case study of delhi pollution

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• 10 November 2023

Why is Delhi’s air pollution so bad right now?

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Air pollution is spiking in Delhi, a megacity of more than 30 million people. Credit: Arun Thakur/AFP via Getty

As the Hindu festival of Diwali kicks off on 10 November, the Indian capital of Delhi, already blanketed in choking smog, is bracing for pollution to worsen. Over the past week, children struggling to breath the acrid air have flooded hospital emergency departments , and schools have been forced to close . Why is Delhi’s air pollution so bad right now?

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doi: https://doi.org/10.1038/d41586-023-03517-1

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Delhi, the world’s most air polluted capital fights back

Subscribe to global connection, vinod thomas and vinod thomas distinguished fellow - asian institute of management, manila, former senior vice president - world bank @vthomas14 chitranjali tiwari ct chitranjali tiwari associate fellow - jk lakshmipat university, jaipur.

November 25, 2020

After an unexpected respite as coronavirus lockdowns stalled economic activity, air  pollution  has returned to  pre-COVID-19 levels in Delhi, the world’s most air polluted capital city  (Figure 1).

Last month, ahead of the usual spike in winter, the Delhi administration launched an antipollution campaign. But to win, nothing short of sustained action on  multiple fronts  will suffice. Other Asian capitals too have faced pollution crises. But Delhi’s is extreme because of a combination of smoke from thermal plants and brick kilns in the capital region, effluents from a congested transportation network, stubble or biomass burning by farmers in neighboring states, and the lack of cleansing winds that causes air pollution to hang over the city. Even as technical solutions are within reach, the campaign must overcome the poor policy coordination among central, city, and local governments.

Delhi’s toxic haze is a deadly health risk to its residents, particularly children, the elderly, and the ill. Particulate matter—PM2.5 and PM10—far exceeds national and World Health Organization limits and is the  main culprit  for Delhi’s high incidence of cardiovascular damage. The city’s toxic air also contains high quantities of sulfur dioxide, nitrogen oxide, and carbon monoxide, putting people at  higher risk  of strokes, heart attacks, and high blood pressure, and worsening the respiratory complications from  COVID-19.

The main sources of Delhi’s particulate emissions are, in equal measure, particles from large power plants and refineries, vehicles, and stubble burning. The experiences of Bangkok, Beijing, and Singapore suggest that an ambitious but feasible goal is to cut air pollution by one-third by 2025, which, if sustained, could extend people’s  lives  by two to three years. The current effort is designed to confront all three sources, but strong implementation is needed.

Delhi is moving simultaneously on three fronts: energy, transport, and agriculture. In each case, East Asia offers valuable lessons.

• Coal-fired plants. Delhi’s environment minister has called for the closure of  11 coal-fired power plants operating within 300 kilometers of Delhi. But policy implementation must improve: All the plants have missed two deadlines to install flue-gas desulfurization units to reduce sulfur dioxide emissions. Last year,  10 coal-fired  power plants missed a December deadline to install pollution control devices.  Beijing provides valuable lessons in cutting concentrations of PM2.5 more than  40 percent  since 2013. Beijing substituted its four major coal-fired stations with natural gas plants. The city government ordered  1,200 factories  to shut with stricter controls and inspections of emitters.  Bangkok  had success with its inspection and maintenance program.
• Cleaner transport . Delhi has tried  pollution checking of vehicles by mobile enforcement teams, public awareness  campaigns , investment in mass rapid transport systems, and phasing out old commercial vehicles. The Delhi government’s recent  push  for electric vehicles shows promise, while the response of industry and the buy-in from customers will be key. Overall results in cutting pollution have been weak because of poor governance at every level. Better outcomes will be predicated on investment in public transportation, including integration of transport modes and last-mile connectivity. Unfortunately, Delhi Transport Corporation’s fleet  shrank  from 6,204 buses in 2013 to 3,796 buses in 2019, with most of the bus fleet aging. Delhi should look at  Singapore’s  regulation on car ownership and use; its improved transit systems; and promotion of pedestrian traffic and nonmotorized transport.
• Better farming practices . Burning of crop stubble in Delhi’s neighboring states has become a serious source of  pollution in the past decade. In 2019, India’s Supreme Court ordered a complete halt to the practice of stubble burning and reprimanded authorities in two of these states, Punjab and Haryana, for allowing this illegal practice to continue. Needed is the  political will to act , as poor farmers complain that they receive no financial support to dispose of post-harvest stubble properly. Delhi’s  “Green War Room”  signaling the fight against the smog, is analyzing satellite data on farm fires from Punjab and Haryana to identify and deal with the culprits. The  Indian Agricultural Research Institute  has proposed a low-cost way to deal with the problem of stubble burning by spraying a chemical solution to decompose the crop residue and turn it into manure. Better coordination is needed. In 2013, when  Singapore  faced a record-breaking haze due to agricultural waste burning in neighboring countries, the Environment Agency and ministries of education and manpower together issued guidelines based on a Pollution Standards Index to minimize the health impacts of haze.  Stubble burning  has been banned or discouraged in China, the United Kingdom, and Australia.

