Story by Soumya Pillai
Produced by Soham Sen, Shruti Naithani, Wasif Khan, and Prashant; Photographs by Manisha Mondal
(1/11/2024)
Delhi's pollution re-run has begun.
People gasping for air. Schools announcing emergency closures. Expats and migrants fleeing to other cities. Hospital emergency rooms choking with patients. Air quality levels climbing sharply. The same story plays out every year from October to December after the monsoon season.
The Diwali festivities, marked by firecrackers, have added to the cloud of pollution enveloping the city. Needles on air quality monitors climbed rapidly, with many stations maxing out. The air quality index (AQI) recorded by the Central Pollution Control Board (CPCB) clocked 328 on Thursday and increased to 339 the day after.
But the causes of Delhi’s pollution are not just crackers and construction activities. The culprits include the unholy trifecta of stubble burning in Haryana and Punjab, the onset of winter winds carrying dust from the Thar Desert, and dropping temperature that trap particulate matter in the air.
ThePrint looks at how and why Delhi is vulnerable every year. It’s the annual ritual of masks and air purifiers.
Dry north-westerly winds
By mid-October every year, the winds over Delhi shift, announcing the onset of winter in northwest and centraBy mid-October every year, the winds over Delhi shift, announcing the onset of winter in northwest and central India.
Mahesh Palawat, vice-president of meteorology and climate change at SkyMet Weather, a private weather forecasting agency, explained that as the monsoon retreats from northwest India around October, wind direction changes from easterly to north-westerly.
During the monsoon, winds from the Bay of Bengal carry moisture and rainfall to northwest India, effectively washing away accumulated pollutants. However, as the monsoon withdraws, the wind speed decreases, and the north-westerly winds are dry.
“From October, the winds that blow over Delhi-NCR come from Pakistan, Punjab, and Haryana. These winds are not strong enough to disperse pollutants generated in the region,” Palawat said.
Additionally, October coincides with the harvest season in Haryana and Punjab, where farm fires release smoke that is carried by these winds to Delhi.
As temperatures fall, the inversion height—an atmospheric layer beyond which pollutants cannot disperse—lowers, worsening the pollution problem. RK Jenamani, a senior scientist at the India Meteorological Department (IMD), illustrated this with a classroom analogy, imagining students as pollution particles.
“While the same number of students can move around and play freely in a larger classroom, when the classroom size shrinks, they look more packed and have difficulty moving freely.” That’s what happens in winter.
Delhi's winter winds
Conditions worsen as the season progresses. By December, Delhi-NCR receives minimal direct sunlight, which is essential for air circulation and pollution dispersion.
Scientists from the Indian Institute of Tropical Meteorology (IITM) in Pune, which also operates the Delhi government’s air quality monitoring platform Decision Support System, explained that when the atmosphere heats up under the sun, it promotes vertical movement, helping pollutant dispersion. Without sunlight, pollutants get trapped near the surface, increasing pollution levels.
“It is a vicious cycle,” said an official. “If there is no sunlight, the atmosphere does not heat up and pollutants do not get dispersed. When pollution rises, a layer is formed around the city, blocking the sunlight, further raising pollution levels.”
Firecrackers
In September, the Delhi government announced a complete ban on firecrackers, including ‘green’ varieties, until 1 January 2025. This has been the standard practice since 2017 but is wilfully flouted. This Diwali was no exception.
“For many, Diwali would be a night of celebration and cracker-bursting, but many residents are left gasping for breath through no fault of their own. We are putting the lives of our children at risk,” said Bhavreen Kandhari, co-founder of Warrior Mom, a network advocating for clean air.
Firecrackers release particulate matter (PM10 and PM 2.5), sulphur dioxide, nitrogen oxides, and carbon monoxide into the atmosphere. These emissions linger long after Diwali. Ultrafine particulate matter, with a diameter of less than 2.5 micrometres, can escape the body’s natural filtration system and clog internal organs.
As the cracker-bursting intensified this festive season, Kandhari, a resident of Defence Colony in South Delhi, started panicking. Her air purifier was unable to cope with the dangerously high pollution levels outside. She frantically rang the helpline numbers of the Delhi Police and Delhi Pollution Control Committee (DPCC) to report the illegal use of firecrackers, but her calls went unanswered.
Environmental experts highlighted that Delhi has consistently failed to implement effective plans to control the annual spike in pollution. They argue that agencies have focussed on reactive measures rather than proactive solutions.
“If you look at data from the last few years, there has been a year-on-year reduction in pollution levels in Delhi every winter season. But this reduction is slow and not enough when the health of residents is at stake. Agencies need to focus on long-term solutions instead of acting only when pollution levels start rising,” said Anumita Roychowdhury, executive director of research and advocacy at the Centre for Science and Environment.
