Delhi's Pollution: A Crisis Unfolding

Delhi, the capital of India, is one of the most polluted cities in the world. In August 2022, a survey of 7,000 cities worldwide by the US-based Health Effects Institute found that Delhi's air pollution was the most harmful. The air pollution in Delhi is caused by a combination of factors, including stubble burning in neighbouring states, vehicle emissions, industrial pollutants, construction dust, landfill fires, and religious festivities such as Diwali. The city's geography, bordered by the Himalayas, also plays a role in trapping pollutants and preventing their dispersion. The poor air quality in Delhi has severe health impacts, including reduced lung capacity, respiratory issues, and early death. Despite the implementation of measures such as driving restrictions and anti-smog guns, Delhi continues to struggle with high levels of air pollution.

Stubble burning in neighbouring states

The air pollution in Delhi, India's capital, is a major concern. It has been labelled as the most harmful of any major city in the world. Stubble burning in neighbouring states is a significant contributor to this issue.

The states of Punjab, Haryana, and Uttar Pradesh have been identified as the main culprits. These states are primarily agrarian, with large-scale rice and wheat production. The quickest and cheapest way for farmers to prepare their fields is to burn them, a practice known as stubble burning. This practice was made illegal in 2015, but it still persists, albeit at a reduced rate. The wind carries the smoke from these fires into Delhi, where it combines with other sources of pollution and meteorological conditions to create a thick cloud of smog.

The contribution of stubble burning to Delhi's pollution varies year-to-year and season-to-season. In the early winter period, it has been known to contribute up to 50% of the city's pollution, with more recent estimates placing it at around 30-35%. The impact is most significant during the turbulent hours of late morning to afternoon. In 2024, between October 12 and October 21, stubble burning accounted for only 0.92% of the PM2.5 levels in Delhi, indicating a downward trend.

The reduction in stubble burning in Punjab, the largest contributor, is notable. However, states like Madhya Pradesh and Rajasthan are witnessing an increase in these activities. The Indian Agriculture Research Institute (IARI), which tracks stubble burning incidents, has stopped updating its public bulletins, which is concerning given the importance of this data in addressing pollution issues.

While stubble burning in neighbouring states has been a major focus of the debate surrounding Delhi's air quality, it is essential to acknowledge that the issue is complex. Local sources within the city, such as vehicular emissions, construction dust, industrial emissions, and the open burning of waste, also play a significant role in Delhi's poor air quality. Therefore, a multi-pronged approach targeting both regional and local contributors is necessary to effectively tackle this severe pollution issue.

Harmful health impacts

Delhi's poor air quality has been linked to a range of harmful health impacts, with pollution levels in the city found to be the most harmful of any major city in the world. The pollution crisis peaks annually, prompting authorities to implement emergency measures such as closing schools, halting construction, and banning highly polluting vehicles.

One of the most vulnerable groups to the harmful effects of pollutants are children. Developing organs in children make them more susceptible, and exposure to air pollution may result in impaired lung development and an increased risk of respiratory infections. In Delhi, it is estimated that poor air quality has irreversibly damaged the lungs of 2.2 million children.

The elderly, particularly those with pre-existing health conditions, are another group at heightened risk. Air pollution can exacerbate existing health issues, compromising the cardiovascular and respiratory systems. For those with respiratory or cardiovascular conditions such as asthma, COPD, or heart disease, the pollutants can lead to worsened symptoms and more severe health complications.

Pregnant women exposed to air pollution face increased risks of preterm birth, low birth weight, and developmental issues in their unborn children. The pollutants can also negatively impact the health of the mother.

Overall, the health impacts of Delhi's air pollution are wide-ranging and severe. The high levels of pollutants in the air have been linked to reduced lung capacity, headaches, sore throats, coughing, wheezing, shortness of breath, fatigue, lung cancer, and even early death. The Indian Meteorological Department has established air quality monitoring stations across Delhi to address the poor air quality, and embassies and international businesses are considering measures such as reducing staff tenures and providing high-end air purifiers.

Vehicular emissions

Delhi, the capital of India, has been found to be the most polluted out of 7000 major cities in the world. The air pollution in Delhi is estimated to kill about 2 million people every year and is the fifth-largest cause of death in India. Poor air quality is a cause of reduced lung capacity, headaches, sore throats, coughs, fatigue, lung cancer, and early death.

The increase in private vehicles is a sign of increased per capita revenue, but it has also led to a surge in traffic congestion and particulate emissions, negatively impacting the citizens of Delhi. Researchers from EPIC India are working with the Government of the National Capital Territory of Delhi (GNCTD) to address this issue by designing and implementing market-based policies. Their goals are to reduce the number of vehicles on the road, incentivize the use of public transportation, and improve the monitoring and enforcement of the vehicular emissions testing regime in India.

