Kiera Jefferson
New Delhi, the capital of India, is one of the most polluted cities in the world. The city's poor air quality has irreversibly damaged the lungs of 2.2 million children, and the high levels of PM2.5 in the air put everyone at risk of cardiac events, heart disease, and cancer of the lungs. The city's pollution is caused by a combination of geographical factors, population density, traffic, and stubble burning in neighbouring states. The Himalayas, which border New Delhi, trap cold air in the city during the winter, leading to a phenomenon called temperature inversion, which prevents pollutants from being dispersed. The city's high population density of 30.2 million people as of 2020, contributes to high levels of traffic, with an estimated 11.2 million registered motor vehicles on the roads as of 2018. Additionally, stubble burning in the neighbouring states of Punjab and Haryana contributes significantly to New Delhi's pollution, with 38% of the city's pollution caused by this practice in 2023.
| Characteristics | Values |
|---|---|
| Air Quality Index (AQI) | Unhealthy for sensitive groups |
| PM2.5 levels in 2019 | 98.6 µg/m³ |
| PM2.5 levels in 2016 | 999 |
| PM10 levels in 2016 | 999 |
| Population | 30.2 million |
| Area | 1,484 km² |
| Population growth | 14% per annum |
| Registered vehicles in 1994 | 2.2 million |
| Registered vehicles in 2018 | 11.2 million |
| Percentage of vehicles that are two-wheelers | 66% |
| Percentage of PM2.5 caused by burning of local organic waste | 24% |
| Percentage of PM2.5 caused by the transport sector | 23% |
| Number of landfills | 3 |
| Cost of environmental damage caused by landfills | $57 million |
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Vehicular pollution
New Delhi, the capital of India, has been deemed the most polluted major city in the world by a US-based Health Effects Institute survey in 2022. The city's poor air quality has irreversibly damaged the lungs of 2.2 million children.
The impact of vehicular emissions on air quality is significant, with India's Ministry of Earth Sciences attributing almost 41% of air pollution to this source in 2018. The high volume of vehicles on the roads, coupled with low average speeds, leads to increased emissions and poor vehicle mileage. The transport sector's contribution to PM2.5 levels, which are fine particulate matter pollutants, is estimated to be approximately 23%.
To combat vehicular pollution, the Delhi Government has implemented several measures. In November 2021, they banned the entry of commercial petrol and diesel vehicles into the city. Additionally, starting in April 2025, fuel stations will stop providing fuel to vehicles older than 15 years. These initiatives aim to reduce the number of older, more polluting vehicles on the roads and improve air quality in the city.
While these measures are a step in the right direction, more urgent action is needed to tackle the city's air pollution crisis. Citizens are encouraged to carpool and maximize the use of public transportation to reduce vehicular emissions.
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Population density
New Delhi is considered the world's most polluted megacity, with a mix of factory and vehicle emissions, as well as seasonal agricultural fires contributing to poor air quality. The city's population density is a significant factor in its high pollution levels. With a population of over 26 million in the metro area, New Delhi is home to twice the population of New York City, despite being half the size of Rhode Island. The city's population is expected to continue growing, with an estimated 39 million people expected to call New Delhi home in the next three years. This rapid growth and urbanisation have led to a dense concentration of people, vehicles, and industries, all contributing to the city's air pollution.
The high population density in New Delhi has resulted in a dense network of roads and vehicles. Cars, buses, and trucks emit carbon monoxide, nitrogen oxides, and particulate matter, with vehicles contributing to 20% of PM2.5 and 36% of NOx emissions. The dense traffic also leads to slow-moving traffic and congestion, further increasing emissions and pollution levels.
The dense population also contributes to industrial pollution, with factories and power plants releasing large amounts of SO2 and NOx. About 90% of Delhi's SO2 emissions originate from industrial sources. The presence of numerous industries in and around New Delhi, attracted by its commercial and economic significance, exacerbates the pollution problem.
The population density in New Delhi also impacts waste management practices. The city lacks adequate sewer infrastructure, and public trash cans are scarce, leading to improper waste disposal and garbage burning, which contributes to air pollution. The density of the population also means that a large number of people are affected by the poor air quality, with an estimated average loss of 12 years from the lifespan of each resident due to the pollution.
The Indian government has implemented various initiatives to combat air pollution in New Delhi, recognising the urgent need to improve air quality. These include banning vehicles over ten years old, promoting the use of compressed natural gas taxis, and forming the Commission for Air Quality Management to enforce pollution control measures. However, the sheer volume and density of the population continue to pose significant challenges in effectively addressing the pollution crisis in New Delhi.
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Stubble burning
New Delhi, the capital of India, has been deemed the most polluted major city in the world. It struggles with high levels of air pollution, which have been linked to around 2 million deaths per year in India, with the young, elderly, and immunocompromised being particularly at risk. The city's poor air quality has also irreversibly damaged the lungs of 2.2 million children.
Most stubble burning takes place in the neighbouring states of Punjab and Haryana, which are primarily agrarian. In 2020, Punjab had 3,611 instances of stubble burning, and Haryana had 527. These numbers decreased in subsequent years, with Punjab reporting 1,057 instances in 2021 and 987 in 2022, while Haryana recorded 468 instances in 2022. However, in 2024, there was a sharp rise in stubble burning in these states, with 872 fire counts reported in Punjab from September 15 to October 13, and Haryana experiencing a similar trend.
