2012托福考试复习：双语阅读篇八

会计考友 · 发表于 2012-8-14 23:21:39

Congested cities are fast becoming test tubes for scientists studying the impact of traffic fumes on the brain.

As roadways choke on traffic, researchers suspect that the tailpipe exhaust from cars and trucks─especially tiny carbon particles already implicated in heart disease, cancer and respiratory ailments─may also injure brain cells and synapses key to learning and memory.

New public-health studies and laboratory experiments suggest that, at every stage of life, traffic fumes exact a measurable toll on mental capacity, intelligence and emotional stability. 'There are more and more scientists trying to find whether and why exposure to traffic exhaust can damage the human brain,' says medical epidemiologist Jiu-Chiuan Chen at the University of Southern California who is analyzing the effects of traffic pollution on the brain health of 7,500 women in 22 states. 'The human data are very new.'

So far, the evidence is largely circumstantial but worrisome, researchers say. And no one is certain yet of the consequences for brain biology or behavior. 'There is real cause for concern,' says neurochemist Annette Kirshner at the National Institute of Environmental Health Sciences at Research Triangle Park in North Carolina. 'But we ought to proceed with caution.'

To be sure, cars and trucks today generate one-tenth the pollution of a vehicle in 1970. Still, more people are on the road and they are stuck in traffic more often. Drivers traveling the 10-worst U.S. traffic corridors annually spend an average of 140 hours, or about the time spent in the office in a month, idling in traffic, a new analysis reported.

No one knows whether regular commuters breathing heavy traffic fumes suffer any lasting brain effect. Researchers have only studied the potential impact based on where people live and where air-pollution levels are highest. Even if there were any chronic cognitive effect on drivers, it could easily be too small to measure reliably or might be swamped by other health factors such as stress, diet or exercise that affect the brain, experts say.

Recent studies show that breathing street-level fumes for just 30 minutes can intensify electrical activity in brain regions responsible for behavior, personality and decision-making, changes that are suggestive of stress, scientists in the Netherlands recently discovered. Breathing normal city air with high levels of traffic exhaust for 90 days can change the way that genes turn on or off among the elderly; it can also leave a molecular mark on the genome of a newborn for life, separate research teams at Columbia University and Harvard University reported this year.

会计考友 · 发表于 2012-8-14 23:21:40

Children in areas affected by high levels of emissions, on average, scored more poorly on intelligence tests and were more prone to depression, anxiety and attention problems than children growing up in cleaner air, separate research teams in New York, Boston, Beijing, and Krakow, Poland, found. And older men and women long exposed to higher levels of traffic-related particles and ozone had memory and reasoning problems that effectively added five years to their mental age, other university researchers in Boston reported this year. The emissions may also heighten the risk of Alzheimer's disease and speed the effects of Parkinson's disease.

'The evidence is growing that air pollution can affect the brain,' says medical epidemiologist Heather Volk at USC's Keck School of Medicine. 'We may be starting to realize the effects are broader than we realized.'

Reviewing birth records, Dr. Volk and her colleagues calculated that children born to mothers living within 1,000 feet of a major road or freeway in Los Angeles, San Francisco or Sacramento were twice as likely to have autism, independent of gender, ethnicity and education level, as well as maternal age, exposure to tobacco smoke or other factors. The findings were published this year in the journal Environmental Health Perspectives.

'Based on our data, it looks like air pollution might be a risk factor for autism,' Dr. Volk says. Still, there are so many possible genetic and environmental influences that 'it is too soon for alarm,' she says.

Exhaust fumes can extend farther from roadways than once thought. Traffic fumes from some major L.A. freeways reached up to 1.5 miles downwind─10 times farther than previously believed. And local weather patterns caused L.A. pollution levels to reach their most intense concentrations, not during normal rush hours, but in the hours before dawn when people are most likely to be at home, according to recent measurements by UCLA and USC researchers.

Scientists believe that simple steps to speed traffic are a factor in reducing some public-health problems. In New Jersey, premature births, a risk factor for cognitive delays, in areas around highway toll plazas dropped 10.8% after the introduction of E-ZPass, which eased traffic congestion and reduced exhaust fumes, according to reports published in scientific journals this year and in 2009. The researchers, Princeton University economist Janet Currie and her colleagues at Columbia University, analyzed health data for the decade ending 2003.

