Delhi’s Air Pollution Crisis: Causes, Trends, and Mitigation Measures

October 28, 2024
Posted by: OptimizeIAS Team
Category: DPN Topics

Delhi’s Air Pollution Crisis: Causes, Trends, and Mitigation Measures

Sub: Env

Sec: Pollution

Why in News

Delhi’s air quality has deteriorated significantly as particulate matter (PM 2.5) levels rise to over 10 times the safe limit prescribed by the World Health Organization (WHO). The seasonal spike in pollution levels, aggravated by stubble burning in neighbouring states, Deepavali festivities, and meteorological conditions, has raised concerns about severe health impacts and the need for coordinated action across states.

Overview of Delhi’s Pollution Problem:

PM2.5 levels in Delhi recently soared to 160 micrograms per cubic meter, surpassing the WHO’s permissible limit of 15 micrograms.

Delhi’s 24-hour average Air Quality Index (AQI) reached 356 on October 23, placing it in the “very poor” category, with predictions of further deterioration if firecracker bans are not enforced during Deepavali.

Stubble burning in Punjab and Haryana coincides with this period, compounding Delhi’s air quality crisis.

According to Climate Trends, 54% of the wind from Punjab and 27% from Haryana carries particulate matter to Delhi. Each stubble-burning incident increases PM2.5 levels by 12.44 units on average.

Transportation within Delhi and vehicles entering the city contribute about 18% of PM2.5 levels. Vehicular emissions are especially high due to Delhi’s dense traffic and industrial activities.

Secondary Inorganic Aerosols (SIAs): SIAs, formed when sulphur dioxide (SO2), nitrogen oxides (NOx), and ammonia (NH3) react to create ammonium sulphate and nitrate, contribute up to 32% of Delhi’s winter pollution. Nearly 84% of SIAs originate outside Delhi, underscoring the need for cross-state solutions.

Meteorological Factors: Winter months bring a sharp reduction in wind speed, which prevents pollutants from dispersing and causes them to remain concentrated near ground level.

AQI Index score:

The AQI transforms complex air quality data of various pollutants into a single number for ease of understanding. The pollutants include PM 10, PM 2.5, Nitrogen Dioxide, Ozone, Carbon, etc.

Pollutants	Description
PM 2.5 and PM 10	These are extremely fine particulate matter (PM) particles. PM 10 and PM 2.5 are smaller than 10 and 2.5 microns in their diameter, respectively. The PM 2.5 particles can easily bypass the nose and throat and can enter the circulatory system. The particles can also lead to chronic diseases such as asthma, heart attack, bronchitis and other respiratory problems. Byproducts of emissions from factories, vehicular pollution, construction activities and road dust, such particles are not dispersed and stay suspended in the air that we breathe.
Nitrogen Oxides (NOx)	It gets in the air from the burning of fuel, with sources including emissions from vehicles and power plants. Short-term exposure to high levels of NO2 can aggravate respiratory diseases like asthma, and lead to other problems such as coughing or difficulty in breathing. Long-term exposure may also contribute to the development of asthma and could increase susceptibility to respiratory infections.
Ozone	The surface-level ozone is among the most significant air pollutants. It is formed by the reaction of atmospheric pollutants in the presence of sunlight. Related health hazards include: Chronic Obstructive Pulmonary Disease (COPD), and cardiovascular and respiratory deaths.
Sulfur Dioxide (SO2)	The largest source of SO2 in the atmosphere is the burning of fossil fuels by power plants and other industrial facilities. Additional sources are industrial processes and natural sources such as volcanoes. Health hazards include: Damage to the cardiovascular system and respiratory illnesses. SO2 can also react with other compounds to form particulate matter. At high concentrations, gaseous SOx can harm trees and plants by damaging foliage and decreasing growth.
Ammonia (NH3)	A broad increase in fertilizer use coupled with large contributions from livestock waste have resulted in the world’s highest concentrations of atmospheric ammonia in India. While gaseous ammonia is a natural part of Earth’s nitrogen cycle, excess ammonia is harmful to plants and reduces air and water quality. In the troposphere ammonia gas reacts with nitric and sulfuric acids to form nitrate-containing particles. Those particles contribute to aerosol pollution that is damaging to human health. Ammonia gas can also fall back to Earth and enter lakes, streams and oceans, where it contributes to harmful algal blooms and dead zones with dangerously low oxygen levels
Lead (Pb)	It is a naturally occurring toxic metal found in the Earth’s crust. But in increased quantities, exposure to it becomes extremely dangerous to health. Important sources of environmental contamination come from mining, smelting, manufacturing and even recycling activities. Young children are particularly vulnerable to lead poisoning because they absorb four to five times as much ingested lead as adults from a given source. Children who survive severe lead poisoning may be left with permanent intellectual disability and behavioural disorders. At lower levels of exposure that cause no obvious symptoms, lead is now known to produce a spectrum of injury across multiple body systems. There is no known safe level of exposure to lead contamination.
Carbon Monoxide (CO)	A toxic, colourless and odourless gas, it is given off when fuel containing carbon, such as wood, coal and petrol, is burned. If CO levels are high enough, a person may become unconscious and die. Long-term exposure has been linked with an increased risk of heart disease.

WHO global air quality norms:

The World Health Organization (WHO) has raised the bar further to safeguard public health even before the global community could comply with the current benchmarks for clean air.

The WHO’s new air quality guidelines — Global Air Quality Guidelines (AQGs) — released September 22, 2021, has redefined the threshold of safe air.

This is the first revision after the last updating in 2005 — about 15 years ago. Currently, 90 per cent of the global population and nearly everyone in India is breathing air that defies the current guidelines of the WHO.

The primary focus is on significant tightening of the guidelines for particulate matter, which is responsible for the highest number of air pollution related deaths worldwide — nearly seven million. The guidelines for key gases have also been revised.

Need for Coordinated Action:

Airshed Approach: The “airshed approach” involves a cross-state, regional strategy to tackle air pollution by addressing sources beyond Delhi’s borders. Coordinated policy measures involving Punjab, Haryana, Uttar Pradesh, and Rajasthan, along with Delhi, are essential for meaningful air quality improvements.

Centralized Monitoring and Forecasting: The Indian Institute of Tropical Meteorology-Pune (IITM-Pune) maintains an air quality forecast system for cities across India, helping predict pollution trends and identify periods when stubble burning may significantly affect Delhi’s AQI.

Government-led Air Quality Early Warning Systems provide valuable data that can inform proactive measures, such as limiting vehicle emissions and restricting industrial activities during high-pollution days.

Long-term solutions include incentivizing alternative crop-clearing methods, increasing green cover, and promoting cleaner transport options.