Cost of air pollution

Death in the Air Infographic by World Bank

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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).
Flickr Photo

Is Summer Air Better than Winter Air?

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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.

 

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!

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!

Do ionizers actually clean air?

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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:

Ionizers 1

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

Ionizers 2

 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:

Ionizers 3

That ionizer shoots out negative ions:

Ionizers 4

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

Ionizers 5

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.

Ionizers 6

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:

Ionizers 7

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:

Ionizers 8

 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?

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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.

 

 

heart

Air pollution can break your heart

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For years, air pollution has been linked to heart disease but scientists haven’t been able to understand how, exactly, it breaks your heart. Last week, researchers in the U.S. released results from a long-term study that shed light; they found that air pollution thickens blood and hardens arteries, accelerating atherosclerosis — a disease in which plaque (calcium, fat, cholesterol and other substances) builds up in arteries, preventing oxygen-rich blood from reaching organs or body parts. This leads to the development of other diseases based on which arteries and body parts are affected, including heart attacks, stroke, or even death.

The study tracked 6795 participants in 6 U.S. cities between the ages of 45-84, all without a previous history of cardiovascular disease. Participants ranged from four ethnicities and came from a variety of socioeconomic backgrounds. Researchers then scanned participants’ arteries over a course of 10 years.  At the same time, they measured concentrations of PM2.5 and traffic-related gases called nitrogen oxides (NOx) outside participants’ homes, while creating estimates for the concentrations of pollution participants inhaled during time spent indoors.

The study found that PM2.5 and NOx were strongly associated with the build up coronary artery calcium, which accelerates atherosclerosis. Joel Kaufman, the lead author and a professor at the University of Washington, explained to ThinkProgress that air pollution may trigger cell inflammation, affecting white blood cells that protect the body against infectious diseases. As white blood cells accumulate, they build up plaque, causing atherosclerosis. This mechanism may explain why air pollution has also been linked to cardiovascular problems and mortality.

In the study, participants’ pollutant concentrations between the years 2000 and 2010 ranged from 9·2 to 22·6 μg/m³ for PM2.5 and 7·2 to 139·2 parts per billion (ppb) for NOx. For every 5 μg/m³ increase in PM2·5 and for every 40 ppb increase in NOx, coronary calcium deposits progressed by about 20%.

Though the results of the study are sobering, it’s important to note that the study was done in the U.S. under air pollution levels that fall well below the World Health Organization’s recommended PM2.5 exposure of 25 μg/m³.

Comparatively, North Indian cities tend to have significantly higher annual average PM2.5 levels, with Gwalior at 176, Patna at 149, and Delhi at 122. Further research needs to be conducted to understand how such high levels impact the severity of plaque build up and heart disease. However, a comprehensive Global Burden of Diseases, Injuries, and Risk Factors Study calculated that about 5.5 million people prematurely died in 2013 because of indoor and outdoor air pollution.

 

能不能降低安全空气的价格而不牺牲效果?

我开始做DIY空气净化器之后,很快就有人冒出来模仿我的DIY。我不介意,因为我把制作说明发布到网上,所以谁都可以做,并不是一定要用我的。不过,我看到两家价格比我便宜,还说我太贵了!

作为一个书呆子,我第一反应是要研究。所以我订了他们的货,发现他们用的风扇更小,而用的HEPA捕捉颗粒效果特别低。HEPA一般能捕捉99%的0.3微米及以上的颗粒;我发现这个更便宜的HEPA捕捉了85.8%(测试)。

有没有办法让HEPA再便宜?

不过,如果能有同样效果但更便宜的HEPA就更好了。所以我开始测试宽度稍微小一点的HEPA。为什么呢?因为HEPA能便宜6%,但是宽度还足够盖上风扇的出风口。

测试

作为一个书呆子,我还是想先去测试,以确认效果没有降低。所以我用DIY 1.0 + 29mm HEPA做了10次过夜房间测试,然后跟我之前发布30mm HEPA的测试比较了

测试是在北京的15㎡卧室里做的。空气测试仪是一台Dylos DC1700,能测到0.5微米颗粒(手提空气测试仪跟大使馆官方测试仪相比,准不准?)。

e

为了算效果,我算了起床之前最后4个小时的颗粒污染浓度,然后跟没开净化器的时候比较。同时我记录了外面的PM 2.5数据。以下是其中一天测试:

q

结果

10次测试,DIY 1.0 + 29mm HEPA平均减少了86%的0.5微米颗粒和91%的2.5微米颗粒。

w

这个测试结果是说明29mm的HEPA效果跟30mm HEPA没有区别。所以我把HEPA的价格降低6%,从80元到75元。书呆子这回高兴了!

