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纳米颗粒:空气中看不见的超微型杀手

The toxic killers in our air too small to see
纳米颗粒:空气中看不见的超微型杀手

After years of headlines about air pollution, we’ve been misled on a few things about the world’s biggest environmental health problem. For example, we’re told that “PM2.5” – solid pollution particles measuring 2.5 micrometres or less – can pass through our lungs and into our blood stream.

多年以来,空气污染往往是媒体头版头条新闻,但有关这个全球最大的环境健康问题,其中一些信息,我们可能被媒体误导了。例如,我们被告知,一种直径测量为2.5微米或更小的悬浮颗粒污染物——PM2.5可以通过我们的肺进入我们的血液。

But, in fact, the vast majority of them can’t.

但在事实上,绝大多数微米颗粒PM2.5是无法进入我们的血液的。
 

We’ve also been told NOx gases – including nitrogen dioxide – are the biggest threat to health within cities. However, NOx is responsible for just 14% of deaths attributed to air pollution in Europe.

我们还被告知,包括二氧化氮在内的氮氧化物气体是城市最大的健康威胁。然而,在欧洲因空气污染而导致的死亡中,死于氮氧化物的仅占14%。

The biggest killer of all never makes the headlines, isn’t regulated, and is barely talked about beyond niche scientific circles (despite their best efforts to change that narrative): it’s nanoparticles.

其实最大的空气污染杀手纳米颗粒(nanoparticles)从来没有上过新闻头条,没有受到监管,也很少在小众的科学圈之外被提及,尽管科学家已尽了最大的努力来改变流行的看法。

PM2.5 may be too small to see, being roughly 30 times smaller than the width of a human hair. But it’s a relative heavyweight. PM2.5 stomps in at 2,500 nanometres (nm), while nanoparticles are 100nm or below. PM2.5 and PM10 (10,000nm) are killers in their own right, typically causing lung and respiratory conditions. Yet nanoparticles can reach, and wreak havoc in, any organ in the body. And because government authorities monitor PM2.5 by mass (million of nanoparticles may not even register a measurement by microgram) – their reports underrepresent the true risks.

悬浮微米颗粒PM2.5比人类头发宽度大约小30倍,小得看不见,但是与悬浮在空气中的纳米颗粒相比,则相对是大块头。PM2.5的直径为2500纳米,而真正的杀手纳米颗粒直径是100纳米或更小。不错,PM2.5和PM10(直径为1万纳米,体积更大的悬浮颗粒)都是杀手,一般会造成人体肺和呼吸器官出问题。但是納米颗粒可以进入人体任何器官肆意破坏。而且政府部门是以重量来测量PM2.5值的高低,但数百上千万的纳米颗粒若以重量计,可能还不到一微克,因此政府部门的空气污染报告往往低估了真正的风险。

The science of why we should be concerned about the total number of particles that we breathe in, not just their mass, has been known for some time. In 2003, Surbjit Kaur was a young researcher finishing her Masters at Imperial College London, when her supervisor suggested she join the Dapple experiment (the Dispersion of Air Pollution and its Penetration into the Local Environment). Kaur designed a personal exposure study, with a team of six volunteers “dressed up like Christmas trees” with various different air pollution sensors, and asked them to travel a set route in central London every day for four weeks.

有关空气污染应该关注人体吸入的颗粒总数,而不仅仅是重量的这门科学,实际已开始好一些时间了。2003年,苏尔布吉特·考尔(Surbjit Kaur)在伦敦帝国理工学院(Imperial College London)完成硕士学位时,她的导师建议她参加名为Dapple(空气污染的扩散及其对周遭环境的影响)的实验。考尔设计的题目是个人暴露于污染空气的研究,由六名志愿者组成的团队大家“装扮成圣诞树”,并带上各种不同的空气污染传感器,连续四周每天在伦敦市中心走一条固定路线。

The volunteers “were a combination of friends and people in the department” says Kaur, who has since left science and now works as a management consultant. “But I couldn’t really ask people to do this if I wasn’t doing it myself.” She joined them out on the roadside, which centred around Marylebone Road, a major seven-lane highway and home to the Madame Tussauds waxwork museum, and its lengthy queues waiting outside. “We went out there knowing that we were going to get ill because of that constant exposure. We began to feel quite grotty after a while.”

