By+Jon+Excell

濃霧茫茫，遮天蔽日，行人步履匆匆，咳聲此起彼伏。這不是世界末日，也不是霧霾天的北京，而是1952年12月5日的倫敦。那場霧霾奪去了成千上萬人的性命，英國政府痛下改革決心，在此后的數(shù)十年中一直致力于空氣污染的整治。如今的倫敦已不復當年“霧都”的景象，卻仍走在治理空氣污染的路上。往者可鑒，來者可追。只要污染存在一日，人們探索的腳步就不會停歇。

Imagine smog so thick that you cant see your feet as you walk through it; so impenetrable that it blots out1） the sun; so toxic that it stings your eyes and leaves you gasping for breath.

It may sound like the backdrop2） to some post-apocalyptic nightmare， but on 5 December 1952， this terrifying scenario became the reality for the people of London. That days incident alone killed thousands and prompted a global transformation in the way we deal with air pollution.

On that cold， clear day in 1952， Londoners huddled around their coal fires for warmth. But while the smoke would normally disperse into the atmosphere， an anticyclone3） hanging over the region created an inversion—trapping the pollution close to the ground and leading to the formation of a sulphurous4）， toxic shroud5） that would blanket the capital for the next five days.

Before the weather conditions changed and the smog retreated， thousands had died. Official estimates at the time put the number of fatalities at 4，000—more civilian casualties than were caused by any single incident during the war—while recent research suggests that it may have caused as many as 12，000 deaths.

“Necessary Evil”

“必要之惡”

Although “pea-soupers，” as the smogs were known， had been an unavoidable feature of Britains major cities for more than a hundred years， the Great Smog of 1952 was the worst.

It also marked something of a turning point： Until then， people had accepted smog as a necessary evil6）. “In Britains coal-fuelled cities， smoke was tolerated for more than a century as a trade-off for jobs and home comforts，” says environmental historian Dr Stephen Mosley. Some even celebrated air pollution as a tangible measure of Britains industrial vitality， while the blazing7） coal fire， with all its cosy connotations of “home and hearth8），” was a luxury few were prepared to give up.

Despite growing public pressure to deal with the issue， the governments reaction was sluggish9）. Initially it even claimed that Decembers high mortality was due to a flu outbreak， and seven months elapsed before it eventually ordered an inquiry.

Four years later， in 1956， the Clean Air Act came into force， banning the burning of polluting fuels in “smoke control areas” across the UK.

The act was truly revolutionary， representing a major global milestone in environmental protection. Public health was vastly improved; flora10） and fauna11） that had all but vanished from urban places by the 1950s began to flourish; and the grand architecture of Britains cities was no longer obscured beneath a thick layer of soot12） and grime13）. In the years that followed， a host of other industrial nations were inspired to follow suit.

Air Issues

空氣問題

But， while air pollution from coal may be a thing of the past， Londons air quality problem hasnt gone away. And with a recent study suggesting that pollution in the capital claims14） as many as 9，500 lives a year， a growing number of scientists， politicians and campaigners believe that on the eve of the Clean Air Acts 60th anniversary， the UK must once again invoke its pioneering spirit.

The study， which was carried out for Transport for London by Kings College Londons Environmental Research Group， attributes these premature deaths to two main pollutants： fine particulates known as PM2.5 and the toxic gas nitrogen dioxide （NO2）.

NO2 levels are of particular concern. London has the worlds highest measured levels of the gas and has breached EU safety limits every year for the last five. In 2015， NO2 levels on Oxford Street broke the annual limit in just four days.

The KCL study estimated that the gas could be to blame for as many as 5，900 premature deaths a year.

While scientists have been aware of NO2s toxic properties for many years， the fact that its usually present with other pollutants has made it difficult to isolate its impact， says Kings College air quality specialist Martin Williams. Only now have researchers been able to conclude that there is an independent effect.

Nevertheless， says the studys author Dr Heather Walton， there is still some uncertainty on exactly how many deaths can be attributed to the gas.

NO2 pollution has a range of sources. But according to the governments Department for Environment and Rural Affairs， emissions from transport account for at least 80%. Diesel15） vehicles， which form more than a third of Londons road traffic， are the biggest culprits16）.

Because of their fuel efficiency and lower CO2 emissions， diesel engines have been heavily incentivised17） over the last couple of decades—with successive governments turning a blind eye to their higher particulate and NOx emissions.

