Severe pollution grips Delhi; AQI more than doubles in four days to 445

Delhi stayed in the grip of "severe" pollution for the second day running and overall Air Quality Index (AQI) surged to 445 on Wednesday, highest recorded figure for this month, after about a fortnight of respite.

 

The AQI has more than doubled in just four days, surging from 193 on December 14 to a staggering 445 on December 18, highlighting the rapid deterioration in Delhi’s air quality. Wednesday’s AQI is also the highest recorded in this month so far, according to data from the Central Pollution Control Board (CPCB).

 

On December 14, Delhi’s AQI had improved to 193, categorised as “moderate,” driven by strong winds and light rainfall earlier this month, which had resulted in one of the cleanest beginnings to December in recent years, according to the CPCB.

 

 

The CBCB data is based on the average of the past 24 hours.

 

An AQI of 50 or below is considered “good”, while “satisfactory” falls between 51 and 100. A “moderately polluted” reading ranges from 101-200, “poor” extends from 201-300, “very poor” is between 301 and 400, and anything above 400 is deemed “severe”.

 

A dense layer of toxic haze is expected to blanket the city in the coming days, with the Indian Institute of Tropical Meteorology (IITM) predicting that air quality will remain in the “severe” category on Thursday. “Meteorological conditions are likely to be unfavourable for effective dispersion of pollutants,” the IITM said.

 

The ventilation index, a critical measure of the atmosphere’s ability to disperse pollutants, is forecast to remain below the favourable threshold of 6,000 m²/s in the coming days. The index is projected at 1,500 m²/s on December 18, 3,000 m²/s on December 19, 2,700 m²/s on December 20, and 3,200 m²/s on December 21, with wind speeds averaging less than 10 km/h.

 

The sudden deterioration coincides with a rise in minimum temperatures, which have increased by 2°C in the past 24 hours. Delhi’s maximum and minimum temperatures range between 21-24°C and 5-8°C, respectively. While maximum temperatures are above normal by up to 2°C, minimum temperatures remain below normal by 1-3°C in most areas.

 

In response to the worsening air quality, the Commission for Air Quality Management (CAQM) on Monday implemented the highest level of pollution control measures under Stage IV of the Graded Response Action Plan (GRAP). The curbs were enforced immediately after air quality crossed into the “severe” category at 10PM.

 

Stage-I and modified Stage-II GRAP measures remain in force, while Stage-III restrictions were operational from November 15 to December 4. Stage-IV measures were previously enforced between November 18 and December 4 before being reintroduced this week.