考尔后来离开了科学界,现在是一名管理顾问。她说,当年这些志愿者“是朋友和我们系里的人组成的。 但如果我自己也不参加的话,我真的不能要求别人去做这个实验”。因此她也加入这个空气污染测试志愿者队伍,来到了以马里波恩路(Marylebone Road)为中心的路边。马里波恩路是一条有七条车道的大道,杜莎夫人蜡像馆(Madame Tussauds)即坐落在这条大道上。她说:“我们到了这条街,知道我们会因为长时间暴露在这样的空气中而生病。过了一会儿,我们开始觉得很不舒服。”

The equipment draped over the volunteers and inside backpacks measured the standard air pollutants, PM2.5 and CO (carbon monoxide). But Kaur also included a brand-new piece of kit that had only just come on the market: a ‘P-Trak’ nanoparticle counter. “We needed to get all sorts of approvals to use them [in the field work] because they looked a bit like Geiger-counters and there were concerns that the public might panic,” she laughs. The device could count nanoparticles right down to 2nm (many times smaller than a human blood cell) by sucking in air, spraying alcohol onto the surface of the particles to make them visible and individually counting by laser beam. Influenced by work emerging from University of Rochester, New York, and the National Public Health Institute, Finland, Kaur had a hunch that counting these “ultrafine particles” could add some interesting data. She wasn’t wrong.

穿戴在志愿者身上和放在背包里的仪器测量了标准的空气污染物,即PM2.5和一氧化碳。但考尔还带有一套刚刚上市的崭新装备“P-Trak”纳米颗粒计数器。她笑着说:“我们需要获得各种各样的批准才能实地使用这种仪器,因为样子看起来有点像测量核辐射的盖革探测器,有关部门担心我们当众使用会引起公众的恐慌。”这个设备吸入空气后,会向空气中的颗粒表面喷洒酒精使其现形,然后通过激光束将颗粒一个个数进去,可以将微小到2纳米的纳米颗粒(比人体血细胞还要小很多倍)的数量精确地计算出来。受纽约罗切斯特大学(University of Rochester)和芬兰国家公共卫生研究所(National Public Health Institute)研究成果的影响,考尔有一种预感,认为计算这些"超细颗粒"的数量可以增加一些有趣的数据。她的预感没有错。

“I expected a certain level of variation [in particle number]”, she says, “but the level of fluctuation really surprised me… The volume of cars that went past had very little impact on people’s exposure to PM2.5. But it had a massive impact on ultrafines.” As the volunteers pounded the pavements, they were exposed to a minimum of 36,000 particles at a time, up to a maximum of 130,000. When they took the same route by bicycle (tricky, but not impossible, with all the equipment), the maximums and minimums went up by another 20,000.

她说:“我预料颗粒数会有一定程度的变化,但没有想到变化幅度很大,确实让我吃惊……过往车辆的数量对人们接触到的PM2.5颗粒数量的影响微乎其微。但对超细颗粒数量则影响巨大。”当志愿者们走在人行道上时,他们一次至少接触了3.6万个超细颗粒,最多达到13万个。当他们骑着自行车走同样的路线时(要带上所有设备,虽然麻烦,但也不是不可能),最大值和最小值又各增加了2万个。

However, the highest averages were recorded inside the cars and buses: the closer to the source of the pollution, the exhaust pipes spewing out the fumes, the higher the total number of nanoparticles. The difference between walking by the kerbside of the road, and by the building side, on the same pavement – just a few short steps – was an average of 82,000 particles versus 69,000. The same readings registered no change in PM2.5.

