Helena Joyce
Delhi, India's capital, has been dubbed the world's most polluted city for years, with its 30 million residents suffering from its catastrophic health impacts. The city's air quality is affected by a range of factors, including vehicular emissions, industrial pollution, crop burning, waste burning, and construction. Vehicular emissions, including cars, scooters, and auto-rickshaws, are a major contributor to Delhi's air pollution, with slow winds and cool temperatures in the winter trapping dust and pollutants, forming smog. Industrial pollution, primarily from power plants, contributes significantly to particulate matter pollution. Crop burning by farmers in neighbouring states, such as Punjab, Haryana, and Uttar Pradesh, also plays a role in Delhi's pollution, as the wind carries the pollutants and dust particles. Waste burning, including garbage and agricultural waste, adds to the city's air pollution, and large-scale construction activities increase dust and pollution levels.
| Characteristics | Values |
|---|---|
| Vehicular emissions | 72% of total air pollution |
| Industrial emissions | 52% of NOx emissions, 90% of SO2 emissions |
| Crop burning | 45% of Delhi's pollution during crop-burning season |
| Stubble burning | 30% of Delhi's pollution during early winter |
| Solid fuel combustion | Predominantly fuel woods, cow dung cakes, crop residues, and municipal solid waste |
| Road dust | 56% of PM10 pollution |
| Construction | Large-scale construction increases dust and pollution |
| Overpopulation | Increases all types of pollution |
| Poor public infrastructure | Low investment in public transport leads to congested roads |
| Garbage dumps | Burning of garbage contributes to smog |
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What You'll Learn
Vehicular emissions
Vehicles contribute to both PM2.5 and PM10 pollution. Of PM2.5 pollution, 20% comes from vehicles, while 9% of PM10 pollution is from vehicles. Of NOx emissions, 36% came from vehicles, and of CO emissions, 83% came from vehicles.
During the winter months, slow winds and cool temperatures trap dust and pollutants closer to the ground, forming smog. This is exacerbated by the burning of firecrackers during Diwali, as well as stubble burning and increased heating requirements during this period. Visibility is often so bad during this time that famous monuments are reduced to smoky blurs on the horizon. The poor visibility has resulted in accidents, notably a 24-vehicle pile-up on the Yamuna Expressway.
To combat the issue of vehicular emissions, the Delhi government has implemented odd-even number plate rules on alternate days, and banned highly polluting vehicles from the roads during high pollution periods. However, the effectiveness of these measures has been questioned, and the metro and bus systems are seen as poorly connected and expensive, giving few incentives for residents to opt for public transport over private vehicles.
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Crop burning
The impact of crop burning on Delhi's air quality varies depending on wind speed and direction. During the crop-burning season, it can account for up to 45% of the city's pollution, with the smoke mixing with fog, dust, and industrial pollution to form a thick haze. In 2017, for instance, smoke from crop residue burning in Punjab and Haryana blew across northern India, leading to elevated pollution levels in several major cities, including Delhi.
The problem of crop burning in India has gained national and international attention, with NASA noting a significant increase in agricultural fires in recent years. This has prompted states like Rajasthan, Punjab, and Haryana to impose fines on farmers who engage in crop burning. The Indian government has also attempted to address the issue through initiatives promoting sustainable management practices, such as converting crop residue into energy.
However, farmers argue that they lack effective alternatives due to the absence of adequate sustainable management practices and support from the government. The tight schedule of the harvest-to-sowing transition under the rice-wheat rotation cropping system in northwestern India further limits the adoption of alternatives. As a result, crop burning persists as a recurring issue, contributing to both environmental degradation and public health crises, especially with the added vulnerability posed by the COVID-19 pandemic.
While crop burning is a significant factor in Delhi's air pollution, it is important to recognize that it is not the sole cause. Other sources, such as vehicular emissions, industrial pollution, road dust, and waste burning, also play a significant role. Treating pollution as solely a seasonal and geographically restricted issue is detrimental to finding a comprehensive solution. A multifaceted approach targeting various sources of pollution is necessary to effectively tackle Delhi's air pollution crisis.
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Industrial pollution
One of the primary sources of industrial pollution in Delhi is the power generation sector. The Badarpur Thermal Power Station, a coal-fired power plant, was a major source of particulate matter pollution, contributing 80-90% of such pollution from the electric power sector in Delhi. While the plant has been shut down since 2018 due to its detrimental environmental impact, the broader power generation sector, including coal-burning power plants, continues to be a significant source of pollution.
In addition to power plants, industrial activities such as factories and construction contribute to Delhi's air pollution. The construction sector, including brick kilns, has been identified as a source of pollution, particularly during the crop-burning season. The use of diesel generators in the construction sector also adds to air pollution levels.
Another significant source of industrial pollution in Delhi is vehicle emissions. While private vehicles like cars, scooters, and auto-rickshaws are major contributors, heavy-duty vehicles like trucks and buses also play a role. Court-ordered restrictions on bus services in Delhi have inadvertently contributed to increased private vehicle ownership and road construction, exacerbating vehicle emissions.
