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關于輻射的真相

A Radiation Reality Check
關于輻射的真相

Do you believe, as I used to, that radioactivity is very rare and very dangerous, restricted to arsenals and power plants? Let's take a look at your kitchen. The bananas are radioactive from their potassium, the Brazil nuts have a thousand times more radium than any other food item, and your dried herbs and spices were irradiated to counter bacteria, germination and spoilage. There's thorium in your microwave oven and americium in your smoke detector.

Elsewhere in the house, cat litter, cigarettes, adobe, granite and brick are all actively radiating you. Always and forever, radiation is both raining down on you from the skies -- striking mile-high Denver two to three times as powerfully as San Diego -- and floating up at you from our bedrock's decaying uranium. Those all-natural mineral waters you soaked in on that spa vacation? Did the brochure mention that hot springs are hot in two senses, as the heat emanates from those same uranium combustions?

Radiance is so pervasive that geologists have uncovered evidence of 14 naturally occurring nuclear reactors. It's coming out of the walls of the U.S. Capitol in Washington and New York's Grand Central Terminal. Your cat is radioactive, your dog is radioactive, your friends and your family are all radioactive, and so, as it turns out, are you. Right now your body is emanating radiant effluvia and, every time you and another human being get together, you irradiate each other.

By the way, do you live in the continental U.S.? In 1997, the National Cancer Institute reported that the Cold War detonations at the Nevada Test Site had polluted nearly the whole of the country with drifting airborne radioactive iodine, creating somewhere between 10,000 and 75,000 cases of childhood thyroid cancer. The Centers for Disease Control and Prevention estimated that of the nearly 600,000 Americans dying of cancer every year, 11,000 will be because of those tests. All those decades worrying about the Soviet Union attacking Americans with nuclear weapons? Instead, while Washington irradiated Americans from Nevada, Moscow irradiated its own citizens with tests from Kazakhstan.

But there is, in all this, some good news.

The source of radioactivity is an atom so obese that it defies the laws of attraction gluing together our material world and spits out little pieces of itself -- two kinds of particles and a stream of gamma rays, similar to X-rays. An overdose of gamma rays is like a vicious sunburn, with skin damage and elevated cancer risks, but those particles are too big to penetrate our skin, meaning that they need to be swallowed or inhaled to wreak damage. Remember the movie 'Silkwood,' with Meryl Streep writhing in naked agony as men with brushes scrubbed her in the shower? They were washing away her exposure. The truly fearful event in a nuclear accident, then, isn't fallout but meltdown, where the core burns through the floor and suffuses the water table. There it causes agricultural mayhem and radioactive dust that you better not breathe.

The good news, though, is in that word: overdose. We're not dropping dead en masse from radiation poisoning or its ensuing cancers on a daily basis because, like all poisons, it isn't the particular atom that will get you. It's the dose. And damage from radioactivity requires a much greater dose than any of us would have believed.

This upheaval in everything we thought we knew comes from two decadeslong studies. The United Nations spent 25 years investigating the Chernobyl disaster and determined that 57 people died during the accident itself (including 28 emergency workers), while 18 children living nearby died in the following years of thyroid cancer from drinking the milk of tainted cows. (Thyroid cancer is very curable, so their deaths could have been prevented by an effective public-health service, but Ukraine's and Belarus's collapsed alongside the Soviet Union's.) In short, the most terrifying nuclear disaster in human history, which spread a cloud the size of 400 Hiroshimas across the whole of Europe, killed 75 people.

Some believe that this number is too conservative, but those beliefs aren't backed by data. One critic is physicist Bernard Cohen, who predicted, 'The sum of exposures to people all over the world will eventually, after about 50 years, reach 60 billion millirems, enough to cause about 16,000 deaths.' To give this number perspective, around 16,000 Americans die every year from the pollution of coal-burning power plants.

Besides the U.N.'s Chernobyl report, the most extensive data on human exposure to radiation is the American-Japanese joint study of hibakusha -- 'explosion-affected persons' -- the 200,000 survivors of Hiroshima and Nagasaki. The expectations at the start of that study (which has taken over 60 years and continues to this day) were that survivorswould be overrun with tumors and leukemia and that a percentage of their descendants would be genetically deformed. Instead, researcher Evan Douple concluded, 'The risk of cancer is quite low, lower than what the public might expect.'