然而,记录到的平均最高值是在汽车和公共巴士内,这说明越接近污染源,即排气管喷出的废气,则纳米颗粒的总数就越高。同一条人行道上,走在街边和走在建筑物旁边,两者虽然只有几步路之远,但差异却很明显,前者纳米颗粒数平均值是8.2万个,而后者平均值则是6.9万个。同样的读数显示PM2.5颗粒数没有变化。

Around 2006, just as Kaur was stepping away from science – her findings having made no difference to how government authorities measured air pollution exposure – a doctoral student at the University of Cambridge picked up the baton. Prashant Kumar had already studied PM2.5 and PM10 for his Masters at the Indian Institute of Technology (IIT) in Delhi. But upon arriving in England for his PhD, “in discussions with my supervisors we found there as very little, or almost nothing, done on the understanding [of nanoparticles]: their measurements, the concentrations in different environments. So I took up that topic as a challenge.” His subsequent flurry of papers published from 2008 onwards have become seminal work on nanoparticle exposure, and led to his professorship at the University of Surrey.

很不幸,考尔的发现对政府部门测量空气污染的方式没有任何影响。大约在2006年,就在她离开科学领域的时候,剑桥大学的一名博士生接过了接力棒。普拉桑特·库马尔(Prashant Kumar)在德里的印度理工学院(Indian Institute of Technology)攻读硕士学位,已经在研究PM2.5和PM10。但在他来到英国攻读博士学位时,他说:“在与我的几位导师讨论时,我们发现他们(对纳米颗粒)的了解很少,甚至几乎不了解。他们的测量,他们的关注是另一方面。所以我决定挑战纳米颗粒这个题目。”从2008年开始,他陆续发表的一系列论文成为有关纳米颗粒污染的开创性研究,并因此成为萨里大学(University of Surrey)的教授。

“The first study I carried out in 2008 was an exploratory analysis,” recalls Kumar. “When the exhaust fumes come out of vehicles, they come out as gases and cool into smaller [nano] particles. Then they start to accumulate to make bigger particles. From the tailpipe you can get 10-to-the-power-of-six (one million) particles per centimetre cubed of air. On the road 100,000, by the roadside 10,000.” His studies found that up 90% of all particles by busy roads are nanoparticles below 100nm.

库马尔回顾说:“我2008年进行的第一项研究是探索性的分析。”他说,汽车废气以气体的形式排放出来,然后冷却成更小的纳米颗粒,然后再开始聚集,形成更大的颗粒。从排气管中每立方厘米的空气你可以得到10的6次方(100万个)颗粒。走在路中间为10万个,路边则是1万个。他的研究发现,交通繁忙的道路上90%以上的颗粒都是直径100纳米以下的超细颗粒。

This is a problem for our health, explains Kumar, “because the smaller particles you have, you have a greater surface area. A greater surface area means more [potential] toxicity, as they are in touch with a greater surface area inside your body.”

库马尔解释说,这对我们的健康是个问题, “因为颗粒越小,表面积越大。更大的表面积意味着更多的(潜在的)毒性,因为其接触到你体内的面积也更大。”

To visualise this, imagine footballs versus golf balls. A football (or soccer ball, for North American readers) has a circumference of 70cm (28in) and a surface area of around 1,500 cm2 (91.5in2). A golf ball is obviously much smaller, with a circumference of about 13cm (5.2in), making its surface area 54cm2 (3.3in2). By volume, you could fit 156 golf balls into the same space as a football, but the total surface area of all those golf balls would be 8,453cm2 – a substantial 6.9 square metres more than the football. On a nano-scale, that difference is amplified. A cloud of a billion 10nm particles has the same mass as just one PM10 particle, but a combined surface area a million times larger. And that surface area comes coated with toxic, unburnt fuel from vehicle exhausts.

为形象地理解这一点,不妨想象一下足球和高尔夫球的对比。一个足球的圆周为70厘米,表面积约为1500平方厘米。高尔夫球显然要小得多,周长约为13厘米,表面积为54平方厘米。如论体积,你可以把156个高尔夫球放进一个足球大小的空间,但所有这些高尔夫球表面积相加将是8453cm2,整整比一个足球大了6.9平方米。在纳米尺度上,这种差异更要大得多。一个由10亿个10纳米颗粒组成的雾团其质量只相当于一个PM10颗粒,但其总表面积却是后者的100万倍。而这些纳米颗粒表面覆盖着来自汽车尾气的未燃烧的有毒燃料。

Another of Professor Kumar’s studies looked at the exposure of children being pushed in prams along the roadside of a small town. “We found that you get a high exposure when waiting at traffic lights, and children get a much higher exposure compared to adults… In some cases it was 20-30% higher exposure [at pram height compared to adult height]. Because their immune system is still developing, they are more vulnerable to the health impact.” The Californian Children’s Health Study, for example, finds that children growing up within half a kilometre of a busy road suffer a significant loss in lung capacity.

