学术英语理工lecture12

How Radiation Threatens Health如何辐射威胁健康

As worries grow over radiation leaks at Fukushima, is it possible to gauge the immediate and lasting health effects of radiation exposure? Here's the science behind radiation sickness and other threats facing Japan。由于担心福岛核电站辐射泄漏,有可能测量辐射的直接和持久的健康影响?这是背后的科学面临辐射病和其他威胁日本。

The japan earthquake and tsunami on match 11,a powerful,magnitude 9.0 quake hit northeastern japan,triggering a tsunami with 10-meter-high waves that reached the U.S. West coast.Here’s the science behind the disaster.在比赛11日日本地震和海啸,强大,日本东北部发生9.0级地震,地震引发的海啸与西方10-meter-high波,达到美国coast.Here灾难背后的科学。

The developing crisis at the Fukushima Daiichi nuclear power plant in the wake of the March 11 earthquake and tsunami has raised concerns over the health effects of radiation exposure: What is a

Though radioactive steam has been released to reduce pressure within the wrecked complex's reactors and there has been additional radiation leakage from the three explosions there, the resulting spikes in radiation levels have not been sustained. The highest radiation level reported thus far was a pulse of 400 millisieverts per hour at reactor No. 3, measured at 10:22 A.M. local time March 15. (A sievert is a unit of ionizing radiation equal to 100 rems; a rem is a dosage unit of x-ray and gamma-ray radiation exposure.) The level of radiation decreases dramatically as distance from the site increases. Radiation levels in Tokyo, about 220 kilometers to the southwest, have been reported to be only slightly above normal.尽管放射性蒸汽被释放减少受损的反应堆内压力和有额外的辐射泄漏的三次爆炸,产生的辐射水平激增并不持久。迄今为止,报道的最高辐射水平是每小时400毫西弗的脉冲在三号反应堆,以当地时间3月15日上午十。(译者按电离辐射的单位等于100雷姆;快速眼动是x射线和伽马射线辐射剂量单位。)的辐射水平显著降低站点的距离增加,辐射水平在东京,西南约220公里处,已报告仅略高于正常。

According to Abel Gonzalez, vice chairman of the International Commission on Radiological Protection who studied the 1986 Chernobyl disaster, current information coming from Japan about levels of radiation leakage are incomplete at best and

speculations about

The health effects caused by radiation exposure depend on its level, type and duration.辐射对健康的影响水平,类型和持续时间。

Radiation level:辐射水平:

The average person is exposed to 2 to 3 millisieverts of background radiation per yearfrom a combination of cosmic radiation and emissions from building materials and natural radioactive substances in the environment.普通人接触到2 - 3毫西弗每yearfrom背景辐射的宇宙辐射和排放的建筑材料和自然环境中的放射性物质。

The U.S. Nuclear Regulatory Commission recommends that beyond this background level, the public limit their exposure to less than an additional one millisievert per year. The U.S. limit for radiation workers is 50 millisieverts annually, although few workers are exposed to anything approaching that amount. For patients undergoing medical radiation there is no strict exposure limit—it is the responsibility of medical professionals to weigh the risks and benefits of radiation used in diagnostics and treatment, according to Langhorst. A single CT scan, for example, can expose a patient to more than one millisievert.

美国核管理委员会建议,在此背景下,公众限制他们接触不到一个1毫希。美国限制辐射工作人员每年50毫希,但很少有工人暴露在接近这个数值。对于接受辐射治疗的病人没有严格Langhorst称医护人员负责医疗辐射的风险与收益用于诊断和治疗,。一个CT扫描,例如,可以使病人不止一个毫西弗。

Radiation sickness (or acute radiation syndrome) usually sets in after a whole-body dose of three sieverts—3,000 times the recommended public dose limit per year, Langhorst says. The first symptoms of radiation sickness—nausea, vomiting, and diarrhea— can appear within minutes or in days, according to the U.S. Centers for Disease Control and Prevention. A period of serious illness, including appetite loss, fatigue, fever, gastrointestinal problems, and possible seizures or coma, may follow and last from hours to months.

辐射病(或急性辐射综合症)通常在全身剂量的三集西弗特- 3000倍推荐每年公众剂量限制,Langhorst说。第一个辐射病症状为恶心、呕吐、腹泻,可以出现在几分钟或几日内,根据美国疾病控制和预防中心一段严重的疾病,比如食欲不振、疲劳、发烧、肠胃问题,癫痫发作或昏迷,最后从小时到几个月。

Radiation type:

Of concern in the current situation is ionizing radiation, which is produced by spontaneously decaying heavy isotopes, such as iodine 131 and cesium 137. (Isotopes are species of the same element, albeit with different numbers of neutrons and hence different atomic masses.) This type of radiation has sufficient energy to ionize atoms (usually creating a positive charge by knocking out electrons), thereby giving them the chemical potential to react deleteriously with the atoms and molecules of living tissues.的担忧在当前形势下是电离辐射,这是自发衰变而产生的重同位素,如碘131和铯131。(同位素是物种相同的元素,尽管不同数量的中子,因此不同的原子质量)。这种类型的辐射能量较大,电离原子(通常是创建一个可通过电子),从而使它们的化学势与原子和分子反应得到正电荷的生活组织。