Delhi, projected to be the world’s most  populous  city by 2030, is motivated by a sense of urgency. Facing a growing environmental and health calamity, antipollution efforts are being strengthened. But to succeed, the different levels of government must harness the political will to invest more, coordinate across boundaries, and motivate businesses and residents to do their bit.

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New Delhi’s Air Turns Toxic, and the Finger-Pointing Begins

Schools and factories close. India’s Supreme Court blasts the government’s do-nothing response. But Delhi residents continue to suffer from the bad air.

By Hari Kumar and Emily Schmall

NEW DELHI — A thick blanket of noxious haze has settled over the Indian capital of New Delhi, burning eyes and lungs, forcing schools to close and prompting ardent calls from residents for action.

India’s leaders have responded with what has become an annual tradition: by pointing fingers at one another.

The central government, run by Prime Minister Narendra Modi, is accusing city officials of inaction, and vice versa. The country’s Supreme Court has stepped in to shut down factories and order farmers to stop burning fields. But the court’s other efforts, which last year included ordering the installation of a pair of air-scrubbing filter towers, have been derided as ineffectual .

The airborne murk and the towers stand as symbols of India’s deep political dysfunction. The choking pollution has become an annual phenomenon , and the country’s scientists can accurately predict the worst days. But deep partisanship and official intransigence have hindered steps that could help clear the air.

New Delhi’s residents don’t agree who is at fault, but they agree that more must be done.

“These last three weeks I became a refugee. I was so sick that I couldn’t take it anymore,” said Jai Dhar Gupta, the owner of a business that sells air pollution mitigation tools, such as home air purifier machines and face masks.

Mr. Gupta, who now lives between Delhi and Mussoorie, a city in the foothills of the Himalayas that boasts better air, became an antipollution activist and entrepreneur in 2013, after developing asthma.

“It’s really sad for a nation where every time there is a health emergency the Supreme Court needs to intervene. That tells you everything about the apathy toward the health and life in our country,” said Mr. Gupta. “Nobody cares.”

The court stepped in over the weekend in response to a petition filed by an 18-year-old environmental activist and after the city had endured pollution levels comparable to levels generated by major wildfires . It criticized officials for what it called their “don’t take any step” position.

Earlier this week, Delhi’s emergency measures went into effect. Construction activity, diesel generators and trucks were banned. Schools were closed and employers were asked to keep half of their staffs at home. Six power plants outside New Delhi were ordered shut down.

Under pressure from the court, city officials also deployed other steps that have inspired more jokes than optimism. They include anti-smog guns that create artificial mist, fire trucks to douse the streets with water and chemical dust suppressants.

“These are hardly measures,” said Bhavreen Kandhari, a member of Warrior Moms, a group of mothers lobbying for cleaner air. “These are reactions, knee-jerk reactions. Till you have the political intent, you know nothing is going to happen.”

Broadly, India’s air quality suffers from its appetite for fossil fuels, which has only grown after two decades of rapid economic growth. Last year, India was home to 15 of the 20 cities with the most hazardous air globally , and health experts have detailed how such conditions can lead to brain damage , respiratory problems and early death.

Weaning the country off coal and other dirty fuels will be difficult, a reality underscored by climate negotiations that took place in Glasgow, Scotland, this month. India already struggles to meet its basic power needs. During the Scotland talks, India and China teamed up to insist upon a last-minute amendment to the language of the accord, to “phase down” coal rather than ease it out.

Mr. Modi argues that India’s increasing use of coal and other fossil fuels is helping build an economy that is lifting millions out of poverty. But emissions from burning coal make the pollution problem worse for city dwellers, particularly the poor, who cannot afford air purifier machines or the electricity to run them.

