delhi pollution 759

Every October as the rains recede, Delhi prepares to choke on poisoned air which peaks for 3 months from around Deepawali. This year the Delhi Government even asked public for suggestions on how to cope with these recurrent foul air episodes, which was particularly bad this year. PM2.5 (particulate matter below 2.5 microns in diameter) concentrations, a good surrogate for all air pollutants, ranged above 500 µg/m3, i.e., nearly ten times the national standard of 60 µg/m3 for a 24 hour period, and twenty times the World Health Organization’s guidelines.

Attempts to tackle Delhi’s air quality woes

Delhi’s extreme air pollution problem, which worsens in winter, is not a new one. In the last two decades it has received more attention than any other urban air pollution problem in the world, but in vain.

To understand the contours of Delhi’s air pollution problem, five detailed studies were done in the last decade. In this period 35 automatic air quality monitoring stations, each costing over Rs 1 crore that generate online data every 15 minutes were installed.

Conversion of public transport vehicles to run on CNG and the introduction of better quality fuel began in the 1990s. Today, Delhi’s fleet of 5,500 buses is the largest CNG fleet in the world. Another 1,000 CNG buses and an equal number of electric buses are to be added by the middle of next year. The use of BS 6 fuel (with one-tenth the sulphur content of fuel supplied today) will become mandatory in India from the middle of 2020. But it became available in Delhi and 19 surrounding districts in Haryana, Rajasthan and UP since end-September.

Twenty years back Delhi had no metro. Today, with 389 km route length and over one billion riders per annum, it has jumped to become the sixth largest metro in the world. The metro was meant to reduce private vehicles on Delhi’s roads. Instead, as some bus commuters shifted to the metro, they made way for more private vehicles on the road, proving that the Jevon’s paradox is at work in Delhi. The building of a large number of flyovers in Delhi also has had the same effect.

Yet, Delhi’s air pollution woes persist. Delhi’s air quality data records indicate that hourly averages of PM2.5 concentrations have regularly peaked in the range 500-1,000 µg/m3 for   over 10 years, particularly in October-November. And there is no sign of abatement.

To stave off the foul air nightmare this winter, several new air pollution mitigation measures have been introduced this year. Fifty four WAYU air filters that can suck dust and burn hydrocarbons in their surrounding air are being installed at some traffic junctions. After introducing it twice in 2016, the even-odd rule, which allows cars with certain number plates to run on alternate days, was re-introduced recently. None of these measures helped, including the even-odd rule, and PM2.5 concentrations remained above 400 µg/m3, making Delhi’s air unbreathable. The Supreme Court appointed Environmental Pollution Control Authority pushed for a temporary ban on non-CNG vehicles, i.e., 85% of registered private vehicles in Delhi, but was opposed on grounds that Delhi’s woefully inadequate public transport system would break down completely if this were done.

Engineering controls have failed

ringA senior functionary of the Central Pollution Control Board once remarked, “We have the same technology as that of developed countries, so why is Delhi’s air quality so poor?” To answer that question, we need to ask whether our environmental managers missed reading the Delhi air quality problem correctly, and failed to provide workable solutions that are appropriate for Delhi.

Take the case of the expensive online monitoring stations that were installed in Delhi. Information theory 101 tells us that online information is useful when immediate action can be done. For example, when there is a process upset in a reactor, the operator takes corrective action immediately. On days that Delhi had high air pollution levels, did the online data help in diverting vehicular traffic away from polluted areas, thus reducing air pollution loads in these areas? Or were commuters diverted from surface transport into the metro, reducing their exposure to air pollution? Apparently not!

Why were passive samplers not made regulatory instruments, despite a proven record of their ability to provide decision-support information that is as good as that provided by automatic stations, but at a cost that is lower by an order of magnitude of 3 times? Or is the classic syndrome of “big toys for the big boys” at work, where the environment managers make believe that big toys can do the job best.