库马尔教授的另一项研究是被成年人用婴儿车推着经小镇路边而过的儿童,其接触空气污染的状况。他说:“我们发现,在等红绿灯的时候,会接触到大量纳米颗粒,而婴儿车中的孩子接触的微细颗粒数量还要大……在某些情况下,会比成年人高出20-30%。由于孩子的免疫系统还在发育,他们更容易受到健康影响。”例如,美国加州儿童健康研究发现,在交通繁忙道路的半公里内长大的儿童肺活量明显受到损害。

Nanoparticles can also pass through the walls of the lungs and into the bloodstream, in a way that larger PM2.5s cannot. Once in the bloodstream they cause the same inflammation damage they inflict on the lungs, except now they can reach any organ or artery in the body. Until recently it wasn’t known exactly what size of particle could make it through, and which remained stuck in the lungs or upper airways.

纳米颗粒还可以通过肺壁进入血液,这是颗粒较大的PM2.5无法做到的。纳米颗粒一旦进入血液,除了可以到达身体的任何器官或动脉,也会造成与肺部相同的炎症损伤。不过直到最近之前,人们还不知道到底直径多大的颗粒能够通过肺壁进入血液,也不知道哪些颗粒会滞留在肺部或上呼吸道。

That final piece of the jigsaw was put in place by a team led by Professor David Newby at the University of Edinburgh in 2017. Dr Jen Raftis, who was part of the research team, says: “There were various ideas about how we could show these nanoparticles [in the blood], various imaging techniques. But no imaging technique really has that kind of resolution. So we decided to use gold.”

爱丁堡大学教授大卫·纽比(David Newby)领导的团队在2017年终於补上了这项研究拼图的最后一块。珍‧拉夫提斯(Jen Raftis)博士是研究小组的一员。她说:“如何让血液中的纳米颗粒现形,我们有各种各样的设想,现实中也有各种各样的成像技术。但是现有的成像技术没有那么高的分辨率。所以我们决定使用黄金。”

A machine borrowed from the Netherlands used electrodes to scatter gold into nanoparticles right down to 2nm in size. First, the Edinburgh team got mice to breathe in the gold nanoparticles; next, it was the human volunteers’ turn. “We used gold because we know it is really safe”, explains Raftis, reassuringly. “It is used clinically because it is inert, it doesn’t react to things or cause oxidative stress in the body.” It is also easy to detect, unlike carbon particles which are effectively camouflaged within our carbon-based bodies.

爱丁堡研究小组使用从荷兰借来的一台机器,通过电极将黄金打碎到仅只有2纳米大小的超微细的颗粒。首先,让老鼠吸入这些黄金纳米颗粒,接下来,让人类志愿者吸入。拉夫提斯以让人放心的口气解释说:“我们使用黄金,因为我们知道黄金真的很安全。黄金可以用于临床是因为黄金是惰性的,不会与任何物质发生反应,也不会引起体内的氧化压力。”黄金也很容易被仪器探测到,不像碳颗粒那样会有效地隐藏在我们碳基生命的人体中,难以查到。

The volunteers gave blood and urine samples 15 minutes and 24 hours after they inhaled the particles. Lo and behold, there was gold in them there samples. The team discovered a 30nm cut-off point; anything below that could be found swimming around in the bloodstream, but anything above that failed to get past the lungs.

