Delhi’s air: Parikshit Ghosh speaks with Mohan P George

  • Blog Post Date 11 March, 2020
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Parikshit Ghosh

Editor-in-Chief, I4I; Delhi School of Economics


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Mohan P. George

Delhi Pollution Control Committee


Edited excerpts from an in-depth interview with Dr. Mohan P George (Senior Scientist, Delhi Pollution Control Committee), conducted by Parikshit Ghosh (Member of the I4I Editorial Board; Associate Professor, Delhi School of Economics) on the crucial public policy problem of air pollution in Delhi.


Parikshit Ghosh: Various factors are discussed in the media as contributors to the heavy pollution in Delhi, such as, vehicular emissions, crop-burning in Punjab and Haryana, and so on. Could you give us a sense of what the major sources are and their relative importance?

Mohan P George: Delhi’s location itself is one source of air pollution. Being in the Indo-Gangetic plain, the city is geographically disadvantaged and has extreme weather patterns. Dust storms in the summer months of April and May bring in particles – mainly PM 10 (particulate matter) – from nearby deserts. Then at the time of agricultural harvest in October-November in Punjab, Haryana and even Western Uttar Pradesh, residual burning takes place and particulates get blown into Delhi as it is downstream. Every particle has its own settling time so some of it settles but when thousands of acres are burning, the smoke goes up and the upper winds carry the particles and smoke – commonly called smog – and bring them to the lower part as well. This happens not just in Delhi but in entire northern India. In this dispersion process, secondary particles get created. Next comes the December-January period with low temperatures and wind speed. The ‘mixing height’ – the point where the pollution disperses – also reduces from 6 kilometres in the summer to as low as 600 meters in the winter.

Another factor is vehicular pollution. Delhi is a big city with about 20 million people and 10 million registered vehicles. With around 1,400 sq. km. area and 30,000 kilometres of roads, one can say that 1.5-2 million vehicles are on the road. The average ridership of a car in Delhi is 1.5. However, I do not think of it as a major source because engines and fuels are improving.

The real problem is road dust. The roads are not washed because we only get one monsoon rain and in fact the actual rainy days in the year are, on average, not more than 20-25 in the rainy season and 2-3 in the winter. When vehicles move on the roads, they cause re-suspension of dust and it takes 7-10 days for it to settle. But then with the movement of wind, it is suspended once again and the result is high PM 2.5 and PM 10.

Then comes construction, which is a never-ending activity. I do not blame the major bodies because they are strictly following the guidelines now: wind-breakers are installed, water is sprinkled, and chemical dust suppressant is used. The issue is unorganised construction in small colonies and so on. Say, I want to extend my balcony. I will purchase a few bags of cement and sand and use the material. If about 10% is left, it will remain at the site for months. With any small movement of wind or vehicles, it will get dispersed in the air.

Speaking of industry, Delhi has both organised and unorganised sectors. Illegal industry is everywhere and it is a major problem as they are still using traditional fuels. On the other hand, legal industries are now only using CNG (compressed natural gas), which is the cleanest fuel available.

So if you ask me to grade the known pollutants I would give the first rank to road dust; then construction; vehicles (they cause a bigger issue in winter); and residue burning in agricultural areas. Of course, there are also factors like local burning, unplanned landfills etc. but things are improving on these fronts. 

Parikshit Ghosh: The account that you have given combines natural sources like dust storms that we can do very little about, but also various kinds of man-made factors. We are seeing that pollution has gone up significantly over time. In your view, what should be the major policy initiatives, and which of those are we currently lacking?

Mohan P George: In terms of policy steps that we have taken, use of fuels such as kerosene and coal in industry has been banned and there has been a move towards CNG and Bs6 diesel. We have closed down thermal power stations and the stations that are now running are all on CNG.

Speaking of construction, there are three sites where demolition waste can be taken for conversion into materials that can be re-used, such as pavements tiles.

To address road re-suspension dust, local bodies have purchased about 60 mechanical sweepers that collect dust and dispose it of in landfills as per standard operating procedures. There are also vehicles fitted with special nozzles that sprinkle water on roads to stop the dust from becoming air-borne. These use treated water from STPs (sewage treatment plants). However, as a scientist, if you ask me if these mechanisms are successful; I would say no, there is a limitation. In Delhi, we park our vehicles wherever we get space. So when these machines come for sweeping, they are only able to work on medians of the road as there are vehicles on the sides and the dust remains. It is only on the major roads that sweeping is taking place successfully. 

Parikshit Ghosh: 60 machines sound too few for a city of this size.

Mohan P. George: We have to start somewhere! I think there is already a plan to increase the number so things should improve. 

Parikshit Ghosh: Right. One of the things I notice – in the last year or so – is  that there is this unpaved strip between the pavement and the road, and on thoseall sorts of paving has gone on.

Mohan P George: Yes, these ‘shoulders’ of the roads are a problem. We either have to green it or pave it. As far as greening is concerned, any hardy variety of grass that survives the extremes of the weather – from 2 to 45 degrees – would suffice. Even if it dries out in the summer months, the roots would stop the dust from dispersing.

