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winter-is-coming

寒冬将至

又一次冬天,又一次PM 2.5来袭!面临北京冬天的PM 2.5,我开始想:冬天PM 2.5到底比夏天严重多少?

我分析了北京和上海美国大使馆近8年的PM 2.5数据,结果冬天平均PM 2.5比北京的夏天多30%。上海的冬天比夏天多60%。

冬天比夏天-北京 冬天比夏天-上海

这有多严重?世界卫生组织PM 2.5的24小时上限是25微克(年上线是10微克!)。那么北京夏天平均PM 2.5是上限的三倍多,在北京冬天是四倍多。

中国全国年图

你不在北京或者上海住吗?其他城市的空气也不安全!

寒冬将至,做好准备!

便宜的空气测量仪准吗?应该买哪一台?对比测试

我2013年创立聪明空气的时候,想要买一个粒子计数器。那时我基本上只有两个选择:买一个260美元的Dylos,或者花费上千美元巨资买一个贵得要命的粒子计数器。

自从那时起,各种新的粒子计数器开始充斥市场,最便宜的仅有人民币99块钱。但是这些粒子计数器有多好用呢?

 

对粒子计数器进行测试

 

为了找到真相,我们测试了三种市场上流行的粒子计数器——Dylos DC1700,Origins Laser Egg,以及一种叫做AirVisual Node的新型粒子计数器。

Dylos

 

Dylos DC1100
Dylos DC1100

Dylos 是聪明空气自从2013年起就开始使用至今的值得信赖的粒子计数器

 

Laser Egg

Origins Laser Egg
Origins Laser Egg

Laser Egg是目前流行的,技术性更强的仪器。

 

Node

Air Visual Node
Air Visual Node

Node是更精致的版本,它有一个大屏幕,包含更丰富的信息,空气污染预报,更好的用户体验,甚至包含了二氧化碳水平监测。

 

allthree

政府空气质量数据对比

我们把三种测试仪放在聪明空气位于东直门外大街的办公室外进行测试,这里距离农业展览馆(政府PM 2.5检测仪位于此)1.3千米。

 

Map of Smart Air Office and Agricultural Exhibition Centre

我们对这些测试仪进行了为期6天的测试。Laser Egg 和 Node 给出的是PM 2.5 微克数值,而Dylos给出的是0.5微米及以上颗粒的数量,所以我们用半官方换算公式(0.5微米及以上颗粒数值-2.5微米及以上颗粒数值)/100,将Dylos读数也换算成PM 2.5微克数值。

以下是我们在北京办公室外进行的第一项测试的结果(测试时间为72小时):

 

 

低浓度PM 2.5环境下的测试

 

接下来我们在PM2.5值很低的几天当中进行了测试。这对我们更加有用,因为一般室内(大多数人使用粒子计数器的地点)的PM 2.5浓度要低于室外水平。所以,这些数据对于测试粒子计数器在低浓度PM 2.5环境中的表现很有用。我们在天空非常清澈晴朗的情况下进行了48个小时的测试。

 

 

粗略来看上面两张图表,三个测试仪的数据跟政府官方数据的走势都很吻合。综合两个测试,我们发现AirVisual Node和Laser Egg与政府公布的PM 2.5的数据相关性达到了r = 0.98。对于不是书呆子的人来说,0.98的相关性算是基本接近完全相同了!Dylos的相关性最低,为r = 0.90,但也算是很高了(这与我们之前的测试结果吻合)。总的来说,三种测试仪测试数据与政府官方数据的相关性都非常高,这说明它们都能很好地反映政府的官方数据。

 

平均偏差

 

另一种测量精确度的方法是看这些数据与政府的官方数据的平均差距。结果证明Node与官方数据最接近:其数值与官方数据平均只相差4.8 微克/立方米。Laser Egg的数据始终与官方数据保持一定差距,二者平均相差6.5微克/立方米, Dylos与官方数据平均相差9.1微克/立方米。

