福島若是不疏散 死亡人數會更少
This spring, four years after the nuclear accident at Fukushima, a small group of scientists met in Tokyo to evaluate the deadly aftermath.
今年春天，也就是福島核事故的四年後，一小羣科學家在東京會晤，旨在評估該事故造成的致命性後果。
No one has been killed or sickened by the radiation — a point confirmed last month by the International Atomic Energy Agency. Even among Fukushima workers, the number of additional cancer cases in coming years is expected to be so low as to be undetectable, a blip impossible to discern against the statistical background noise.
一個月前，國際原子能機構(International Atomic Energy Agency)證實，此次事件中無人因輻射患病或死亡。即使是在福島核電站的工作人員中，預計未來幾年增加的癌症病例數也極少，難以與統計學背景噪音相區分。
But about 1,600 people died from the stress of the evacuation — one that some scientists believe was not justified by the relatively moderate radiation levels at the Japanese nuclear plant.
然而，卻有約1600人因疏散帶來的壓力死亡。與會的一名科學家認爲，以日本核電站相對中等的輻射暴露水平，出現如此多的死亡案例並不合理。
Epidemiologists speak of “stochastic deaths,” those they predict will happen in the future because of radiation or some other risk. With no names attached to the numbers, they remain an abstraction.
流行病學家提出了“隨機死亡”一說，他們預測，因爲輻射或其他危險，未來會發生這種情況。1600這個數字沒有對應的名字，他們只是一個抽象的概念。
But these other deaths were immediate and unequivocally real.
但這些死亡案例是切切實實發生的事實。
“The government basically panicked,” said Dr. Mohan Doss, a medical physicist who spoke at the Tokyo meeting, when I called him at his office at Fox Chase Cancer Center in Philadelphia. “When you evacuate a hospital intensive care unit, you cannot take patients to a high school and expect them to survive.”
我前往費城拜訪在東京會議上發過言的醫學物理學家莫漢·多斯(Mohan Doss)博士，在他的辦公室裏，他告訴我：“當時政府基本上已經慌了手腳。你把患者撤離了醫院重症監護病房並轉移到高中裏，總不能指望他們還能活得好好的。”
Among other victims were residents of nursing homes. And there were the suicides. “It was the fear of radiation that ended up killing people,” he said.
類似的受害者還有住在養老院的人。此外還有自殺者。多斯博士表示：“可以說，是對輻射的恐懼最終造成了人們的死亡。”
Most of the fallout was swept out to sea by easterly winds, and the rest was dispersed and diluted over the land. Had the evacuees stayed home, their cumulative exposure over four years, in the most intensely radioactive locations, would have been about 70 millisieverts — roughly comparable to receiving a high-resolution whole-body diagnostic scan each year. But those hot spots were anomalies.
其實，大部分的放射性沉降物都已經被東風清掃到海上去了，剩下的那些在擴散作用下，單位土地上的濃度也已經降到很低。倘若那些被疏散的人員留在家裏，即使是在輻射最強的地區，他們四年受到的累積輻射暴露劑量大約也只有70毫西弗，大致相當於每年接受一次高分辨率全身掃描診斷。需要注意的是，這些核熱點地區還都是異常環境。
By Dr. Doss’s calculations, most residents would have received much less, about 4 millisieverts a year. The average annual exposure from the natural background radiation of the earth is 2.4 millisieverts.
根據多斯博士的計算，在不撤離的情況下，大部分居民受到的輻射應該也少得多，約爲每年4毫西弗。而地球的年平均天然本底輻射就有2.4毫西弗。
How the added effect of the fallout would have compared with that of the evacuation depends on the validity of the “linear no-threshold model,” which assumes that any amount of radiation, no matter how small, causes some harm.
要比較放射性沉降物與疏散行動這兩者的附加影響，依賴於“線性無閾值模型”的有效性，而該模型假定，任何劑量的輻射——哪怕它非常非常小——都會造成一定的危害。
Dr. Doss is among scientists who question that supposition, one built into the world’s radiation standards. Below a certain threshold, they argue, low doses are harmless and possibly even beneficial — a long-debated phenomenon called radiation hormesis.
