Source Pollution

10 Facts About Air Pollution

We get many questions about air pollution in our office, and understandably so. It’s a topic that isn’t well understood or well-reported about in certain parts of the countries in which we work. In some cases, it is difficult to distinguish research-backed findings from common beliefs. To contribute to collective learning, here is a quick list of top 10 facts about air pollution.

  1. Air pollution is made up of chemicals, particulates, and biological materials. Common  components include, but are not limited to: nitrogen, sulfur, carbon monoxide, carbon dioxide, dust, and ash.
  2. Air pollution is caused by both human and natural contributors. Industries, factories, vehicles, mining, agriculture, forest fires, volcanic eruptions, and wind erosion all cause air pollution.
  3. According to the Global Burden of Disease report (2013), air pollution contributes to more than 5.5 million premature deaths every year. Another report by the International Energy Agency estimates the number to be 6.5 million deaths per year.
  4. Research has linked air pollution to multiple diseases: acute lower respiratory infections, chronic obstructive pulmonary disease, lung cancer, tuberculosis, low birth weight, asthma, and cataract.
  5. According to the WHO, 98% of cities in low- and middle-income countries with more than 100,000 habitants have unsafe levels of air pollution.
  6. Of the top twenty most polluted cities in the world, 13 are in India and 3 are in China. Delhi ranks as 11th most polluted, whereas Beijing ranks as 57th most polluted.
  7. Over half of India’s population—660 million people—live in areas with unsafe levels of air pollution.
  8. On average, Indians living in polluted areas will lose 3.2 years of their lives due to air pollution.
  9. In 2014, India and China tied at 155 among 178 nations in rankings measuring how countries are tackling air pollution in the world, despite both countries having some of the worst air quality in the world.
  10. Pregnant women who live in  high traffic areas have a 22% higher risk of having children with impaired lung function than those living in less polluted areas.
Flickr Photo

Is Summer Air Better than Winter Air?


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


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.


cars delhi

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

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.




Air pollution can break your heart

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.


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

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.

Does Spring bring better air to Delhi?

Spring in Delhi, is the air clean?
Spring in Delhi, is the air clean?

Delhi Winters are notoriously known for bad levels of air pollution, but we often hear that air gets cleaner come Spring. We were curious what was happening in our own backyard, so we put out our Dylos Particle Counter on a rooftop near our Saket office.  The Particle Counter measures particle counts between 0.5 to 2.5 micron in size per 0.01 cubic ft. From this number, we can estimate PM 2.5, which are microns approximately 30 times smaller than human hair. PM 2.5 is considered harmful to human health since these particles can get lodged deep into the lungs and cause respiratory and cardiovascular problems.

Here is the data from November 2015 – March 2016. Though air pollution levels do drop in March, notice that the month still had zero days of ‘good’ or ‘moderate’ quality air. Due to fluctuations in hourly air quality, some of the maximums in March are higher than the average pollution levels between November and February.

Though Delhi air may get better in the Spring, it doesn’t improve enough to be considered clean or healthy. Keep those masks and air filters handy!

Smart Air Filters featured in The Hindu

On March 31, Smart Air Filters was exclusively featured in The Hindu’s Business Line. In “Making cleaner air affordable the DIY way,” Chetna Mehra highlighted our commitment to providing clean air at a low-cost. Here’s an excerpt from the article – you can read more here.

If you are living in Delhi, you are already deprived of clean air, and may be ready to pay a hefty price to get lungfuls of this precious resource. But how much should clean air cost? Most will say it should be free; but the most affordable tag on it now is ₹3,400.

Social innovation firm Smart Air is selling affordable DIY (do-it-yourself) air-purifiers that clean indoor air as well as any expensive air-purifier available in Indian market in the ₹16,000-30,000 price range.

To find out more about our range of clean air products, check out our online shop.

How healthy are Delhi kids’ lungs?

From: The Hindu

In 2008, the Chittranjan National Cancer Institute (CNCI) in Kolkata published the results from a study examining the health of lung function among school children, aged 4-17, in Delhi. To test whether children in Delhi fared worse than those outside of the city, the study compared 11,628 children from different parts of Delhi to 4,536 children in rural West Bengal and rural Uttaranchal—notably less polluted areas—over the course of 3 years.

