Delhi's Air Pollution: A Crisis Unveiled

New Delhi, India's capital and a major commercial and economic powerhouse, has been facing severe air pollution, becoming the most polluted city in the world. In November 2024, the city's air quality deteriorated to hazardous levels, with a 24-hour AQI reading of 491, causing a public health crisis. The primary sources of pollution include stubble and crop burning, vehicular emissions, industrial pollution, and construction. The low wind speeds and temperature inversions in New Delhi trap smoke and emissions, exacerbating the problem. The government has implemented various measures to combat pollution, including banning older vehicles, regulating dust, and providing health advisories. However, the annual crisis persists, and the government faces criticism for its slow response.

Stubble burning and crop residue burning

Stubble burning is a major contributor to New Delhi's air pollution problem. It occurs when farmers burn the stubble, or leftover straw, from their paddy fields to clear the soil for the next crop. This practice creates a massive public health crisis, as the fumes pollute the air and endanger the health of people living in northern India, including New Delhi. In 2020, it was estimated that farmers in northern India burn about 23 million tonnes of paddy stubble each year. The smoke from stubble burning can travel as far as 250km, adding to the toxic haze hanging over the city.

While the Indian government has tried to stop stubble burning by offering alternative technologies, such as the Happy Seeder, a machine that removes paddy straw while sowing wheat for the next harvest, some farmers say they cannot afford the cost of these machines, which can be as much as $15,000. In addition, the machines require a tractor to work, and there can be long wait times and dwindling stock. As a result, some farmers feel they have no choice but to continue burning their stubble.

The share of stubble burning in New Delhi's pollution can range from 1% to 42%, depending on wind speed and direction. In 2020, the average contribution of stubble burning to the city's pollution grew to 15%, up from 10% in 2019. To address this issue, the government of Punjab launched the MSP scheme, which provides incentives for alternative crops to reduce stubble burning. The Nature Conservancy is also working to help farmers extinguish agricultural fires and improve their soil health.

In addition to these efforts, some experts have suggested tackling the issue at its root by subsidizing crops other than paddy, which is the source of most stubble burning. By incentivizing farmers to plant more fruits and vegetables, India could increase its vitamin and protein intake while also reducing the number of open fires. This approach would also create more greenery, further improving air quality.

Stubble burning is not the only source of New Delhi's air pollution. Other factors include vehicular emissions, industrial pollution, dust, incineration, and wood, cow dung, and landfill fires, especially during the colder months. However, stubble burning remains a significant contributor to the city's poor air quality and a pressing issue that requires a combination of short-term and long-term solutions.

Vehicular emissions

New Delhi, the capital of India, has been dubbed the most polluted city in the world. The city's air quality levels are a severe health risk, with low wind speeds and temperature inversions trapping smoke and emissions, creating long-lasting smog.

The high levels of vehicle emissions in New Delhi are due in part to a court-ordered restriction on bus services, which has led to an increase in private car usage and road construction. In 2021, New Delhi recorded PM2.5 levels as high as 339.5 μg/m³, a level that is extremely dangerous. The city's air quality index (AQI) has been consistently in the \"unhealthy\" to \"poor\" range, with lower readings still averaging 100 to 130 μg/m³, indicating a persistent issue with air pollution.

To combat vehicular air pollution, the Delhi Government has implemented measures such as stopping fuel stations from providing fuel to vehicles older than 15 years and banning the entry of commercial petrol and diesel vehicles. These measures aim to reduce the number of older, more polluting vehicles on the roads. Additionally, the Graded Response Action Plan (GRAP) has been implemented, which includes strict vehicle emission checks as part of its Stage I actions.

Industrial pollution

New Delhi, the capital of India, is the world's most polluted city. The air pollution in New Delhi is a result of various factors, including industrial pollution, vehicular emissions, stubble-burning, and more.

Factories, power plants, and industrial zones release large quantities of smog, haze, and industrial effluence, which varies depending on the product being manufactured. Industrial sources contribute about 90% of Delhi's SO2 emissions and 52% of NOx emissions. Of the PM10 pollution, 10% comes from industrial point sources. The drift/mist emissions from the wet cooling towers are also a source of particulate matter as they are widely used in industry for dissipating heat in cooling systems.

The service sector in the city has seen large-scale expansion, with many people migrating to work in fields such as IT, telecommunications, tourism, and the hotel industry. While this has boosted the economy, it has also increased pollution due to the massive increase in anthropogenic activity and the construction of new buildings.

Government Initiatives to Combat Industrial Pollution

The Delhi government has implemented several measures to combat air pollution, including the formation of the Commission for Air Quality Management (CAQM) to enforce pollution control in the National Capital Region (NCR). A 10-member Pollution Control Team manages complaints via the "Green Delhi" app, regulates dust, and bans diesel gensets in select areas. To address the issue more holistically, a proposed initiative includes planting 1.35 billion new native trees over ten years along a 1,600 km long ecological corridor from Gujarat to Delhi, connecting to the Sivalik Hills range.

Low wind speeds and temperature inversions

Delhi, the capital city of India, is the world's most polluted city. Each winter, from October to February, the air quality index (AQI) levels in Delhi routinely eclipse 700, posing severe health risks.

Temperature inversions occur when a layer of warm air caps and traps cold air beneath it, leading to a massive trapping of pollution under the inversion layer. Cooler earth surfaces during winter reduce temperatures near the ground, preventing the air from rising and dispersing. This phenomenon is commonly known as "winter inversion" and results in the deadly smog experienced every winter in Delhi.

The combination of low wind speeds and temperature inversions traps smoke and emissions, creating long periods of smog in Delhi. This smog is a toxic mix of smoke and fog that blankets the city during the winter months. The stillness of the air prevents the dispersal of pollutants, leading to a build-up of harmful substances that pose severe health risks to the population.

To address the issue of low wind speeds and temperature inversions in New Delhi, the government has implemented various action plans. These include the formation of the Commission for Air Quality Management (CAQM) to enforce pollution control and the implementation of the Graded Response Action Plan (GRAP), which categorises air quality into four escalating stages, triggering stricter pollution control measures.

Firecrackers and toxic metals

New Delhi is India's capital and one of the country's most polluted cities. The city's air quality routinely eclipses 700 on the Air Quality Index (AQI) during winter, from October to February, posing severe health risks.

One of the major causes of New Delhi's air pollution is the use of firecrackers during the Hindu festival of Diwali. The smoke emitted from firecrackers causes toxic smog that can take days to clear. While PM2.5 levels surge on Diwali night, studies have found that pollution levels generally normalise within 24 hours. However, this does not counter the concerns of health experts, who state that the smoke emitted from firecrackers can be more hazardous than other sources of pollution.

Arun Kumar Sharma, a community medicine professor at New Delhi's University College of Medical Sciences, has stated that the smoke produced by firecrackers contains heavy metals like sulphur, lead, and toxic gases like carbon monoxide. These fumes of heavy metals are dangerous to the respiratory system. Further supporting this claim, a study by Airvoice revealed a significant PM2.5 spike from Diwali firecrackers.

Additionally, toxic metals like aluminium, manganese, and cadmium are also released during firecracker burning. These metals can persist in the air after the initial pollution spike, posing longer-term respiratory health risks. As a result, authorities in New Delhi and some other states have banned the use and sale of firecrackers since 2017, encouraging people to opt for more sustainable options like environmentally friendly firecrackers and light shows. However, the rule is often flouted, as firecrackers remain easily accessible from roadside stalls and stores.

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