After New York traffic managers rerouted streets in Times Square recently to lessen congestion, air-pollution levels in the vicinity dropped by 63%.

Scientists are only beginning to understand the basic biology of car exhaust's toxic neural effects, especially from prenatal or lifetime exposures. 'It is hard to disentangle all the things in auto exhaust and sort out the effects of traffic from all the other possibilities,' says Dr. Currie, who studies the relationship between traffic and infant health.

Researchers in Los Angeles, the U.S.'s most congested city, are studying lab mice raised on air piped in from a nearby freeway. They discovered that the particles inhaled by the mice─each particle less than one-thousandth the width of a human hair─somehow affected the brain, causing inflammation and altering neurochemistry among neurons involved in learning and memory.

To study the effect of exhaust on expectant mothers, Frederica Perera at Columbia University's Center for Children's Environmental Health began in 1998 to equip hundreds of pregnant women with personal air monitors to measure the chemistry of the air they breathed. As the babies were born, Dr. Perera and colleagues tested some of the infants and discovered a distinctive biochemical mark in the DNA of about half of them, left by prenatal exposure to high levels of polycyclic aromatic hydrocarbons in exhaust.

By age 3, the children who were exposed prenatally to high exhaust levels were developing mental capacities fractionally more slowly. By age 5, their IQ scores averaged about four points lower on standard intelligence tests than those of less exposed children, the team reported in 2009. The differences, while small, were significant in terms of later educational development, the researchers said.

By age 7, the children were more likely to show symptoms of anxiety, depression and attention problems, the researchers reported this year in Environmental Health Perspectives.

'The mother's exposure─what she breathed into her lungs─could affect her child's later behavior,' Dr. Perera says. 'The placenta is not the perfect barrier we once thought.'

拥堵的城市正快速成为科学家用来研究汽车废气对人类大脑影响的试管。

如今的交通越来越拥堵，研究人员怀疑，各类轿车和卡车释放的尾气，特别是已经被证明会造成心脏病、癌症和呼吸道疾病的碳微粒，可能还会伤害对学习和记忆起关键作用的脑细胞及突触。

最新的公共卫生研究和实验室实验表明，在生命的每个阶段，汽车废气都会对人的心智能力、智力和情感稳定能力造成一定程度的损害。南加州大学（University of Southern California）流行病学专家Jiu-Chiuan Chen说，越来越多的科学家正在努力研究汽车尾气是否会损害人的大脑，以及为何会造成损害。他在研究交通污染对美国22个州7,500名女性大脑健康的影响。他说，这方面有关人类的数据还很新。

没人知道经常吸入大量汽车尾气的上班族大脑是否会受到持续的影响。研究人员只是按照人们所居住的地点以及空气污染最严重的地区对潜在影响进行了研究。专家说，即便汽车尾气对司机的认知能力有慢性影响，可能也会由于影响太小而不容易得到可靠的测量，另外还可能会被压力、饮食或锻炼等其他对大脑有影响的健康因素所掩盖。

荷兰科学家最近发现，最近的研究表明，只要在一般的街道上吸入30分钟的尾气，就会导致控制行为、个性和决策的大脑区域加强脑电活动，这些变化是压力的迹象。哥伦比亚大学（Columbia University）和哈佛大学（Harvard University）的研究团队今年分别发布报告说，吸入含有大量汽车废气的普通城市的空气达到90天，就会改变老年人基因开启和关闭的方式；同时还会在新生婴儿的基因组中留下一个伴随其终身的分子标记。

会计考友 · 发表于 2012-8-14 23:21:41

纽约、波士顿、北京、波兰克拉科的各研究团队发现，汽车废气严重城市的儿童比生长于较干净空气环境下的儿童平均智力测验成绩差，也更容易产生忧虑、焦虑和注意力不集中的问题。波士顿其他大学研究人员今年发布报告说，生活在汽车废气微粒和臭氧浓度较高地区的老年人，易发生记忆和推理能力老化现象，使他们比同龄人的心理年龄老五岁。汽车废气也可能增加患老年痴呆症（Alzheimer's disease）的风险，并加快帕金森氏症（Parkinson's disease）的恶化。

