The air quality was recorded in the “poor” category across Faridabad, Gurgaon, Noida, Greater Noida and Ghaziabad on Sunday, data from a government agency showed. The presence of pollutants PM 2.5 and PM 10 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 236 in Faridabad, 242 in Gurgaon, 268 in Noida, 273 in Greater Noida and 300 in Ghaziabad, according to the CPCB's Sameer app.
On Saturday, it was 171 in Faridabad, 204 in Gurgaon, 233 in Noida, 226 in Greater Noida and 240 in Ghaziabad.
The CPCB states that an AQI in the "poor" category may cause 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.