Noida (UP), Dec 30 (PTI) The average air quality plunged to “very poor" category in Ghaziabad, Noida and Greater Noida while it stayed “poor” in Faridabad and Gurgaon, revealed the CPCB data for the last 24 hours on Wednesday.

The presence of pollutant PM 2.5 and PM 10 remained high in the five immediate neighbourhoods of Delhi, the Central Pollution Control Board’s air quality index showed.

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 Wednesday was 310 in Ghaziabad, 315 in Greater Noida, 302 in Noida, 289 in Faridabad and 227 in Gurgaon, according to the CPCB's Sameer app.

The CPCB states that prolonged exposure to the “poor” category of air may cause breathing discomfort to people while exposure to “very poor” air may lead to respiratory illness.

The average AQI on Tuesday was 283 in Ghaziabad, 272 in Greater Noida, 258 in Noida, 291 in Faridabad and 214 in Gurgaon.

On Monday it was 256 in Ghaziabad, 237 in Greater Noida, 225 in Noida, 296 in Faridabad and 226 in Gurgaon.

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.