According to the index, an AQI between zero 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'.
The air quality was recorded in the very poor category in Ghaziabad, Noida, Greater Noida, Faridabad and Gurgaon, according to data issued by a government agency on Tuesday.
Pollutants PM 2.5 and PM 10 remained prominent in the air of the five immediate neighbours of Delhi, according to the air quality index (AQI) maintained by the Central Pollution Control Board (CPCB).
According to the index, an AQI between zero 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’.
The average 24-hour AQI at 4 pm on Tuesday was 395 in Ghaziabad, 370 in Noida, 366 in Greater Noida, 372 in Faridabad and 314 in Gurgaon, according to CPCB’s Sameer app.
The CPCB states that an AQI in the very poor category may cause respiratory illness on prolonged exposure.
On Monday, it was 360 in Ghaziabad, 352 in Noida, 372 in Greater Noida, 336 in Faridabad and 280 in Gurgaon.
On Sunday, it was 390 in Ghaziabad, 322 in Noida, 388 in Greater Noida, 353 in Faridabad and 300 in Gurgaon.
The AQI for each city is based on the average value of all monitoring stations there. Ghaziabad, Gurgaon and Noida have four such stations while Greater Noida and Faridabad have two stations each, according to the app.