Written by Prarthana Sheopuri. Managing Editor, I Kid You Not.

Delhi’s Air Quality Index (AQI) has been in the news lately because the air in Delhi is very polluted. As per a recent report, New Delhi is the world’s most polluted city.

It gets worse in November, primarily because of the weather getting colder and stubble burning in Punjab (explained below)

In the month of November, for the past many years, Delhi’s air becomes even worse – often going into the ‘severe’ to ‘very poor’ category

Recently, the overall AQI of Delhi was 472, whereas Noida and Gurugram, which are a part of the national capital region, recorded an AQI of 562 and 539 respectively. They too classified as ‘severe’.

Schools were forced to either shut down or go online whereas some government officials have been asked to work from home as well. The suffering especially with regard to health is stark and real.

Let’s understand what AQI means and how it is calculated.

What is AQI, or Air Quality Index?

The Air Quality Index (AQI) is a measure that is used to understand how clean or polluted the air is. The scale goes from 0 to 500, and it is used to measure air quality on a daily basis.

The higher the AQI, the worse or more polluted the air.

Here’s a great table that explains it

How is the AQI calculated?

Calculating the AQI of a particular place is a complex procedure.

But, to put it simply, here’s how it’s done.

We told you in the table above that there are six AQI categories – from good and satisfactory to moderately polluted, poor, very poor, and severe. The AQI is decided based on these categories.

Basically, (and this is explaning it very simply) – the average of all pollutants is measured for an hour or 8 hours, i.e 1/4th of a day or a full day.

At least 18 hours are monitored to get a daily average. Currently, Particulate matter: PM_2.5 and PM₁₀ is measured to arrive at the AQI, as it travels deep into the respiratory tract reaching the lungs causing coughing, sneezing, runny nose and shortness of breath.

You may ask, how do you decide what category it is on a particular day?

This is done based on the values of eight main air pollutants in a 24-hour period (we tell you below which ones), and what their health impacts would be.

These eight pollutants are:

PM10, PM2.5 – Particulate Matter
NO2 – Nitrogen Dioxide
SO2 – Sulphur Dioxide
CO – Carbon Monoxide
O3 – Ozone
NH3 – Ammonia
Pb – Lead 

(they are mentioned in the table above).

What are  PM_2.5 and PM₁₀?

The PM-Particulate matter is the microscopic (extremely small) matter (substance/object) suspended (hanging) in air or water and 10 and 2.5 is actually the diameter of the particles. 

PM is measured as micrograms per cubic metre. PM_2.5  is finer or smaller in size and is more likely to travel into and deposit on the surface of the deeper parts of the lung, while PM₁₀ is more likely to deposit on the surfaces of the larger airways of the upper region of the lung. PM_2.5 is more dangerous because it can get into the deep parts of the lungs, or even into the blood.

So, why is Delhi’s AQI so bad and full of all these harmful pollutants?

Here’s a quick look at the reasons behind such high AQI

• Delhi shares its border with Haryana and Uttar Pradesh. One of the main reasons for increasing air pollution levels in Delhi is the burning of rice stubbles in Punjab, Haryana and Uttar Pradesh. These states set fire to approximately 35 million tonnes of crops. The wind carries all the pollutants and dust particles along with it.
• Pollution caused by vehicles is another reason contributing to this air pollution and smog. 
•  As the winter season sets in, dust particles and pollutants in the air don’t move, resulting in smog (a term used to describe a mix of smoke and fog)
• Large-scale construction in Delhi-NCR is increasing dust and pollution in the air. 
• Industrial pollution and garbage dumps are building up smog in the air.
• Despite the ban on firecracker sales, people ended up bursting them this Diwali. It may not be the top reason but it definitely contributed.

The reasons for burning of stubbles by farmers

Paddy (rice) is harvested, in mid to late October. After this is done, the farmers need to clear the land to start the next cycle of sowing wheat. However, after harvesting the paddy, the fields are left with stalks about two feet high, and the farmers have very little time to prepare their fields. This is why they burn the stubble (leftover stalks) to clear the fields. 

Is stubble burning the only option – is there no better way?

It’s not the only option, but it is the cheapest and the easiest option for the farmers, who are often operating on little margins for making money.

Getting human labour to clear the fields is expensive – as is the cost of then carrying the residue somewhere else (tractors, fuel etc)

Another way out is to sell or give away paddy straw to generate energy. Sadly such industrial units are fewer in number and can’t keep pace with the amount of waste paddy straw generated.

The bio-decomposer is yet another way, it’s a microbial solution sprayed to help decompose the stubble. However, it can take around 20 to 25 days for the stubble to decompose, thereby it isn’t a practical solution, as there is only a small window between the harvest of paddy and the sowing of the next crop before the winter sets in.

Can the government not help?

It can, and it does try.

The central government, for instance, provides a subsidy (financial help) of 50 per cent to individual farmers and 80 per cent to farmers’ groups or cooperative societies to buy stubble management machines – these are machines like the Happy Seeder that are crop residue management machinery, which basically push the residue deep into the ground, so there’s no need to burn it.

Unfortunately, most of these machines are either underutilised or not used at all.

Why’s that?

This is because while the machines are either free or cheaper because of the government’s supprt, it is still a cost for the farmers as they need to put the fuel to run these, which is expensive and most farmers can’t afford it.

Other steps being taken to control air pollution

Vehicular pollution is being combatted through better public transport facility and strict driving rules and regulations. 

The Centre’s air quality panel has directed authorities to impose a ban on construction and demolition in the NCR region (which is lifted now)

Action plans to deal with the reduction and disposal of industrial waste are being set by the said state governments. Hopefully, these will prove fruitful in reducing pollution. 

Guidelines to protect oneself

1.  Stepping out or indulging in outdoor activities, during early morning and in the evening , is best avoided due to “severe” levels of air pollution in the city.
2. Wear anti pollution masks that filer out the PM10 and PM2 pollutants
3. Try to stay indoors. Go out when it’s bright and sunny.
4. Avoid stepping out if you have breathing difficulty.
5. Drink an adequate amount of water as it helps in flushing toxins from the body.
6. Avoid strenuous activity, as that might lead to inhalation of minute pollutants.
7. Eat fruits like avocado, berries,  muskmelon, guavas, bananas, grapefruit and papaya, which are loaded with vitamin C and magnesium. These fruits are rich in antioxidants and anti-inflammatory compounds and help in boosting immunity.
8. Use nasal filters or air purifiers, which help in short-term relief.

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