志愿者在吸入黄金纳米颗粒的15分钟以及24小时后,提供了血液和尿液样本。你想不到吧,他们的血液和尿液的样品里真的发现了金子。研究小组还发现了一个30纳米的分界点。在流动的血液中可以发现低于30纳米大小的颗粒,而大于30纳米的物质则无法渗透过肺部进入血液。

“Obviously with humans we couldn’t perform a biopsy, but with the mice we did”, says Raftis. “We found the biggest accumulations [of particles] in the lungs primarily, but the liver next, because your liver is where the blood passes through first… the pore size in the kidney is 5nm, so nothing bigger than that would pass through the kidney… There could be accumulations in other parts of the body as well, because pore sizes across the body differ.” Gold was still present in the urine of the volunteers three months later.

拉夫提斯说:“我们显然不能对人类进行活组织检查,但却可以对老鼠做尸检。我们发现肺部积累的颗粒最多, 其次是肝脏,因为血液首先经过的是肝脏。肾脏表面的渗透孔大小是5纳米,因此大于5纳米的任何东西都无法渗透进肾脏……但身体的其他部位则可能有颗粒积累 , 因为整个身体不同部位的表皮孔隙大小是有差别的。三个月后,志愿者的尿液中仍然发现含有黄金微粒。

David Newby, funded by the British Heart Foundation, then took the study further. Again, it had been theorised – but not proven – that nanoparticle build-up in the arteries could lead to strokes and heart disease. He approached hospital patients who were due to undergo surgery to remove a fat deposit (known as a ‘plaque’) from an artery. If they breathed in gold nanoparticles, would these be found on the plaque removed during surgery a day later?

随后英国心脏基金会(British Heart Foundation)资助爱丁堡大学教授大卫·纽比的团队继续此项研究。再一次,大卫‧纽比要用实验证明一个理论。当时这个还未获得证实的理论是,纳米颗粒污染物在人体动脉中聚集可能导致中风和心脏病。大卫·纽比接触了一些即将接受切除动脉脂肪沉积(即动脉斑块)手术的病人。如果让这些病人在手术的前一天吸入黄金纳米颗粒,第二天手术后能否在他们切除的斑块上发现这些黄金粒子?

“Yes, we found gold in the plaque,” says Raftis, still excited by the finding. “It was indicative that air pollution particles of this size and structure can be delivered to a plaque within 24 hours of inhaling them. That’s quite a big risk for patients with heart disease… as air pollution is a whole of life exposure. We just did a one-off experiment, but this is happening every single day.”

拉夫提斯说:“是的,我们在斑块上发现了黄金颗粒。”她此时谈到这一发现,仍然很兴奋。她说:“这表明,这种大小和结构的空气污染颗粒可以在吸入24小时内被吸附到动脉斑块上。对心脏病患者来说,这是相当危险的事,因为我们人一生都会呼吸到被污染的空气。而我们做的只是一次性的实验,但这种事每天都在发生。”

Think of a plaque as the scene of a car crash, and the artery as a road; nanoparticles are more cars piling up behind it, causing a bigger blockage. The nanoparticles can also be the cause of the crash, inflaming the artery with toxic chemicals stuck to their surface (Newby’s predecessor Professor Ken Donaldson had highlighted the toxicity of nanoparticles back in the 1990s). The Global Burden of Diseases study estimates that air pollution could account for 21% of all deaths due tostroke and 24% of deaths from ischaemic heart disease. Traffic fumes had long been considered the smoking gun, but the bullet had proved elusive. Now, many think that the bullet is nanoparticles.

不妨把动脉想象成道路,动脉斑块想象成车祸现场,纳米颗粒就是被堵在车祸现场越积越多的汽车,结果造成动脉交通更严重的堵塞。而且纳米颗粒也可能就是造成动脉车祸的原因,因为这些颗粒表面附着的有毒化学物质会使动脉发炎,纽比的前任肯·唐纳(Ken Donaldson)森教授早在上世纪90年代就强调了纳米颗粒的毒性。“全球疾病负担”(Global Burden of Diseases)组织的研究估计,空气污染可能导致21%的中风死亡和24%的缺血性心脏病死亡。交通废气一直被认为是空气污染危害人体健康的确凿证据,,但这只行凶的枪发射出来的子弹却很难找到。现在,许多人认为子弹已找到,就是纳米颗粒。

Most countries including the US and the EU have legal limits for the most harmful air pollutants, including PM2.5, NOx, carbon monoxide and sulphur dioxide. But no similar regulatory limits exist for nanoparticles. The typical rebuttal is that “PM2.5 includes everything down to 1nm”, which technically it does, but as we have seen, literally millions of nanoparticles still give a low PM2.5 reading. A low PM2.5 reading on government website or mobile phone app can therefore give a false impression of clean air when it is, in fact, swirling with particles entering our arteries.