Furthermore, industrial activities in residential areas have been identified as sources of pollution. In 2024 and 2025, surprise inspections in East Delhi found several industrial units violating environmental norms, including discharging untreated, highly toxic, and carcinogenic effluents into the Yamuna river. These units were engaged in activities such as electroplating and metal processing, operating in densely populated residential zones without adequate pollution control measures.
The cumulative impact of these industrial sources of pollution has severe health consequences for Delhi's residents. Research has linked air pollution to irreversible lung damage, weakened immune systems, and increased risks of cancer, epilepsy, diabetes, and other serious illnesses.
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Solid fuel combustion
The health implications of solid fuel combustion are severe. The World Health Organization (WHO) estimates that indoor smoke inhalation from solid fuels may cause approximately 1.6 million premature deaths globally each year. In India, environmental and occupational risk factors contribute to nearly 40% of the national disease burden, with indoor and outdoor air pollution ranking as leading risk factors. The impact of solid fuel combustion on respiratory health has been documented in studies conducted in Nepal and India since the mid-1980s, with a focus on women and children who are often exposed during cooking.
In Delhi specifically, solid fuel combustion contributes to the city's poor air quality. While 90% of Delhi's households use LPG for cooking, the remaining 10% rely on wood, crop residue, cow dung, and coal, contributing to domestic fuel burning emissions. During the winter, when heating demands increase, the burning of local organic waste, including wood and cow dung cakes, further exacerbates air pollution, with a 2023 study attributing 24% of PM2.5 concentrations in Delhi to this practice.
The impact of solid fuel combustion on Delhi's air pollution is also evident during the crop-burning season, when farmers burn crop stubble, contributing up to 30-50% of the city's pollution during the early winter period. This practice, along with biomass burning for heating, significantly affects Delhi's air quality. The collaboration between IIT Delhi and IIT Kanpur highlights biomass burning as the primary cause of Delhi's air pollution after the festivals of Vijayadashami and Diwali.
To address the issue of solid fuel combustion in Delhi, authorities have implemented various measures. The Pusa Bio-decomposer initiative aims to help farmers avoid stubble burning by providing alternative crop options. Additionally, the Delhi Metro is transitioning to solar energy, and the government has banned older diesel and petrol vehicles while introducing stricter emission standards for combustion engines. These efforts reflect a recognition of the health emergency posed by air pollution and a commitment to improving air quality in Delhi.
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Firecrackers
Delhi has been dubbed the most polluted city in the world, with air pollution causing irreversible lung damage in 2.2 million children. The city's pollution is caused by a range of factors, including road dust, vehicles, industrial point sources, and domestic fuel burning. One significant contributor to Delhi's poor air quality is the burning of firecrackers during the religious festival of Diwali, which falls within the winter months of October to January.
The burning of firecrackers during Diwali has been linked to a small but statistically significant increase in air pollution in Delhi. Studies have shown that firework emissions negatively impact air quality, with SO2 concentrations found to be significantly higher during and after the festival. The metals released by firecrackers also contribute to heavy air pollution. The impact of firecrackers on air quality varies across different locations within Delhi, with the pollution worsening in the aftermath of the festival as particles remain suspended in the air for longer due to low temperatures, wind speed, and high relative humidity.
To combat the issue of firecracker pollution, the Delhi government has implemented a range of measures. In 2016, the government restricted cars on roads on certain days, known as the odd-even rule, and temporarily shut down schools and power plants. More recently, in October 2024, the Delhi Pollution Control Committee announced a complete ban on the manufacturing, storage, selling, and bursting of all types of firecrackers until January 1, 2025. This ban was imposed to curb the increasing pollution levels in the city, particularly during the winter months when air quality deteriorates due to various factors, including firework usage.
The firecracker ban in Delhi has sparked discussions about the root causes of air pollution and the need for regulatory interventions. Avinash Chanchal, deputy programme director at Greenpeace South Asia, emphasized that air pollution in Delhi is a year-round issue, not just a seasonal or farmer-related problem. He pointed out that transportation, power plants, waste burning, and construction also contribute significantly to the city's poor air quality. Sunil Dahiya, founder of Envirocatalysts, echoed similar sentiments, calling for stricter regulations on big polluting industries, such as coal-fired power stations and steel plants.
While the firecracker ban in Delhi is a step towards improving air quality, it is essential to address the various other sources of pollution in the city. By tackling the root causes and implementing effective measures, Delhi can work towards reducing the catastrophic health impacts of air pollution on its residents.
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Frequently asked questions
Delhi's pollution has multiple sources, including vehicular emissions, industrial pollution, crop and stubble burning, and waste burning. Vehicular emissions alone contribute about 72% of the total air pollution in Delhi.
According to a 2016 study, the main sources of PM2.5 pollution in Delhi are road dust (38%), vehicles (20%), domestic fuel burning (12%), and industrial sources (11%). For PM10 pollution, 56% comes from road dust, 10% from concrete batching, 10% from industrial sources, and 9% from vehicles.
During the crop-burning season, the practice can account for up to 45% of Delhi's pollution. Farmers in neighbouring states burn rice stubbles, and the wind carries the pollutants and dust particles into Delhi.
