The air quality in Ghaziabad, Noida, Greater Noida, Faridabad and Gurgaon was recorded in the "very poor" category, which may cause respiratory illness on prolonged exposure, according to data issued by a government agency on Tuesday.
Pollutant PM 2.5 and PM 10 remained prominent in the air of the five immediate neighbours of Delhi, the air quality index (AQI) maintained by the Central Pollution Control Board (CPCB) stated.
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 Tuesday was 394 in Ghaziabad, 372 in Noida, 379 in Greater Noida, 354 in Faridabad and 324 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 Monday, it was 412 in Ghaziabad, 369 in Noida, 384 in Greater Noida, 352 in Faridabad and 271 in Gurgaon.
On Sunday, it was 394 in Ghaziabad, 331 in Noida, 352 in Greater Noida, 311 in Faridabad and 303 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.
(This story has not been edited by NDTV staff and is auto-generated from a syndicated feed.)