Ironically， the effect of diesel engines has been made worse by the use of technology designed to make them less polluting. “Diesels emit particles in much larger quantities than petrol cars so were fitted with particle filters，” says Williams. “These trap the particles on filters， but every now and again they have to be burned off—NOx in emissions is converted to NO2 which helps to oxidise and burn off particles in the filter. To solve the particle problem， NO2 emissions were being increased.”

Breathing Easier？

呼吸更輕松？

The good news is that NO2 levels are beginning to fall. Selective catalytic reduction systems， which are able to remove many of the NOx emissions from exhausts， are now legally required on many of the most polluting diesel vehicles， and the KCL study points to a modest decline in concentrations over the past few years.

Newer， less polluting vehicles are being rolled out across the capital. More than 1，200 hybrid buses now operate in London， including the new diesel-electric Routemaster18）—which according to TFL produces a quarter of the NOx and particulate emissions of conventional diesel buses. TFL is also expected to shortly announce the introduction of the worlds first zero-emissions double-decker19）.

Efforts are also underway to clean up the citys taxi fleet， with TFL recently announcing that from January 2018， all new taxis licensed in London must emit less than 50g/km of CO2 and have a zero-emission range of 30 miles. Earlier this year Metrocab， a battery-powered vehicle that uses a small combustion engine20） as a range extender， became TFLs first licensed zero-emission-capable taxi. And the London Taxi Company recently unveiled the prototype TX5， a lightweight， battery-powered black cab that it plans to put into production during 2016.

There is also the much trumpeted21） Ultra Low Emission Zone： From 2020， all vehicles entering Londons existing congestion charge zone will need to meet exhaust emissions standards or pay an additional daily charge to travel.

But many claim these developments dont go far enough. The mayors office has faced heavy criticism for ditching its initial plans to simply ban the most polluting vehicles from the emission zone. Whats more， a recent survey of 500 businesses found that 23% would rather pay a charge than upgrade their vehicles.

Precedent for Change

改革先例

Others point to the far wider-reaching changes of the Clean Air Act as an example of how people can adapt. “Before the Clean Air Act， people said ‘the government doesnt have the money; the poor are going to starve or freeze. And that wasnt what happened，” says Simon Birkett， founder of campaigning group Clean Air in London. “Once these limits are put in place， people find the cheapest way of complying with them.”

Still， perhaps the main lesson to be learned from history is that it is exceptionally challenging to persuade people to change their habits—and to persuade government to force this change.

“The right to burn a coal fire in ones own home was seen as an inviolable22） freedom in the past， and not until the 1952 smog did the government feel that it had sufficient public support to make changes that affected personal liberty，” Mosley says. “Lets hope that it wont be a case of history repeating itself.”

試想一下，你走在濃濃的霧霾中，甚至看不見自己的腳;霧霾遮蔽天日，透不進陽光;霧霾毒性很強，讓你眼睛酸痛，呼吸困難。

這聽起來也許像是有關末世之后的一場噩夢中的場景，但是在1952年12月5日，這恐怖的一幕對倫敦居民來說成為現(xiàn)實。僅僅是那一天的霧霾事件就導致數(shù)千人死亡，這也促使全世界對待空氣污染的態(tài)度開始發(fā)生轉變。

1952年的那一天寒冷又晴朗，倫敦居民圍在自家的煤火前取暖。但是煙霧沒有像往常一樣消散于大氣中，籠罩在倫敦上空的高氣壓形成了反向運動，將污染物困在地表，形成了一層由硫化物構成的有毒覆蓋物，在接下來的五天里籠罩整個首都。

等到天氣狀況改善，煙霧散去，數(shù)千人已經(jīng)喪命。當時官方估計的死亡人數(shù)為4000人——比戰(zhàn)時任何一次事件導致的平民傷亡人數(shù)都要多。不過，最近的研究顯示，那次事件導致的死亡人數(shù)可能高達12000人。