Graphic by Soham Sen
Graphic by Soham Sen
External factors
Mahendra Singh, a farmer in Punjab’s Malerkotla district, tightly secured his mouth and nose with a piece of cloth as he inspected the stubble standing in the field.
And then he set the stubble on fire.
Within minutes, the fire spread through the fields, engulfing him in a cloud of thick, black smoke.
“Pollution is a problem only in Delhi,” he said, and started coughing. His eyes have turned red from the exposure and the skin on his arms is sore.
These fumes will travel over 300 kms to reach Delhi, choking its residents for weeks.
Despite efforts by the central and state governments to promote mechanised alternatives like Rotavators and Happy Seeders, many farmers in Punjab, Haryana, and western Uttar Pradesh opt for burning stubble left after harvest as a quick, cost-effective solution.
Data from the Union environment ministry indicates a decline in stubble fires in Punjab and Haryana. In 2023, Punjab reported 36,663 stubble fires, down from 49,922 in 2022. Similarly, Haryana recorded only 2,303 stubble fires in 2023, down from 3,661 in 2022.
Graphic by Soham Sen
Graphic by Soham Sen
However, stubble burning is not the only source of cross-border pollution affecting Delhi. Industrial fumes from Haryana and Uttar Pradesh are major factors as well. A 2018 study by The Energy Resources Institute (TERI) estimated that industries account for nearly 27 per cent of PM10 and 30 percent of PM 2.5 levels in Delhi during winter.
Internal sources
Delhi has its own pollution sources—vehicular emissions, dust from construction, unpaved roads, and open burning of waste. These pollution sources keep Delhi’s ambient air pollution high year-round.
A joint study by IIT-Kanpur, IIT-Delhi, and TERI revealed that vehicular emissions alone accounted for nearly 36 per cent of the city’s PM 2.5 in summer and 30 per cent in winter. The contribution of construction and road dust was around 15-20 per cent in winter.
The Centre for Science and Environment analysed PM2.5 concentration levels from 15 September to 28 October in the ‘pre-Diwali’ period, and found that stubble burning in Haryana and Punjab is responsible for less than 5 per cent of Delhi’s air pollution. Other sources that contributed significantly were waste burning, construction, and industry emissions.
During winter, temporary sources like open bonfires, open kitchens, and tandoors also start contributing to the high levels of pollution.
“Delhi has a high baseline pollution; we saw that during the Covid-19 lockdown. The government must adopt solutions that discourage people from using private vehicles and move to public transport systems. There needs to be a behavioural change in the community as well,” said Roychowdhury.
A recent study by CSIR-National Environmental Engineering Research Institute noted that the baseline pollution for Delhi is 20–36 microgram per metre cube (ug/m3) for PM2.5 and 12–63 ug/m3 for nitrogen oxide.
Delhi's pollution plan is a failure
The government has failed Delhi. The Supreme Court has pulled up both state and central governments for their myopic vision and making environment protection laws toothless.
Reiterating that the right to clean air is essential to the right to life, the apex court has also criticised the Commission for Air Quality Management (CAQM) for its meekness in coordinating between states, implementing effective strategies, and penalising polluters.
“Please tell your chairperson of CAQM not to bail out these officials. We know what is happening on the ground,” the bench said, referring to the commission’s soft approach on penalising state government officials responsible for controlling stubble fires.
Efforts such as anti-smog guns, water sprinkling, and smog towers have proven ineffective in dispersing pollutants. Authorities are now considering cloud seeding as a solution.
An anti-smog gun near India Gate | Photo: Suraj Singh Bisht | ThePrint
An anti-smog gun near India Gate | Photo: Suraj Singh Bisht | ThePrint
Environmentalists argue that the focus has been on short-term fixes such as the Graded Response Action Plan (GRAP) rather than permanent solutions.
“When pollution levels rise, the government agencies sprinkle water on roads. Is that a permanent solution? Even a common citizen can see the lack of vision in the government’s pollution management plan,” said Vimlendu Jha, a Delhi-based environmentalist.
At Anand Vihar in New Delhi | Photo: Manisha Mondal | ThePrint
At Anand Vihar in New Delhi | Photo: Manisha Mondal | ThePrint
As November approaches, 72-year-old Rajneesh Saha, a chronic asthmatic, has started packing his bags. He’s going to escape the winter pollution by travelling to Bengaluru where his son lives. The southern city’s notorious traffic is a lesser evil.
“My asthma has worsened over the years, and my doctors advise me to take a break from Delhi during winter. My ageing organs cannot take this load,” said Saha.
Edited by Prashant
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