也许有一点需要注意的是,Laser Egg在空气污染程度较轻的时候,PM2.5数值始终偏低。这表示存在这种可能性:Laser Egg会低估真实的室内空气质量,给出一个让人觉得空气足够安全的假象。但是尽管如此这些偏差也不能算大。

picture2 picture1 picture3

 

“空气末日”测试

 

为了检验测试仪在超高浓度污染环境中的精确性,我们在面积为15平方米的密闭房间内点燃了一支香烟。这样做的目的是要看看粒子计数器在一个总体污染浓度很高的环境中(包括严重污染水平)的读数精确性如何。在一位长期吸烟爱好者和一个与我们有合作关系的北京NGO的帮助下,我们成功地让这个密闭房间中的PM 2.5浓度达到了1,000微克/立方米!

 

“空气末日”测试

 

为了完成这个测试,我们还同时使用了另一台测试仪(Sibata LD-6S)进行对比参照。这是一台工业PM 2.5 粉尘测试仪,精确性为±10%,重复性误差为±2%。因此我们使用LD-6S作为我们的参照基准。

 

11
“空气末日”测试结果

 

通过以上数据,我们可以很清楚地看到Laser Egg和Dylos在污染浓度超高的情况下读数有些“跟不上”了,相比之下,Node 和LD-6S的读数保持着很高的一致性,它们都能测量出超过1,000微克/立方米的浓度值。当然,在实验之外的环境中我们基本不会遇到需要检测这样高浓度污染的情况,但是这个测试显示了Node在高污染水平下的精确性。

 

关键信息

总体来说,跟政府的测试仪相比,这三种测试仪给出的读数都相当精确。聪明空气团队认为,它们都能够较为准确地反映出家中的AQI指数。三者之中,Node得分最高,因为它在室外测试环境下与政府测试仪之间的偏差最小,并且在我们的“超级严重污染”测试中也表现出了最高的精确性。

 

可用性

既然三个测试仪的精确性都很高,现在的问题主要集中在:它们是不是方便使用?它们各自有着什么样的特点?

 

Dylos (1800元)

Dylos在这个比较中真的不怎么给力。它没有手机连接线,而且下载数据也是个痛苦的事儿——这还是在你已经有一根“老学院派式的”针型数据线的前提下。

 

Laser Egg (499元)

Laser Egg是一款入门级的粒子测试仪。它有简单的界面并且能给出非常精确的读数。它没有那么多功能,但是在它的专攻领域——PM2.5检测中表现很好。

 

AirVisual Node (988元)

就视觉上来看,Node功能最强大。对初级入门者来说,它能测量二氧化碳浓度,温度,还有湿度。这些功能使得它更像是一个综合的“环境监测器”,而不仅仅是个粒子计数器。如果你所处的空间不大又同时有好多人在里面,那么二氧化碳浓度能够显示你所在的空间是否太小了。如果你的房间内因为新装修过或者有新家具而存在室内空气污染源(挥发性有机化合物),高浓度的二氧化碳能够表明这些室内污染物正在累积。Node的用户设计能显示过去24个小时中室内和室外空气AQI和二氧化碳指数,也能预测未来几天的情况,还有关于何时打开窗户或者何时戴口罩的建议。通过对Node一段时间的使用,我们发现这些功能在我们的办公室内还是很有用的。

 


通过了测试以后,我们将会在聪明空气淘宝商店中开始发售AirVisual Node。无论是在家中使用还是用作实验目的(如果你像我们一样也是个书呆子),我们愿意为需要一个靠谱测试仪的人提供多一个选择。去看看吧!

接下来的几个月里,我们希望能对更多空气测试仪(粒子计数器)进行测试,并且进行一些花费更高的测试。这只是一个开始!如果通过我们的独立测试确认了更多靠谱的测试仪,我们有可能也会把它们放到我们的淘宝货架上来。

Cost of air pollution

Death in the Air Infographic by World Bank

对不起,此内容只适用于美式英文。 For the sake of viewer convenience, the content is shown below in the alternative language. You may click the link to switch the active language.

