Why is Delhi’s air much worse than you think

Delhi's annual tryst with fatal levels of air pollution has begun, and so has the cacophony on how to reduce it. If you are a denizen of the city, your groaning respiratory system and watery eyes must be telling you that things are bad. But what makes things as bad as they are and is there a solution in sight?

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Every year, post Dussehra, Delhi loses sight of the Sun. There are many factors contributing to these nightmarish levels of air pollution. Weather, geography, local pollution (traffic, industries, etc.), agricultural practices, water security and climate change are the key factors at play.

On surface it looks like an insurmountable problem but it is not as complex as the Indian polity makes it out to be. It is also not as simple to fix as commentary from the courts and media suggest. 

Everyone is obsessing over crazy high PM2.5 levels but it is only one of the many toxins that are rendering the air unbreathable. Concentration of most of the 'criteria' pollutants has significantly increased in the air right now compared to the start of October when air quality was safe as per the Indian standards.

The term criteria pollutants is used for those for which acceptable levels of exposure can be determined and for which an ambient air quality standard has been set, e.g., carbon monoxide, nitrogen dioxide, ozone, PM2.5, PM10 and sulphur dioxide.

What, why and how of PM 2.5

What is PM2.5?

PM2.5 are fine inhalable particles, with diameters that are generally 2.5 micrometres and smaller. How small is 2.5 micrometres? The average human hair is about 70 micrometres in diameter— making it 30 times larger than the largest PM2.5 particle. It is even smaller than a normal red blood cell. 

Why is it bad?

PM2.5 poses serious health problems because they can get deep into lungs and some may even get into the bloodstream. Exposure to such particles can affect both lungs and heart. Numerous scientific studies have linked PM2.5 pollution exposure to a variety of problems, including premature death in people with heart or lung disease; nonfatal heart attacks; irregular heartbeat; aggravated asthma; decreased lung function; increased respiratory symptoms, such as irritation of the airways, coughing or difficulty breathing.

How is it measured?

The traditional way of measuring PM2.5 is to pass the air over a series of filter papers that are designed to progressively remove smaller particles. For instance, the first filter paper will remove particles bigger than 10 micrometres, the next filter paper will capture particles in the range of 2.5–10 micrometres and finally the last filter paper will collect all the particles smaller than 2.5 micrometres or PM2.5. Then these filter papers are weighed to get the concentration of PM2.5 which is generally mentioned in terms of micrograms of PM2.5 in every one cubic metre of air or µg/m3. The Indian standard for PM2.5 is 60µg/m3 for daily level and 40µg/m3 for annual level.

Nowadays automatic machines continuously measure PM2.5 concentration on a near real-time basis, but the reliability of their data varies wildly based on the technology used for measurements. Beta Attenuation Monitors are the most accurate and reliable real-time technology and are also the most expensive. Sensor-based monitors are the least accurate or reliable.

PM2.5 and PM10 refer to particulate matter, the numbers are the size (in microns) of the particles. In general, the smaller the particle, the more damage it causes to human and animal health because the deeper it can penetrate into biological systems.

PM2.5 concentration is up by 350 percent. PM10 concentration is up by 170 percent, carbon monoxide concentration is up by 150 percent, nitrogen dioxide and ammonia concentration is up by 80 percent, while sulphur dioxide concentration is up by 25 percent.

The present PM2.5, PM10 and carbon monoxide levels are well above the national short-term exposure standard level, whereas nitrogen dioxide, ammonia and sulphur dioxide levels are alleviated but still under the standard.

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These gases are highly toxic to human health and also cause chemical reactions in the atmosphere  under certain weather conditions that lead to formation of secondary PM2.5.

Oxides of nitrogen, volatile organic compounds, sulphur dioxide and ammonia, in particular, considerably contribute to the formation of secondary PM2.5. During winter, this secondary PM2.5 makes up to a quarter of all PM2.5 in the Delhi air.

Why does the concentration of these pollutants rise around this time?

Mid-September, when the monsoon starts to retreat and temperature starts to fall, something very interesting happens in the atmosphere above the landlocked Indo-Gangetic Plains.

It is a basic principle of climatology that warm air rises and cold air descends through the atmosphere. Also, normally, the higher you go, the cooler it is, which cools down the warmer air that has risen from the surface level and warms the cooler air that descends to take its place, thus creating the basic circulation of air and weather systems in the atmosphere.

During summer and monsoon, the temperature of air is maximum at the ground and it falls consistently as we move higher up into the atmosphere. As the monsoon begins to retreat, this normal atmospheric state is flipped on its head, or inverted. The air near the ground gets colder than the air above it as land cools down and heats up much faster than air and water. This phenomenon is called winter inversion and the height where the flip happens is called mixing height.

