经济学人：空气污染来袭 如何保护我们的肺
Science and technology: Air-pollution: Breathtaking
科学与技术：空气污染：屏气吞声
科学与技术：空气污染：屏气吞声
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Air-quality indices make pollution seem less bad than it is.
空气质量指数粉饰了空气污染情况。
Smoking a whole packet of cigarettes in a day once or twice a year would certainly makesomeone feel ill, but probably would not kill him.
一天抽完一整包烟，一年这么抽个一两天，必然会让人感觉不适，但也许还不足以致命。
Smoking even one cigarette every day for decades, though, might do so.
但如果每天抽一支，数十年如一日下去，就可能会让你丧命了。
That is the difference between acute and chronic exposure, and it is a difference most peopleunderstand.
这就是急性暴露和慢性暴露的区别，大多数人都能理解这两者的不同之处。
What they may not understand is that the same thing applies to air pollution.
但是同样的情况放到空气污染上，他们可能就没弄明白了。
On a day-to-day basis, the forecasts most cities offer turn red only when pollution levels riseto a point where they will cause immediate discomfort.
大多数城市的每日天气预报里，只有当空气污染达到能让人当即感到不适的程度时，才会出现红色的警示。
That makes sense, for it lets people such as asthmatics take appropriate action.
这些警示有一定的作用，可以供如哮喘病一类的患者因时制宜。
But it might also lead the unwary to assume, if most days in the place he inhabits are green,that the air he is breathing is basically safe.
但也会让没有戒备心的人误以为，既然当地绝大多数时候空气质量状况指标为绿色，那么他们呼吸的空气基本上就是安全无害的。
This may well not be the case.
但事实很可能并非如此。
In London, for example, a study published last year by researchers at King’s College suggestedair pollution shortens the city’s inhabitants’ lives by nine to 16 months.
比如在伦敦，国王学院的研究人员去年发表的一项研究称，空气污染会使伦敦居民的寿命减少9至16个月。
To investigate the matter, The Economist crunched a year’s worth of data collected from May2015 onwards in 15 big cities.
为了探明究竟，《经济学人》杂志用电脑处理了来自15个大城市于2015年5月开始收集、为期一年的数据量。
They were gathered by Plume Labs, a firm based in Paris, which uses them to produce acommercial air-quality app.
这些数据由巴黎的Plume Lab公司收集，并用于制作一款商业化的空气质量应用软件。
The three pollutants of most concern in rich countries are nitrogen dioxide (NO2, a brownishgas emitted by car exhausts, and particularly by diesels) , ozone (a triatomic form of oxygenthat irritates lungs) and soot-particles smaller than 2.5 microns across (which makes them tinyenough to get deep into the lungs) .
在富裕国家，最引人担忧的三种污染物分别是二氧化氮 (NO2，汽车——特别是柴油汽车尾气中的一种棕色气体) 、臭氧 (分子由三个氧原子构成，对肺部有危害) 以及截面直径小于2.5微米的烟尘颗粒 (体积微小，可以深入肺部)。
These pollutants can cause a variety of medical difficulties, including asthma, heart disease,lung cancer and stunted lung growth in children.
这些污染物会造成一系列的医疗难题，包括哮喘、心脏病、肺癌和儿童肺部的发育不良。
Levels of NO2 in London and Paris are routinely higher than World Health Organisation (WHO)guidelines about what constitutes a long-term hazard, known as the annual average limit—andthat goes, too, for particulate matter.
伦敦和巴黎的二氧化氮含量通常高于世界卫生组织 (WHO) 的参考值，二氧化碳浓度长期高于这一参考值就会对人体造成伤害，这个参考值即年平均浓度限值——这一标准同样适用于细微颗粒物。
In London, during daytime, the concentration of NO2 exceeded the WHO’s limit by 41%, onaverage, over the 12 months examined.
根据这一年的数据记录，伦敦白天的二氧化氮浓度平均要超出世界卫生组织限值的41%.
In Paris, where the national index said air quality was “good” or “very good” four days out offive, our analysis found that at least one of the three main pollutants exceeded the WHO’s limitat some point almost every day.
在巴黎，国家空气指数显示，每五天之中有四天的空气质量都是 “良好” 或者 “优质”，但是我们的分析结果表明，全天之内三种污染物无一超标的天数屈指可数。
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A further problem is that setting day-to-day limits is a local matter.
另一个问题是，每日的平均浓度限值是由当地定制的。
So, not only do they rarely take long-term risk into account, they also vary from place to place.
所以，这些标准不仅很少考虑长期风险，而且每个地区的标准都不尽相同。
In Britain’s index a concentration of NO2 up to five times the WHO’s annual average limitcounts as “low”.
根据英国的空气质量指数，二氧化氮浓度高达世界卫生组织年平均浓度限值的5倍时才能算作 “差”。
America is more conservative.
