The air quality was recorded in the "very poor" category in Ghaziabad, Noida, Greater Noida, Gurgaon and Faridabad, according to data issued by a government agency on Sunday. Pollutant 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).
As per 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 Sunday was 394 in Ghaziabad, 331 in Noida, 352 in Greater Noida, 311 in Faridabad and 303 in Gurgaon, according to the CPCB's Sameer app.
The CPCB states that an AQI in the very poor category may cause respiratory illness on prolonged exposure. On average, AQI on Saturday was 338 in Ghaziabad, 302 in Noida, 308 in Greater Noida, 278 in Faridabad and 281 in Gurgaon.
On Friday, it was 423 in Ghaziabad, 415 in Noida, 420 in Greater Noida, 392 in Faridabad and 342 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.