Delhi’s air quality has plunged this week, with dense smog on Wednesday making the Indian capital the most polluted city in the country for the third day in a row.
A thick blanket of pollution covered the city, reducing visibility, as local measurements for the Air Quality Index (AQI) soared above 440, forcing authorities to reinstate the most stringent measures under a pollution control programme known as the Graded Response Action Plan (Grap).
AQI is a measure of five major air pollutants and is considered “good” when under 50. Any number above 400 is considered “severe”, meaning the smog should be considered harmful to even healthy individuals and outdoors activity should be avoided where possible.
Several AQI monitoring stations in Delhi crossed 450 on Wednesday morning, entering a category the Central Pollution Control Board (CPCB) refers to as “severe-plus”.
Similar conditions were reported across the National Capital Region (NCR), which includes satellite cities of Delhi such as Faridabad, Noida, and Gurugram.
The worsening of pollution levels, which officials say is likely to persist in the coming days, has raised significant health concerns, prompting authorities in the Indian capital to order some school classes be conducted online.
Data from the CPCB shows that the concentration of PM2.5 – microscopic particulate matter that can enter the bloodstream through the lungs and poses serious long-term risks to respiratory and cardiovascular health – stood at 251.5 micrograms per cubic metre on Tuesday evening. That figure is over 16 times the World Health Organisation’s (WHO) prescribed safe limit.
Experts have attributed the worsening air quality to a combination of stagnant winds, high humidity, and emissions from local sources, including vehicle and industrial pollution.
The India Meteorological Department (IMD) reported that low windspeeds have caused pollutants to remain trapped near the ground, while high humidity has also contributed. Visibility across the region has dropped sharply, with Delhi airport activating contingency procedures for dense fog-like conditions.
Authorities imposed a complete ban on construction and demolition activities in Delhi and its surrounding areas late on Monday night. The entry of non-essential diesel trucks into the capital has also been prohibited, and operations of older vehicles restricted.
Offices – both private businesses and for the public sector – have been asked to operate at 50 per cent capacity, with the remaining workforce advised to work from home.
VIDEO | Delhi continues to reel under intense cold and fog cover. Air Quality Index in the national capital also plummets to 'severe'. Drone visuals from Ashram area. #DelhiWeather #WeatherUpdate
— Press Trust of India (@PTI_News) December 18, 2024
(Full video available on PTI Videos - https://t.co/n147TvrpG7) pic.twitter.com/rgG1qV2BDJ
State governments in the NCR have also been empowered to implement additional curbs, including an odd-even vehicle scheme where cars are permitted or banned from the road based on the final digit of their registration numbers. The scheme is enforced from 8am to 8pm, alternating vehicular access accordingly.
The health impact of the current air quality has become a growing concern, with the CPCB advising vulnerable groups – including children, the elderly, and individuals with pre-existing respiratory or cardiovascular conditions – to stay indoors as much as possible.
Authorities have urged residents to use air purifiers indoors, wear N95 masks outdoors, and limit physical activity in polluted areas to reduce health risks. In reality, however, pollution masks are rarely seen on the streets of the capital.
The CPCB forecasts that pollution levels wil remain in the “severe” category on Thursday, though slight improvements are expected by 19 and 20 December with a possible shift to the “very poor” category as windspeeds increase.
This week represents the second time this winter that the fourth and highest stage of Grap restrictions have been enforced. Authorities previously imposed similar measures in November when AQI levels also exceeded 450. Temporary relief came earlier this month when pollution levels dipped, leading to the rollback of restrictions.
