Why in news?

Delhi’s air quality has hit its worst levels since 2019, with the Air Quality Index (AQI) deteriorating to 494 on November 18, categorized as severe+. A combination of stubble burning, calm winds, low temperatures, and high humidity has caused pollutants, particularly PM 2.5, to accumulate.

The toxic air prompted the suspension of physical classes in schools and universities, delays and cancellations of flights, and widespread public health concerns.

Meteorologists attribute the smog to thermal inversion and stagnant winds, with no improvement expected until later in the week when wind speeds might increase.

What’s in today’s article?

• Why Delhi-NCR struggles with severe air pollution every winter?

Why Delhi-NCR struggles with severe air pollution every winter?

• Background
  • Although emissions remain similar throughout the year, pollution and hazardous air quality worsen in Delhi-NCR during winter months.
  • New Delhi faced hazardous air quality when the Air Quality Index (AQI) crossed 400 on November 12.
  • Since then, the situation has worsened as AQI deteriorated to 494 on Nov 18.
  • Thick smog continues to blanket the city, severely limiting visibility and disrupting both traffic and flight operations.
• Top contributor to air pollution in Delhi
  • A study by the Centre for Science and Environment reveals that during the time period of October 12- November 3, 2024:
    • vehicular emissions are the largest contributor to Delhi’s air pollution, accounting for 51.5 per cent of the city’s pollution;
    • Neighbouring districts add 34.97 per cent,
    • farm fires contribute 8.19 per cent, and
    • dust particles make up 3.7 per cent of the total air pollution in the city.
• Major factors responsible for winter pollution
  • Crop burning in surrounding states
    • Farmers in states like Punjab, Haryana, and Uttar Pradesh burn crop stubble to clear fields as an immediate and simple solution after harvest.
    • This practice releases massive amounts of smoke and significantly harmful particles into the air.
    • These particles are then carried into Delhi by winds, significantly worsening the levels of pollution.
  • Frozen, unmoving winter air
    • During the winter months, Delhi’s cold weather causes air to be severely frozen and still.
    • This means that pollutants such as smoke, dust, and factory pollutants are caught near the ground, stuck in one place.
    • As a result, it accumulates smog, reducing air quality and increasing health risks for people.
  • Temperature inversion
    • The stability in the atmospheric layer because of thermal inversion combined with low wind speed has trapped the pollutants.
      • A temperature inversion is a layer in the atmosphere where the temperature increases with height, which is the opposite of what usually happens. 
      • In normal conditions, air temperature decreases as altitude increases.
  • Overpopulation
  • With a population of over 20 million, Delhi’s fast-paced urban growth puts immense pressure on its infrastructure.
  • More people means more cars, more waste, and significantly increased energy consumption, all of which contribute to higher pollution levels.
  • Vehicular emission
    • Delhi’s roads are crowded with vehicles, many of which are old and release high levels of harmful gasses. 
  • Fireworks during festivals
    • Despite the firecrackers being banned, they continue to burst during festivals like Diwali. These fireworks release severely harmful chemicals, including sulfur dioxide and airborne particles.
  • Construction and dust
    • Big building sites and roads that are being built produce a lot of dust, especially during dry weather.
  • Other factors
    • Bare, open lands and fields also generate dust, especially during windy conditions, further deteriorating air quality.
    • Additionally, wildfires and the burning of waste produce harmful smoke and soot, adding to the pollution with toxic particulates and gases.
    • Industrial emissions, including sulfur dioxide, nitrogen oxides, and volatile organic compounds, lead to the formation of secondary pollutants like ozone.