The impact of stubble burning on Delhi's air quality is influenced by wind patterns. Westerly winds carry the pollutants from Punjab and neighbouring Pakistan towards the capital. A western disturbance over the Himalayan region can alter wind patterns, leading to the concentration of pollutants in Delhi. Additionally, the Himalayas can trap cold air in Delhi during the winter, causing temperature inversion and preventing vertical air movement, which further exacerbates the pollution problem.
The increase in stubble burning in Punjab and Haryana has been attributed to various factors. One factor is the Punjab Subsoil Preservation Act of 2009, which banned the growing of paddy during the peak evapotranspiration period, reducing the time window for farmers to burn stubble. Additionally, government policies that delayed rice planting in northwest India may have played a role. By pushing back the sowing of rice to take advantage of monsoon rains and reduce groundwater irrigation, farmers became more reliant on fire to quickly clear fields.
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Landfills
New Delhi has been named the world's most polluted capital city for several years running. The city's landfills are a major contributor to its poor air quality. There are three landfills ringing Delhi: Bhalswa, Ghazipur, and Okhla. These landfills have far surpassed their capacity and continue to receive waste daily.
The Ghazipur landfill, located in the eastern district of Delhi, is India's tallest garbage mountain, standing at over 65 meters high. It was established in 1984 and was designed to hold waste up to 20 meters high. However, it surpassed this capacity by 2002 and has continued to grow. The landfill is now a massive "garbage mountain" that poses significant environmental and health hazards. The decomposition of organic waste in the landfill emits substantial amounts of methane, a potent greenhouse gas, and other toxic gases and particulate matter that contribute to air pollution and global warming.
The Bhalswa landfill in north Delhi has also seen major fires that have disrupted the lives of nearby residents, filling the air with harmful black smoke. The Okhla landfill is scheduled to complete reclamation by March 2023, with Ghazipur and Bhalswa following in December 2024. However, these dates are unlikely to be met due to the competing cycle of biomining and daily trash deliveries.
Landfill blazes are a common occurrence due to the large amounts of flammable waste discarded on-site. The methane produced by decomposing waste can self-ignite at temperatures between 60-70 °C, which are easily reached during the warmer months. These fires release toxic fumes and particulate matter into the surrounding areas, causing respiratory and other health issues for residents. In addition, the garbage has led to groundwater contamination, further impacting the health of the local population.
To address the landfill issue, the National Green Tribunal mandated biomining in the landfills in 2019. Biomining involves removing waste from landfills, sorting it, treating it, and reclaiming usable resources and landfill space. Waste pickers, who recycle around 20-25% of the city's daily waste output, also help alleviate the strain on landfills and promote responsible waste management. However, the lack of proper waste segregation at the source remains a challenge, contributing to the overfilled landfills in Delhi.
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Temperature inversion
New Delhi, the capital of India, is subject to a high level of pollution year-round. The city's poor air quality has irreversibly damaged the lungs of 2.2 million children, and the air pollution in Delhi was found to be the most harmful of any major city in the world in an August 2022 survey of 7,000 world cities.
One of the main causes of this is a phenomenon known as temperature inversion. Normally, air temperature decreases with increasing altitude, and this condition is called unstable due to the constant movement between cold and warm layers. However, temperature inversion is when the normal decrease in air temperature with increasing altitude is reversed, i.e., the air above is warmer compared to the air below, thus restricting the vertical movement of air. This prevents air near the ground from rising and mixing out air pollutants, thereby trapping air near the surface and allowing pollutants to accumulate with nowhere to go.
In New Delhi, the Himalayan mountain range to the north plays a significant role in the temperature inversion phenomenon. During the winter months, the Himalayas trap cold air in Delhi, leading to temperature inversion and preventing pollutants from being distributed. This, combined with the practice of stubble burning in neighbouring states, contributes to the high levels of air pollution in New Delhi.
Additionally, the city's high population density and traffic contribute to the pollution. With over 10 million vehicles in Delhi, including 7 million mopeds and motorcycles, the city struggles with poor emissions standards and older vehicles with incomplete or dirty combustion, injecting small metallic compounds into the air.
The temperature inversion in New Delhi has kept air quality at dangerous levels for extended periods, with air quality indexes skyrocketing and forcing residents to remain indoors. The inversion prevents pollutants from being dispersed, leading to a toxic haze that blankets the city.
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Frequently asked questions
The Himalayas, which border New Delhi, form a barrier that prevents air from dissipating. A lack of strong winds makes it difficult for air to circulate, causing pollutants to become concentrated in smaller areas.
Vehicular emissions are a major source of air pollution in New Delhi. As of 2018, there were an estimated 11.2 million registered motor vehicles on the roads. Other sources include stubble burning, landfill fires, and the burning of local organic waste.
New Delhi's poor air quality has irreversibly damaged the lungs of 2.2 million children. When levels of PM2.5 reach the "unhealthy" bracket, everyone is at risk of health issues, including cardiac events, heart disease, and respiratory problems.