Passive sampler

Delhi’s rapid vehicular growth and continued poor air quality in the last two decades quite clearly indicates that the Delhi metro, while facilitating public transport, did not contribute to improving the city’s air quality because it did not wean away a sufficient number of private vehicle riders. The Delhi metro has in fact added to pollution loads as last mile connectivity from metro stations to onward destinations is largely by autos, and not by non-polluting trips, i.e., by walk and cycles. If the last mile ride is by battery-operated autos, the point of pollution is transferred from the prime mover to the power plant, where air pollution causes significant crop yield losses and respiratory illness in a radius upto 25 km around thermal power plants, and which has so far remained unadressed. And if the auto is fossil fuelled, it adds to Delhi’s air pollution.

Has using CNG and lower sulphur content liquid fuels helped? Yes, they have reduced SO2 concentrations in Delhi, but not that of NO2 and PM2.5. The cost of moving to cleaner fuels is hidden in the large investment that refineries made to remove additional sulphur from crude oil, and vehicle manufacturers in fine tuning engines.

The National Environmental Engineering Research Institute that fabricated the WAYU air filters that were recently installed in Delhi, claims that these machines have an effective pollution cleaning area of 500 m2, i.e., an of 25 m x 20 m; that makes it a large room cleaner. The claimed filtering efficiency of ~80% for PM2.5 and ~40-50% for hydrocarbons in open spaces is still to be demonstrated. Even if that efficiency were achieved, how many hundreds or thousands of such machines would Delhi require? How often would the filters have to be replaced in Delhi’s choked air? And is the cleanup cost just the price of the machine, i.e., Rs 60,000, or should running and maintenance costs be added?

The efficacy and cost-benefit of the measures taken to control pollution in Delhi is yet to be adequately evaluated. Such an evaluation must also be communicated in a language that people understand.  Linking Delhi’s air quality to incidence and prevalence of respiratory illnesses like asthma is better understood by public rather than expressing pollution concentrations as µg/m3 or air quality as AQI. This would also help understand to what extent air quality standards have helped in improving environmental health.

In a rare moment of truth, a former Ministry of Environment official admitted three years ago that, “We have failed to control Delhi’s air pollution.” So what went wrong? Delhi’s environmental managers followed “handed down wisdom” from North countries that used engineering control systems, consequently technological solutions, to control their pollution problems after having polluted their cities.

Two factors impede engineering control systems from delivering tangible results in Delhi. First, the average wind speeds in tropical countries are significantly lower than in temperate countries.

wind speed

World wind speed map

For example, Delhi’s annual average wind speed is ~2.6 m/s, whereas London’s is double that.

Ground level pollution concentration is inversely proportional to wind speed. Given the same pollution load, Delhi’s ground level pollution concentrations will be twice that of London. Moreover, Delhi and much of North India have bad inversions in winter. Given this climatic disadvantage, the cost of using engineering control systems is Delhi prohibitively high, that is if it works at all.

wind speed2


Additional pollution loads and adverse meteorology contribute to high pollution levels in October-November.  Deepawali crackers and burning stubble from kharif paddy harvests in Punjab, Haryana and Western UP cause a greater pollution load for about 2-3 weeks in these months. And a post monsoon wind shift blowing from the south-east to north-west waft pollutants from stubble burning in North India directly into Delhi and carry them further south-east along the Indo-Gangetic plain.

October-November have the lowest wind speeds (<1 m/s—see fig) in the year. Moreover, they also have the greatest frequency of temperature inversions. These meteorological phenomenons greatly impede pollution dispersion, and along with the higher loads that Deepawali and stubble burning cause, are responsible for Delhi’s post monsoon air pollution woes.

air quality

PM2.5 trend from Oct 1, 2017 to Feb 25, 2018 for 17 locations in Delhi

(Source: CSE’s analysis of CPCB air quality data from 17 monitoring stations)

And this has been happening year after year.


Comparison of PM2.5 concentration for 4 locations-2017-18 and 2016-17

(Source: CSE’s analysis of CPCB air quality data from 4 DPCC monitoring stations– Mandir Marg, Punjabi Bagh, RK Puramand Anand Vihar)

The second factor that works against engineering control systems is Delhi’s city structure. Delhi is two cities rolled into one–an older one built much earlier, with narrow streets meant for animal carts and pedestrians; and a newer one built more recently, with broad streets for high density flow of fossil fuelled vehicles. Like most other cities in developing countries, Delhi is a semi-fossil fuelled city that cannot be changed easily. The old city’s narrow streets act as box traps for air pollutants; and above-grade metro deck in some parts of the old city only make pollution trapping worse.

