The Taxonomy of Air Pollution

Abhilasha Purwar
Sep 7 · 8 min read

Air Pollution, Air Quality Index (AQI), Concentration, PM2.5, PM10, SOx, NOx, VOC, Carbon Emissions, Tailpipe emissions, stack emissions, local pollutants, air-shed pollution, transboundary pollution; damn it is confusing and daunting. For how much air quality affects day to day life of an ordinary person, we have managed to make it a pretty complicated subject and daunting subject to understand

Recently, I had the mixed fortune of visiting Kathmandu and Bangalore; both cities with excellent overall air quality yet horrendous pollution exposure; and gave me first-hand exposure to misinformation, unawareness, and system failures around air pollution. And given the world infamy of India’s capital, New Delhi, as the most polluted city in the world; we as citizens ought to have a national Ph.D. in this subject.

Air-shed vs. Local vs. Hyperlocal pollution

The type and source of emissions really affect the downstream on quantity, toxicity, and effects of that pollution. For instance, North India and Delhi/NCR specifically suffer from major air-shed pollution. Between October & November, we burn about 20 million tonnes of crop waste across 12 million hectares of open fields. The plumes then travel all the way from the source in Punjab to Calcutta clouding the entire North Indian plains, cities, towns, and villages alike is a great Indian smog. Tier 2–3 cities in Kanpur, Varanasi, and Patna with their local traffic problems and issues of low fuel standards, old vehicle inventory add a nice toxic layer of vehicular tailpipe emissions on it. A solid double attack from top and bottom guarantees blackened lungs and adverse health effects.

Bangalore, on the other hand, is a special type of air pollution hell. From air quality measurement standards, Namma Bengaluru has one of the best & crispiest air in all Indian metropolitan cities. Blessed with the metrological lottery of high wind speed, around the year humidity, and moderate temperature, the pollution crisis of the city is a true policy and system shame. Nestled in the double-digit forest state of Karnataka and neighbors (TN & AP have 10%+ forest cover and Kerala at 20%), Bangalore as a city, is sitting on one of the best air quality real-estate in the country. But in terms of exposure, I fear, denizens of the city are not far behind their North Indian counterparts.

The horror story of Bangalore traffic is now well known to everyone, across the country, potentially the world. The silicon valley of India commutes people in 30+ minutes for 3–5 km distances, the pace of a subnormal amateur runner. This guarantees that an average trip to the office, school, gym, shops, restaurants, hell the hospital and pharmacy would guarantee you a road time of 1–2 hours per day. Added to it is the comically low fuel and vehicle standards in the city. For an economic powerhouse with 70.8 billion USD+ of GDP, the abundance of 10 to 15-year-old poor quality diesel vehicles is either a joke or real ignorance. Given how rich and technologically advanced the city is, anyone stating the fact that owner of black fume spewing bike, car, auto, mini truck or bus can’t afford a better replacement is definitely joking. Even a focused financial credit line purely to replace polluting vehicles out of the market would find ample customers and economics in the Bangalore economy.

Bangalore, has a high inventory of poor standard, old, diesel vehicles, which leads to high levels of SOx and NOx emission. Also unlike emissions from a polluting industry or coal-power plant, which goes into the atmosphere via a chimney at an average height of 50 ft aka 7 floors. In contrast, tailpipe emissions come to rise up right from your feet to your nose, with a quick entry into your bloodstream via your spongy lungs and instant delivery to brain delivering nausea and headache in short term and cancer and a whole plethora of respiratory diseases in the long run.

Chemical vs Physical Toxin

Kathmandu, in many ways, is like Bangalore just less economically and naturally blessed. Kathmandu is valley nestled in beautiful deep-green forest range mountains of Nagarjun, Shivpuri, and the Godavari. Out in the mountains, you are breathing some of the finest oxygen-filled air in the world, and in the city, you are inhaling some of the most toxic mixes of CO, SOx, NOx, VOCs, Benzene, and PM in the world. While PM2.5 & PM10 are the major pollutant trouble for North India, in the Nepalese toxin cocktail, they seem more benign than ice in an alcoholic beverage.

Pollution and emissions typically refer to overproduction of certain chemical compound, which may or may not exist in the natural state in the world. For instance, PM is literally dust. Now this dust can have natural sources like a desert storm (though in which case particles are much bigger and not so dangerous) or anthropogenic sources like burning coal which creates these tiny dust particles categorized as PM1, PM2.5 & PM10 which wreak great havoc on human health. Some pollutants like NOx, SOx, VOCs, Benzene, the side-effects of years of beautiful progress in the subject of chemistry are not really produced by Mother Nature (except for some rare angry activities like Volcanic eruption and forest fires).

Similarly, these pollutants react with the human body in different manners. Like PM2.5 & PM10; typically has a much more physical element to its damage than chemical, i.e. very tiny particles of dust rush through our nostrils, trachea, bronchi (small pipes leading to the lungs filled with tiny hair and mucus lining meant to trap such particles) and go settle in our alveoli (air sacs) leading to the famous black lung pictures, reduced lung capacity, and ultimately high risk of cancer. The human body typically reacts to this PM (small dust particle) onslaught by producing a lot more mucus which allows oxygen & nitrogen molecules to pass through but stops this PM substance. As a fun experiment, after a long day in Delhi, go home and grab a white handkerchief and literally dig your nose and observe the nose waste.

