Delhi's Air Quality Deteriorates to 'Very Poor' Category

  • 04 Nov 2023

A layer of haze enveloped Delhi and its neighbouring areas as the capital's air quality slipped into the 'very poor' category, primarily attributed to temperature drop and calm winds during the night.

On 3rd Nov, the Air Quality Index (AQI) in Delhi reached 372 at 10 am, marking the highest level this season, with a 24-hour average AQI of 359.

Key Points

  • 'Severe' Air Quality in Certain Areas: Several areas within Delhi, such as Nehru Nagar, Sonia Vihar, Rohini, Wazirpur, Bawana, Mundka, Anand Vihar, and New Moti Bagh, experienced a significant deterioration in air quality, plunging into the 'severe' category.
  • Elevated PM2.5 Levels: The concentration of PM2.5, fine particulate matter harmful to the respiratory system, in these areas exceeded the safe limit by six to seven times, reaching up to 60 microgrammes per cubic meter.
  • Air Quality in Neighboring Areas: The AQI in nearby regions included 280 in Ghaziabad, 318 in Faridabad, 254 in Gurugram, 333 in Noida, and 372 in Greater Noida.
  • Air Quality Categories: The Air Quality Index categorizes air quality as good, satisfactory, moderate, poor, very poor, and severe, with values ranging from 0 to 500.
  • Major Contributors to Air Quality: According to a model-based system by the Indian Institute of Tropical Meteorology (IITM), vehicular emissions (11% to 16%) and stubble burning (7% to 16%) are the primary contributors to Delhi's air quality.
  • Restrictions on Buses: Starting from November 1, only electric, CNG, and BS VI-compliant diesel buses are permitted to operate between Delhi and the cities and towns in Haryana, Uttar Pradesh, and Rajasthan within the NCR region, following directions from the Commission for Air Quality Management.
  • BS VI Emission Standards: To combat pollution, India mandated that all vehicles sold must adhere to the Bharat Stage VI (BS-VI) emission standards.
  • These standards regulate the amount of air pollutants vehicles can emit and focus on improving emission control, fuel efficiency, and engine design.
  • Persistent 'Very Poor' Air Quality: The Centre's Air Quality Early Warning System for Delhi predicts that Delhi's air quality will remain in the 'very poor' category for the coming days, highlighting the ongoing air pollution concerns.

Reasons behind Rising Pollution Levels in Delhi during Winters

Stubble Burning

  • Farmers in Punjab and Haryana burn crop residues, generating significant smoke and particulate matter.
  • Stubble burning contributes to Delhi's pollution, reaching up to 25% according to SAFAR.
  • Emission of toxic pollutants such as Carbon Monoxide (CO), methane (CH4), and carcinogenic polycyclic aromatic hydrocarbons.

Wind Direction

  • Wind direction, predominantly northwesterly post-monsoon, carries pollutants from Haryana and Punjab to Delhi.
  • A shift in wind direction can reduce pollutant influx, improving air quality.
  • For example, wind direction change from north to northeast on October 25, 2023, led to marginal air quality improvement.

Temperature Inversion

  • Inversion occurs when warm air aloft traps cold air and pollutants near the ground.
  • Common during Delhi's cold, calm winter weather.
  • Accumulates pollutants from various sources, creating a thick layer of smog.

Dry and Still Air

  • Reduced rainfall and low wind speed in winter prolong the suspension of pollutants in the air.
  • Pollutants are not washed away or diluted, leading to persistent smog.

Vehicular and Industrial Emissions

  • High population and vehicle density in Delhi result in significant emissions of harmful gases and particles.
  • Industries contribute by burning fossil fuels and releasing chemicals.
  • Vehicular emissions account for approximately 25% of Delhi's PM2.5 levels.

Dust Storms, Firecrackers, and Biomass Burning

  • Dust storms bring particles from arid regions.
  • Firecrackers during festivals add smoke and metals to the air.
  • Domestic biomass burning for heating releases carbon monoxide and particulate matter.
  • Biomass burning contributes to 17-26% of particulate matter in Delhi during winters (IIT-Kanpur study).

Government Initiatives to Control Delhi's Pollution

Green War Room

  • A nine-member team monitors actions of 20 government agencies against pollution in real-time.

Anti-Pollution Campaign "Yuddh Pradushan Ke Viruddh"

  • Includes tree transplantation and other initiatives.

Green Delhi App

  • Allows citizens to report pollution instances like garbage burning, industrial emissions, or traffic congestion.


  • Developed by PUSA institute to help farmers decompose crop residue without burning.
  • Free spraying of bio-decomposer in Delhi's farmlands.

Water Sprinklers

  • Use of water sprinklers, mechanized road sweeping machines, anti-smog guns, and sprinkling facilities on high-rise buildings.

Industry Pollution

  • Monitoring and enforcement of clean and authorized fuel usage in industries.
  • Extension of piped natural gas (PNG) and creation of the first e-waste eco-park.

PUC Certificates

  • Enforcement of pollution under control (PUC) certificates for vehicles.
  • Ban on trucks carrying non-essential goods.
  • Hiring 1,000 private CNG vehicles to enhance public transport.

Smog Towers

  • Installation of smog towers with fans and filters to purify the air.
  • First smog tower set up at Connaught Place showing positive effects.

Pollution Hotspots

  • Identification of 21 pollution hotspots.
  • Deployment of special teams to monitor and mitigate pollution sources in these areas.