To tackle the problem of vehicular emissions in Delhi, there have been calls for more public transport links in the National Capital Region (NCR). Citizens are also encouraged to carpool and maximize the use of public transportation. Additionally, EPIC India is working to enhance the Pollution Under Control Certificates (PUCC) system by identifying incentives for drivers and operators to ensure robust emissions testing.

While stubble burning, firecrackers, and industrial activities are also significant contributors to Delhi's air pollution, the constant presence of vehicular emissions cannot be overlooked. The Indian Institute of Tropical Meteorology (IITM) study emphasized the need to minimize emissions from key constant sources, including vehicles, to improve the air quality in Delhi and the entire NCR.

Lack of wind and mountainous geography

Delhi's air pollution is a pressing issue that has attracted the attention of various stakeholders, including the government, environmentalists, and the public. While multiple factors contribute to the city's poor air quality, the lack of wind and the region's mountainous geography play a significant role in exacerbating the problem.

The lack of wind in Delhi is a critical factor contributing to the city's poor air quality. Wind plays a vital role in dispersing pollutants, and when wind speeds are low, pollutants tend to accumulate in the atmosphere. This phenomenon is particularly pronounced during specific seasons, such as the months leading up to winter and the early winter period. For example, in February 2023, scientists attributed the rise in pollution in Delhi to vehicular emissions and the lack of wind. The stagnant air allowed secondary pollution from vehicles to accumulate, leading to a severe deterioration in air quality.

The geographical features surrounding Delhi also influence the city's air quality. The Himalayas, located north of Delhi, impact wind patterns and contribute to the region's poor air quality. During the winter months, the Himalayan mountain range blocks the north-eastern winds from Central Asia, leading to stagnant air in Northern India. This lack of wind, coupled with the burning of crops in nearby states, results in a buildup of pollution levels. The geographical trap formed by the Himalayas and other geographic features, such as the Indo-Gangetic plains, the Central Highlands, and the Thar Desert, contributes to the concentration of pollutants in the region.

The impact of the Himalayas on Delhi's air quality is further exacerbated by the phenomenon of temperature inversion. During winter, the mountains trap cold air in Delhi, preventing vertical air movement. As a result, pollutants are trapped and unable to disperse, leading to a further deterioration of air quality. This effect is similar to the conditions observed in interior California and Salt Lake City, where high-pressure systems can stagnate overhead, trapping pollutants and reducing air quality.

The mountainous geography surrounding Delhi, particularly the Himalayas, plays a significant role in the region's air quality. The mountains influence wind patterns and can block or redirect wind flows, impacting the dispersion of pollutants. While the geographical features alone may not be the primary cause of Delhi's air pollution, they contribute to the severity of the problem by trapping pollutants and creating stagnant air conditions.

Addressing the lack of wind and the impact of mountainous geography on Delhi's air pollution requires a comprehensive approach. Strategies such as the proposed 1,600 km long and 5 km wide green ecological corridor along the Aravalli Range could help mitigate the concentration of pollutants. Additionally, implementing measures to reduce stubble burning, vehicular emissions, and industrial activities can lessen the overall pollution levels, making the region less susceptible to the negative impacts of geographical and weather conditions.

Construction and industrial pollutants

Delhi, the capital of India, has been labelled the most polluted major city in the world. The air pollution in Delhi is estimated to kill about 2 million people annually and has irreversibly damaged the lungs of 2.2 million children. The city's air quality index (AQI) has reached as high as 1,700 in some parts, far exceeding the maximum index of 50 deemed healthy by the World Health Organization.

Industrial activities also play a crucial role in Delhi's air pollution. Several industrial areas in Delhi have been identified as "critically polluted clusters," with high concentrations of harmful pollutants such as PM10, PM2.5, NO2, and CO. The increase in the number of registered and operating industries in Delhi has led to a rise in air pollutant concentrations. Industrial emissions account for a significant portion of Delhi's air pollution, with NOx emissions from industrial sources contributing 52%, SO2 emissions at 90%, and industrial emissions making up 18% of air pollution according to one study. The presence of polluting industries in and around Delhi, including power plants and other industrial sources, exacerbates the city's air quality issues.

The impact of industrialization on air quality is evident in Delhi, with the city consistently ranking among the most polluted metropolitan areas globally. The industrialization of Delhi has contributed to economic development but has also deteriorated the environment and public health. The workers in these industries and their families are at an increased risk of respiratory diseases due to exposure to pollutants.

To address the issue of construction and industrial pollutants in Delhi, authorities have implemented measures such as regulating construction dust and banning diesel generators. However, more comprehensive and effective strategies are needed to tackle the city's poor air quality and mitigate its impact on the health and well-being of its residents.

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