Cities also suffer from growing car emissions and the fires that the poorest residents burn to cook food and keep warm, especially when colder weather hits in November. New Delhi’s air quality takes a particular hit from the burning of crop stubble by farmers in the neighboring states of Punjab and Haryana. The bad air settles over the Indo-Gangetic plain of northern India, trapped on either side by the Thar Desert and the Himalayas, forming a toxic stew.

Mr. Modi’s government says that Delhi, which is run by an opposition political party, has failed to enforce its own pollution-reduction policies, such as a limit on vehicular traffic on days when pollution surges. Earlier this week, Adesh Gupta , the Delhi president of Mr. Modi’s Bharatiya Janata Party, said that Delhi’s top elected official, Arvind Kejriwal, should resign.

“Instead of making Delhi a world-class city as he claimed, Kejriwal has made it a smog city,” Mr. Gupta said.

Delhi officials in turn say Mr. Modi’s government has failed to persuade farmers in nearby states to stop clearing their fields with fires.

“Farmers in neighboring states are compelled to burn stubble as their governments are doing nothing for them,” Mr. Kejriwal said.

The Supreme Court stepped in last year, too, ordering the two sides to take steps like enforcing a ban on farm fires and capturing power plant emissions. It also ordered Delhi early last year to build the two experimental smog towers, despite experts’ doubts about their impact. A study last year in the peer-reviewed journal Atmosphere called the approach unscientific.

“Can we vacuum our air pollution problem using smog towers? The short answer is no,” the researchers said.

Still, they are a tempting refuge for people desperate to escape the city’s bad air.

As a coppery sun set behind smoky skies, Jasmer Singh rested under a smog tower in central Delhi as it sucked in polluted air. A monitor measuring the levels of dangerous particulate matter showed that the air it spit out was slightly cleaner, but far from what the World Health Organization considers safe.

Still, Mr. Singh, a volunteer at a nearby Sikh temple, said, “around here, the air is good, lighter and better.”

Some members of both Mr. Modi’s party and the opposition say they want to take a serious, nonpartisan look at the problem.

“The blame game will be always there,” said Vikas Mahatme, a lawmaker with the B.J.P. Summing up the attitudes of many politicians, he said, “Why one should bother about other states? They are not voters to consider.”

Still, getting all sides to work together will be difficult, he acknowledged. “We are not very active,” he said. “I tell you freely.”

Hari Kumar is a reporter in the New Delhi bureau. He joined The Times in 1997. More about Hari Kumar

Emily Schmall is a South Asia correspondent based in New Delhi. More about Emily Schmall

Air pollution: A case study on the impact of COVID-19 on Delhi city

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Umang Khandelwal , Mayur Shirish Jain , Kunwar Raghavendra Singh; Air pollution: A case study on the impact of COVID-19 on Delhi city. AIP Conf. Proc. 27 July 2023; 2721 (1): 040033. https://doi.org/10.1063/5.0153967

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India is the second most populated country globally and requires massive urban infrastructure. As a result of this rapid growth, air quality in cities has deteriorated. A World Health Organization survey found that 147 males and 136 females per 100,000 persons in India are died by air pollution. In recent times, Delhi, the capital city of India, experienced the worst condition of air pollution. Therefore, different air pollutants were assessed for Delhi city using the Central Pollution Control Boards report in this study. The study indicated that a city’s air quality has considerably beyond the safety limitations of the Central Pollution Control Board. From the study, it is clear that the various activities in the city are causing air pollution, but neighboring towns are equally responsible for it. Countries suffered enormous economic losses due to the COVID-19 shutdown, but air quality improved. Pollution levels fell by half during the shutdown. The Delhi government established an odd/even system and educated the people on the benefits of carpooling to curb air pollution. Recently, smog towers were installed to clear a larger volume of polluted air and supply fresh air to the surrounding community. The study recommends that reducing pollution is not just a government duty, but the general public still plays an important role.

