The air quality stayed in "very poor" category in Noida, Greater Noida, Ghaziabad and Faridabad, and "poor" in Gurgaon in the National Capital Region (NCR) on Thursday, according to a government agency.
Although concentration of major air pollutants PM 2.5 and PM 10 remained high in the five neighbouring cities 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 Thursday was 328 in Ghaziabad, 327 in Greater Noida, 305 in Noida, 304 in Faridabad and 293 in Gurgaon, according to the CPCB's Sameer app. On Wednesday, it was 360 in Ghaziabad, 340 in Greater Noida, 327 in Faridabad, 309 in Noida, and 288 in Gurgaon.
Till Tuesday, all five of Delhi's neighbouring cities had their air quality in the "severe" category for over a week, according to data.
PM 2.5 and PM 10 were the prominent pollutants in Noida, Greater Noida, Ghaziabad, Faridabad and Gurgaon, according to the CPCB.
The CPCB states that an AQI in the "very poor" category may cause respiratory illness on prolonged exposure, while "poor" may lead to breathing discomfort to most people on prolonged exposure.
The AQI for each city is based on the average value of all stations there. Noida, Faridabad, Ghaziabad have four stations each, while Gurgaon has three and Greater Noida two, according to the app.
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