Explainer: What Are The Factors Behind Toxic Smog, Severe Air Quality In Delhi

Delhi today woke up to a thick layer of toxic smog as the air quality dropped to the 'severe plus' category for the first time this season. Schools have been closed for two days in the National Capital Region and all emergency measures, including a ban on commercial four-wheelers and construction activities, will be initiated soon.

The overall Air Quality Index (AQI) in Delhi at 8 am today stood at 346, according to the Central Pollution Control Board (CPCB). Air quality in Delhi's Lodhi Road, Jahangirpuri, RK Puram, and IGI Airport (T3) areas remains severe, with AQI readings of 438, 491, 486, and 473, respectively.

On Friday, levels of the most dangerous PM2.5 particles - so tiny they can enter the bloodstream - were almost 35 times the daily maximum permissible by the World Health Organization, according to monitoring firm IQAir.

While a cocktail of factors is responsible for the pollution, the chief culprits have been vehicular emissions, smoke from stubble burning, and low wind speed.

For the last couple of years, Delhi winters have been synonymous with a thick layer of hazardous smog, with the pollution peaking from November 1-15 when the number of stubble burning incidents in neighbouring Punjab and Haryana increase, studies by the Delhi Pollution Control Committee showed.

This year, Punjab recorded a sudden surge in stubble burning after a relatively smoke-less October, data showed. The state saw a 740 per cent increase on Sunday with 1,068 farm fire incidents - the highest in a single day in the current harvesting season. Saturday witnessed only 127 stubble-burning incidents.

The weather department has said that due to the rise in farm fires, no improvement in Delhi's air quality is expected over the next two days.

Last year, the Centre for Science and Environment in a study concluded that vehicular emissions contributed to nearly 51 per cent of the PM 2.5 levels in the national capital region.  Industries and construction activities contributed to 11 and 7 per cent respectively.

Meteorologists have also stated that the absence of rainfall has led to Delhi registering its worst air quality in October 2023 since 2020.

The Delhi government launched a 15-point action plan last month to mitigate air pollution during the winter season, with a strong emphasis on addressing dust pollution, vehicular emissions, and open burning of garbage.