Air Pollution in Delhi: A Discussion on Causes, Impacts, and Solutions

Delhi’s persistent air pollution crisis, emblematic of the broader environmental challenges facing rapidly urbanizing cities, arises from a complex interplay of human-made activities and natural phenomena. Every winter, the city is engulfed in a toxic haze, driven by key contributors such as vehicular emissions, industrial pollutants, stubble burning, and dust. Recent data from the Centre for Science and Environment (CSE) underscores the scale of these challenges, highlighting the urgent need for comprehensive air quality management.

Monitoring Air Quality: System of Air Quality and Weather Forecasting And Research (SAFAR)

The System of Air Quality and Weather Forecasting And Research (SAFAR) plays a crucial role in monitoring Delhi's air quality. A joint project between the Indian Institute of Tropical Meteorology (IITM) and the India Meteorological Department (IMD), SAFAR provides real-time air quality data and weather forecasts to help manage pollution levels. 

Air Quality Index (AQI) and NAAQ Standards

Understanding air pollution in Delhi requires monitoring and quantifying the level of pollutants in the air. The Air Quality Index (AQI) is a widely used tool to measure how safe the air is for breathing.

1. Air Quality Index (AQI)

The Air Quality Index (AQI) is a standardized measure used to report air quality and the associated health effects of air pollution. It provides a scale ranging from 0 to 500, where higher values indicate poorer air quality. The AQI is categorized into six levels: Good, Satisfactory, Moderately Polluted, Poor, Very Poor, and Severe. Values above 500 are considered hazardous.

The AQI reflects the concentrations of key air pollutants, including PM2.5, PM10, NO₂, O₃, CO, SO₂, and others, monitored at various stations. The National Air Quality Index (NAQI), developed by the Central Pollution Control Board (CPCB), is based on the 24-hour average concentrations of these pollutants. It is typically measured in micrograms per cubic meter (µg/m³).

Each pollutant’s quantity is adjusted to a common scale, where the pollutant with the highest sub-index value determines the AQI for that location and time. As a result, AQI reflects the overall pollution level based on the most harmful pollutant.
2. National Ambient Air Quality (NAAQ) Standards
The CPCB is empowered under the Air (Prevention and Control of Pollution) Act to set standards for ambient air quality. The National Ambient Air Quality Standards were notified in November 2009, establishing the permissible limits for pollutants across India. These standards were revised from earlier 1994 and 1998 guidelines to set stricter limits for pollutants, making them uniform nationwide.
Pollutants covered under NAAQ standards include:

• Sulphur Dioxide (SO₂)

• Nitrogen Dioxide (NO₂)

• Particulate Matter (PM10 and PM2.5)

• Ozone (O₃)

• Carbon Monoxide (CO)

• Ammonia (NH₃)

• Lead

• Benzene

• Arsenic

• Nickel

These standards ensure that air quality is maintained within limits that safeguard public health, reducing the risk of respiratory diseases, heart conditions, and environmental degradation.

Picture: AQI data for the last 30 days (Source: https://www.aqi.in/in/dashboard/india/delhi/new-delhi)

            Picture: (https://www.news18.com/india/delhi-air-pollution-aqi-999-anand-vihar-severe-category-weather-noida-gurgaon-8653183.html)

Delhi’s air quality has been consistently poor, particularly in areas like Anand Vihar, where the AQI has frequently reached hazardous levels, peaking at 999 on several occasions. On 2nd November 2023, the AQI in Anand Vihar was 999, and the city’s overall AQI averaged around 500. Similar hazardous levels were recorded on 17th October and 6th November 2023. The AQI peaked again on 18th November 2024, at 828, indicating that the situation remains critical. According to an AQI report from 11th October 2024, Delhi ranked as the fourth most polluted city in the world. The detrimental effects of this pollution are so severe that even non-smokers in Delhi are exposed to the equivalent of 30 cigarettes a day, underscoring the dangerous health risks posed by the city's air quality.

