New Delhi has endured its most polluted December since 2018, with the month's average air quality index (AQI) settling at a hazardous 349. With no significant improvement expected in the final two days of the year, this grim average is set to solidify, marking a severe public health crisis for the national capital.
A Month of Severe and Very Poor Air
The data reveals a disturbing trend. This December's average AQI of 349 is higher than the 294 recorded in December 2023 and approaches the 360 mark set in 2018, the worst in recent years. The city suffered through five severe air days, where the AQI soared above 400. A particularly dangerous stretch occurred from December 13 to 16, with three consecutive severe days. One of these, December 14, entered the severe-plus category with an AQI of 461.
The month also recorded four poor air quality days, while every other day was classified as very poor. This stands in stark contrast to December 2023, which saw more moderate and poor days, aided significantly by intense rainfall. Last December received 53.8mm of rain over five days, an excess of 564%, which helped cleanse the air. This year, no such relief was witnessed.
Experts Point to Trapped Local Pollutants
Environmental scientists express deep concern because this spike occurred after the period of significant stubble burning from neighbouring states had subsided. Anumita Roychowdhury, executive director of research and advocacy at the Centre for Science and Environment (CSE), argued that this indicates adverse meteorological conditions are trapping persistent local and regional emissions.
"Slow and incremental measures are clearly insufficient," Roychowdhury stated. "The region must accelerate and scale its efforts to nearly eliminate combustion emissions from vehicles, industry, power plants, waste burning, and construction, while aggressively suppressing dust sources."
PM2.5 Levels Far Exceed Safety Limits
An analysis by the Centre for Research on Energy and Clean Air (CREA) provided alarming specifics. Between December 1 and 27, Delhi's average PM2.5 concentration was 207 micrograms per cubic metre. This is 3.5 times above India's daily national ambient air quality standard of 60 micrograms per cubic metre and a staggering 13.8 times above the World Health Organization's daily safe guideline of 15.
The historical context is equally worrying. The average PM2.5 concentration for December 2024 was 170, compared to 201 in 2023, 177 in 2022, and a peak of 230 in 2018.
Dipankar Saha, former head of the Central Pollution Control Board's air laboratory, emphasised the role of weather. "Meteorological factors play the most important role in the dispersion and dilution of a homogeneous air mass across the entire region. Within this air mass, air quality remains largely similar," he explained.
This December's crisis caps a troubling winter season. October 2024 was the second most polluted October in five years with an AQI of 223. November, though slightly better than 2023 with an AQI of 357 compared to 375, remained in the very poor category and recorded three severe days.