However, off late, with PM levels breaching 200–300 ug/m3 in most North Indian cities for extended periods of time, this typical human body reaction has gotten fairly compromised. Instead, people experience more wheezing which is mucus (and a mix of mucus and PM) deposition in deeper pipes of lungs for prolonged periods of time. Note that, most of this physical damage to alveoli aka air sacs is fairly irreversible in nature, as the vacuum cleaning technology to suck this dirt from tiny corners of human-lung-sacs is fairly behind.

On contrary, gaseous pollutants like NOx, SOx, CO can pass through the bodily defense of hair & mucus, straight to alveoli, penetrate the blood and reach major organs like brain, heart, liver directly in a matter of seconds. Thus unlike PM, which gets trapped at lungs for major exposure, NOx and SOx deliver immediate symptomatic headache. CO, in fact, has a high-speed chemical reaction with oxygen-carrying hemoglobin in the blood, converting it to useless carboxyhemoglobin, and is capable of delivering death at concentrations as low as 667 ppm. If you are a pregnant woman, this same CO can affect oxygen delivery to the fetus impending its early stage growth, and obviously your brains, livers and other parts affecting your health.

This chemical vs physical nature of the reaction of various pollutants directly affects toxicity levels aka how much can you safely consume before real damage begins. Similarly, the speed of symptoms varies, with NOx, SOx, and Benzene (especially) delivery nerve-racking headaches at high-speed, while PM is the more slow and steady provider of cough and asthma. While PM typically brutally damages lungs over years, VOCs (depending on toxicity) can deliver fast damage to the central nervous system.

The ultimate long-term disease from all these individual elements of the cocktail is quite mixed and expansive. Just like these buddies don’t exist in air in isolation and are always found in gangs, their health effects cover full range & scale of asthma, bronchitis, chronic obstructive pulmonary disease (COPD), coronary artery disease, congestive heart failure, cancer, dry throat, emphysema, fatigue, headaches, leukaemia, nonfatal heart attacks, and so on. Based on the concentration levels of each pollutant and their exposure, you will experience a mix of such disease & symptoms. Referring to my personal example, Delhi provides me with prolonged cough & wheezing while Bangalore is excelling in its supply of nausea & headache. Only time and prolonged exposure outcomes will reveal the final disease combination, but given my experience, I’d place my bet on COPD.

Life of the pollutant

Now, this is where air pollution, emissions, and air quality gets really tricky. After being released from the source aka say diesel vehicle tailpipe, the chemicals and compounds go through many reactions in the air/ atmosphere to change their shape, size, and toxicity. For instance, very small like nanoparticles coagulate within seconds and minutes to deliver microparticles like PM1, PM2.5 & PM10. The more the humidity more the coagulation. Similarly, NOx & SOx refer to a whole range of gases from NO, NO2, SO, SO2, SO3 and so on, which oxidize, coagulate with PM2.5, mix with each other and morph into new shapes & designs.

A basic rule of chemistry, is that everything is a poison after a level, case in point for global sugar madness; how quick and how little. A simple thumb rule for pollutants is that faster the reaction speed, lower its shelf life, greater its toxicity. Case in point CO, which turns to non-toxic CO2 in time or PM2.5 the slow poison that persists in the air for weeks, if not months. This “life” character of pollutants combined with metrological fortune is on full display in Bangalore or Kathmandu, where roads are critically polluted while a park or bedroom-balcony just a few meters away would provide cool, fresh, and crisp air. Delhi and North India, in contrast, have slow steady poison on the streets, in the parks, in the bedrooms, and the schools.

This also makes it tricky for measurement and reporting. To address the small-attention span of media, the air pollution conversation often lands on a made-up index called Air Quality Index, which takes toxicity levels of various pollutants into account, and provides a single number to represent air pollution/ quality in your locality.

But, presumably, your friend was overdosing on some fun concoction of 10 beer, 5 tequila shots, 3 lines of cocaine, 2 ecstasy pills, and 1 stamp of acid. Will you give the emergency doctor the total dollar bill for the nights’ festivities or will you try to recall individual indulgences.

Pick your cause and your disease

In the nutshell, India provides ample opportunity to experience every kind of major pollutant and their side-effects. In the same way, it also provides a variety of methods, styles, and avenues to actually go and solve this pollution trouble. While, the debate on what exactly is the leading source of pollution i.e. vehicles, power plants, crop fires, is a complicated and never-ending one; the answer for the real cause is unanimous. It is simply, you lack of awareness and understanding, a sense of indifference and normalization, and complacency to taking action.

Air quality across India is toxic, hazardous, and deadly. On average, we lose anywhere from 2 to 10 years of our life to the poison that we inhale with every breath. Either you can pick air pollution as a “cause” you will fight for, or it will deliver you a cause to die for.


Blue Sky Thinking

Using Technology & Data to save the Planet

Abhilasha Purwar

Written by

Founder & CEO, Blue Sky Analytics

Blue Sky Thinking

Using Technology & Data to save the Planet

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