ACT阅读：外刊——雾霾会进入大脑

　　ACT是一个学术能力测试，我们向来认为ACT分数和学生本身的英语能力、学科知识成正相关的。今天课窝网就分享一篇外刊阅读文章，多多阅读课外书籍对大家的备考是非常有益的。

　　英国兰卡斯特大学的Maher及其团队，发表在《美国国家科学院院刊》上的最新研究就发现：

　　“雾霾等空气污染，损伤的不仅是我们的肺，还会损害我们的大脑。”

　　David ShukmanScience editor, BBC News

　　Tiny particles of pollution have been discovered inside samples of brain tissue, according to new research.

　　Suspected of toxicity, the particles of iron oxide could conceivably contribute to diseases like Alzheimer’s – though evidence for this is lacking.

　　The finding – described as “dreadfully shocking” by the researchers – raises a host of new questions about the health risks of air pollution.

　　Many studies have focused on the impact of dirty air on the lungs and heart.

　　Now this new research provides the first evidence that minute particles of what is called magnetite, which can be derived from pollution, can find their way into the brain.

　　Earlier this year the World Health Organisation warned that air pollution was leading to as many as three million premature deaths every year.

　　TRACING ORIGINS

　　The estimate for the UK is that 50,000 people die every year with conditions linked to polluted air.

　　The research was led by scientists at Lancaster University and is published in the Proceedings of the National Academy of Sciences (PNAS).

　　The team analysed samples of brain tissue from 37 people – 29 who had lived and died in Mexico City, a notorious pollution hotspot, and who were aged from 3 to 85.

　　The other 8 came from Manchester, were aged 62-92 and some had died with varying severities of neurodegenerative disease.

　　The lead author of the research paper, Prof Barbara Maher, has previously identified magnetite particles in samples of air gathered beside a busy road in Lancaster and outside a power station.

　　She suspected that similar particles may be found in the brain samples, and that is what happened.

　　“It’s dreadfully shocking. When you study the tissue you see the particles distributed between the cells and when you do a magnetic extraction there are millions of particles, millions in a single gram of brain tissue – that’s a million opportunities to do damage.”

　　Further study revealed that the particles have a distinctive shape which provides a crucial clue to their origin.

　　Magnetite can occur naturally in the brain in tiny quantities but the particles formed that way are distinctively jagged.

　　By contrast, the particles found in the study were not only far more numerous but also smooth and rounded – characteristics that can only be created in the high temperatures of a vehicle engine or braking systems.

　　Prof Maher said: “They are spherical shapes and they have little crystallites around their surfaces, and they occur with other metals like platinum which comes from catalytic converters.

　　“So for the first time we saw these pollution particles inside the human brain.

　　“It’s a discovery finding. It’s a whole new area to investigate to understand if these magnetite particles are causing or accelerating neurodegenerative disease.”

　　For every one natural magnetite particle identified, the researchers found about 100 of the pollution-derived ones.

　　The results did not show a straightforward pattern. While the Manchester donors, especially those with neurodegenerative conditions, had elevated levels of magnetite, the same or higher levels were found in the Mexico City victims.

　　The highest level was found in a 32-year-old Mexican man who had been killed in a traffic accident.

　　DISEASE RISK?

　　Dubbed “nanospheres”, the particles are less than 200 nanometres in diameter – by comparison, a human hair is at least 50,000 nanometres thick.

　　While large particles of pollution such as soot can be trapped inside the nose, smaller types can enter the lungs and even smaller ones can cross into the bloodstream.

　　But nanoscale particles of magnetite are believed to be small enough to pass from the nose into the olfactory bulb and then via the nervous system into the frontal cortex of the brain.

　　Prof David Allsop, a specialist in Alzheimer’s and other neurodegenerative diseases, is a co-author of the study and also at Lancaster University.

　　He said that pollution particles “could be an important risk factor” for these conditions.

　　“There is no absolutely proven link at the moment but there are lots of suggestive observations – other people have found these pollution particles in the middle of the plaques that accumulate in the brain in Alzheimer’s disease so they could well be a contributor to plaque formation.

　　“These particles are made out of iron and iron is very reactive so it’s almost certainly going to do some damage to the brain. It’s involved in producing very reactive molecules called reaction oxygen species which produce oxidative damage and that’s very well defined.

　　“We already know oxidative damage contributes to brain damage in Alzheimer’s patients so if you’ve got iron in the brain it’s very likely to do some damage. It can’t be benign.”

　　Other experts in the field are more cautious about a possible link.

　　Dr Clare Walton, research manager at the Alzheimer’s Society, said there was no strong evidence that magnetite causes Alzheimer’s disease or makes it worse.

　　“This study offers convincing evidence that magnetite from air pollution can get into the brain, but it doesn’t tell us what effect this has on brain health or conditions such as Alzheimer’s disease,” she said.

　　“The causes of dementia are complex and so far there hasn’t been enough research to say whether living in cities and polluted areas raises the risk of dementia. Further work in this area is important, but until we have more information people should not be unduly worried.”

　　She said that in the meantime more practical ways of lowering the chances of developing dementia include regular exercise, eating a healthy diet and avoiding smoking.

　　这一下子颠覆了人们的认知，多年来人们对雾霾的认知大都停留在对呼吸道、肺脏的危害上，但最新的研究却发现，其对大脑的伤害完全不亚于肺脏。

　　空气污染会对大脑造成永久性损坏。

　　简单说就是：长期处于污染空气中的大脑会永久受损，会变傻变笨，会孤独、抑郁、痴呆。

　　而当这一研究放在人体身上时，结果则更加震撼。

　　不同于PM2.5~10的粗颗粒污染物（如沙尘暴），PM小于2.5的雾霾可以通过呼吸道直达我们的大脑。

　　污染物由肺入脑的过程

　　雾霾中的金属纳米粒子会助推老年痴呆的发生，这些粒子绝非身体所需，它通常来源于高温下融化的铁和燃料燃烧，以及汽车尾气的排放。

　　而长期暴露在污染空气中的儿童和青少年，更易受到伤害，通过鼻腔吸入的金属纳米粒子进入大脑，造成不可逆的永久伤害。

　　左起图一为健康大脑，图二、三、四依次为被空气污染、老年痴呆症以及毒品侵蚀的大脑

　　这在对1952年经历伦敦雾霾事件的儿童健康追踪中，已得到证实，60多年过去了，雾霾仍给一些人留下了后遗症。

　　美国波士顿大学心理学家Shakira Franco Suglia，曾对参与调查的200名平均年龄10岁的波士顿儿童进行随机调查。

　　结果发现那些成长在严重空气污染区域的孩子，在认知能力测试，记忆力测试以及IQ测试上面的成绩，均显著低于居住在未污染城市的孩子。

　　美国芝加哥拉什医学院教授Jennifer的研究团队，则把研究样本和规模扩展得更大，他们对养老院的19000名年长女性的记忆能力和居住的地址进行比对研究。

　　最终发现，那些常年生活在空气污染严重地区的被试者，晚年的记忆衰退更严重，更容易患上老年痴呆症。

　　亚洲清洁空气中心执行总监Bjarne Pedersen表示，空气污染每年在全世界造成的过早死亡人数达700万以上。

　　世界卫生组织2015年公告也显示，全世界每年有800万人死于空气污染。

　　以上就是小编为大家介绍的关于外刊阅读之环境问题，面对环境问题每个人都有不可推卸的责任。更多ACT官网报名、ACT考试费用等问题可以咨询我们。