Understanding the Sources: Anthropogenic and Natural Contributors

Delhi’s air quality deteriorates due to a mix of human activities and natural phenomena, amplified by unfavorable meteorological conditions. Data from the Centre for Science and Environment (CSE) and other studies help highlight the dominant sources of air pollution:

1. Anthropogenic Sources: The Major Culprits

• Vehicular Emissions: The Primary Contributor (51.5%)
  Vehicular emissions are the largest local pollution source. Delhi have over 13.2 million registered vehicles in 2021. Diesel-powered vehicles, including trucks and buses, emit significant amounts of particulate matter (PM) PM2.5, PM10, Nitrogen oxides (NOx), and carbon monoxide (CO). Despite the enforcement of BS-VI standards and the increasing adoption of electric vehicles (EVs), these efforts are yet to make a noticeable impact due to the sheer volume of vehicles and growing urban sprawl.
  • Two-wheelers alone contribute nearly 20% of PM2.5 emissions, highlighting the need for stricter regulations in this sector.
  • Studies estimate that replacing older diesel vehicles with EVs could reduce particulate emissions by up to 30% over the next decade.

• Stubble Burning: A Seasonal Aggravator (30.34%)
  Agricultural stubble burning in Punjab, Haryana, and Uttar Pradesh contributes significantly to Delhi’s winter pollution. Farmers burn crop residues to prepare fields for the next planting season, releasing large amounts of PM2.5 and carbon dioxide (CO₂) into the air. Despite the availability of alternatives like Happy Seeders, the economic and logistical challenges farmers face make stubble burning a persistent issue.
  • In 2023 alone, over 75,000 farm fires were reported in Punjab and Haryana during the October-November period.
  • Efforts like the bio-decomposer developed by the Indian Agricultural Research Institute (IARI) have shown potential in reducing the need for burning, yet adoption remains limited.

• Dust Pollution: A Constant Irritant (3.7%)
  Dust from construction activities, unpaved roads, and demolition sites significantly contributes to PM10 levels. Despite regulations mandating dust control measures like covering construction materials and using anti-smog guns, enforcement remains inconsistent.
  • Construction activities contribute up to 10% of particulate emissions annually.
  • Mechanized road cleaning, though implemented, covers less than 40% of Delhi’s road network, leaving a significant portion unaddressed.

• Industrial Emissions and Waste Burning
  Industries located within Delhi and in neighboring areas contribute heavily to the release of pollutants such as sulfur dioxide (SO₂), volatile organic compounds (VOCs), and PM2.5. Illegal burning of municipal waste and plastic further exacerbates the problem.

2. Natural Factors: The Invisible Forces

While human activities dominate, natural factors also play a crucial role in aggravating pollution levels.

• Unfavorable Wind Direction: The northwesterly winds carry pollutants from Punjab and Haryana into Delhi, while additional pollutants from Uttar Pradesh also reach the city.

• Temperature Inversion
  During the winter months, temperature inversion traps pollutants near the ground. Normally, warm air rises and disperses pollutants. However, in inversion conditions, a layer of cooler air becomes trapped beneath a warmer layer, preventing air mixing and causing pollutants to accumulate near the surface.
• Wind speeds drop to as low as 1–3 km/h during winter, compounding the problem. 
• The relative humidity often exceeds 80%, allowing particulate matter to condense into dense smog.

• Geography and Topography
  Delhi’s location in the Indo-Gangetic Plain exacerbates its pollution woes. The city is bordered by the Aravalli Hills, which act as a barrier, preventing the dispersal of pollutants. The plain’s flat terrain allows pollutants to accumulate and stagnate.

• Dust Storms from the Thar Desert
  Seasonal dust storms originating from the Thar Desert and sometimes from Middle Eastern deserts contribute to PM10 levels. These natural dust events can increase particulate matter concentrations by up to 30% during peak storm periods.

Impacts: Health, Economic, and Social Consequences

The consequences of air pollution in Delhi extend well beyond environmental degradation, profoundly affecting public health, economic productivity, and overall quality of life.

1. Health Implications: An Escalating Public Health Emergency

• Premature Deaths and Life Expectancy
  According to the Energy Policy Institute at the University of Chicago (EPIC), prolonged exposure to PM2.5 could reduce the average life expectancy of Delhi’s residents by 11.9 years. A study by IIT Kanpur estimates that air pollution in Delhi causes 10,000 premature deaths annually due to respiratory and cardiovascular diseases.
• Children and the elderly are particularly vulnerable, with rising cases of asthma, bronchitis, and lung cancer.

