Delhi’s air quality on Tuesday deteriorated to the “very poor” category for the first time this season. Government-run monitoring agency System of Air Quality and Weather Forecasting and Research, or SAFAR, said the air quality index was not likely to improve for the next two days.
Air pollution typically worsens during the winter months from October to December. It was in the “poor category” for six consecutive days after it began to decline on October 7 for the first time in over three months.
The overall air quality index or AQI was 307 at 2.30 pm in Delhi. An index reading between 0 and 50 puts the air quality in “good” category. A reading between 51 and 100 puts it in the “satisfactory” category, between 101 and 200 in the “moderate” category, and between 201 and 300 in the “poor category”. The air quality is said to be “very poor” when the index value falls between 300 and 400. An index value between 400 and 500 puts the quality in the “severe” category.
The 24-hour average AQI was 261 on Monday, the worst since February, according to PTI. It was 216 on Sunday and 221 on Saturday.
“In Delhi, the development of strong surface level inversion and sudden local calm surface wind conditions led to a low ventilation coefficient and accumulation of pollutants near the surface. The calm night time surface wind condition is likely to continue for the next two days. AQI is likely in the very poor to poor category for the next two days.”— SAFAR
Northwesterly winds bring in pollution from farm fires in Punjab and Haryana to the city. A senior scientist at the Delhi Pollution Control Committee said the dip in the air quality can be attributed to low wind speed and temperatures which allowed accumulation of pollutants. He also said stubble burning and low ventilation index, the speed at which pollutants can get dispersed, were other contributing factors.
“An increase in stubble burning fires observed yesterday around Punjab, Haryana, and neighbouring border regions with SAFAR synergised fire count estimated as 675 on 12th October but, the transport wind direction is not favourable and hence only marginal stubble contribution in PM2.5 is expected.”— SAFAR
Meanwhile, the pollution control board data showed that PM10 (particulate matter with a diameter of less than 10 microns) in the Delhi and National Capital Region was at 300 microgram per cubic meter, PTI reported. This is the highest recorded levels this season so far. PM10 levels below 100 microgram per cubic metre are considered safe in India.
On Tuesday morning, the maximum wind speed was 4 kilometers per hour, according to the India Meteorological Department. Low temperatures and stagnant winds help in accumulation of pollutants near the ground, affecting air quality.
Last year, New Delhi suffered nine consecutive days in late October and early November when the air quality was hazardous. Authorities had declared a public health emergency and closed schools and all construction activity as pollution in the city hit its worst level.
An analysis by the Council on Energy, Environment and Water, a Delhi-based think tank, said that transportation contributes 18% to 39% to the Capital’s air pollution, the highest among any other factors. This is followed by road dust which contributes 18% to 38%, industries contribution was 2% to 29%, thermal power plants was 3% to 11% and construction adds 8%.
From October 15, the Delhi government will enforce stricter measures to control air pollution as part of its Graded Response Action Plan, first started in 2017. The measures include increasing the number of buses and metros, stopping use of diesel generators and hiking parking fees.