大多数国家,包括美国和欧盟,都对微米颗粒PM2.5、氮氧化物、一氧化碳和二氧化硫等最有害的空气污染物有法律限制。但对纳米颗粒则没有类似的监管约束。有关方面典型的反驳是,法律规定的“PM2.5已包括最小到直径1纳米的所有微细颗粒”。技术上PM2.5确实包括了纳米颗粒,但正如我们所见,数百万计的纳米颗粒在PM2.5的测量读数中几乎无法显示。因此,在政府网站或手机应用程式上,PM2.5读数可能很低,给人一种空气很干净的假象,但此时空气中实际有大量微细颗粒正在进入我们的动脉血管。

A 2018 report on ultrafine particles below 100nm for the UK Department for Environment, Food and Rural Affairs (Defra), found that because “there are currently no emissions ceilings or emission reduction targets set on [nanoparticles]… there are no guidelines or common sources of emission factors of [nanoparticles] to enable inventories to be developed.” The one regulation that does exist, the Euro 6 vehicle emissions test, includes a particle number limit, and measures down to 23nm. But that means, says the Defra report, “more than 30% of [nanoparticles] in urban environments may not be included”, and covers only a fraction of those below the 30nm threshold identify by the Edinburgh gold study.

2018年一份为英国环境、食品和农村事务部(Defra)所作,有关直径低于100纳米的超细颗粒污染物的报告发现,因为“目前没有针对纳米颗粒的排放上限或减排目标之规定……也没有关于纳米颗粒的指引或可供查阅的纳米颗粒排放因素列表的途径。”目前存在的唯一法规是欧盟汽车尾气排放6号标准测试,其中一项是废气颗粒数限制,测量的颗粒直径已缩小到23纳米。但是,Defra的报告说,这意味着“城市空气中超过30%的纳米颗粒可能不包括在内”,并且只覆盖了爱丁堡大学黄金纳米颗粒研究所确定的30纳米分界值以下颗粒之一小部分。

Perhaps the only good news is that while particle number doesn’t correlate well with particle mass (PM2.5) measurements, it does tend to correlate with NOx readings. Like nanoparticles, NO2 is highest closest to its source, and then quickly dissipates. NO2 even reacts with other gases in the air to form some of the nanoparticles. So tackling NO2 can often work as a proxy to reduce nanoparticles. “They do correlate well,” says Kumar, “because they are coming from the same source.”

也许唯一的好消息是,虽然纳米颗粒数与PM2.5的测量值之间没有很好的相关性,但确实与氮氧化物的读数相关。像纳米颗粒一样,二氧化氮(NO2,氮氧化物的一种)离排放源最近,但很快就会消散。NO2甚至会与空气中的其他气体发生化学反应,形成某些类型的纳米颗粒。因此,减少NO2的排放通常也可以起到减少纳米颗粒的作用。库马尔说:“两者之间确实相互关联,因为两者都来自同一个排放源。”

The solution for NOx and nanoparticles are also the same: replacing combustion with electrification. Electric cars still kick up road dust, but they emit no combustion-derived nanoparticles or NOx; and while power stations are needed to take the electricity, we spend far more time standing by roads than we do standing by power station chimneys (although this is all the more reason to rapidly move to 100% renewable energy). True zero-emissions transport, such as walking and cycling, are even better. The quicker we can make this transition, the more lives will be saved. In the interim, we also need to reduce our exposure by physically separating people from combustion-based traffic, via segregated cycle lanes, and green barriers – trees, hedges and climbing plants – inbetween pavements and roads.

