‘Nitrogen dioxide pollution is a growing issue for South Asian cities’

Part 1: Health Effects Institute researcher Pallavi Pant speaks about air pollution challenges faced by south Asian cities

By Jayanta Basu
Published: Friday 16 September 2022

A recent global study by the United States-based Health Effects Institute (HEI) identified Delhi as the highest polluted city globally, followed by Kolkata among the most populous 103 cities out of 7,200. Here is the first part of Jayanta Basu speaking to HEI scientist Pallavi Pant, who was pivotal in preparing the Air Quality and Health in Cities: A State Of Global Air Report


Jayanta Basu: Your previous reports have covered regions and countries. Why did you decide to look at data in terms of cities this time? 

Pallavi Pant: This is our first attempt at understanding air pollution data at the city level, especially for fine particulates like PM 2.5 and nitrogen dioxide. Sources of pollution in cities stand slightly different than at national level assessments. 

South Asian cities, like the countries, have very high levels of PM 2.5. These countries usually have high average levels as well.

However, sources of pollution have become stronger in some of the large and populous cities. This is how you see New Delhi, Kolkata and Dhaka topping the most polluted list.

JB: What about the smaller cities?

PP: The complete list of over 7,200 cities includes smaller towns with fewer populations in South Asia. Many smaller cities in Uttar Pradesh have higher pollution levels than Delhi, Kolkata or other big cities in South Asia.

High air pollution is not a problem for just the big cities like Delhi, Kolkata, Dhaka or Karachi; it is happening within most cities in South Asia.

We found that PM 2.5 levels in many South Asian cities are going up and the levels are higher than they were 10 years ago. More people are migrating to bigger cities for better employment opportunities and getting exposed to high levels of PM2.5.

JB: Is shared air space and consecutive shared pollution a concern for South Asia?

PP: The air is very similar in South Asian countries and we are definitely seeing impacts of air pollution sources within one country affecting the other. In fact, India, Pakistan, Bangladesh and Nepal have a lot of shared air spaces. 

Read more: Air pollution deaths: What troubles Delhi today may haunt Mumbai tomorrow

As we discussed, even rural areas in South Asia are battling air pollution concerns. 

The report shows how PM 2.5 and Nitrogen dioxide (NO2) impact our health. NO2 primarily originates from traffic as well as from power plants and industries. 

We did not cover ozone in this report but may do so in the next one.

JB: Is there any combined effect from the pollutants because we are generally exposed to them all simultaneously?

PP: Researchers have been looking into this and there are an increasing number of analyses looking at the combined effect of the mixture of all the pollutants. However, we are still not in a position to clearly pinpoint the extent and impact of exposure to the combined effect of the pollutants.

JB: South Asian cities do not seem as affected by nitrogen dioxide pollution as PM 2.5. 

PP: Nitrogen dioxide gas is generated mainly from vehicular combustion, which is a major problem for several big and industrialised cities.

In South Asian cities, ownership of private vehicles is less compared to developed countries. However, the numbers are increasing, which is a cause of concern, despite the fact that new vehicles use modern technologies to minimise emissions.

Even then, South Asian cities, including Indian ones, are among the 20 most polluted. Cities like Mumbai and Bengaluru are quite close to the top. 

So South Asian cities do have a problem with nitrogen dioxide spewing from vehicles, which may be growing. But we still can fix it if we emphasise more on public transport and cleaner modes of vehicles. 

However, the age of the vehicles is generally younger in South Asian cities.

Read more: Step towards transparency: Rajasthan pollution control board shares emissions data online

JB: What about the major sources of PM 2.5 pollution in Delhi or Kolkata, who lead the most polluted populous city list?

PP: Waste burning, vehicular pollution, power plants and industries are big concerns for cities like Kolkata or Delhi. Moreover, there are some regional and seasonal sources like crop burning, which may happen in one place but eventually get transported over a long distance. 

Construction activity is also a major source of fine particulate pollution. Brick kilns are major polluters in cities of Pakistan, Bangladesh and Nepal. 

It is true that as cities expand and develop, there are bound to be more emissions and poorer air quality. But we really hope that the air pollution lessons learnt from industrialised countries, especially from the US, the United Kingdom and other European countries, need to be put into the policies and on-ground implementation of developing countries before the situation goes too far.

Some policies implemented in India, like moving from Bharat stage IV emission standards to VI, are expected to show some results over the next few years. In cities like Dhaka, there is an increasing push toward electric vehicles.

In Pakistan and a few other areas, there has been a strong push to change technologies in brick kilns to reduce emissions, which is useful both in the context of improving air quality and countering climate change. 

(This is the part 1 of the interview with Pant, click here to read the second part)

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