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High-Resolution Mapping of Air Pollution in Delhi Using Detrended Kriging Model

• Published: 27 July 2022
• Volume 28 , pages 39–54, ( 2023 )

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• Md H. Rahman 1 ,
• Shivang Agarwal 1 ,
• Sumit Sharma 1 ,
• R. Suresh 1 ,
• Seema Kundu 1 ,
• Stijn Vranckx 2 ,
• Bino Maiheu 2 ,
• Lisa Blyth 2 ,
• Stijn Janssen 2 ,
• Sousa Jorge 2 ,
• Prashant Gargava 3 ,
• V. K. Shukla 3 &
• Sakshi Batra 3  

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Air quality information is not captured adequately due to limited numbers of air quality monitoring stations across many cities worldwide. Limited studies apply advanced spatial mapping techniques to predict pollutant concentrations in highly polluted regions with high spatial variability. This paper demonstrates an advanced detrending spatial mapping technique to assess the variations of particulate matter concentrations across different land use categories in a highly polluted city—Delhi—and estimate population-weighted average concentrations in the city. The “Detrended Kriging” method uses the city’s monitored datasets and land use information to predict pollutant concentrations. Concentrations are detrended based on high-resolution local land use characteristics and then interpolated using ordinary kriging before retrending again. The model estimates population-weighted concentrations (more important for health exposures) of PM 2.5 (113 µg/m 3 ) and PM 10 (248 µg/m 3 ) for Delhi and finds them to be 21–36% higher than the monitored values in the crucial winter season of 2018. The model demonstrates satisfactory performance on both spatial and temporal scales in Delhi and shows high index of agreement (d = 0.86 for PM 10 and 0.81 for PM 2.5 ), low RMSE (27.3 µg/m 3 for PM 10 and 11.8 µg/m 3 for PM 2.5 ), and low bias (− 1.6 µg/m 3 for PM 10 and − 0.5 µg/m 3 for PM 2.5 ) for the detrended kriging model, in comparison to ordinary kriging (PM 2.5 (d = 0.54, RMSE = 13.81, bias =  − 0.86) and PM 10 (d = 0.33, RMSE = 41.73, bias =  − 4.7)) and inverse distance weighting method (PM 2.5 (d = 0.65, RMSE = 16.08, bias = 2.93) and PM 10 (d = 0.55, RMSE = 46.10, bias = 7.8)). Statistical measure “d” varies between 0 (no agreement) and 1 (perfect match).

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Source: Land-use data was developed through Copernicus Global Land Cover Layers: CGLS-LC100 for 2011 using Landsat Copernicus satellite

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Availability of Data and Material

Dataset used as input is available on the public domain https://app.cpcbccr.com/ccr/#/caaqm-dashboard-all/caaqm-landing/data . The datasets generated during and/or analyzed during the current study are available from the corresponding author on request.

Code Availability

The code/software generated during the current study is available from the corresponding author on reasonable request.

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Acknowledgements

We want to thank Dr. Arindam Dutta for helping prepare charts for Fig.  5 . We would also like to thank Dr. Prateek Sharma, Professor TERI SAS, for his guidance on statistical analysis.

We want to acknowledge and thank the Central Pollution Control Board of India for providing funding support for this work under the EPC grants 201713263.

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TERI, The Energy and Resources Institute, IHC Complex, Lodhi Road, New Delhi, 110003, India

Md H. Rahman, Shivang Agarwal, Sumit Sharma, R. Suresh & Seema Kundu

VITO, Flemish Institute for Technological Research, Boeretang 200, 2400, Mol, Belgium

Stijn Vranckx, Bino Maiheu, Lisa Blyth, Stijn Janssen & Sousa Jorge

Central Pollution Control Board, CPCB, East Arjun Nagar, Delhi, 110032, India

Prashant Gargava, V. K. Shukla & Sakshi Batra

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Conceptualization: Sumit Sharma, Lisa Blyth, Stijn Janssen. Methodology, software: Stijn Vranckx, Bino Maiheu, Writing: Md. H. Rehman, Shivang Agarwal, Sumit Sharma. Data handling: Sousa Jorge, R Suresh, Md. H. Rehman, Shivang Agarwal, V K Shukla, Sakshi Batra. Supervision: Sumit Sharma. Writing—reviewing and editing: Prashant Gargava, Stijn Janssen.

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Correspondence to Sumit Sharma .

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Rahman, M.H., Agarwal, S., Sharma, S. et al. High-Resolution Mapping of Air Pollution in Delhi Using Detrended Kriging Model. Environ Model Assess 28 , 39–54 (2023). https://doi.org/10.1007/s10666-022-09842-5

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Received : 01 June 2021

Accepted : 22 June 2022

Published : 27 July 2022

Issue Date : February 2023

DOI : https://doi.org/10.1007/s10666-022-09842-5

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• Indian J Community Med
• v.38(1); Jan-Mar 2013

“Air pollution in Delhi: Its Magnitude and Effects on Health”

Centre for Community Medicine, All India Institute of Medical Sciences, New Delhi, India

Baridalyne Nongkynrih

Sanjeev kumar gupta.

