Delhi overtook Lahore in Pakistan to become the world’s most polluted city on Friday, as thick smog blanketed the capital of more than 20 million people and air quality reached hazardous levels.
Swiss air quality monitor IQAir put Delhi’s air quality index (AQI) at 334, rated hazardous, making it the most polluted major city in the world. India’s official Central Pollution Control Board (CPCB) recorded a higher reading of 403, which falls in the “severe” category.
The two readings differ because IQAir and the CPCB use different scales and methods to measure pollution. On the CPCB scale, an AQI of up to 50 is considered good, 51 to 100 is satisfactory, 101 to 200 is moderate, 201 to 300 is poor, 301 to 400 is very poor, and anything above 400 is severe.
01. Smog cuts visibility across the capital
Visibility dropped sharply as smog hung over the city through the morning. Delhi’s air has stayed in the “very poor” range since early November, with calm winds and dry weather trapping pollutants close to the ground.
The pollution worsened after Diwali, when fireworks added to smoke from vehicles, construction dust and farm fires in nearby states. The Commission for Air Quality Management had already put Stage III of its Graded Response Action Plan (GRAP) in place across the capital region before the festival, bringing in curbs on construction and older vehicles.
02. What severe air means for your health
At severe levels, the air can affect even healthy people and seriously worsen the condition of those with heart or lung disease. Doctors advise people to avoid outdoor exercise, keep windows shut, and wear a mask when stepping out.
Children, older people and those with asthma or other breathing problems face the highest risk. Schools and offices often move classes and work online when the AQI stays severe, and the GRAP rules can be tightened further if the air does not improve.
Delhi faces the same crisis every winter. Cold, still air traps smoke and dust over the Indo-Gangetic plain, and the mix of traffic fumes, construction dust, industrial emissions and stubble burning in Punjab and Haryana pushes the AQI to dangerous levels year after year.