• Respiratory and Cardiovascular Issues
  Elevated PM2.5 levels are linked to increased hospital admissions for chronic obstructive pulmonary disease (COPD) and heart attacks. During peak smog periods, hospitals report a 20–25% increase in respiratory distress cases.

1.1 Effects on Children and the Elderly

Children and the elderly are especially vulnerable to the health impacts of air pollution. Children, who breathe faster than adults, are more likely to develop respiratory problems like asthma. Exposure to pollution during pregnancy can also harm brain development, leading to lower intelligence and attention span. In addition to respiratory problems, children are at risk of learning difficulties and behavioral issues due to the neurotoxic effects of air pollution.

1.2 Effects on Plants and Animals

Air pollution also harms plants and animals in Delhi. Pollutants like PM2.5, PM10, and ozone reduce photosynthesis in plants by blocking stomata and hindering sunlight and carbon dioxide absorption. They also cause leaf damage, stunted growth, and reduced biomass production.

For animals, the effects are equally damaging. Delhi is home to more than 250 species of migratory birds, 150 species of butterflies and 10 species each of animals comprising hyena, fox, jackal, Nilgai, mongoose, and porcupines etc. Exposure to pollutants leads to respiratory issues, neurological problems, reproductive issues, and weakened immune systems. Stray animals in the city have been observed with symptoms like nausea, vomiting, and eye redness. Pet animals exhibit signs of lethargy and unease, linked to the escalating pollution levels. Wildlife, particularly birds, is also suffering from changes in mating behaviors due to exposure to air pollution.

2. Economic Costs: A Staggering Burden

The economic costs of air pollution are immense, with healthcare expenses, lost productivity, and infrastructure damage amounting to approximately USD 95 billion annually, equivalent to 3% of India’s GDP.

• School closures due to hazardous air quality disrupt education, particularly for younger children, who lose critical learning time.
• Businesses report a 15–20% decline in productivity during peak smog days due to health-related absenteeism.

3. Social and Environmental Impacts

• Reduced Visibility and Traffic Accidents
  Dense smog reduces visibility to less than 50 meters on some days, leading to transportation disruptions and increased road accidents.
  • Delhi Traffic Police reported a 20% rise in road accidents attributed to low visibility in 2023.

• Damage to Heritage Sites
  Pollutants like SO₂ and NOx contribute to the degradation of iconic monuments like the Red Fort and India Gate, necessitating costly preservation efforts.

Government Policies and Measures

• The National Clean Air Programme (NCAP) is a long-term initiative by the Government of India to reduce air pollution in 131 cities across 24 states. The program was launched in January 2019 by the Ministry of Environment, Forest and Climate Change (MoEFCC).
• The System of Air Quality and Weather Forecasting And Research (SAFAR) is a national initiative introduced by the Ministry of Earth Sciences (MoES) to measure the air quality of a metropolitan city, by measuring the overall pollution level and the location-specific air quality of the city. The system is indigenously developed by the Indian Institute of Tropical Meteorology (IITM), Pune and is operationalized by the India Meteorological Department (IMD).
• A Graded Response Action Plan is a set of emergency measures implemented in the Delhi-NCR region to combat air pollution, where the response actions escalate based on the severity of air quality as measured by the Air Quality Index, with different stages triggered depending on how poor the air quality becomes; essentially, the more polluted the air, the stricter the measures enforced to mitigate it.
• For Reducing Vehicular pollution

