The average air quality across Ghaziabad, Noida, Greater Noida, Fridabad and Gurgaon was recorded "very poor", which may cause respiratory illness to people on prolonged exposure, for a third day in a row, according to data issued by a government agency on Wednesday.
Pollutants PM 2.5 and PM 10 also remained 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).
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 Wednesday was 328 in Ghaziabad, 322 in Noida, 337 in Greater Noida, 307 in Faridabad and 316 in Gurgaon, according to CPCB's Sameer app.
On Tuesday, it was 356 in Ghaziabad, 335 in Noida, 375 in Greater Noida, 310 in Faridabad and 302 in Gurgaon.
On Monday, it was 369 in Ghaziabad, 368 in Noida, 349 in Greater Noida, 353 in Faridabad and 306 in Gurgaon.
On Sunday, it was 416 in Ghaziabad, 416 in Noida, 402 in Greater Noida, 366 in Faridabad and 288 in Gurgaon.
The CPCB states that an AQI in the "very poor" category may cause respiratory illness to people on prolonged exposure.
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.
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