In the year 1900, European and North American cities were non-fossil fuelled cities. Over the next 100 years, they increased their urbanization from 17% to 75% and built fully fossil fuelled cities. Upwards of 0.3 Mtoe of energy is required to build 1 km2 of a greenfield fully fossil fuelled city, or convert a semi-fossil fuelled one into a fully fossil fuelled one. That entails a minimum investment of Rs 2,000 crores per km2. The Europeans and Americans siphoned money to build their cities from their hinterlands, colonies and through unequal exchange with developing countries. Developing countries will find it hard pressed today to make such large investments for converting their cities into fully fossil fuelled ones, and therefore will have to be content with their cities remaining semi-fossil fuelled cities.

Old Delhi’s narrow streets, the addition of ~70,000 new vehicles per annum to the existing 1 crore registered vehicles in Delhi, low wind speeds and adverse meteorology make a perfect recipe for high pollution loads and poor dispersion that contribute to Delhi’s filthy air. Little of this that can be changed using engineering controls, and the little if any that can be done will be prohibitively expensive. The use of engineering controls in Delhi is akin to a walker having to walk ever faster to remain in the same place.

Haze in Delhi’s old city

Administrative controls—more likely to work

Since studies done on Delhi’s air pollution place transport emissions as the largest contributor (18-39%) to PM2.5 concentrations, followed by edaphic source (soil) dust (18-38%) and industry emissions (2-29%), let us deal with transport emissions.

A vast majority of trip modes in Delhi are by walk. Ironically, pavements and cycle paths get the least investment. In India of trips other than by walk and non-fossil fuelled transport modes, e.g., bicycles, almost 80% are by buses and trains and the energy expended by them is only 30% of the total transport sector energy expenditure. Whereas car trips constitute 8% of all trips but consume 40% of energy expended. The emissions of a person going by bus or train is ten times less than if he went by car. If our past transport planning was responsible for this, surely there is now a need for a re-think on whether we have done things the right way to minimize emissions. And this includes retrofitting Delhi with CNG as a fuel.

Energy use and emissions in various transport modes in India in 2012

Trip modeCarAutoPlane2-wheelerBusTrain
Energy use (Mega Joules/passenger.kilometer for single occupancy)
CO2 emissions (kg/ for single occupancy)
Per cent travel ( by each mode (%)830.61066.412
Per cent of total energy expended by each mode (%)4011217282

Applying the philosophical principle of Occam’s Razor (avoid excessively complex solutions) to Delhi’s intractable pollution problem indicates that minimizing emissions if not eliminating them is a better solution than to first allow pollution then look for clean up solutions later. Consequently, administrative controls methods, which uses non-engineering measures to eliminate or minimize emissions, should be given priority over engineering controls.

Transport emissions are very amenable to minimization through administrative controls by reduction of  trip[2] frequency and distance, and altering trip mode, first from private to public transport, and next from fossil fuelled public transport to non-fossil fuelled transport such as bicycles.

Trip distance reduction, for example, can be done in Delhi by mandating that school children go by school buses to neighbourhood schools that were not more than 2 km from home. Neighbourhood schools are in vogue in several developed countries. If the average travel distance saved by each of Delhi’s 7.5 million school children is 8 km per day (assuming that 90% of these trips are by bus and 10% by cars), about 250 million litres of diesel/petrol costing ~Rs 1,800 crores per annum, would be saved. The reduced emissions would improve air quality in Delhi significantly. Moreover, neighbourhood schools will improve educational standards in government schools and reduce the cultural divide between the rich and the poor.

