Explaining Northern India's Oppressive Smog

Explaining Northern India's Oppressive Smog

By Mukila Maitha


Hazy skies. Indira Gandhi International Airport, New Delhi. December 27, 2019.

Mukila Maitha, Associate Professor of Geography at Harper College in Palatine, Illinois, was a 2020 participant in the CAORC-AIIS Faculty Development Seminar to India. In this essay, he examines the factors behind Delhi’s suffocating smog and what is being done to lessen its impact. All photos provided by the author unless otherwise noted.


When introducing the study of atmospheric processes, I often ask students why they think this topic is important to study. One of the top reasons given is because atmospheric pollutants can have adverse effects on human health and structures. The nature of air pollution and the environmental factors that affect pollutants, such as winds, topography, and temperature inversions, are a regular part of my physical geography courses. Little did I know, prior to being accepted on this program, that I would have the opportunity of being immersed in some of the world’s most polluted air. In spite of some trepidation, due to seasonal allergies, my excitement about visiting India was undiminished.


Blue skies over the Hindu Kush Mountains. December 27, 2019.

As a roughly 16-hour flight from Chicago concluded on December 27, 2019, the route took us over the stunningly rugged Hindu Kush Mountains, under gorgeous blue skies. As the plane began to descend into New Delhi’s Indira Gandhi International Airport, the blue skies transitioned to a tan tint due to the haze that had smothered northern India since October. Early November had been particularly bad with flight cancellations in New Delhi, driving local authorities to impose restrictions to curb what a senior government official referred to as “gas-chamber” pollution.

The hazy, polluted skies over Delhi and other cities across northern India are caused to a great extent by the large scale burning of rice and wheat residues in the states of Punjab and Haryana in late October and early November. Other major contributors include urban industrial activities, dust, waste incineration, fireworks from the annual Diwali festival, and vehicle emissions. Meteorological conditions and the topography of the region conspire to hold pollutants in place over long periods of time during the winter months. During the winter, cold air descends over the Hindu Kush and Himalayan Mountains into the Indo-Gangetic Plain. This colder air displaces and gets trapped beneath warmer air creating a temperature inversion. This trapped air can then absorb pollutants over long periods of time.

In 2019, Delhi’s air pollution was reported as the worst in the world. Using the U.S. Environmental Protection Agency’s Air Quality Index (AQI), New Delhi air quality for the month of December 2019 was classified as “Very Unhealthy” based on hourly measurements taken throughout the month.

Hazy Skies. Janpath Rd, Connaught Place, New Delhi. December 30, 2019.
Less haze. Janpath Rd, Connaught Place, New Delhi. January 1, 2020.



We learned during one of the seminar's lectures that air quality over northern India severely worsened after regulations to control groundwater depletion in Punjab and Haryana were enacted in 2009, which delayed the transplanting of rice after the onset of the monsoons. This, in turn, delayed rice harvests and intensified the burning of field residues, as eager farmers began preparing their fields to plant winter wheat. The timing of residue burning shifted to a later period of time with lower temperatures and wind speeds, which facilitated the accumulation of particulate matter from residue burning in the lower atmosphere. Laws outlawing the practice of crop burning have been in place for many years, but enforcement has been weak in a country that is the world’s second largest rice producer.

Particulate matter masks turned out to be an essential travel accessory.

Delhi’s pollution haze contains particulate matter (PM10 and PM 2.5) and various trace gases, including nitrogen oxides (NOx), sulfur oxides (SOx), and carbon monoxide (CO) which can adversely affect human health. A range of respiratory and eye irritations and illnesses can arise from exposure to air that contains these substances and the effects are often more severe for young children and persons with compromised immune systems or respiratory conditions.

Smoggy skies and evening rush hour traffic. New Delhi.

Long-term exposure to fine particulate matter could lead to chronic bronchitis, and increased risk of heart disease and lung cancer. According to a study published in 2018, every Indian state had ambient concentration levels that exceeded those recommended by the World Health Organization. The ambient levels varied geographically, with the highest levels in the states of Bihar, Uttar Pradesh, Rajasthan, Jharkhand, Delhi, Haryana, and Punjab.

Recognizing the need for coordinated action across state boundaries, economic sectors, and broad segments of society, the Government of India launched the National Clean Air Programme (NCAP) in early 2019. This provided a collaborative framework through which states and large city governments could work together to set air pollution control targets and address regional issues such as agricultural residue burning. This program required cities to develop Clean Air Plans (CAPs) that contained mitigation measures. The measures identified in Delhi’s CAP include restrictions on older vehicles, increasing the use of Compressed Natural Gas (CNG) and electric vehicles in public transportation, implementing emission standards for power plants, limiting the use of diesel generators, and introducing construction dust control measures.


Yellow truck powered by Compressed Natural Gas (CNG), which pollutes less than gasoline, in New Delhi traffic.

Additional actions to tackle air pollution include innovations that reduce or eliminate emissions, such as a device created by Delhi-based Chakr Innovation that removes particulate matter from exhaust air, the Punjab Agricultural University’s tractor-mounted planter that sows seeds without the need to remove and burn stubble, and solar-powered ferry and electrical boats built by NavAlt to reduce transportation emissions. The use of particular household plants has been promoted as a relatively low cost and environmentally friendly measure for improving indoor air quality. Concerted efforts by government, the private sector, and civil society should lead to significant decreases in air pollution that mirror the recent and earlier experiences of Beijing, China, and Los Angeles in the United States.

CAORC’s 2020 faculty development seminar to India was organized with the American Institute of Indian Studies and supported by the U.S. Department of State’s Bureau of Educational and Cultural Affairs and the following U.S. National Resource Centers in South Asian Studies: Columbia University, Cornell University, Syracuse University, University of California, Berkeley, University of Washington, and University of Wisconsin, Madison.

Learn more about CAORC Faculty Development Seminars.

About the Author

Mukila Maitha is Associate Professor of Geography at Harper College in Palatine, Illinois. He was among 16 faculty participants in the seminar “Exploring Urban Sustainability through India’s Cities,” an intensive capacity-building and curriculum development seminar held in India from December 26, 2019–January 10, 2020.


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