The air quality plunged to the "severe" level in Ghaziabad, Noida, Greater Noida and Faridabad while it stayed in the "very poor" zone in Gurgaon on the first day of 2021, according to the 24-hour data issued by a government agency on Friday.
Presence of pollutant PM 2.5 and PM 10 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 pmonFriday was 470 in Ghaziabad, 434 in Greater Noida, 455 in Noida, 421 in Faridabad and 376 in Gurgaon, according to CPCB's Sameer app.
The CPCB states that an AQI in the "severe" category affects healthy people and seriously impacts those with existing diseases while the air quality in the "very poor" zone may lead to respiratory illness on prolonged exposure.
The average AQI on Thursday was 343 in Ghaziabad, 394 in Greater Noida, 369 in Noida, 344 in Faridabad and 317 in Gurgaon. On Wednesday, it was 310 in Ghaziabad, 315 in Greater Noida, 302 in Noida, 289 in Faridabad and 227 in Gurgaon.
On Tuesday it was 283 in Ghaziabad, 272 in Greater Noida, 258 in Noida, 291 in Faridabad and 214 in Gurgaon. On Monday it was 256 in Ghaziabad, 237 in Greater Noida, 225 in Noida, 296 in Faridabad and 226 in Gurgaon. On Sunday it was 407 in Ghaziabad, 418 in Greater Noida, 405 in Noida, 404 in Faridabad and 359 in Gurgaon, according to CPCB.
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.