• The odd-even scheme restricts the vehicles on the road based on their license plate numbers. Private vehicles with registration numbers ending with an odd digit will be allowed on roads on odd dates and those with an even digit on even dates.
• BS VI (Bharat Stage Emission Standards 6) was introduced in Delhi earlier than originally planned due to the city's severe air pollution issues.
• National Electric Mobility Mission Plan (NEMMP) is a government initiative in India aimed at promoting the adoption of electric vehicles by providing incentives to buyers, fostering domestic manufacturing of EV technology, and developing charging infrastructure, with the goal of achieving significant market penetration for hybrid and electric vehicles in the country. Replacing older diesel vehicles with electric vehicles could reduce particulate emissions by up to 30% in the next decade in delhi.
• Red Light On, Gaadi Off is a campaign launched by the Delhi government to encourage people to switch off their car engines while waiting at red traffic lights, aiming to reduce vehicular pollution in the city; essentially meaning "when the red light is on, turn your car off.
• Ban on Firecrackers: The Delhi Pollution Control Committee (DPCC) issued a complete ban on firecrackers in Delhi on October 14, 2024. The ban applies to all types of firecrackers, including online sales, and will remain in effect until 1^st January, 2025. The ban was imposed to combat air pollution, which can increase during the festive season.
• BS-III petrol and BS-IV diesel vehicles remain banned for the general public as part of measures aimed at curbing vehicular emissions, a significant contributor to Delhi's deteriorating air quality.
• A "crop burning ban" in Delhi is primarily aimed at tackling the severe air pollution caused by farmers burning agricultural residue (stubble) in nearby states like Punjab and Haryana, which significantly contributes to the hazardous air quality in the Delhi region during winter months; this practice is legally prohibited by the Supreme Court and enforced by the Commission for Air Quality Management (CAQM) to reduce pollution levels in the capital city.
• Delhi has made significant progress in introducing electric vehicles (EVs) and compressed natural gas (CNG) vehicles to reduce air pollution.
• Monitoring and Data Collection Efforts: There are seven manual stations and 40 Continuous Ambient Air Quality Monitoring Stations (CAAQM) in Delhi.
• Use of Anti-smog guns: Anti-smog gun is a device designed to reduce air pollution by spraying water into the atmosphere so that all the dust and polluted particles gets clear from the environment. The Delhi government deploys mobile anti-smog guns to spray water on roads to reduce dust levels. These guns are operated in three eight-hour shifts per day.

Stubble should be managed using machines such as Happy seeder, super seeder, balers and Shredders.
A Happy Seeder is a machine that sows seeds and removes crop residue at the same time, helping to improve soil and save on input costs.
A baler or hay baler is a piece of farm machinery used to compress a cut and raked crop into compact bales that are easy to handle, transport, and store.
A farm shredder is a machine used in agriculture to cut, shred, or crush plant residues like crop stalks, grass, and branches into smaller pieces, making them suitable for composting, mulching, or easy disposal. It helps manage farm waste efficiently and promotes sustainable practices.

Reducing Delhi's air pollution can be achieved by utilizing crop residues and stubble as valuable resources instead of burning them. They can be repurposed as cattle feed or transformed into eco-friendly products like cardboard, paper, books, plates, cutlery, straws, organizers, fire- and water-proof tiles, and baskets. Additionally, stubble can be processed to produce bioethanol, promoting sustainable waste management and reducing harmful emissions.

Solutions: Toward Cleaner Air

1. Policy and Regulatory Measures

• Expanding Public Transportation: Enhancing the city’s public transport network and incentivizing electric vehicle adoption can significantly reduce vehicular emissions.
• Congestion Pricing: Implementing a congestion tax could reduce traffic volume in key areas.

2. Technological and Agricultural Innovations

• Bio-Decomposers: The Pusa Bio-Decomposer, developed by the Indian Agricultural Research Institute (IARI), is a capsule created through the extraction of fungal strains that accelerate the breakdown and decomposition of paddy straw more efficiently than usual.

• Artificial rain, or cloud seeding, is a weather modification technique that involves dispersing substances like silver iodide into the clouds to induce precipitation. It is increasingly explored as a strategy for pollution control, as the rain helps to settle airborne pollutants and improve air quality in heavily polluted regions
• Construction Dust Management: Enforcing stricter dust control measures, including the mandatory use of anti-smog guns and green barriers.

3. Regional Cooperation and Public Awareness

• Inter-State Collaboration: Establishing a Regional Air Quality Management Authority to ensure better coordination between Delhi and neighboring states.
• Public Engagement: Raising awareness about the health impacts of pollution and encouraging behavioral changes, such as reducing private vehicle use.

A Shared Responsibility

Delhi’s air pollution crisis demands a multi-pronged approach, with contributions from all stakeholders government, industry, and citizens. While the challenge is daunting, coordinated action, technological innovation, and sustained public engagement can pave the way for cleaner air and a healthier future.