Air pollution is responsible for many health problems in the urban areas. Of late, the air pollution status in Delhi has undergone many changes in terms of the levels of pollutants and the control measures taken to reduce them. This paper provides an evidence-based insight into the status of air pollution in Delhi and its effects on health and control measures instituted. The urban air database released by the World Health Organization in September 2011 reported that Delhi has exceeded the maximum PM10 limit by almost 10-times at 198 μ g/m3. Vehicular emissions and industrial activities were found to be associated with indoor as well as outdoor air pollution in Delhi. Studies on air pollution and mortality from Delhi found that all-natural-cause mortality and morbidity increased with increased air pollution. Delhi has taken several steps to reduce the level of air pollution in the city during the last 10 years. However, more still needs to be done to further reduce the levels of air pollution.

Pollution refers to the contamination of the earth's environment with materials that interfere with human health, quality of life or the natural functioning of the ecosystems. The major forms of pollution include water pollution, air pollution, noise pollution and soil contamination. Other less-recognised forms include thermal pollution and radioactive hazards. It is difficult to hold any one particular form responsible for maximum risk to health; however, air and water pollution appear to be responsible for a large proportion of pollution related health problems.

Of late, the air pollution status in Delhi has undergone many changes in terms of the levels of pollutants and the control measures taken to reduce them. This paper provides an evidence-based insight into the status of air pollution in Delhi and its effects on health and control measures instituted.

Status of Air Pollution in Delhi

Delhi (or the National Capital Territory of Delhi), is jointly administered by the central and state governments. It accommodates nearly 167.5 lakh people (2011 Census of India).( 1 )

Metros across the world bear the major brunt of environmental pollution; likewise, Delhi is at the receiving end in India.

A study funded by the World Bank Development Research Group was carried out in 1991-1994 to study the effects of air pollution.( 2 ) During the study period, the average total suspended particulate (TSP) level in Delhi was approximately five-times the World Health Organization's annual average standard. Furthermore, the total suspended particulate levels in Delhi during this time period exceeded the World Health Organization's 24-h standard on 97% of all days on which readings were taken. The study concluded that the impact of particulate matter on total non-trauma deaths in Delhi was smaller than the effects found in the United States of America, but found that a death associated with air pollution in Delhi caused more life-years to be lost because these deaths were occurring at a younger age.

A report by the Ministry of Environment and Forests, India, in 1997 reviewed the environmental situation in Delhi over concerns of deteriorating conditions.( 3 ) Air pollution was one of the areas of concern identified in this study. It was estimated that about 3000 metric tons of air pollutants were emitted every day in Delhi, with a major contribution from vehicular pollution (67%), followed by coal-based thermal power plants (12%). There was a rising trend from 1989 to 1997 as monitored by the Central Pollution Control Board (CPCB). The concentrations of carbon monoxide from vehicular emissions in 1996 showed an increase of 92% over the values observed in 1989, consequent upon the increase in vehicular population. The particulate lead concentrations appeared to be in control; this was attributable to the de-leading of petrol and restrictions on lead-handling industrial units. Delhi has the highest cluster of small-scale industries in India that contribute to 12% of air pollutants along with other industrial units.

Vehicular pollution is an important contributor to air pollution in Delhi. According to the Department of Transport, Government of National Capital Territory of Delhi, vehicular population is estimated at more than 3.4 million, reaching here at a growth rate of 7% per annum. Although this segment contributes to two-thirds of the air pollution, there has been a palpable decline compared to the 1995-1996 levels.

The PM 10 standard is generally used to measure air quality. The PM 10 standard includes particles with a diameter of 10 μm or less (0.0004 inches or one-seventh the width of a human hair). These small particles are likely to be responsible for adverse health effects because of their ability to reach the lower regions of the respiratory tract. According to the Air Quality Guideline by the World Health Organization, the annual mean concentration recommended for PM 10 was 20 μg/m 3 , beyond which the risk for cardiopulmonary health effects are seen to increase.( 4 ) Major concerns for human health from exposure to PM 10 include effects on breathing and respiratory systems, damage to lung tissue, cancer and premature death. Elderly persons, children and people with chronic lung disease, influenza or asthma are especially sensitive to the effects of particulate matter. The urban air database released by the World Health Organization in September 2011 reported that Delhi has exceeded the maximum PM 10 limit by almost 10-times at 198 μg/m 3 , trailing in the third position after Ludhiana and Kanpur.( 5 ) Vehicular emissions and industrial activities were found to be associated with indoor as well as outdoor air pollution in Delhi [ Table 1 ].( 6 – 9 )