雖然一百多年里，這種被稱作“黃色濃霧”的霧霾一直都是英國各大城市無可避免的特征，但1952年的大霧卻是最嚴重的。

這場霧霾在某種程度上也是一個轉折點：在那之前，人們已接受了霧霾，將其看做是必要之惡?！耙粋€多世紀以來，在英國燒煤的城市中，人們?nèi)淌軣熿F，將其視為就業(yè)和家庭舒適的代價?！杯h(huán)境歷史學家斯蒂芬·莫斯利博士說道。有些人甚至贊美空氣污染，認為那是英國工業(yè)活力的有形體現(xiàn)，而煤塊燃起的熊熊火焰帶有“溫暖的家”的溫馨內(nèi)涵，這種奢侈沒幾個人準備放棄。

盡管民眾要求應對這一問題的呼聲日益高漲，政府的反應卻是一拖再拖。起初，政府甚至聲稱12月份的死亡人數(shù)之所以高是因為爆發(fā)了流感。又過了七個月，政府最終才下令調查。

四年之后的1956年，《空氣潔凈法案》開始實施，禁止在全英國的“煙霧控制區(qū)”燃燒會造成污染的燃料。

這項法案具有真正的革命性意義，是全世界環(huán)保事業(yè)一座重要的里程碑。公共健康得以大幅度改善;20世紀50年代在城市地區(qū)幾乎絕跡的動植物又開始繁衍生長;英國城市里宏偉的建筑也擺脫了厚厚的煤煙和灰塵，得以展現(xiàn)真容。接下來的幾年，其他許多工業(yè)國家也受到了啟發(fā)，紛紛效仿。

空氣問題

不過，燃煤造成的空氣污染也許已是陳年往事了，但倫敦的空氣質量問題還沒有消除。最近的一項研究表明，倫敦的污染問題每年導致多達9500人死亡，越來越多的科學家、政壇人士和活動人士認為，在《空氣潔凈法案》誕生60周年前夕，英國必須再一次發(fā)揚敢為人先的精神。

該研究是由倫敦國王學院環(huán)境研究小組應倫敦交通局的需求完成的。研究將這些人的過早死亡主要歸因于兩種污染物：一種是叫做PM2.5的細微顆粒物，另一種是有毒氣體二氧化氮。

二氧化氮濃度尤其令人擔心。倫敦空氣中測得的該氣體的濃度是全球最高的，在過去五年中每年都突破了歐盟設定的安全限值。2015年，牛津街的二氧化氮水平僅僅在四天內(nèi)就沖破了全年的限值。

據(jù)倫敦國王學院的研究估算，每年多達5900人因為二氧化氮而過早死亡。

國王學院的空氣質量專家馬丁·威廉姆斯稱，雖然科學家們多年來都知道二氧化氮有毒性，但是由于該氣體通常與其他污染物同時出現(xiàn)，科學家們很難單獨測定其影響。直到現(xiàn)在研究人員才能得出結論，二氧化氮本身就對人體有影響。

然而，該研究報告的作者希瑟·沃爾頓博士稱，到底有多少人的死因是二氧化氮，這一點仍然無法完全確定。

二氧化氮污染有很多源頭，但是按照英國環(huán)境和農(nóng)業(yè)部的說法，至少有80%的二氧化氮來自于交通工具排放的廢氣。占倫敦路面車輛三分之一以上的柴油車是罪魁禍首。

柴油機由于燃油效率較高，二氧化碳排放量又較低，因而在過去的幾十年中得到了大力推廣，連續(xù)幾屆政府都對其較高的顆粒污染物和氮氧化物排放視而不見。

諷刺的是，由于使用了為減輕污染而設計的技術，柴油機的污染反而更嚴重了?！安裼蛙嚤绕蛙嚺欧诺念w粒物多得多，因此柴油車上裝有顆粒物過濾器，”威廉姆斯說，“這些過濾器把顆粒物留在上面，但是顆粒物時不時要被燒掉——汽車排放的氮氧化物會轉化為二氧化氮，后者有助于氧化并燃燒過濾器中的顆粒物。為了解決顆粒物的問題，二氧化氮的排放卻增加了。”

呼吸更輕松？

好消息是二氧化氮濃度開始下降了。許多污染最嚴重的柴油車如今已經(jīng)按照法律規(guī)定安裝了選擇性催化還原系統(tǒng)，這種系統(tǒng)可以去除廢氣中的許多氮氧化物。倫敦國王學院的研究也表明，過去幾年中二氧化氮濃度的確略微有所下降。

