The air quality improved to "moderate" category in Gurgaon, while it was recorded "very poor" in Ghaziabad and "poor" in Noida, Greater Noida and Faridabad, according to data issued by a government agency on Saturday.
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 Saturday was 307 in Ghaziabad, 254 in Greater Noida, 215 in Noida, 241 in Faridabad and 165 in Gurgaon, according to CPCB's Sameer app.
On Friday, it was 252 in Ghaziabad, 214 in Greater Noida, 201 in Noida, 207in Faridabad and 208 in Gurgaon.
The CPCB states that an AQI in the “very poor” category may cause respiratory illness to people on prolonged exposure, while "poor" may cause breathing discomfort to most people on prolonged exposure.
An AQI in the "moderate" category 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.