Radiologist John Moulder analyzed the results of one group of 50,000 survivors, about 5,000 of whom had developed cancer: 'Based on what we know of the rest of the Japanese population, you would have expected about 4,500 of them. So we have 5,000 cancers over 50 years where we would expect 4,500.' Assuming that the 500 additional cases are all due to radiation, that means a rate of 1%. And there was no increase in inherited mutations. Remember: These aren't victims of a power plant breakdown; they are survivors of a nuclear attack.

For the Fukushima disaster of 2011, the consensus estimate is a 1% increase in cancer for employees who worked at the site and an undetectable increase for the plant's neighbors. Just think of the difference between the overwhelming nuclear fears and nightmares we've all suffered from since 1945 and that range of increased risk: 0% to 1%. And if that's not enough to question everything you thought you knew about radiation, consider that, even after the catastrophe in Japan, the likelihood of work-related death and injury for nuclear plant workers is lower than for real estate agents . . . and for stockbrokers.

Here's the truth about you and radiation: There's no reason to worry about power-plant meltdowns or airport scanners, where the X-rays have been replaced by millimeter wave machines. And don't worry about those radioactive everyday items. By scientific measures, the average American gets 620 millirems of radiation each year, half from background exposure, and that number needs to reach 100,000 to be worrisome.

Instead of fretting about these things, have your basement tested for radon. Monitor how many nuclear diagnostics and treatments, from X-rays to CT scans, you and your family get. Use sunscreen. And follow the advice of the woman who defined 'radioactivity,' Marie Curie: 'Now is the time to understand more, so that we fear less.'

你是否曾經與我一樣,相信放射性是非常罕見并且極度危險的東西?并且只有在軍工廠和核電站才能覓到它的蹤跡?讓我們來看看你的廚房吧。由于含有鉀元素,香蕉具有放射性;巴西堅果里含有的鐳元素是其他食物的上千倍;你的干香草和香料經受過輻射殺菌處理,目的是消滅細菌、抑制萌芽、防止腐敗。你的微波爐里有釷元素,而你的煙霧感應器中則有镅元素。

環顧你家四周,貓沙盆、香煙、土坯、花崗巖和磚塊都在永不停歇地輻射你。每時每刻,你不僅會受到來自天空的輻射—高原之城丹佛市受到的輻射是 地亞哥的兩至三倍—還會受到來自地下基巖鈾衰變的輻射。那么你在溫泉假期時享受的全天然礦物質溫泉水呢?宣傳小冊子有沒有提到溫泉水的熱度有兩個方面的含義,因為水溫就來自于鈾衰變所產生的熱量?

輻射無處不在,地質學家們甚至已經發現了14處天然核反應堆存在的證據。輻射來自于華盛頓國會山和紐約中央車站的 壁之中。你的寵物貓、寵物狗、朋友和家人都具有輻射性。你自己也同樣如此。現在,你的身體正釋放出生物電,每次你與另外一個人接觸時,你們都會互相輻射。

順便提一句,你是否居住在美國本土?1997年,美國國家癌癥研究所(National Cancer Institute)發布的報告稱,由于放射性碘在空氣中的擴散,冷戰時期在內華達試驗場(Nevada Test Site)進行的核爆炸試驗已經對整個國家構成了污染,并導致了10,000例至75,000例兒童甲狀腺癌的出現。據美國疾病控制與預防中心(Centers for Disease Control and Prevention)估計,在每年近600,000名死于癌癥的美國人中,有11,000名患者的病因是由內華達的核試驗導致的。記不記得在冷戰的幾十年間對蘇聯使用核武器攻擊美國人的擔憂?事實上,美國政府用內華達的核試驗輻射了美國人民,而蘇聯政府則用哈薩克斯坦的核試驗輻射了蘇聯人民。 紐約時報中英文網 http://www.gwbyzx.live

但是,盡管如此,我還是有一些好消息。

放射性產生的根源是一個太不穩定的原子違背了萬有引力定律(我們物質世界存在的基本原理)并發生分裂,釋放出兩種粒子和一束類似于X光的γ射線。過量暴露在γ射線中就好像惡性曬傷一樣,會造成皮膚損傷并提高罹患癌癥的風險,但由于粒子的體積太大,所以它們無法穿透我們的皮膚,也就是說這些粒子要被人類吞入或吸入才會造成損傷。記得電影《絲克伍事件》(Silkwood)嗎?在片中,當梅麗爾·斯特里普(Meryl Streep)飾演的角色赤身淋浴時,一些男人用刷子洗刷她,她痛苦地扭曲著身體。這些人正是試圖沖刷掉她所受到的輻射。核事故中真正可怕的不是放射性塵埃而是堆芯熔毀,堆芯熔毀能夠燒穿地表并滲入地下水。堆芯熔毀可以帶來農業災害和不宜吸入的放射性塵埃。

