The average air quality was recorded in the "very poor" category in Ghaziabad, Noida, Greater Noida and Faridabad, while it was "poor" in Gurgaon, according to data for a 24-hour period issued by a government agency on Saturday.
Pollutants PM 2.5 and PM 10 were 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 Saturday was 348 in Ghaziabad, 360 in Greater Noida, 346 in Noida, 311 in Faridabad and 230 in Gurgaon, according to the CPCB's Sameer app.
On Friday it was 304 in Ghaziabad, 312 in Greater Noida, 261 in Noida, 256 in Faridabad and 163 in Gurgaon.
The CPCB states that an AQI in the "very poor" category may cause respiratory illness on prolonged exposure, while that in "poor" category may cause breathing discomfort to most people 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.
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