有关氮氧化物和纳米颗粒的解决方案也一样,即用电取代石化燃料作为能源。电动汽车仍然会扬起道路尘土,但它们不会释放由燃烧产生的纳米颗粒或氮氧化物。虽然仍需要发电站来获取电力,但我们在公路上花费的时间远远超过了站在发电站烟囱旁的时间,尽管发电站的碳排放是我们必须快速转向100%可再生能源的更充分理由。而更好的选择是使用真正的废气零排放交通工具,如步行和骑自行车。我们越快完成这一转变,就能挽救更多的生命。在此期间,我们还需要通过建立隔离自行车道和绿色屏障,即人行道和道路之间的树木、树篱和攀爬植物等绿色隔离带,将行人与以燃烧排气车辆为主的交通道隔离开来,从而减少我们对废气的接触。

Kaur still finds her own habits influenced by her nanoparticle research, over a decade later. “My friends find it hilarious that I’m hugging the building side when I walk along a pavement!” she laughs. “Wherever possible I cut through the park or I take the side roads.”

十多年后,考尔发现自己的习惯仍然受到当年纳米颗粒研究的影响。她笑着说:“当我走在人行道上的时候,我的朋友们觉得我总是贴着建筑物的一边走很滑稽!而且只要有可能,我就抄近路穿过公园,或者走小路。”

In Edinburgh, Raftis goes a step further. “I stopped burning candles in my house. I don’t use or have a log burner at home, even though I like them... I always have the extraction on when I cook food. I don’t go for runs along roads, I always run in a park. I don’t drive and don’t think I consciously could do unless it was an electric car.” She cycles, despite the proximity to high particle counts, because “even if you cycle in heavy traffic you are offsetting the exposure to air pollution with exercise.”

在爱丁堡,拉夫提斯走得更远。她说:“我不再于家中点蜡烛。虽然我很喜欢木材熊熊燃烧的火炉,但我家里不会使用,也不会有烧木头的炉子。我做饭的时候总要打开抽油烟机。我不会沿着马路跑步,跑步我总是选在公园。我不开车,也有意识地认为我不应该开,除非是开电动汽车。”但拉夫提斯骑自行车,尽管附近空气的颗粒物含量很高,因为“即使你在交通拥挤的时候骑自行车,你也可以通过锻炼来抵消空气污染。”

I ask her if emissions regulation and policy should shift more towards nanoparticle exposure. She is not a policy person, she tells me, but quickly adds: “I just don’t know why they haven’t. I mean, you feel like you are researching and researching and producing data and nothing gets done about it, only lip service. I feel it has to move along with the technology. PM2.5 is [just] what the monitors measure.”

我问她,限制废气排放法规和政策是否应该更多地转向规限纳米颗粒的污染。她告诉我,她不是政策制定者,但很快又补充道:“我不知道他们为什么不这么做。我的意思是,你觉得你在研究,再研究,也产生了数据,却什么反应也没得到,只是口头说所而已。我觉得这个问题必须随着技术的发展而发展。PM2.5正是监测仪所测量出来的。”

Within the same town or city, our daily exposure to air pollution can differ greatly by person, by mode of transport, by the routes we take. Most cities or countries measure this with a handful of stationary monitoring stations, which can only test the air immediately next to them. We don’t, however, spend our lives standing still.

身处同样一个城镇或城市,我们每天接触到的空气污染程度,会因人、因交通方式,以及行经的路线而有很大差异。大多数城市或国家通过几个固定的监测站来测量,这些监测站检测到的只是附近的空气。然而,我们不会一辈子都会待在某个地方不动。

“I still find it fascinating”, says Kaur, speaking to me from her Thames-side offices, overlooking the London Mayor’s office. “If you are introducing air pollution policy for the wellbeing of humans, and you base that guidance on data that isn’t relevant, are you really helping people or are you actually hindering?”

考尔在她泰晤士河畔的办公室,远望着伦敦的市长官邸,对我说:“我仍然觉得这个研究很迷人。如果政府推出的空气污染政策是为了人类的福祉,但其政策的指导依据却是不相关的数据,那么你到底是真的在帮助人们,还是在防碍他们?”
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