Delhi Pollution: Understanding The Complex Causes And Effects

Delhi's air pollution has been described as a medical emergency by the city's chief minister, Atishi. The air quality in Delhi has been rated as hazardous, with pollutants reaching more than 60 times the safe levels recommended by the World Health Organization. The high levels of pollution in Delhi can be attributed to a combination of factors, including unfavourable meteorological conditions, an increase in farm fires, and the city's geographical location, which traps pollutants. Other factors include construction activities, vehicle emissions, factory pollution, and the use of biomass sources for cooking, such as cow dung cakes. The pollution has led to the implementation of emergency measures, including school shutdowns, bans on construction work, and restrictions on vehicle movement.

Construction activities and vehicle movements

Delhi's air pollution has been worsening, with the Air Quality Index (AQI) recording a reading of 465, classified as "severe plus category". This has prompted local authorities to implement emergency measures, including banning construction activities and restricting vehicle movements.

Construction Activities

Unregulated construction sites and the production of bricks and concrete have been identified as major contributors to Delhi's poor air quality. A study by the Indian Institute of Technology Kanpur found that the process of mixing concrete alone contributes an estimated 10% of coarse pollutants in Delhi's air. Poor building standards and antiquated practices, such as mixing concrete in pits by manual labour to reduce costs, further exacerbate the problem. The city's inability to adequately process construction waste, with an estimated daily production of 3,600 tonnes of waste compared to a processing capacity of only 1,000 tonnes, also plays a significant role.

Vehicle Movements

The transport sector, including vehicular emissions and dust kicked up by cars, is a primary source of pollution in Delhi. The number of vehicles on Delhi's roads has increased significantly, with a four-fold rise between 2010 and 2018, contributing to higher emissions. The slow average speed of vehicles, between 20-30 km/hr, leads to poor vehicle mileage and increased emissions. Commercial four-wheelers, such as app-based cab aggregators like Ola and Uber, have been flagged as major polluting sources, with high vehicle kilometres travelled (VKT) of approximately 145,000 km per year per car. Cars from outside Delhi, contributing to 25-45% of overall emissions from four-wheelers, further worsen the situation.

Unfavourable meteorological conditions

The ventilation index, which determines how quickly pollutants disperse, fell to 2,500 sqm/second, hindering the removal of harmful particles from the air. Delhi's pollution is exacerbated by pollutants from distant sources, carried by wind patterns, and the timing of stubble burning, which coincides with the onset of winter and unfavourable meteorological conditions.

Temperature inversions during this period trap pollutants close to the ground, increasing their concentration and leading to a sharp decline in air quality. The impact of stubble burning is particularly noticeable, with the fine particulate matter released, especially PM2.5 and PM10, penetrating deep into the respiratory system and causing respiratory ailments.

The region's Commission for Air Quality Management has also identified unfavourable meteorological conditions, an increase in farm fires, and north-westerly winds transporting pollutants to Delhi as the primary causes of the sudden spike in AQI. In response to the deteriorating air quality, local authorities have implemented emergency measures, including school shutdowns, a ban on construction work, and restrictions on vehicle entry, particularly diesel trucks and older diesel vehicles.

Waste burning and factory emissions

Delhi's air pollution has emerged as a global emergency, with the city making headlines worldwide due to the onset of winter months. The air quality in the Indian megacity of Delhi has deteriorated to hazardous levels, with pollutants reaching more than 60 times the World Health Organization's recommended safe levels.

Waste burning is a significant contributor to Delhi's air pollution. Data from the Central Pollution Control Board (CPCB) shows that between October 7 and November 21, 966 complaints were made regarding garbage burning and open dumping of waste. Senior officials have acknowledged that the problem of garbage and leaf burning has become a major source of pollution in the city, with a strong burning smell lingering in the air. The Environment Pollution (Prevention and Control) Authority (EPCA) chairperson, Bhure Lal, has instructed enforcement agencies to take strict action against garbage burning and open fires, particularly in the 13 pollution hotspots identified by the Delhi government. The contents of the waste burned include plastic, rubber, and metal, which release carcinogenic substances into the atmosphere.