美国相对谨慎些。
It draws the line at two-and-a half times the WHO limit.
他们把该值定在WHO限值的2.5倍。
Worse, in some cases there is no pretence of objectivity.
更糟的情况是，部分地区连客观现实都懒得粉饰了。
The website of Belgium’s BelATMO index, for example, warns that this is “a qualitativerepresentation” of air quality that “has little scientific meaning”.
例如，比利时的BelATMO空气质量指数网站上，就有警告说世界卫生组织的年平均浓度限值仅仅是空气质量的一种 “定性描述”，而且 “科学意义不大”。
Cities also vary in the way they present pollution data.
每个城市呈现空气污染数据的形式也各不相同。
Most do so on a scale of ten or 100, which is then segmented into four to six bands labelledlow, moderate and so on.
大多数城市采用了十分制或百分制，将其划分成四到六个层次，分别代表着低质量、中等质量等等。
Some places draw the line between “low” and “moderate” at the level at which pollution startsto cause immediate health effects, reserving the red band for smog that severely affects mostpeople.
在一些地方，以空气污染程度能否对人体健康造成迅疾危害来区分空气质量“低”和“中等”，等到几乎所有人都受到雾霾严重影响的时候才显示红色警告。
Others divide the scale into equal chunks, each representing the same additional daily risk ofdying or being admitted to hospital because of pollution.
另外一些地区把空气污染等级均匀划分，每增加一级，空气污染造成的日死亡风险或者住院率相同增长。
Offcial indices also fail to capture patterns of variation within a day.
官方的空气质量指数也未能表现出一天之内的空气质量变化模式。
These can be important—and people might be able to modify their behavior if they understoodthem.
而这一变化模式十分重要，如果人们能明白这种模式，他们可能就会据此调整自己的生活习惯。
Our analysis suggests, for example, that Parisians who head out for work at 9am and return at6pm could reduce their average daily commuting intake of NO2 by 16% by travelling both waysan hour earlier.
举个例子，我们的分析表明，在巴黎，上午9点出门上班并且下午6点下班回家的人，如果往返都提前一个小时，那么他们日常通勤时吸入的二氧化氮可以减少16%。
Going two hours earlier would cut the intake by 28%.
如果提前两个小时，他们吸入的二氧化氮则会相比减少28%。
Weekly cycles also exist.
每周空气质量变化也有规律可循。
Parents in Brussels and Paris might be wise to schedule their children’s indoor activities, such asswimming lessons, on Saturdays and outdoor stuff like football practice on Sundays.
在布鲁塞尔和巴黎，明智的家长会把孩子游泳课程这样的户内活动安排在周六，把踢足球训练之类的户外活动安排在周日。
That is because, during daytime hours, the concentration of NO2 in those cities was, onaverage, about 20% lower on Sundays.
这是因为在这两个城市的白天时段，平均下来周日的二氧化氮浓度要低大约20%，
In Amsterdam it was 16% lower.
在阿姆斯特丹则会低16%。
In all three places, fine-particle pollution also fell on Sundays, as did ozone in the summermonths.
在这三个地方，周日的细微颗粒物污染也更少，就好像在夏季臭氧浓度也会减少一样。
The best pollution advice of all to people in these cities, though, is: move to America.
然而关于空气污染这一问题，给这三座城市的居民最好的建议是：搬到美国去。
In New York, levels of NO2 were 20% below the WHO limit, and that is pretty typical of placesin the United States, where diesels are less common than in Europe.
在纽约，二氧化氮浓度比世界卫生组织的标准低20%，这是美国的一典型，因为这里的柴油机比欧洲少得多。
As the inscription under the Statue of Liberty has it, “Give me your huddled masses, yearningto breathe free.”
就像自由女神底下的铭文说的那样：“让你那挤成一团的人民过来这里，他们渴望自由呼吸。”
重点讲解
1.Air-pollution 空气污染
例句:They say gas guzzlers are contributing to air pollution.
他们说高耗油汽车是造成空气污染的原因之一。
2.air quality 空气质量
例句：It's unclear whether government vehicles have a huge negative impact on Beijing's airquality.
目前尚不清楚政府公车是否对北京空气质量产生了非常严重的负面影响。
3.at least 至少
例句:He's been away for at least a week.
他走了总有一个星期吧。
4.heart disease 心脏病
例句:It reduces the risks of heart disease.
这降低了患心脏病的风险。
5.day-to-day 日常的
例句:Christopher will direct day-to-day operations.
克里斯托弗将管理日常的运营。
6.on average 平均
例句:American shares rose, on average, by 38%
美国股票价格平均上涨了38%。
7.long-term 长期的
例句:Businesses will have to aim at long-term growth.
企业必须以长期增长为目标。
8.the Statue of Liberty 自由女神像
例句:The Statue of Liberty embodies the spirit of freedom.
自由女神像体现了热爱自由的精神。
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