The air quality in Noida improved to "moderate" category, while it was recorded "poor" in Ghaziabad, Greater Noida, Gurgaon and Faridabad, according to data issued by a government agency on Sunday.
Pollutants PM 2.5 and PM 10 also remained high 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 Sunday was 240 in Ghaziabad, 255 in Greater Noida, 199 in Noida, 219 in Faridabad and 233 in Gurgaon, according to CPCB's Sameer app.
On Saturday it was 307 in Ghaziabad, 254 in Greater Noida, 215 in Noida, 241 in Faridabad and 165 in Gurgaon.
The CPCB states that an AQI in the "poor" category may cause breathing discomfort to most people on prolonged exposure, while "moderate" can cause breathing discomfort to people with asthma, lungs and heart diseases.
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.
