The national capital's air quality was recorded in the "moderate" category on Saturday, and is likely to turn "poor" in two days due to low temperatures and slow wind speed.
Delhi's 24-hour average air quality index was recorded at 189 on Saturday. It was 180 on Friday.
An AQI between 0 and 50 is considered "good", 51 and 100 "satisfactory", 101 and 200 "moderate", 201 and 300 "poor", 301 and 400 "very poor", and 401 and 500 "severe".
"As predicted, the PM2.5 contribution (in pollution) is increasing, which is a characteristic of winters. The air quality is likely to deteriorate to the lower end of poor quality on Monday," the System of Air Quality and Weather Forecasting and Research (SAFAR) said.
PM2.5 is tiny particulate matter, less than 2.5 microns in diameter. It can enter deep into the lungs and even into the bloodstream.
It said an increase in farm fires was observed on Friday around Punjab, Haryana and neighbouring border regions and it is likely to impact Delhi in the coming days.
Also, there is a marked dip in minimum temperatures recorded in Delhi. On Saturday, it settled at 20.3 degrees Celsius, which was a notch below normal.
The minimum temperature is likely to drop to 19 degrees Celsius by Wednesday.
Low temperatures and stagnant winds aid in the accumulation of pollutants near the ground, affecting air quality.
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