The World Bank released a new report titled “The Cost of Air Pollution: strengthening the economic case for action” and in it they detail how air pollution is now the 4th leading risk factor for deaths worldwide. That’s worse than the deaths attributed to alcohol and drug use, HIV/AIDS, and even malaria. Besides the other reasons for reducing air pollution (climate change, our health, etc.) the economic one is probably the one that will communicate the strongest to everyone as air pollution costs the global economy in terms of foregone labor income to the tune of $225 Billion each year globally.

Click here for full report.

Click here to view the infographic in higher resolution.

Air pollution has emerged as the fourth-leading risk factor for deaths worldwide. While pollution-related deaths mainly strike young children and the elderly, these deaths also result in lost labor income for working-age men and women. The loss of life is tragic. The cost to the economy is substantial. The infographic below is mainly based on findings from The Cost of Air Pollution: Strengthening the economic case for action, a joint study of the World Bank and the Institute for Health Metrics and Evaluation (IHME).
Air pollution has emerged as the fourth-leading risk factor for deaths worldwide. While pollution-related deaths mainly strike young children and the elderly, these deaths also result in lost labor income for working-age men and women. The loss of life is tragic. The cost to the economy is substantial. The infographic below is mainly based on findings from The Cost of Air Pollution: Strengthening the economic case for action, a joint study of the World Bank and the Institute for Health Metrics and Evaluation (IHME).
AQI levels across China

今天美国大使馆公布AQI是零!夏天的PM2.5一定低吗?

2016年9月9日-今天的中国空气污染地图。

来源://aqicn.org

美国大使馆正在显示PM2.5 的AQI是零!夏天真是这么好吗?其他地方呢?在下面了解更多。

几个月以前我们发布了北京夏天和冬天的空气污染水平变化报告。根据另外四个城市的美国大使馆数据,我们能够在更大范围内对中国主要城市夏天和冬天的污染变化情况有个了解。


美国大使馆推特账户

这次我们分析了上海、成都、广州和沈阳的大使馆数据。根据过去7年的数据,我们计算出了每个城市空气污染的月度和季度情况。

结果如何呢?通过对这四个城市的分析,我们证实了之前的关于夏天空气要比冬天更好的结论;四个城市的夏季PM 2.5数值平均要比冬季低29%。

 

 

可能的原因是,冬天的时候,通常情况下分散分布的空气污染物由于大气逆温现象,会在小范围内聚集。大气逆温现象是冷空气处于暖空气层下方,积聚在地球表面的一种大气现象。夏天的热量会阻碍大气逆温现象的出现。

在这四座城市里,夏天的PM2.5 水平只有冬天的71%。但这绝不是说夏天的PM2.5 水平就符合WHO(世界卫生组织)的标准。事实上,我们所分析的城市的夏天污染平均水平 (60微克/立方米)超出了WHO 24小时上限(10微克/立方米)的600%。

所有这些城市中,上海和广州的夏季污染水平最低(49微克/立方米,WHO上限的5倍)。夏季污染最严重的城市(除了北京)是成都。

 

 


空气污染水平月度情况:

 

根据美国大使馆的数据,我们也画出了所有城市空气污染水平的月度变化图,从这些图表可以很容易看出哪些城市污染水平最严重,以及在哪些月份比较严重。

 

以上图表明确显示了每个城市PM 2.5值的年度变化情况:污染水平在冬半年(十月—三月)上升,而在夏半年(四月—九月)有所下降。大多数城市7月和8月空气最好,虽然北京7月污染指数出现了一个令人费解的峰值——这很有可能是因为北京夏天较少出现可以吹走污染物的风。实际上,北京全年的空气污染变化是所有城市中最小的——污染数值持续保持在平均80微克/立方米的水平以上。

12月和1月在各个城市中都是污染最严重的月份,这很可能是因为冬季供暖会燃烧更多矿物燃料。

 

您可以在淘宝或者PayPal上找到我们200元和470元的空气净化器。也可以通过参加我们的沙龙活动,对我们的空气净化器和口罩测试有更多了解。

Flickr Photo

Is Summer Air Better than Winter Air?

对不起,此内容只适用于美式英文。 For the sake of viewer convenience, the content is shown below in the alternative language. You may click the link to switch the active language.

