Explained: What Is Causing A Drop In Delhi's Air Quality?
Weak winds, falling temperatures and seasonal pollution sources have pushed Delhi’s air quality into the ‘very poor’ zone, with conditions likely to worsen in the coming days.
The air quality in Delhi and the National Capital Region (NCR) has been deteriorating since Diwali. The national capital’s air quality remained in the ‘very poor’ category on Monday, Nov. 3, with an overall Air Quality Index (AQI) of 324 recorded at 6:05 a.m., according to the Central Pollution Control Board’s (CPCB) Sameer app. The Air Quality Early Warning System (AQEWS) pegged the AQI at 316 by 9:45 a.m., still ‘very poor’. On Sunday, Nov. 2, the city had already recorded a worse reading of 366.
The sustained pollution can be attributed to weak wind movement, which has reduced the dispersion of particulate matter, and to a gradual dip in minimum temperatures by 1°C to 3°C over the last 24 hours.
Weather Conditions Behind Poor Air Quality
According to the Air Quality Early Warning System for Delhi, the wind speed dropped below 5 kmph from the northwest during evening and night hours of Nov. 2, allowing pollutants to settle close to the ground.
The city recorded a temperature of 20.2°C on Nov. 3 around 10 a.m., while the humidity was reported at 64%, as per the latest India Meteorological Department (IMD) bulletin.
The Air Quality Early Warning System for Delhi has predicted that the air quality is likely to remain ‘very poor’ on Nov. 3 and Nov. 5, and may slip into the ‘severe’ category on Nov. 4. The trend is expected to persist over the next week.
What Are The Key Pollution Sources In Delhi?
Delhi’s toxic air has multiple sources: vehicle emissions, construction dust, demolition activity, and industrial output, all being significant contributors. Seasonal events such as the burning of crop residue and Diwali fireworks worsen the situation. Stubble burning in neighbouring states like Punjab and Haryana is a recurring issue, as northwesterly winds carry smoke from the fields into Delhi’s atmosphere, adding to the city’s concentration of fine particulate matter (PM2.5).
Why Does Delhi Suffer More Than Other Indian Cities?
Geographically, Delhi is disadvantaged. The city sits in a landlocked plain surrounded by mountains and plateaus, forming a natural basin that traps pollutants. The onset of winter further aggravates the crisis, as cooler air and temperature inversions prevent pollutants from rising and dispersing into the upper atmosphere.
What Do AQI Categories Mean For Health?
According to the Central Pollution Control Board (CPCB), the Air Quality Index (AQI) categorises air quality into six levels, each indicating different health impacts.
An AQI reading between 0 and 50 is considered ‘Good,’ posing minimal health impact. Levels between 51 and 100 fall under the ‘Satisfactory’ category, which may cause minor breathing discomfort to sensitive individuals. The ‘Moderate’ range, from 101 to 200, can lead to breathing difficulties for people with lung, asthma, or heart conditions. When the AQI rises to ‘Poor’ (201-300), prolonged exposure may cause discomfort even among the general population. The ‘Very Poor’ category, ranging from 301 to 400, can result in respiratory illnesses with extended exposure.
AQI levels between 401 and 500 are deemed ‘Severe,’ affecting even healthy individuals and posing serious health risks to those with pre-existing diseases.