Air pollutants in Delhi

Effects of Air Pollution on Health

A large number of studies in Delhi have examined the effect of air pollution on respiratory functions and the associated morbidity. The most comprehensive study among them was the one conducted by the Central Pollution Control Board in 2008, which identified significant associations with all relevant adverse health outcomes.( 10 ) The findings were compared with a rural control population in West Bengal. It was found that Delhi had 1.7-times higher prevalence of respiratory symptoms (in the past 3 months) compared with rural controls ( P < 0.001); the odds ratio of upper respiratory symptoms in the past 3 months in Delhi was 1.59 (95% CI 1.32-1.91) and for lower respiratory symptoms (dry cough,wheeze, breathlessness, chest discomfort) was 1.67 (95% CI 1.32-1.93). Prevalence of current asthma (in the last 12 months) and physician-diagnosed asthma among the participants of Delhi was significantly higher than in controls. Lung function was reduced in 40.3% individuals of Delhi compared with 20.1% in the control group. Delhi showed a statistically significant ( P < 0.05) increased prevalence of restrictive (22.5% vs. 11.4% in control), obstructive (10.7% vs. 6.6%) as well as combined (both obstructive and restrictive) type of lung functions deficits (7.1% vs. 2.0%). Metaplasia and dysplasia of airway epithelial cells were more frequent in Delhi, and Delhi had the greater prevalence of several cytological changes in sputum. Besides these, non-respiratory effects were also seen to be more in Delhi than in rural controls. The prevalence of hypertension was 36% in Delhi against 9.5% in the controls, which was found to be positively correlated with respirable suspended particulate matter (PM 10 ) level in ambient air. Delhi had significantly higher levels of chronic headache, eye irritation and skin irritation.

Several other community-based studies have found that air pollution is associated with respiratory morbidity.( 11 – 13 ) Numerous studies have reported an association between indoor air pollution and respiratory morbidity.( 14 – 19 )Some of these studies have concentrated on children's respiratory morbidity.( 15 , 17 , 19 ) Other studies in children have found similar correlations between particulate matter in ambient air and attention-deficit hyperactivity disorder( 20 ) between vehicular air pollution and increased blood levels of lead (a potential risk factor for abnormal mental development in children)( 21 ) and between decreased serum concentration of vitamin D metabolites and lower mean haze score (a proxy measure for ultraviolet-B radiation reaching the ground).( 22 )

Studies that have examined the compounding effect of meteorological conditions on air pollution found that winter worsened the air quality of both indoor air and outdoor air. They also found a positive correlation between the winter weather and rise in the number of patients with chronic obstructive airway disease in hospitals.( 12 , 16 )

There was a relative paucity of studies that measured outdoor air pollutant levels first hand and then tried to objectively correlate them to adverse health effects. However, some studies measured air pollutant levels and found a correlation with health-related events.( 17 , 19 )

A time-series study on air pollution and mortality from Delhi found that all-natural-cause mortality increased with increased air pollution.( 23 ) In another study, gaseous pollutants, in spite of being at a level lower than the permissible level, showed more consistent association with respiratory admissions.( 24 ) In a hospital-based study, an increase in emergency room visits for asthma, chronic obstructive airway disease and acute coronary events was reported with an increase in air pollutant levels.( 25 ) These studies are summarized in Table 2 .

Effects of air pollution in Delhi on health

Control Measures Instituted by the Government of Delhi

The nodal ministry for protecting the environment is the Ministry of Environment and Forests at the Centre and the Department of Environment of the Government of National Capital Territory of Delhi. The Central Pollution Control Board set up in 1974 under the Water Act is the principal watchdog for carrying out the functions stated in the environmental acts, implementation of National Air Quality Monitoring Programme and other activities. The Delhi Pollution Control Board is the body responsible at the state level.

From time to time, the judiciary has taken strong note of the deteriorating environmental conditions in Delhi in response to public litigations. One of the earliest such instances was the judgement passed by the Supreme Court of India to deal with the acute problem of vehicular pollution in Delhi in response to a writ petition filed in 1985. Subsequently, it ordered the shutdown of hazardous, noxious industries and hot-mix plants and brick kilns operating in Delhi.