Ionizing radiation takes different forms: In gamma and x-ray radiation atoms release energetic light particles that are powerful enough to penetrate the body. Alpha and beta particle radiation is lower energy and can often be blocked by just a sheet of paper. If radioactive material is ingested or inhaled into the body, however, it is actually the lower energy alpha and beta radiation that becomes the more dangerous. That's because a large portion of gamma and x-ray radiation will pass directly through the body without interacting with the tissue (considering that at the atomic level, the body is mostly empty space), whereas alpha and beta radiation, unable to penetrate tissue, will expend all their energy by colliding with the atoms in the body and likely cause more damage. 电离辐射呈现出不同的形式:在伽马射线和x射线辐射原子释放出高能量的光粒子,强大到足以穿透身体。α和β粒子辐射是低能量,通常可以被一张纸。如果被吞食或吸入放射性物质进入体内,但是,它实际上是低能量的α和β辐射成为更加危险。这是因为大部分射线和x射线辐射会直接穿过身体没有与组织互动(考虑到在原子层面,身体大部分是空的空间),而α和β辐射,无法穿透组织,将花费他们所有的能量与体内原子发生碰撞,可能造成更大的伤害。

In the Fukushima situation, the radioactive isotopes detected, iodine 131 and cesium 137, emit both gamma and beta radiation. These radioactive elements are by-products of the fission reaction that generates power in the nuclear plants. 在福岛的情况下,检测到放射性同位素,碘131和铯131,发射γ和β辐射。这些放射性元素副产品裂变发电的核电站。 The Japanese government has evacuated 180,000 people from within a 20-kilometer radius of the Fukushima Daiichi complex. They are urging people within 30 kilometers of the plant to remain indoors, close all windows, and to change clothes and wash exposed skin after going outside. These measures are mainly aimed at reducing the potential for inhaling or ingesting beta-emitting radioactive material.日本政府已经疏散180000人从福岛第一核电站周边20公里范围内的复杂。他们敦促核电站30公里内的居民呆在室内,关闭所有窗户,改变衣服,清洗暴露在外的皮肤外面后,这些措施主要是为了减少潜在的摄入或吸入可释放β射线的材料。Exposure time:曝光时间:

A very high single dose of radiation (acquired within minutes can be more harmful than the same dosage accumulated over time. According to the World Nuclear Association, a single one-sievert dose is likely to cause temporary radiation sickness and lower white blood cell count, but is not fatal. One five-sievert dose would likely kill half of those exposed within a month. At 10 sieverts, death occurs within a few weeks.

非常高的单剂量的辐射(在几分钟内获得可以比相同的剂量累积更有害。根据世界核协会,一个one-sievert剂量可能引起暂时的辐射疾病,降低白细胞计数,但不是致命的。一个five-sievert剂量可能会杀死那些暴露在一个月内的一半。10西弗特,在几周内发生死亡。 The effects of long-term, low-dose radiation are much more difficult to gauge. DNA damage from ionizing radiation can cause mutations that lead to cancer, especially in tissues with high rates of cell division, such as the gastrointestinal tract, reproductive cells and bone marrow. But the increase in cancer risk is so small as to be difficult to determine without studying a very large exposed population of people. As an example, according to Langhorst, 10,000 people exposed to a 0.01-sievert whole-body dose of radiation would potentially increase the total number of cancers in that population by eight. The normal prevalence of cancer, however, would predict 2,000 to 3,300 cancer cases in a population of 10,000, so

长期的影响,低剂量辐射更难以衡量。从电离辐射可引起DNA损伤突变导致癌症,尤其是在组织细胞分裂率高的,如胃肠道、生殖细胞和骨髓,但增加癌症风险很小,很难确定没有研究一个非常大的暴露人口的人。作为一个例子,根据Langhorst,10000人暴露于0.01 -sievert全身剂量的辐射可能会增加癌症的人口总数八。正常的癌症患病率,然而,将预测2000年至3300年癌症病例在10000人口,所以“你如何看待八个多余的癌症?”Langhorst问道。

Chernobyl's lessons:切尔诺贝利核事故的教训:

According to Gonzalez, some of the emergency workers at Chernobyl received several sieverts of radiation, and many were working

The Tokyo Electric Power Co. (TEPCO), the plant's owners, has evacuated most of its workers, but 50 remain at the site to pump cooling seawater into the reactors and prevent more explosions. These workers are likely exposing themselves to high levels of radiation and braving significant health risks.

The thousands of children who became sick in the aftermath of the Chernobyl disaster were not harmed from direct radiation or even from inhalation of radioactive particles, but from drinking milk contaminated with iodine 131. The isotope, released by the Chernobyl explosion, had contaminated the grass on which cows fed, and the radioactive substance accumulated in cows' milk. Parents, unaware of the danger, served contaminated milk to their children.

When it comes to radiation exposure, professionals who frequently work with radioactive materials, whether in a hospital or a nuclear power plant, abide by the ALARA principle:

辐射时,专业人士经常使用放射性物质,无论在医院还是一个核电站,遵守原则:和“低至合理可行”。辐射限制保守组低于水平诱导辐射病或涉嫌造成长期健康影响。临时接触剂量多次

这些限制,但是,不一定是危险的。

News of the U.S. Navy repositioning its warships upwind of the reactor site, the distribution of potassium iodide pills by the Japanese government, and images of officials in hazmat suits using Geiger counters to measure radiation levels among babies may stoke the public's fears—but, for now, these measures are ALARA in action, or