HEPA价格对比

从性价比看,淘宝上Blue Air HEPA要359元,IQ Air要2,150元(还有长期使用成本对比)。

r

书呆子注释:实验重做

做实验的时候,科学家注重replication(重做)。如果一个现象是真的,应该能在不同的实验当中重做而得到类似的结果。虽然做这次测试的时候,重做不是主要的目标,这系列的测试是我测试DIY 1.0的第三个系列的测试 (包括早期测试200天长期寿命测试)。再加上美国医生Dr. Saint Cyr的测试,被重做的次数已经足够。

公开数据

跟之前一样,为了其他学霸同胞们,我发在下面布了原始数据和测试方法细节。

原始数据

1

2

3

4

 

户外PM 2.5的波动

我觉得这种几个小时的测试比常见的20分钟测试(比如CADR测试)更好,因为这是我们用空气净化器的更常见的方式。不过,八个小时测试的短处是,做测试的时候,外面的PM 2.5有可能会上升或者下降。如果外面PM 2.5下降,会夸大净化器的效果。如果外面PM 2.5上升,会低估净化器的效果。

如果算10次测试的平均值,这些波动应该会互相取消,但是还是值得分析数据,确定外面PM 2.5的波动没有影响结果。这10次测试当中,两天(9/25和11/10)的PM 2.5数据有比较大的波动。我去掉这两天的数据之后,平均消除的颗粒数据基本没变:84%的0.5微米颗粒和91%的2.5微米颗粒。

测试中户外PM 2.5

也值得看看测试的那10天,外面PM 2.5是不是跟北京平常PM 2.5水平一样。这10次测试的时候,外面PM 2.5平均值是116微克。这个比北京近5年的平均PM 2.5高差不多20微克(以我分析的美国大使馆PM 2.5数据为准)。所以这些测试能够代表北京常见的PM 2.5水平或者甚至更高的水平。

5

Feeling the heat? You’re feeling the pollution too.

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.

Had trouble breathing lately? It might be because despite popular opinion, Delhi’s air pollution levels aren’t doing so great in the summer heat.

Our team regularly monitors air quality through the Air Quality Index Widget on our phone, which uses U.S. Embassy Air Quality data. The U.S. Embassy converts P.M. 2.5 (mg per cubic meter) to an Air Quality Index (AQI) to easily guide health decisions. It is fairly typical for Delhi figures to be in the orange or red zone, considered unhealthy at an AQI of 151 to 200, in the summer. Winters typically see figures in the ‘Very Unhealthy’ violet category with an AQI ranging from 201 to 300.

US embassy AQI
U.S. Mission NowCast Air Quality Key

 

Though April AQIs have been, on average, showing moderate AQIs below 100, the pollution levels in the last week of April spiked.

April 28th, 29th, and 30th averaged at ‘very unhealthy’ levels of air pollution with average AQIs of 248, 246, and 300, respectively. Such high levels of pollution can cause significant aggregation for those with heart or lung problems.

The highest hourly averages on these days were above 500, with the maximum of 592 on 29th April. To put this into perspective, the U.S. Embassy Air Quality key maxes out at 500, which marks the maximum in the worst category, ‘hazardous.’ Hazardous levels of air pollution may cause serious heart and lung risks, even leading to mortality amongst those with cardiopulmonary disease. At levels above an AQI of 500, these effects may worsen.

Though there are is no evidence to help us understand the unusual spike, the high amount of air pollution may be a result of two on-going activities. One, the end of April brings an end to the wheat season. To clear the land of wheat stubbles in preparation of planting other crops, farmers often burn the wheat residue. According to Umendra Dutt of the Kheti Virasat Mission, however, only 16% of wheat reside is burned, so it is unclear how strongly the activity contributes to the PM 2.5 levels. Two, water-parched areas in Uttarakhand have resulted in an unusual number of forest fires. As of last weekend, 427 fires were simultaneously burning in the region, with reports of air pollution and poor air visibility.

Though the reasons for the poor air quality is unknown, Delhi government has yet to put precautions in place to protect public health. Contrastingly, China has frequently triggered red alerts in cities across the country when smog levels rise to unusual levels. Red alerts, which include recommendations that people should stay indoors and vehicles should be restricted, are issued when regions see an AQI of 300 or above. Delhi is seeing almost double this number during peak pollution hours, yet the government has taken limited precautions beyond odd-even. Until institutional factors are not addressed, air pollution will persist in high amounts. Such factors include industrial policies in Delhi and neighboring regions, implementation of policies restricting crop burning, and measures to reduce negative health and environmental impact of droughts.