The CPCB states that an AQI in the "very poor" category can lead to respiratory illness. (File)
The air quality remained ''very poor'' in Noida, Greater Noida, Ghaziabad, Gurugram and Faridabad in the National Capital Region (NCR) on Sunday, according to a government agency.
Concentration of major air pollutants PM 2.5 and PM 10 also remained high in 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 0 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 was 388 in Greater Noida, 384 in both Noida and Ghaziabad, 354 in Faridabad and 306 in Gurugram, according to the CPCB's Sameer app at 4 pm on Sunday.
It was 368 in Greater Noida, 363 in Ghaziabad, 358 in Gururgram, 356 in Noida and 348 in Faridabad on Saturday.
Prominent pollutants in Gurugram, Greater Noida and Ghaziabad were PM 2.5 and PM 10 on Sunday, the app stated, adding that prominent pollutant in Noida and Gurgaon was PM 2.5, it added.
All five satellite cities of Delhi have four air quality monitoring stations except for Greater Noida, which has two. The AQI for each city is based on the average value of all stations there, according to the app.
The CPCB states that an AQI in the "very poor" category can lead to respiratory illness on prolonged exposure.