長傑克遜23日與10位參議員會面，並就「環境工作小組」有關飲用水含六價鉻的議題，為他們進行簡報。
傑克遜談到環保署目前對於六價鉻風險評估的情況，即重新審查2008年開始進行的六價鉻和癌症之間最新的科學關聯性。此項風險評估將在2011年獨立同儕審查之後完成，並成為更新飲用水法規的起步。
Tap water from 31 of 35 U.S. cities tested contains hexavalent chromium, or chromium-6, according to laboratory tests commissioned by the nonprofit Environmental Working Group and revealed in a report Saturday. The highest levels were detected in Norman, Oklahoma; Honolulu, Hawaii; and Riverside, California.
The cancer-causing chemical is best known to the general public from the 2000 movie "Erin Brockovich," starring Julia Roberts.
The film dramatized the plight of the cancer-stricken residents of Hinkley, California, who in 1996 won a $333 million settlement from Pacific Gas and Electric Co. for contaminating their tap water with hexavalent chromium.
The Environmental Working Group says, "Despite mounting evidence of the contaminant's toxic effects, including a U.S. Environmental Protection Agency draft toxicological review that classifies it as 'likely to be carcinogenic to humans' when consumed in drinking water, the agency has not set a legal limit for chromium-6 in tap water and does not require water utilities to test for it."
Hexavalent chromium is discharged from steel and pulp mills as well as metal-plating and leather-tanning facilities. It can pollute water through erosion of soil and rock, the EWG report shows.
The National Toxicology Program has found that hexavalent chromium in drinking water shows clear evidence of carcinogenic activity in laboratory animals, increasing the risk of otherwise rare gastrointestinal tumors.
In response to this study and others, California officials last year proposed setting a public health goal for chromium-6 in drinking water of 0.06 parts per billion.
Levels of the carcinogen in 25 cities tested by Environmental Working Group were higher than California's proposed public health goal.
Tap water from Norman, Oklahoma, with a population of 90,000, contained more than 200 times California's proposed safe limit. Norman is home to the University of Oklahoma.
"At least 74 million Americans in 42 states drink chromium-polluted tap water, much of it likely in the form of cancer-causing hexavalent chromium," the Environmental Working Group says in its report. "Given the scope of exposure and the magnitude of the potential risk, the EPA should move expeditiously to establish a legal limit for the chemical in tap water and require water utilities to test for it."
EPA Administrator Lisa Jackson met with 10 U.S. senators Wednesday to brief them on the issue of chromium-6 in drinking water as reported by the Environmental Working Group.
Jackson described EPA's current chromium-6 risk assessment, a review the agency started in 2008 in response to new science showing a link between chromium-6 ingestion and cancer.
This risk assessment, which would be the first step to updating the drinking water regulations, will be finalized after an independent scientific peer review in 2011.
全文及圖片詳見：ENS報導
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