The average air quality improved from severe level and was recorded in very poor category in Ghaziabad, Noida, Greater Noida, Faridabad and Gurgaon, according to a 24-hour data issued by a government agency on Friday.
Presence of pollutant PM 2.5 and PM 10, though, 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 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 onFriday was 391 in Ghaziabad, 376 in Greater Noida, 386 in Noida, 328 in Faridabad and 302 in Gurgaon, according to CPCB's Sameer app.
The average air quality in Noida, Greater Noida, Ghaziabad and Faridabad was recorded in severe category for three days in a row till Thursday, according to the agency.
The CPCB states that an AQI in the very poor category may cause respiratory illness on prolonged exposure while severe affects even healthy people and seriously impacts those with existing diseases.
The average AQI on Thursday was 440 in Ghaziabad, 448 in Greater Noida, 441 in Noida, 408 in Faridabad and 361 in Gurgaon. On Wednesday it was 472 in Ghaziabad, 476 in Greater Noida, 462 in Noida, 428 in Faridabad and 340 in Gurgaon. On Tuesday, it was 458 in Ghaziabad, 450 in Greater Noida, 437 in Noida, 407 in Faridabad and 377 in Gurgaon. 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.