NEW DELHI: Toxic smog hung over the city on Monday and more stations recorded ‘severe’ air quality, even though the overall Air Quality Index of the capital remained in the upper levels of the ‘very poor’ zone. The smog that had formed in the morning persisted through the day due to calm wind conditions and pollution kept soaring as the day passed.
The city’s average AQI was 373 at noon and worsened to 380 by 3pm and 386 by 6pm. For Delhiites, it was the familiar November air nightmare all over again with many complaining of itchy eyes, mild headaches and difficulty in breathing as pollution levels kept soaring, with a possible spike in NO2 and ozone, experts said.
During the morning hours, a total of eight city areas were in the “severe” category, with Anand Vihar, with an AQI of 425, being the most polluted, followed by Vivek Vihar at 424.
By late afternoon, the number of stations reporting ‘severe’ air had risen to 11, and to 16 , by 7pm. At 7 pm, Anand Vihar was the most polluted area of the city with an AQI of 442, followed by 435 at East Delhi’s Vivek Vihar. Other polluted areas included Alipur, Nehru Nagar in South Delhi, Sector-8 of Dwarka, Bawana, Jahangirpuri, and Wazirpur, among others.
The city’s average AQI, on a scale of 0 to 500, was 381 on Monday against 382 a day earlier. The PM2.5 level oscillated between 171.8 to 180.7 micrograms per cubic metre on Monday, against the national safe standard of 60 units and WHO’s 15 units for 24 hours.
“The hazy weather is indeed smog as many areas were under severe or very poor levels. Tiny pollutants such as PM2.5 in the air can settle deep in the lungs, triggering severe health issues. During this time, when pollution levels are heightened, those with pre-existing health conditions are especially vulnerable to respiratory distress,” said Shambhavi Shukla, programme manager, Air Quality Programme, Centre for Science and Environment (CSE). Experts also pointed out that a decrease in temperatures and low wind speed are adding to pollution.
“The decreasing temperature and wind speed contribute to pollution stagnation, while lower mixing depth traps pollution near the surface. This pollution mixes with fog, forming smog, which reduces visibility and leads to the grey skies we are seeing now,” said Sunil Dahiya, Founder and Lead Analyst, Envirocatalysts.
According to the air quality early warning system, the city may see very poor air quality for the next two days, after which the AQI may turn severe. It added that low wind speed for the next few days won’t favour the dispersion of pollutants. “Meteorological conditions are likely to be extremely unfavourable for the dispersion of pollutants… The air quality is likely to be in the very poor category on November 4. The air quality is likely to remain very poor from Nov 5 to 7. Outlook for the subsequent six days: Air quality is likely to be in very poor to severe category,” IITM’s air quality early warning system bulletin said.
According to IITM’s Decision Support System (DSS), the contribution of farm fires to the city’s PM2.5 levels increased to 19.7% on Monday against 15% a day earlier. Experts, however, also pointed to the role played by smog, sunlight and vehicular emissions in raising pollution levels.
“Ozone forms when nitrogen dioxide (NO2) reacts with volatile organic compounds (VOCs) under sunlight. Fossil fuel combustion releases particulate matter and NO2, while stubble burning raises pollution levels as well, also emitting high VOC levels, fuelling high ozone formation. As temperatures rise during the day, ozone concentrations spike, as shown in monitoring data across Delhi NCR,” said Dahiya.
The city recorded a maximum temperature of 32.1 degrees Celsius, two notches below normal, against 33.2 degrees Celsius a day earlier. The minimum temperature was recorded at 16.6 degrees C, a notch above normal, against 16.5 degrees C a day earlier. The maximum and minimum temperatures on Tuesday are likely to hover around 32 and 16 degrees Celsius, respectively.
Meanwhile, Gurgaon on Monday recorded its most polluted 24 hours of the season, with air quality dipping to ‘very poor’ as cold weather conditions set in and calm winds couldn’t clear away the toxic haze. Gurgaon’s 24-hour average AQI touched 310 on Monday, a 10% increase from 281 (poor) the day before.