 

Summer is here, bringing with it clearer skies and certainly cleaner air. Right?

Summer always seems to drive out the dense clouds of pollution that suffocate many Indian cities. However, while summer air is in fact cleaner than air during other seasons, it’s still far from safe according to the standards set by the World Health Organization (WHO).

During the winter, cold air traps pollutants close to the ground, a process called an “inversion.” Summer heat prevents this inversion, which does improve the air quality. However, average air conditions in India are still clearly not ideal.

Here’s a map of today’s pollution levels across India:

 

pollution levels
Source: https://aqicn.org/map/india/

 

On a day like today, when the AQI in Chennai, Hyderabad, Kolkata, Mumbai and New Delhi is in the ‘unhealthy’ or ‘very unhealthy’ range, we often wonder at Smart Air if the pollution in summer really is any better than the winter.

We got to the bottom of it by analyzing the US Embassy’s data in New Delhi and US consulates’ data in Mumbai, Chennai, Hyderabad, and Kolkata. So is summer air really better than winter air? We took the data from the past two years (June 2014 to June 2016) and broke it down into four seasons: winter (December to February), summer (March to June), monsoon (July to September), and post-monsoon (October to November). Next, we calculated the average particulate pollution (PM2.5) levels for each season.

Across the five cities we looked at, PM 2.5 levels were 26% better in the summer—118 micrograms in the winter compared to 49 micrograms in the summer. That means summer air is better.

Let’s take a look at the difference in PM2.5 between the five cities during different seasons:

 

 

US Embassy Air Quality Data
U.S. Department of State Data, June 2014 – June 2016. Air quality data may not be validated or verified

 

But how good is “better?” Here in India, “better” is nowhere near “safe.” Over the course of the two years we analyzed, average annual pollution levels in all five cities never fell below even the WHO’s more lenient (24-hour) exposure limit (25 micrograms per cubic meter). In fact, the average pollution levels across all the cities we tested was about 500% the WHO annual limit (10 micrograms) and 200% of the more lenient 24-hour limit (25)!

 

The lowest summer pollution level we found was Chennai (31 micrograms). But even that lowest summer level still surpassed the WHO limits.

Below are the 2-year graphs for each city. You can see that each city has two distinct swells in PM2.5 levels during the winter, each followed by 2 clear dips during the summer. Interestingly enough, comparing the summer and winter levels of each city from 2014-2015 to 2015-2016 shows some cities’ PM2.5 levels improving, while others’ increase between years. Most notably, Chennai’s winter pollution levels dropped significantly between years as did Hyderabad’s, while New Delhi and Kolkata experienced clear increases. However, we’re not sure whether or not this improvement and worsening of PM2.5 levels can be attributed to cities’ environmental efforts (or lack thereof).

The conclusion? The evidence is quite clear: summer air is in fact better than winter air. However, despite all the blue skies and warm days we’ve been having lately, there’s still a need to protect yourself inside and outside the house. Don’t mistake “better” for “safe.” Neither summer nor winter air meets WHO health standards and summer air is still of significant concern to public health.

 

Chennai US Department of State
U.S. State Department Data – June 2014 to June 2016. Data may not be fully verified or validated.

 

US Embassy Air Quality
U.S. State Department Data – June 2014 to June 2016. Data may not be fully verified or validated.

 

US Embassy Air Quality Data
U.S. State Department Data – June 2014 to June 2016. Data may not be fully verified or validated.

 

US Embassy Air Quality Data
U.S. State Department Data – June 2014 to June 2016. Data may not be fully verified or validated.

 

US Embassy Air quality data
U.S. State Department Data – June 2014 to June 2016. Data may not be fully verified or validated.

 

图片 1

空气污染口罩真的管用吗?

当全国各地的中国人(以及一大批住在中国的外国人)早晨醒来时都不得不面对严重的空气污染时,现实迫使十几亿中国人民需要在一个原本复杂的科学问题上成为专家——口罩真的管用吗?