Vehicular Policy

Control measures so far instituted include introduction of unleaded petrol (1998), catalytic converter in passenger cars (1995), reduction of sulfur content in diesel (2000) and reduction of benzene content in fuels (2000). Others include construction of flyovers and subways for smooth traffic flow, introduction of Metro rail and CNG for commercial transport vehicles (buses, taxis, auto rickshaws), phasing out of very old commercial vehicles, introduction of mandatory “Pollution Under Control” certificate with 3-month validity and stringent enforcement of emission norms complying with Bharat Stage II/Euro-II or higher emission norms. Introduction of The Air Ambience Fund levied from diesel sales and setting up of stringent emission norms for industries and thermal power stations are the other measures. Environmental awareness campaigns are also carried out at regular intervals. The Delhi Pollution Control Board conducts monthly Ambient Air Quality Monitoring at 40 locations in Delhi, and takes corrective action wherever necessary.

Industrial Policy

The first Industrial Policy for Delhi was introduced in 1982. Subsequently, a second Industrial policy (2010–2021) was issued by the Department of Industries, Government of Delhi. It is a comprehensive document envisioning higher industrial development in Delhi, with one of its mandates being to develop clean and non-polluting industries and details of steps to be undertaken in this direction have been described.

There are many other organizations that work synergistically with the government efforts to reduce air pollution. These include the Centre for Science and Environment and The Energy and Resources Institute, and the Indian Association for Air Pollution Control. Representatives of the industries include Confederation of Indian Industry and Society of Indian Automobile Manufacturers. Government agencies like Factories Inspectorate are also involved in the control of pollution. Research and academic institutions include National Environmental Engineering Research Institute, Indian Institute of Technology, Council of Scientific and Industrial Research institutions, Indian Agricultural Research Institute and various other academic institutions in and around Delhi. Professional organizations like the Indian National Science Academy, the Indian Institute of Chemical Engineers and the Indian Institute of Engineers are also involved in pollution control.

Benefits Accrued as a Result of Control Measures

Since the first act on pollution was instituted, huge progress has been made in terms of human resource, infrastructure development and research capability. Some studies tried to gather evidence for the effectiveness of control measures by comparing pre- and post-intervention health status. The study conducted by the Central Pollution Control Board demonstrated that spending 8-10 h in clean indoor environment can reduce health effects of exposure to chronic air pollution.( 10 ) A recent study found significant improvement in the respiratory health following large-scale government initiatives to control air pollution.( 26 ) It was reported that use of lower-emission motor vehicles resulted in a significant gain in disability-adjusted life-years in Delhi.( 27 ) Another study found significant evidence for reduction in respiratory illness following introduction of control measures.( 24 )

Most of the studies were ecological correlation studies, which are severely limited in their ability to draw causal inferences. But, considering the context that demanded the research, these were probably the best available designs to produce preliminary and,sometimes, policy-influencing evidences, as any other methodology would be unethical or operationally impossible.

The Government of National Capital Territory of Delhi has taken several steps to reduce the level of air pollution in the city during the last 10 years. The benefits of air pollution control measures are showing in the readings. However, more still needs to be done to further reduce the levels of air pollution. The already existing measures need to be strengthened and magnified to a larger scale. The governmental efforts alone are not enough. Participation of the community is crucial in order to make a palpable effect in the reduction of pollution. The use of public transport needs to be promoted. The use of Metro rail can be encouraged by provision of an adequate number of feeder buses at Metro stations that ply with the desired frequency. More frequent checking of Pollution Under Control Certificates needs to be undertaken by the civic authorities to ensure that vehicles are emitting gases within permissible norms. People need to be educated to switch-off their vehicles when waiting at traffic intersections. Moreover, the “upstream” factors responsible for pollution also need to be addressed. The ever-increasing influx of migrants can be reduced by developing and creating job opportunities in the peripheral and suburban areas, and thus prevent further congestion of the already-choked capital city of Delhi.

Health, as we all know, is an all-pervasive subject, lying not only within the domains of the health department but with all those involved in human development. Many great scholars from Charaka to Hippocrates have stressed the importance of environment in the health of the individual. Therefore, all those who play a role in modifying the environment in any way, for whatever reason, need to contribute to safeguard people's health by controlling all those factors which affect it.

Source of Support: Nil

Conflict of Interest: None declared.

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