該假設是構成全球防輻射標準的組成部分之一，但多斯博士等科學家對它提出了質疑。他們認爲，只要低於某一特定的閾值，低劑量的輻射就是無害的，甚至還可能是有益的，這就要說到一種長期飽受爭議的現象，稱爲輻射興奮效應(radiation hormesis)。
Recently he and two other researchers, Carol S. Marcus of Harbor-U.C.L.A. Medical Center in Los Angeles and Mark L. Miller of Sandia National Laboratories in Albuquerque, petitioned the Nuclear Regulatory Commission to revise its rules to avoid overreactions to what may be nonexistent threats.
最近，多斯博士和其他兩名研究人員：加州大學洛杉磯分校港口醫療中心（Harbor-U.C.L.A. Medical Center，位於洛杉磯）的卡羅爾·S·馬庫斯(Carol S. Marcus)以及桑迪亞國家實驗室（Sandia National Laboratories，位於阿爾伯克基市）的馬克·L·米勒(Mark L. Miller of Sandia)一同上書美國核能管理委員會(Nuclear Regulatory Commission)，要求修訂有關法規，已避免人們對可能並不存在的威脅反應過度。
The period for public comments is still open, and when it is over, there will be a mass of conflicting evidence to puzzle through.
目前仍處於公開徵求意見期間，等這一階段結束後，還有一大堆相互矛盾的證據有待探討和研究。
A full sievert of radiation is believed to eventually cause fatal cancers in about 5 percent of the people exposed. Under the linear no-threshold model, a millisievert would impose one-one thousandth of the risk: 0.005 percent, or five deadly cancers in a population of 100,000.
一般認爲，一個西弗的輻射最終會引起5%的受暴露者中發生致命性癌症。在線性無閾值模型中，輻射劑量每增加一毫西弗，就會將該風險相應提高千分之一，也就是0.005%，換句話說，每10萬人中將增加5例致命性癌症。
About twice that many people were evacuated from a 20-kilometer area near the Fukushima reactors. By avoiding what would have been an average cumulative exposure of 16 millisieverts, the number of cancer deaths prevented was perhaps 160, or 10 percent of the total who died in the evacuation itself.
從福島反應堆方圓20公里範圍內疏散的人數約有20萬。按照上面的計算，規避了該地區平均16毫西弗的累積暴露輻射劑量後，可防止160人因癌症死亡，只佔疏散行動本身造成的總死亡人數的1/10。
But that estimate assumes the validity of the current standards. If low levels of radiation are less harmful, then the fallout might not have caused any increase in the cancer rate.
而且上述估算值還是在假設當前標準有效的前提下做出的。倘若低水平的輻射危害性低於預設，那麼這些放射性沉降物很可能根本不會引起癌症患病率的增加。
The idea of hormesis goes further, proposing that weak radiation can actually reduce a person’s risk. Life evolved in a mildly radioactive environment, and some laboratory experiments and animal studies indicate that low exposures unleash protective antioxidants and stimulate the immune system, conceivably protecting against cancers of all kinds.
輻射興奮效應的概念又進一步提出，微弱的輻射反而會降低個人的風險。生命的演化本來就是在輕度的放射性環境中發生的，還有一些實驗室實驗和動物研究表明，低水平的輻射暴露可激發保護性抗氧化劑並刺激免疫系統，據此可以相信這對多種癌症都有預防作用。
Epidemiological studies of survivors of Hiroshima and Nagasaki have been interpreted both ways — as demonstrating and refuting hormesis. But because radiation regulations assume there is no safe level, clinical trials testing low-dose therapy have been impossible to conduct.