倫敦全市都在推行更新、污染更小的汽車。如今有超過1200輛混合能源公交車在倫敦投入使用，包括新型的柴電混合動力“路霸”巴士。倫敦交通局稱，這種巴士排放的氮氧化物與顆粒物只有傳統(tǒng)柴油巴士的四分之一。倫敦交通局還有望在近期宣布引進世界上第一輛零排放雙層巴士。

當局也正在努力凈化倫敦的出租車。倫敦交通局最近宣布，從2018年1月起，倫敦所有獲得許可的出租車的二氧化碳排放量都必須少于每公里50克，并且實現(xiàn)30英里行程內(nèi)零排放。今年（編注：指2015年）早些時候，Metrocab成為倫敦交通局核準的第一輛零排放出租車。該車由電池提供動力，用一個小內(nèi)燃機來續(xù)航。最近倫敦出租車公司還推出了TX5原型車。這是一款電力驅動的黑色輕型出租車，計劃于2016年投入生產(chǎn)。

此外還有得到大力宣傳的超低排放區(qū)政策：自2020年起，所有進入倫敦現(xiàn)行的交通擁堵收費區(qū)的車輛都需要達到廢氣排放標準，否則就要繳納額外的日通行費。

但是很多人認為這些進步都不夠徹底。市長辦公室最初計劃在排放區(qū)內(nèi)徹底禁止污染最嚴重的車輛，后來又放棄這一計劃，因此飽受批評。此外，最近一項針對500家公司的調查發(fā)現(xiàn)，23%的公司寧可交錢，也不愿意升級他們的車。

另外有人指出，《空氣潔凈法案》所帶來的深遠變化是人們適應能力的例證。“在頒布《空氣潔凈法案》之前，大家都說‘政府沒有錢，窮人就等著挨餓受凍吧。但這種情形并沒有發(fā)生，”活動團體“倫敦清潔空氣”創(chuàng)始人西蒙·伯基特說，“一旦這些限制落實到位，人們就會找到最經(jīng)濟的辦法來遵守這些規(guī)定?！?/p>

即便如此，我們可以從歷史中學到的主要教訓也許是：勸說人們改變習慣極具挑戰(zhàn)性，勸說政府強迫人們做出改變也是如此。

“人們過去認為，在自己家中燒煤取火的權利是不可侵犯的自由。直到1952年的霧霾事件發(fā)生后，政府才覺得自己擁有足夠的公眾支持來進行有礙個人自由的改革，”莫斯利說，“希望歷史不會重演?！?/p>

1. blot out：把……弄模糊，遮蔽

2. backdrop [?b?k?dr?p] n. 背景

3. anticyclone [??nti?sa?kl??n] n. [氣]反氣旋，高（氣）壓

4. sulphurous [?s?lf?r?s] adj. [化]硫的;含硫的;來源于硫（或硫的燃燒）的

5. shroud [?ra?d] n. 遮蔽物;幕;罩

6. a necessary evil：（要獲得好處而無法避免的）不得已的事;必要之弊害

7. blazing [?ble?z??] adj. 燃燒的;熊熊的

8. home and hearth：溫暖舒適的家庭生活

9. sluggish [?sl?ɡ??] adj. 緩慢的，慢的

10. flora [?fl??r?] n. 植物群（尤指某一地區(qū)或某一時期的植物群）

11. fauna [?f??n?] n. 動物群（尤指某一地區(qū)或某一時期的動物群）

12. soot [s?t] n. 煤煙，油煙

13. grime [ɡra?m] n. （深嵌的）污垢，煤灰，煤塵

14. claim [kle?m] vt. （戰(zhàn)爭、疾病、事故）奪去（生命），導致（死亡）

15. diesel [?di?z（?）l] adj. 裝有柴油機的，內(nèi)燃機傳動的

16. culprit [?k?lpr?t] n. 罪犯;導致過錯的人;引起不良后果的事物

17. incentivise [?n?sent?va?z] vt. 以獎勵推廣（某事）

18. Routemaster：“路霸”巴士，倫敦的紅色雙層巴士，現(xiàn)已成為倫敦的標志之一。

19. double-decker：雙層公共汽車

20. combustion engine：內(nèi)燃機

21. trumpet [?tr?mp?t] vt. 吹噓

22. inviolable [?n?va??l?b（?）l] adj. 不可侵犯的;不可褻瀆的