Factory emissions also play a role in Delhi's poor air quality. According to India's Ministry of Earth Sciences, 18% of air pollution in Delhi is attributed to industrial emissions. A study in 2016 broke down the sources of air pollution in Delhi, revealing that 11% of PM2.5 pollution and 10% of PM10 pollution came from industrial point sources. Additionally, 52% of NOx emissions and a significant 90% of SO2 emissions were linked to industrial activities. The impact of factory emissions is more harmful as they are emitted closer to the population, posing a direct health risk to residents.

The combination of waste burning and factory emissions, along with other factors such as vehicle emissions, dust, and agricultural practices, has led to a severe air pollution crisis in Delhi. The situation has prompted local authorities to implement emergency measures, including school shutdowns, bans on construction activities, and restrictions on vehicle movements, to combat the worsening air quality and protect the health of Delhi's residents.

Cooking fuel and biomass

The use of biomass fuel in India is dependent on a variety of factors, including socio-economic status, availability, and traditions. Biomass fuel is used for cooking and general heating needs. The combustion of biomass releases a complex mixture of various harmful compounds, including NOx, SO2, organic carbon (OC), elemental carbon (EC), Polycyclic Aromatic Hydrocarbons (PAH), Non-methane Hydrocarbons (NMHC), and Volatile Organic Compounds (VOC). These emissions contribute to indoor and outdoor air pollution, causing severe health issues for the population.

Biomass fuel use is particularly prevalent in rural areas, with almost 50% of the world's population and up to 90% of rural households in developing countries relying on biomass fuels. In India, about 80% of rural households use biomass fuel for cooking. The highest exposures to indoor air pollution occur during the burning of biomass fuel for cooking, with women and children being the most vulnerable due to their proximity to the cooking area.

The emissions from biomass fuel combustion have been linked to a range of adverse health effects, including chronic obstructive pulmonary disease (COPD), tuberculosis (TB), cataract, and adverse pregnancy outcomes such as stillbirths, low birth weight, and intrauterine growth retardation. According to the World Health Organization, indoor air pollution from biomass burning and the use of traditional cookstoves (chulha) cause approximately 300,000 to 400,000 deaths in India annually.

The use of biomass fuel is driven by factors such as poverty, inaccessibility to cleaner cooking fuels, and a lack of awareness about the harms of biomass emissions. Efforts have been made to study the emissions from solid biomass fuels and evaluate their emission factors. Additionally, initiatives such as the Great Green Wall of Aravalli, a 1,600-kilometer-long ecological corridor, have been implemented to combat pollution in India.

To reduce the health risks associated with biomass fuel use, it is crucial to promote universal access to clean fuel or cleaner technology within the framework of rural development. Additionally, increasing awareness about the harmful effects of biomass fuel emissions and providing alternatives can help reduce the reliance on biomass fuel for cooking and heating needs.

Geographic and climatic constraints

Delhi's pollution issue is heavily influenced by its unique geographic and climatic characteristics. The city is situated in a basin-like topography, surrounded by mountains and nineteen districts. This geographical configuration creates a natural trap for air, allowing hot air to disperse pollutants in the summer. However, during the colder months, the air cools down and becomes denser, settling over the city like a lid. This dense, cold air traps pollutants, preventing their dispersal and leading to a concentration of harmful substances.

The climatic conditions in Delhi further exacerbate the pollution problem. Cold air is denser than warm air, and during the winter, it settles closer to the ground, creating an inversion layer. This inversion layer acts as a lid, trapping pollutants and preventing their vertical dispersion. The combination of geographic constraints and climatic conditions results in a potent mixture of trapped pollutants, significantly impacting the air quality in Delhi.

Additionally, the region's meteorological conditions, including low wind speeds, contribute to the pollution problem. Calm or light wind conditions prevent the dispersion of pollutants, allowing them to accumulate in the air. This stagnation of air masses further intensifies the concentration of harmful substances, worsening the air quality.

The impact of these geographic and climatic constraints is evident in the severe pollution levels that Delhi experiences, particularly during the colder months. The trapped pollutants, combined with emissions from various sources, create a toxic mix of fog and smoke, often referred to as smog. This smog reduces visibility and poses significant health risks to the residents of Delhi, leading to the implementation of emergency measures to mitigate the situation.

To address the challenges posed by geographic and climatic constraints, it is essential to implement comprehensive strategies. These strategies may include promoting the use of cleaner fuels, improving transportation systems, regulating construction activities, and implementing effective waste management practices. By addressing these constraints and implementing sustainable solutions, Delhi can work towards improving its air quality and reducing the health risks associated with pollution.

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