然而,令人欣慰的事情就在于“過量”一詞。人類不會因為放射性毒害或由此引發的癌癥而每天大量死亡,這是因為與所有的有毒物質一樣,罪魁禍首不是特定的原子,而是劑量。放射性造成損傷所需的劑量遠遠超過我們通常認為的水平。

人類對核輻射了解的劇變來源自兩項歷時數十年的研究。聯合國花費25年的時間調查了切爾諾貝利事故,研究結果表明,事故直接導致的死亡人數是57人(其中包括28名搶險工人),另有18名居住在附近的兒童由于飲用了受污染奶牛的奶于事故發生數年中死于甲狀腺癌。(甲狀腺癌是容易治愈的一種疾病,因此兒童們的死亡本可以通過有效的公共醫療服務避免,但是隨著蘇聯的解體,烏克蘭和白俄羅斯的公共醫療服務名存實亡。)簡而言之,人類歷史上最嚴重的、放射性塵埃在整個歐洲擴散的面積相當于廣島400倍的核事故最終導致的死亡人數是75人。

有一些人認為,上述數字太過保守,但是他們的論點并沒有得到數據的支持。一位批評家是物理學家伯納德·科恩(Bernard Cohen),他曾經預言到:“在50年以后,全球所有人類接受的輻射總量將最終達到600億毫侖目,足以令約16,000人喪生。”我們可以換個角度來看待這個數字,美國每年因火力發電廠污染而導致死亡的人數也高達16,000人。

除了聯合國圍繞切爾諾貝利事故的報告以外,關于人類輻射最詳實的調查就數美日兩國聯合進行的幸存者研究了—這里的幸存者指的廣島和長崎20萬名“受原子彈爆炸影響的人群”。在研究伊始(該研究已經進行了60多年并且仍在繼續),研究人員預計幸存者將大規模罹患腫瘤疾病和白血病,他們的后代中也將有一部分人難逃基因畸形的厄運。然而,研究人員埃文·杜普勒(Evan Douple)總結道:“幸存者罹患癌癥的風險相當低,低于公眾的預期水平。”

放射學學者約翰·莫爾德(John Moulder)對50,000名幸存者的資料進行了分析,他們中的5,000人罹患了癌癥:“基于我們對其他日本民眾患癌率的了解,這50,000名幸存者中的癌癥患者人數本應為4,500人。所以,從這50年來看,這是一個5,000例病例與4,500例病例的區別。”假設這多出來的500例病例都是由輻射導致的,那么這意味著這個比例為1%。另外,輻射并沒有帶來遺傳性突變的增加。記住:他們并不是核電站損毀的受害者;他們是核打擊的幸存者。

對于2011年的福島核事故來講,外界普遍預計現場員工的患癌率將提高1%,并且周圍居民的患癌率也將略有增加。回想一下,相較于實際增加的0%至1%的風險,我們自1945年以來承受了多少關于核安全方面的擔憂和恐懼啊!如果這并不足以使你對自己原本對于輻射的了解產生那么一點兒懷疑的話,那么請思考一下,即使在日本福島核事故發生后,核電站工人的因公死傷比率也低于房地產中介和股票經紀人的因公死傷比率。

關于人類和核輻射的真相在于:你沒有理由去擔心核電站的堆芯熔毀或機場的掃描儀,機場的X光掃描儀現在已經被毫米波掃描儀所取代了。你也不需要擔心日常生活中具有放射性的物體。科學測量結果顯示,普通美國人每年受到的輻射為620毫侖目,其中一半屬于天然本底輻射,而低于100,000毫侖目的輻射完全不需要擔心。

與其煩惱這些事情,你還不如請人測試一下地下室的氡值。記錄你自己和家人進行核醫療診斷和治療的次數(包括X光掃描和CT掃描)。使用防曬霜。并且聽從曾對“放射性”做出過定義的居里夫人(Marie Curie)的意見:“現在是時候加深了解了,這樣我們的恐懼才會減輕。”

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