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更新时间:2014-4-24 14:44:31 来源:华尔街日报中文网 作者:佚名

A Radiation Reality Check

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.'


环顾你家四周,猫沙盆、香烟、土坯、花岗岩和砖块都在永不停歇地辐射你。每时每刻,你不仅会受到来自天空的辐射—高原之城丹佛市受到的辐射是 地亚哥的两至三倍—还会受到来自地下基岩铀衰变的辐射。那么你在温泉假期时享受的全天然矿物质温泉水呢?宣传小册子有没有提到温泉水的热度有两个方面的含义,因为水温就来自于铀衰变所产生的热量?

辐射无处不在,地质学家们甚至已经发现了14处天然核反应堆存在的证据。辐射来自于华盛顿国会山和纽约中央车站的 壁之中。你的宠物猫、宠物狗、朋友和家人都具有辐射性。你自己也同样如此。现在,你的身体正释放出生物电,每次你与另外一个人接触时,你们都会互相辐射。

顺便提一句,你是否居住在美国本土?1997年,美国国家癌症研究所(National Cancer Institute)发布的报告称,由于放射性碘在空气中的扩散,冷战时期在内华达试验场(Nevada Test Site)进行的核爆炸试验已经对整个国家构成了污染,并导致了10,000例至75,000例儿童甲状腺癌的出现。据美国疾病控制与预防中心(Centers for Disease Control and Prevention)估计,在每年近600,000名死于癌症的美国人中,有11,000名患者的病因是由内华达的核试验导致的。记不记得在冷战的几十年间对苏联使用核武器攻击美国人的担忧?事实上,美国政府用内华达的核试验辐射了美国人民,而苏联政府则用哈萨克斯坦的核试验辐射了苏联人民。


放射性产生的根源是一个太不稳定的原子违背了万有引力定律(我们物质世界存在的基本原理)并发生分裂,释放出两种粒子和一束类似于X光的γ射线。过量暴露在γ射线中就好像恶性晒伤一样,会造成皮肤损伤并提高罹患癌症的风险,但由于粒子的体积太大,所以它们无法穿透我们的皮肤,也就是说这些粒子要被人类吞入或吸入才会造成损伤。记得电影《丝克伍事件》(Silkwood)吗?在片中,当梅丽尔·斯特里普(Meryl Streep)饰演的角色赤身淋浴时,一些男人用刷子洗刷她,她痛苦地扭曲着身体。这些人正是试图冲刷掉她所受到的辐射。核事故中真正可怕的不是放射性尘埃而是堆芯熔毁,堆芯熔毁能够烧穿地表并渗入地下水。堆芯熔毁可以带来农业灾害和不宜吸入的放射性尘埃。



有一些人认为,上述数字太过保守,但是他们的论点并没有得到数据的支持。一位批评家是物理学家伯纳德·科恩(Bernard Cohen),他曾经预言到:“在50年以后,全球所有人类接受的辐射总量将最终达到600亿毫仑目,足以令约16,000人丧生。”我们可以换个角度来看待这个数字,美国每年因火力发电厂污染而导致死亡的人数也高达16,000人。

除了联合国围绕切尔诺贝利事故的报告以外,关于人类辐射最详实的调查就数美日两国联合进行的幸存者研究了—这里的幸存者指的广岛和长崎20万名“受原子弹爆炸影响的人群”。在研究伊始(该研究已经进行了60多年并且仍在继续),研究人员预计幸存者将大规模罹患肿瘤疾病和白血病,他们的后代中也将有一部分人难逃基因畸形的厄运。然而,研究人员埃文·杜普勒(Evan Douple)总结道:“幸存者罹患癌症的风险相当低,低于公众的预期水平。”

放射学学者约翰·莫尔德(John Moulder)对50,000名幸存者的资料进行了分析,他们中的5,000人罹患了癌症:“基于我们对其他日本民众患癌率的了解,这50,000名幸存者中的癌症患者人数本应为4,500人。所以,从这50年来看,这是一个5,000例病例与4,500例病例的区别。”假设这多出来的500例病例都是由辐射导致的,那么这意味着这个比例为1%。另外,辐射并没有带来遗传性突变的增加。记住:他们并不是核电站损毁的受害者;他们是核打击的幸存者。



与其烦恼这些事情,你还不如请人测试一下地下室的氡值。记录你自己和家人进行核医疗诊断和治疗的次数(包括X光扫描和CT扫描)。使用防晒霜。并且听从曾对“放射性”做出过定义的居里夫人(Marie Curie)的意见:“现在是时候加深了解了,这样我们的恐惧才会减轻。”