Greater use of bicycles can be encouraged by increasing the number of bicycle pathways, cycle parking bays at metro stations and allowing bicycles to be carried onto metro trains. These measures will help in partially replacing autos with bicycles to do last mile connectivity to metros stations, thus reducing emissions. If 5% of metro riders switched from autos to bicycles for their last mile connectivity distance of 6 km each day, about 7.5 million litres of diesel/petrol, costing Rs 50 crores, would be saved each year, improving Delhi’s air quality.

There are other ways of reducing transport emissions. One of them is a vehicle (bicycles, 2-wheelers, cars) share schemes. A subscriber to such a scheme can pick up a vehicle from any point and drop it off at another point in the scheme’s jurisdiction. Access to a vehicle is gained by using a common key or by punching a password to a server through a mobile phone. The vehicles could be tracked using GPS trackers.

Over 1,000 cities around the world, including four in India, operate such schemes. Car share systems have become popular in cities like York. A variation of this scheme is vehicle-pooling, which is already being implemented on a small scale.

Emission can also be reduced by declaring certain parts of the city, e.g., Connought Place, as “vehicle-free.” As a public service, a few electric vehicles for senior citizens, and a cycle share scheme for general public may be allowed. Such vehicle-free zones exist in many cities. Likewise, vehicle registration and parking fees in inner city areas could be hiked, as has been done in many parts of the world. One way streets could also be increased significantly.

If annual carbon and energy footprinting by all organizations–government ministries and departments (central and state), enterprises (corporations, firms, shops and establishments) were mandated by law, like financial audits, and footprints were to be reduced by 3% per year, Delhi could halve its carbon and energy footprint in 20 years.

Implementing administrative controls requires public will

Can the present environment managers (Environmental Pollution Authority, Delhi Pollution Control Committee, Ministry of Environment, Forests and Climate Change) implement such measures? I doubt it. Their jurisdiction, as defined by environmental laws, is narrow and confined to pollution control (read “largely end of the pipe control”). Environmental managers require the cooperation of other departments to implement the above suggestions, and obtaining that is an uphill task. The more important question is whether the Union and the Delhi governments have the will to cleanup Delhi.

It is only Delhi’s citizens who can have such administrative control measures implemented by collectively pushing for them. If Delhi’s citizens wish to have cleaner air, they will have to fight for it.

Long run solution is de-growth

But the story does not end there. Administrative control of emissions is a transient measure that can minimize pollution loads, but cannot control Delhi’s adverse climate and the city’s structure, the city’s environmental nemesis. If the city is allowed to expand its pollution load will increase, and administrative controls, however good they may be, will not save Delhi from becoming a hell on earth.

Mathura, a small city located 100 km south of Delhi has an interesting tale to tell. Like Delhi it has low wind speeds and winter inversions that are worse than Delhi’s. A paper by Padmanabhamurthy and Mandal published in Mausam, the India Meteorological Department’s journal, in 1979 warned that Mathura has a high pollution potential. Yet, the UP Pollution Control Board website reports the Air Quality Index (AQI) for Mathura to be moderate (138-149) in October 2019. Whereas Delhi’s AQI for the same period was poor (average of 239), and had even dipped to the severe category (400-500) on occasion. Mathura did not suffer the same fate of poisoned air that Delhi did because of its relatively small pollution loads.

The moral of the story—Engineering control measures have not saved Delhi from the ravages of air pollution despite expensive cleanup measures adopted so far because of the low pollution load carrying capacity the city has.  Administrative control measures, which help curb pollution loads, may be a better way to control air pollution in Delhi, but require massive public support in the face of stiff resistance from Delhi’s environmental managers who are entrenched in engineering control methodology.

In the long run, even administrative controls will not help a growing Delhi as it will fall into the trap of the Jevon’s Paradox. Stopping Delhi’s growth, capping its emissions, and moving towards de-growth can de-toxify Delhi’s atmosphere.

Sagar Dhara is an environmental engineer specialized in risk analysis

Originally published in Firstpost, 28 Nov 2019

[2] A trip is the travel made by a person from one point to another. A trip is characterized by its distance, frequency and mode. A trip mode is the type of transport mechanism used. Walking, cycling, going by a bullock cart, bus, car, etc are different trip modes.



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