The AQI for each city is based on the average value of all stations there. (Representational)
The average air quality remained "severe" in Ghaziabad, Noida, Greater Noida and Faridabad and "very poor" in Gurgaon for a third day in a row, according to data issued by a government agency on Saturday.
Pollutants PM 2.5 and PM 10 although 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 Saturday was 423 in Ghaziabad, 438 in Greater Noida, 434 in Noida, 416 in Faridabad and 316 in Gurgaon, according to CPCB's Sameer app.
On Friday, it was 458 in Ghaziabad, 464 in Greater Noida, 475 in Noida, 467 in Faridabad and 367 in Gurgaon, according to CPCB's Sameer app.
On Thursday, it was 429 in Ghaziabad, 410 in Greater Noida, 412 in Noida, 447 in Faridabad and 364 in Gurgaon.
On Wednesday, it was 388 in Ghaziabad, 398 in Greater Noida, 348 in Noida, 367 in Faridabad and 276 in Gurgaon.
The CPCB states that an AQI in the "severe" category affects healthy people and seriously impacts those with existing diseases, while "very poor" may cause respiratory illness on prolonged exposure.
The AQI for each city is based on the average value of all stations there. Ghaziabad and Gurgaon have three such stations while Noida, Greater Noida and Faridabad have two stations each, according to the app.
(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)