南加州大学凯克医学院(USC's Keck School of Medicine)流行病学家沃尔克(Heather Volk)说，越来越多的证据表明空气污染会影响大脑；我们现在开始意识到，这种影响的范围比我们想象的要大。

Agence France-Presse/Getty Images南加州大学凯克医学院流行病学家沃尔克说，越来越多的证据表明空气污染会影响大脑。通过研究出生记录，沃尔克博士和她的同事发现，不考虑性别、民族、教育水平、母亲年龄及吸烟影响等因素的影响，住在洛杉矶、旧金山或萨克拉门托的主路或高速路1,000英尺（约300米）以内的母亲，她们的孩子患孤独症的可能性是一般人的两倍。该研究结果今年发表于《环境与健康展望》（Environmental Health Perspectives）期刊上。

沃尔克博士说，从我们的数据来看，空气污染好像有可能是导致孤独症的一个风险因素；不过存在太多可能的遗传和环境影响，因此现在就发出警告还太早。

废气从道路扩散到其他地方的范围可能比我们所认为的要远。洛杉矶某些主要高速公路的汽车废气顺风扩散的距离长达1.5英里，比之前人们所认为的要远10倍。根据加州大学洛杉矶分校（UCLA）及南加州大学研究人员最近的测量，由于当地的天气状况所致，洛杉矶污染程度达到最强浓度的时间并不是在通常的高峰时段，而是在人们最有可能在家的天亮之前的几个小时。

科学家认为，改善交通拥堵的简单措施有助于减少某些公共健康问题。据几家科学期刊今年以及2009年发布的相关研究报告显示，在新泽西州采用E-ZPass系统后，交通堵塞得以缓和，废气排放得以减少，高速公路收费站附近区域的早产率也下降了10.8%，早产是导致认知能力迟滞的风险因素。从事该项研究的研究人员是普林斯顿大学（Princeton University）经济学家居里（Janet Currie）和她在哥伦比亚大学的同事，他们分析了1993年至2003年十年间的健康数据。

近期纽约交通管理机构为减缓拥堵而更改了时代广场（Times Square）街道的路线后，附近地区的空气污染水平下降了63%。

科学家刚刚开始探究汽车尾气对神经产生有害影响的基本生物学原理，特别是出生前及终身吸入尾气的情况。居里博士的研究课题是交通和婴儿健康之间的关系，她说，很难排除汽车尾气对所有这些的影响并从所有其他可能性中厘清汽车尾气的影响。

在美国最拥堵的城市洛杉矶，研究人员将附近高速公路的空气输入实验室，并在这种空气中饲养老鼠。他们发现老鼠吸入的颗粒对大脑产生了影响，导致脑部发炎并使控制学习和记忆的神经发生神经化学变化。每个颗粒比人类头发宽度的千分之一还要小。

为了研究废气对孕妇的影响，哥伦比亚大学儿童环境健康中心（Center for Children's Environmental Health）的佩拉雷（Frederica Perera）从1998年开始为几百名孕妇配备私人空气监测器，测量她们所吸入空气的化学性质。婴儿出生时，佩拉雷博士及其同事对部分婴儿进行了测试，发现其中约半数婴儿的DNA中都存在一个明显的生物化学标记，这是婴儿出生前从废气中吸收的大量多环芳香族碳氢化合物所留下的。

该研究团队2009年发布报告说，在三岁时，出生前受过大量废气影响的儿童心智能力的开发相对比较缓慢。五岁时，他们的智商测验成绩比较少受废气影响的儿童平均约低四分。研究人员说，差别虽然不大，但在随后的教育开发方面影响却十分显著。

他们今年发表于《环境与健康展望》的报告称，七岁时，这些儿童更有可能显现出焦虑、抑郁和注意力不集中的症状。

佩拉雷博士说，母亲的肺里吸入什么样的空气，可能会影响孩子后来的行为；胎盘并不像我们曾经认为的那样是一个完美的屏障。</p>

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[托福阅读] 2012托福考试复习：双语阅读篇八

2012托福考试复习：双语阅读篇八

2012托福考试复习：双语阅读篇八