从那时开始到现在,我已经给中国各地数以百计的人做过演讲,来分享如何保护自己免受空气污染侵害的知识。在这些演讲中,我听到了一些来自聪明又富有怀疑精神的人们的质疑。在这里我想回答这些疑问,因为很幸运地,聪明又富有怀疑精神的科学家们(再加一个献身科学的书呆子——我自己)已经用实实在在的实验和数据回答了这些质疑。

  1. “口罩不能过滤掉非常微小的颗粒”

怀疑派说:

最危险的颗粒是那些最小的颗粒。但是口罩这么薄,怎么可能捕捉到最小的颗粒?

科学测试:

爱丁堡大学的研究人员测试了不同种类的常用口罩。他们通过使用柴油发电机(模仿汽车排气装置)向不同口罩排放废气,然后用一个粒子计数器测出有多少颗粒穿透了口罩。下面是我画的实验示意图:

图片 1

一个重要的细节:他们使用的粒子计数器能够测量到小至0.007微米的颗粒。我们这里讨论的可是真正的微小颗粒!

首先他们用一个简单的棉质手帕做了测试。有时我在中国看到骑自行车的人会戴着这种手帕。

2

结果不是很好,过滤了28%的颗粒。

下一个测试的是便宜的医用口罩。

3

效果不错!这个结果会让人感到意外(在密封性测试中它的表现会差大概20%,参考下面文章,但是已经比大部分人们直觉认为的结果好得多)。

然后他们又测试了一些自行车用口罩:

4

大部分能够达到80%。

接下来测试了一些便宜的3M口罩:

5

这些口罩的都过滤了95%以上的颗粒。非常棒!

结论:即使是非常微小的颗粒,口罩也能过滤掉。

2.  “好吧,就算口罩能够过滤小颗粒,但是当你戴着口罩时,空气就从口罩的边缘漏进去了。”

怀疑派说:

理论上口罩是管用的,但是这些测试不是在真人脸上做的。当你真的戴着口罩时,它不能很好地贴合脸部,所以它们还是没用。

科学测试:

这个问题更难回答,因为你必须在实际戴着口罩的时候测试口罩效果。为了做到这一点,你需要一个非常昂贵的密封性测试仪器。幸运的是,在我好几周不断的请求下,3M公司终于同意我用他们在北京的实验室。

11

蓝色管子采集口罩外的空气,白色管子从口罩内采集空气(密封测试细节) 。

生活在北京的Richard Saint Cyr医生也做了口罩密封测试。所以我把我的数据跟他的数据做了个整合。这是不同口罩在我们脸上的效果:

12

口罩对大多数人效果也这么高吗?

明确一点很重要:在我脸上做的测试不一定适用于其他人。但是,也有更广泛的实验数据。香港的研究者测试了22位中国人,结果发现3M口罩在他们脸上平均效果达到了99.5%。这个结果相当于Saint Cyr医生和我的测试结果中的最好成绩了。所以有实验数据说明在中国人的脸上,口罩也可以达到很高的密封性。

 

好口罩是贵的口罩吗?

下面的图是口罩测试结果和价格对比。

13

好在有效的口罩并不需要花费昂贵的价钱。而且为了呼吸到洁净的空气,我们不需要买个市面上最贵的口罩。

 

注意:关于气体污染

口罩的测试结果很好,但是也要注意:这些测试都是关于颗粒污染的。大部分市面上销售的口罩都不是用来过滤二氧化氮(NO2)或者臭氧(O3)的。所以口罩不是我们100%的保护伞。

 

    3.  有实验证明戴口罩有利于健康吗?

这可能是最难回答的一个问题了。然而,还是可以参考两个可靠的研究。研究人员在北京随机分配一组人戴着或者不戴口罩在北京走路,然后测量他们的心率和血压(12)。

Mask Study Blood Pressure CN

戴着口罩的时候,参加者血压更低而且心率更有规律。

15

结论:口罩可以过滤十分微小的颗粒,当你戴着口罩时也是这样。而且有专业研究结果表明戴着口罩有利于健康。这些应该足够让怀疑派们信服啦!