在關於廣島和長崎核爆倖存者的流行病學研究中，支持和反駁輻射興奮效應的解讀皆有之。但防輻射法規假定並不存在“安全的輻射水平”，使得人們無法進行測試低劑量輻射療法的臨牀試驗。
One experiment, however, occurred inadvertently three decades ago in Taiwan after about 200 buildings housing 10,000 people were constructed from steel contaminated with radioactive cobalt. Over the years, residents were exposed to an average dose of about 10.5 millisieverts a year, more than double the estimated average for Fukushima.
一次意外事故卻給研究者帶來了一個實驗的機會。三十年前，臺灣約200棟樓房的建築鋼筋受到了放射性鈷的污染，涉及1萬名居民。多年來，他們的年平均輻射暴露劑量約爲10.5毫西弗，是福島居民平均估計值的兩倍以上。
Yet a study in 2006 found fewer cancer cases compared with the general public: 95, when 115 were expected.
但2006年的一項研究發現，與普通民衆相比，這些居民中的癌症病例反而減少了（預期爲115例，實際爲95例）。
Neither the abstract of the paper nor of a second one published two years later mention the overall decrease. (The authors speculated that the apartment dwellers may have been healthier than the population at large.) The focus instead was on weaker results suggesting a few excess leukemia and breast cancer cases — and on a parsing of the data showing an overall increased cancer risk for residents exposed before age 30.
該論文的摘要及兩年後發表的第二篇論文都沒有提到總共減少了多少病例。（作者推測，這些公寓居民可能比普通民衆更爲健康）相反，這些論文將重點放在了一些說服力較弱的結果之上：白血病和乳腺癌病例略有增加，還有一項數據分析顯示，總體而言，在30歲前受到輻射的居民中癌症風險有所增加。
More recently, a study of radon by a Johns Hopkins scientist suggested that people living with higher concentrations of the radioactive gas had correspondingly lower rates of lung cancer. If so, then homeowners investing in radon mitigation to meet federal safety standards may be slightly increasing their cancer risk. These and similar findings have also been disputed.
最近，約翰斯·霍普金斯大學(Johns Hopkins)的科學家進行了一項關於氡氣的研究，結果表明，生活在較高濃度的這種放射性氣體中的人肺癌的發生率相對較低。如果是這樣的話，出資設法降低氡氣濃度以滿足聯邦安全標準的業主們可能正好適得其反——反倒稍微增加了自己的癌症風險。只是，諸如此類的研究結果也一直存在着爭議。
All research like this is bedeviled by “confounders” — differences between populations that must be accounted for. Some are fairly easy (older people and smokers naturally get more cancer), but there is always some statistical wiggle room. As with so many issues, what should be a scientific argument becomes rhetorical, with opposing interest groups looking at the data with just the right squint to resolve it according to their needs.
所有這些研究都受到“混雜因素”的困擾，也就是說，他們必須考慮到人羣之間的某些差異。有些混雜因素相當簡單（老年人和吸菸者自然更容易得癌症），不過，在統計學上對此也往往留有校正的餘地。由於存在這許多問題，原本應該是科學爭論的東西變成了文字遊戲，對立的利益集團從自己的需要出發，只看那些有利於自己的數據，卻刻意忽視了其他。
There is more here at stake than agonizing over irreversible acts, like the evacuation of Fukushima. Fear of radiation, even when diluted to homeopathic portions, compels people to forgo lifesaving diagnostic tests and radiotherapies.
與其去糾結福島疏散行動等不可逆的行爲，眼下還有更多利害攸關的事。人們對輻射——哪怕是稀薄到順勢療法的那種極低水平的輻射也滿懷恐懼，以至於放棄了可以挽救生命的診斷測試和放射治療。
We’re bad at balancing risks, we humans, and we live in a world of continual uncertainty. Trying to avoid the horrors we imagine, we risk creating ones that are real.
人類並不擅長在風險與我們自己之間權衡，更何況，我們還生活在一個充滿了不確定性的世界裏。爲了躲避想像中的危機，我們往往寧願甘冒風險，哪怕此舉會釀出真正的禍事來。