As the winter progresses, this natural phenomenon starts to take place at progressively lower elevation. At the start of the season, it is usually at 3 km height above the ground and at the peak of winter the mixing height drops down to 900 metres.

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This natural event is critical because it literally puts a ceiling over cities in North India (and Delhi in the present case) effectively stopping the vertical movement of air.

During the rest of the year, air pollution generated in these cities rises up to the upper atmosphere and gets diluted and dispersed. At the onset of the winter inversion, the air at the surface is stopped from rising by the layer of warm air above the city. And this ceiling is moving down with each passing day.

It is like being in a room where the ceiling is descending at a rapid pace. The room might have had enough floor space for you to live comfortably with all your furniture at the start but soon you need to fight with your furniture to have enough space to continue standing.

We can do nothing about this cyclic natural shrinking of air space above the cities. At best we can reduce other sources of pollution and adopt more efficient machines that cause less air pollution, if we do not want our lungs to be crushed under the weight of a closing air space.

But the madness in Delhi in particular and North India in general is that during this period, when air space is rapidly shrinking, people like to burn things to choke the living life out of the space.

Farm stubble fires and festive firecrackers (Diwali and New Year particularly) are the worst possible indulgences during winter inversion but have become an addiction.

What is not being measured despite the spotlight on PM2.5?

Not all PM2.5 is the same. Its toxicity level can drastically vary based on the chemical properties of the material the particles are made of which, in turn, is dependent upon the source of the particle.

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For instance, a regular dust particle originating from soil or sand is not toxic but a particle originating from burning of diesel is carcinogenic by nature and highly toxic to the human body. It is like breathing in talcum powder or cyanide powder, both are white powders but the harm they will inflict on the human body are significantly different. Current measurement methods are blind to this variable toxicology of PM2.5.

Technologies that can identify the source of PM2.5 are available. They can even determine which source is responsible for what percentage of PM2.5 concentration in the air in what are called source apportionment studies. But even these more detailed studies do not provide information on toxicity of the particles in PM2.5.

This missing toxicity information from the measured PM2.5 concentration is frequently used by special interest groups to argue against any resistance posed on their products in the State's attempt to clean the air.

The automobile industry has been using this gap in PM2.5 measurement to frequently throttle ban on diesel car sales, citing official measurements that generally put contribution of diesel cars to overall PM2.5 concentrations at a low 2–5 percent, without informing that this small percentage is much more toxic than dust, which generally contributes around 15 percent.

This lack of understanding on the toxicity of different particles also affects air pollution control policies as it manipulates priorities. For instance, the Delhi government is spending millions of rupees on sprinkling water on roads to wash down road dust, which is fine, but does nothing to control toxic PM2.5 that is a more potent health concern.

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Further, this excessive focus on PM2.5 also allows governments to overlook controlling gaseous pollutants, ignoring they are responsible for almost quarter of PM2.5 in the air during winter. Measures to reduce the emissions of these precursor gases would be beneficial in reducing overall levels of PM2.5.

What is being manipulated?

Over a quarter million measurements are published daily by the official real-time monitoring network of the country. We are living in a data overload and yet paradoxically there are more doubts around sources of air pollution today than existed a decade ago. Lack of protocols on how to process and read this real-time data has had a major role to play in this ignorance through information.

Before the spread of real-time monitoring, the Central Pollution Control Board (CPCB) had full control over the raw data and the general public was completely dependent upon their interpretation of the data.

Now, with real-time data being put directly in the public domain, everyone has an opinion on the status of air. In fact, summary numbers calculated by different government agencies for the same place from the same monitoring network no longer match. This is because each agency uses a different averaging period [CPCB uses 4 p.m. to 4 p.m., Indian Institute of Tropical Meteorology, Pune (IITM) uses noon to noon, India Meteorological Department (IMD) uses 8 a.m. to 8 a.m.] and a varying combination of monitors.

The Western world has developed and codified detailed methods to ensure no creative accounting can be done by State and non-state actors to make a place clearer or dirtier than it actually is. Unfortunately, no such thing has been done in India.

Public opinion, governments and sadly even courts are easily confused and manipulated by these creative accounting techniques.

The recent outrage of the courts regarding the introduction of the odd–even car rationing scheme to arrest worsening air quality is an example of this manipulation.

Despite credible evidence that vehicles are one of the primary source of both PM2.5 and gaseous pollution and restricting them can help ease the grip of pollution when the weather is hostile, smartphone analysts deemed it a failure because they did not see air quality improve to satisfactory levels immediately, ignoring the fact that the scheme cannot reverse winter inversion, it can only save a few additional breaths for worsening weather.

Smog towers are yet another grift riding high on the power of data manipulation. But then, humans have always had a tendency to build Towers of Babel.