3m-fitting

穷人密封性测试

哪种口罩戴在你的脸上效果最好?我很有幸地拜访了一个实验室,在那里做了一个非常昂贵的密封性测试。但是我们中很少有人能有机会接触到价值10,000美元的仪器。所以普通大众应该怎么办呢?

Mask Fit Test Picture - CN

访问3M实验室的时候,我了解到了一种测试方法,我把它称作是“穷人密封性测试”。它的结果不如真正的密封性测试精确,但是可以帮你识别出口罩是不是有较为严重的漏气情况。其实很简单:

  1. 戴上口罩。确保上端的金属条紧紧贴合着你的鼻子。
  2. 如果口罩是头戴式(有两根皮筋),确保一根皮筋在你的耳朵下方,另一根在上方,像下面这样:

maxresdefault      3. 用手轻轻固定住口罩,猛吸一口气。吸气的时候,注意是否能感觉到口罩边缘有一股气流或者凉风。特别注意一下鼻子周围的区域。

4.  如果你感觉到有漏气的现象,调整口罩再试一次。如果试过几次之后都不能解决问题,那就得换一个别的口罩了。

3m-fitting

如果你的口罩没有呼吸阀,你也可以通过这种猛吸气的方式对口罩做个测试。

 

希望能你呼吸到安全的空气!

1

Do ionizers actually clean air?

对不起,此内容只适用于美式英文。 For the sake of viewer convenience, the content is shown below in the alternative language. You may click the link to switch the active language.

The other day, someone on Quora asked whether ionizer fans actually purify the air. This is an important question because ionizer purifiers are all over the place. For example, I was at a friend’s apartment in the US, and I saw his tower fan had an ionizer button on it:

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It’s also important because several friends in China have sent me links to products like this:

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Amazing! A “miraculous purifier” that removes PM 2.5 and formaldehyde in just 30 seconds. And all that for far cheaper than regular purifiers and even cheaper than building your own purifier.

If this is true, my life in Beijing is now so much easier. But is it true?

So how do ionizers work? 

Here’s my bedroom, with an ionizer and bad particles in the air:

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That ionizer shoots out negative ions:

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Those ions cause the particles to stick to surfaces, like my bed, the wall, and the floor:

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That’s the principle behind ion generators. It’s hard to see it happening with these tiny particles, but you’ve seen it on a visible scale if you’ve seen someone rub a balloon on their hair and then stick it to a wall.

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But wait #1

A summary of scientific tests of air purifiers found that most ionizers have no noticeable effect on particulate levels (p. 8). Their conclusion is that most ionizers are too weak to have an effect. Studies do show an effect if they use very strong ionizers–much stronger than most ionizers on the market (p. 19).

But wait #2

OK, so regular ionizers don’t work, but we can use a big one! The problem is, when you put that many ions into the air, it produces ozone. Ozone is harmful, so that’s not good!

But wait #3

Even if we use a really strong ionizer and even if we can accept the ozone, you might have noticed that the ionizer didn’t actually filter out the particles. It just made them stick to my bed, wall, and floor.

First, that’s gross. Since the particles floating around here in Beijing include things like arsenic cadmium, and lead, I’d rather not have them stick to my pillow.

Second, they’re still a danger. The particles are just sticking to my bed. So let’s say Thomas comes home:

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When I sit down on my bed, I’ll dislodge those particles, and they’ll float back into the air. Here’s my super scientific rendering of that process:

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Those problems are what led Consumer Reports to publish tests and warn people not to buy the Sharper Image Ionic Breeze. Sharper Image sued Consumer Reports; Consumer Reports won.

So when people send me links asking about these “miraculous” purifiers, I tell them to steer clear.

Careful not to overgeneralize

But let’s not draw too broad of a conclusion here. This doesn’t mean ALL air purifiers are junk. Instead, I use HEPA filters. HEPAs actually capture particles, and they are backed by empirical tests (1, 2, 3, 4, 5, 6). Here’s a little test I did with HEPA filters in Beijing:

 

cars delhi

A $3 billion pollution ‘solution’ in Delhi – but will it work?

