Noida: The air quality remained "poor" in Noida, Greater Noida, Ghaziabad, Gurgaon and Faridabad in the National Capital Region (NCR) on Sunday, a government agency said.
Presence of pollutant PM 2.5 also 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 on Sunday was 242 in Gurgaon, 234 in Faridabad, 288 in Ghaziabad, 273 in Noida and 270 in Greater Noida, according to the CPCB's Sameer app.
On Saturday, it was 256 in Gurgaon, 246 in Faridabad, 238 in Ghaziabad, 231 in Noida and 228 in Greater Noida.
The CPCB states that an AQI in the "poor" category may cause breathing discomfort to most people on prolonged exposure, while that in the "very poor" zone may cause respiratory illnesses on prolonged exposure.
The average AQI last Sunday was 448 in Ghaziabad, 441 in Noida, 417 in Greater Noida, 425 in Gurgaon and 414 in Faridabad.
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.