Children are thought to be particularly susceptible to air pollution. They have higher oxygen demands then adults, leading to higher respiration rates. Their airways are also smaller than those of adults, so they are more likely to get inflammation due to air pollution. And because their immunity is still building up, they are more prone to illnesses from pollution than adults. If they are exposed to chronic pollution, children may develop lung damage into adult life.

The results from the study, summarized below, indicate that Delhi children show significantly worse outcomes for respiratory health and lung function compared to those in the control group. Children from lower socioeconomic groups usually fare worse because they have higher exposure to outdoor and indoor pollutants. The study further stated that children spend 2/3 of their time indoors, meaning air quality at schools and homes have a significant impact on health.

Many of the solutions to improve health outcomes for Delhi’s children necessitate policy changes — ensuring that schools are built far away from polluting sources, stricter monitoring of polluting sources, and better access to health services, to name a few. But ensuring kids avoid physical activity during high-pollution hours and wear anti-pollution masks whenever possible can help. For clean air indoors, check out Smart Air Filters’ low-cost air purifiers.


Smart Air Filters featured on CNN Money

Charles Riley, a journalist with CNN Money, recently published a long-form article on Delhi’s air quality and its impact on individuals—particularly children and those with asthma. Smart Air Filters was thrilled to be featured as one of the groups making Delhi’s air cleaner through our low-cost, DIY air filters. The article also featured Saurabh Bhasin, a lawyer taking up legislative battles with the Supreme Court and Dr. Naresh Trehan, who has called for government reforms to promote cleaner air.

Check out the full article on CNN Money’s website.

Air Quality Around the World

In the last couple of posts, we have mentioned that 13 of the world’s 20 most polluted cities are in India. The rest are in Pakistan, Qatar, Turkey, Iran, and Bangladesh. But the top 20 rankings made us wonder, how does India compare to the rest of the world? To find out, we selected a few cities from around the globe and mapped the World Health Organization’s 2014 air quality data. Due to variations in the frequency of data collection, WHO’s database contains data collected anywhere from 2010-2013, varying by city and country. The map below shows the outdoor air quality as measured by PM 2.5, or particulate matters that are two and a half microns or less in width. PM 2.5 are approximately 30 times smaller than human hair. Due to their size, they can lodge deeply into lungs and lead to health problems.

Air quality is drastically different across continents, but even cities with seemingly clean air see high-pollution days. Recently, the city of Stuttgart, Germany issued an air pollution warning and asked residents to leave cars at home in lieu of public transport to bring down pollution levels. Though Stuttgart averages healthy levels of air pollution on an annual basis, the city saw 64 days of pollution above EU’s recommended 40 µg/m³ for PM 10 in 2014. Stuttgart government issued the air pollution warning after pollution levels rose to 89 µg/m³ (PM 10) on January 19, 2016.

Similar to Stuttgart, other cities in Europe have taken measures to bring down air pollution. Even though these pollution levels are significantly better off than India’s, they are still above WHO and EU’s recommended levels. In 2014, Paris—like New Delhi—implemented an odd-even scheme to bring down pollution levels. Milan took more drastic measures in 2015 by banning all cars, motorcycles, and scooters between 10 am and 4 pm for a three-day period to bring down pollution levels. Contrastingly, London has introduced a congestion charge for those seeking to drive in the city during the day on weekdays. Beijing has also taken various measures, including putting limits on cars, factories, and construction sites on days with high levels of smog.

As Delhi government continues its debate on how to move forward with the odd-even policy, scholars from the Energy Policy Institute at the University of Chicago the Evidence for Policy Design group at Harvard University examined preliminary data to understand the pilot period’s impact. They found that the odd-even pilot reduced hourly particulate air pollution concentration by 10-13%, but doubted the scheme could work long-term. In Mexico City, a similar scheme led to worse pollution outcomes when households purchased second cars  or old, polluting cars to overcome the odd-even rule. The scholars called for a pilot on congestion charges akin to London’s to understand how this could lead to long-term reductions in air pollution.

As Delhi’s debates on how best to curb air pollution continue, however, many of the other cities that see dangerously high levels of pollution in India necessitate a louder public debate. Here is a chart showing the top 20 polluted cities around the world as compiled by the World Economic Forum. If you live in one of these cities, start the conversation!