对不起,此内容只适用于美式英文。 For the sake of viewer convenience, the content is shown below in the alternative language. You may click the link to switch the active language.

Last week, the Ministry of Urban Development announced a Rs. 19,762 crore ($2.95 billion) solution to reduce vehicular pollution in Delhi. If approved, the proposal will seek to reduce emissions from the over 8.8 million vehicles in the city, mostly owned by the rising middle and upper classes.  Despite this class differential in vehicular emissions, some of the improvements sought include:

  • Seven pilot parking management districts
  • An integration of  207 metro stations with other forms of public transit systems
  • Construction of cycling tracks and footpaths with crossings at least every 250 meters, with first use of street space to pedestrians
  • Removal of choke points across the city
  • A procurement of 2,000 new buses immediately and 4,000 new buses in the next phase
  • Development of a Bus Rapid Transit System on high-density routes
  • Parking fees and congestion tax to discourage private vehicles

While several of these suggestions, namely parking management districts and imposing congestion taxes, may curb vehicle use, the rest of the plan largely ignores the intersection of class and the environment in the city. Academics such as Asher Ghertner and Sunalini Kumar have argued that past environmental efforts in Delhi have largely failed due to “bourgeois environmentalism” wherein middle class biases and interests take over environmental efforts that are genuinely in the public interest.

This may very well be the case with the Ministry’s air pollution proposals, which largely focus on bus and metro expansion. In today’s age, car ownership is no longer a practical necessity but rather a symbol of class, prestige, and status. In 2001, Delhi had 900,000 registered private cars. Today, there are more than 2.6 million. Though small in comparison to the city’s population, the increasing use of cars in a deeply congested city is unlikely to be deterred by  building new bus and metro routes. In fact, the Supreme Court acknowledged the problem in January when it asked DMRC to explore the option of creating a ‘premium‘ class service on the Delhi Metro to make the train seem more friendly for the wealthy.

We’ve already seen a big failure in convincing the middle class to use public transport through the Bus Rapid Transit system in 2008, which displaced cars from three lanes to two and dedicated a special lane to bus use. Rather than getting support, the BRT received a hugely negative and critical media campaign by middle-class journalists who lived in colonies along the route. Their complaints centered on the fact that the special bus route increased car travel times by 20 minutes or more, leading to inconveniences for car users. This argument went to the Supreme Court when an activist argued that the BRT system ignored the “wealth creators” of the city who preferred cars. It seems that these reactions to public transport have gone unnoticed in the latest proposals.

Also ignored are larger contributors to air pollution than cars—trucks and two-wheelers—which contribute to 24-25% and 18% of PM 2.5, respectively. Cars, on the other hand, contribute to 14-15%. While public transport may attract owners of two-wheelers, typically lower-middle class, it won’t make big progress in changing truck usage. Policies considering trucks and two-wheelers seem absent from the proposals.

Ultimately, Delhi’s air pollution solutions need a broader perspective and incentive model that accounts for the behaviors driving modes of transport. If Delhi is to curb pollution, it needs to create marketing and norms to get managers, CEOs, members of parliament, and other middle- or upper-class individuals to prioritize public transport. The idea is not as crazy as it sounds; such consumers readily take on public transport in cities like London and New York. However, behavioral nudges must come along-side policies that disincentive car ownership by higher costs to purchasing cars, especially second cars. A prime example is Singapore’s Vehicle Quota System, which makes vehicles 3-5 times the actual cost, thereby incentivizing people to use public transport. The same must go for two-wheelers, and strict environmental regulations must be put on exhaust of all vehicles, including trucks.

It’s time to create norms that are set for everyone, not just the poor. Just as lower-class auto drivers have been forced into using CNG to curb pollution, and over 3 million squatters have been evicted from their land for ‘polluting’ the land, it’s time to create policies that promote the middle- and upper-classes to create a better environment. Though increasing public transport is well-intentioned, it is not the answer. The Ministry of Urban Development must take into account deeper considerations of culture, behavior, and norms and use the increasingly expanding world of marketing and behavioral economics to change what is normal.