The other thing – something that is new – which is being used is anti-smoke gun. For instance, if there is a big construction site, water is thrown on the boundaries or in a circular pattern, creating a canopy of droplets to settle the dust. Similarly, there are many other innovative methods and devices that are coming up and are at the testing stage. 

Parikshit Ghosh: One policy plan that has received a lot of media attention is the odd-even policy of the Delhi government. In the public domain at least, it is not very clear what the effects of this intervention are and whether it holds any promise in reducing pollution levels in the city. I would like to seek your views on this.

Mohan P George: A positive thing about odd-even is that it involves the public. The message being sent out is that the government alone cannot do it and the public has to come out and participate in the mission as well – which is a good thing.

If you ask me if the intervention is making a difference, I would say yes but with a limitation. The contribution of cars to air pollution is about 8%. Half of them are being allowed to come on the roads, which means 4%. Then there are various exemptions, for example, for ladies, implying that we are practically talking about 2-3% reduction under ideal conditions. Exact measurements are not possible in an open dynamic system as the wind is not fixed.

Nevertheless, taking away half the cars from the roads means something as some fuel is not burnt. Further, there is more space on the roads, cars can move at a higher speed and on higher gears and hence, emissions are reduced.  

Parikshit Ghosh: As a scientist in the Pollution Control Board, what are the main challenges you face?Let me mention 2-3 things. One is, of course, funding. Also, in terms of scientific expertise that you would want to input into policy, it would not happen unless politicians, bureaucrats, as well as the public are supportive. So thinking about political will in supporting pollution-fighting measures that you are recommending, and eventually also public awareness about the issuesand the solutions, do you see a problem?

Mohan P George: Delhi is the most-studied, most-monitored, and most-discussed city. It has had five source-apportionment studies in eight years. There are 40 real-time monitoring stations. Unedited data is made available in the public domain with a time lapse of maximum 15 minutes, which is a rarest of rare thing for any pollution control system. This helps create mass awareness of the actual condition and even 4th or 5th grade children are familiar with the term PM 2.5, or whether AQI (air quality index) is hazardous or severe on a particular day. So it is a great thing that the public knows about the problem.

Besides, we are privileged to have the latest, state-of-the-art monitoring systems. Of course there is a staff crunch, but overall the government and bureaucrats are supportive. 

Parikshit Ghosh: Let me follow up on that with a concrete test case, if you will. Regarding the crop-burning problem, I believe there are technological solutions like happy seeder machines or spacing out harvest periods. So why has anything not been done? It seems there is a failure in terms of the political will or public awareness or something else. What is your reading on that particular case?

Mohan P George: The problem of agricultural burning and impact on northern India was flagged for the first time in 2012. Between then and now, so many steps have been taken. The problem is huge: we are talking about 29 million tonnes of agricultural waste, and it has to be managed within 15 days. Yes, techniques such as happy seeder and super chopper are available but there is a mind-set issue. It will help if state governments reach out to farmers one-on-one and convey this information.

In the 80s and 90s, harvests were annual and agricultural residue was hardly 6 inches, and it has now become 1.5-2 feet. Hence, the volumes have gone up drastically and we do not fully know how to manage them. There will be a rule; they will not burn it; there will be prosecution and so on. I hope we move towards a real resolution of the issue soon. 

Parikshit Ghosh: Do you think that there is enough awareness among the general public about the long-term health consequences of air pollution? Of course, everybody can see that it makes breathing difficult and people are coughing, but medical research has found that it has significant mortality effects in the long run. Ultimately policies, especially costly ones, will require public support. Is this unfinished business?

Mohan P George: I do not fully agree with the data around death rates. The health impacts in the Indian context are not yet clear and more research is required. While foreign experiments have value, we cannot simply generalise what is found in Europe as geographical conditions are different and particulates are different. Hence, we cannot make simple comparisons between Sweden and India or Beijing and Delhi. A lot of the particulates here are wind-blown dust and are not all that toxic; it is not totally tailpipe emissions. We need impact studies and work is going on. 

Parikshit Ghosh: Before we end, let me ask you a very general question about how you see the prospects. In many of the industrialised countries of today, there was a point when they had pollution problems. One example is the London smog which led to a lot of policy measures and a sort of a reversal of what was going on. Do you think India can achieve dramatic improvement of that kind? I believe Beijing also has turned around. How much worse will it get before it gets better?

Mohan P George: A recent long-term study by the Centre for Science and Environment (CSE)shows a 25% reduction in Delhi’s air pollution in the last four years. This figure may be debatable but one thing that the scientific community agrees upon is that pollution is not increasing, which is something we should be pleased about. Comparing AQI data of 2017, 2018 and 2019, the number of ‘severe’ days are going down and ‘moderate’ days are increasing. This is not to say that the situation is very good but somewhere, change is taking place.

Can we solve this problem in a watertight compartment of Delhi only? No. We have to go back to air-shed management. We have to take as Indo-Gangetic plain, or at least as NCR (national capital region). 

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