The air quality was recorded in the "moderate" category across Ghaziabad, Noida, Greater Noida, Gurgaon and Faridabad, according to data issued by a government agency on Sunday.
Pollutants PM 2.5 and PM 10 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 195 in Ghaziabad, 182 in Greater Noida, 174 in Noida, 180 in Faridabad and 195 in Gurgaon, according to CPCB's Sameer app.
On Saturday, it was 244 in Ghaziabad, 229 in Greater Noida, 167 in Noida, 145 in Faridabad and 217 in Gurgaon.
The CPCB states that an AQI in the "moderate” category may cause breathing discomfort to the people with lungs, asthma 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.