The average air quality was recorded in "poor" category across Ghaziabad, Noida, Greater Noida, Faridabad and Gurgaon, according to data issued by a government agency on Friday.
Pollutants PM 2.5 and PM 10 also remained high in the air of the five immediate neighbours of Delhi, as per the air quality index (AQI) maintained by the Central Pollution Control Board (CPCB).
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 Friday was 252 in Ghaziabad, 214 in Greater Noida, 201 in Noida, 207in Faridabad and 208 in Gurgaon, the CPCB's Sameer app stated.
The CPCB states that an AQI in the "very poor" category may cause respiratory illness to people on prolonged exposure, while "poor" may cause breathing discomfort to most people on prolonged exposure.
On Thursday, it was 346 in Ghaziabad, 303 in Greater Noida, 292 in Noida, 286 in Faridabad and 251 in Gurgaon.
The AQI was 388 in Ghaziabad, 342 in Greater Noida, 292 in Noida, 312 in Faridabad and 265 in Gurgaon on Wednesday and on Tuesday, it was 320 in Ghaziabad, 253 in Greater Noida, 214 in Noida, 296 in Faridabad and 241 in Gurgaon.
On Monday, it was 318 in Ghaziabad, 294 in Greater Noida, 290 in Noida, 265 in Faridabad and 296 in Gurgaon.
On Sunday, the AQI was 260 in Ghaziabad, 300 in Greater Noida, 251 in Noida, 264 in Faridabad and 297 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.)