A metro train runs on its track amid dense haze and low visibility, in Noida.
The air quality deteriorated but remained "very poor" in Noida, Greater Noida, Ghaziabad and Faridabad while it continued to stay "poor" in Gurgaon in the National Capital Region (NCR) on Wednesday, according to a government agency.
Concentration of major air 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'.
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The average 24-hour AQI was 389 in Ghaziabad, 368 in Greater Noida, 345 in Noida, 331 in Faridabad and 290 in Gurgaon,, according to the CPCB's Sameer app at 4 pm on Wednesday. It was 356 in Greater Noida, 340 in Ghaziabad, 270 in Gurgaon, 321 in Noida and 318 in Faridabad on Tuesday.
PM 2.5 and PM 10 were prominent pollutants in all these cities, according to the app.
All five satellite cities of Delhi have four air quality monitoring stations except for Greater Noida, which has two. The AQI for each city is based on the average value of all stations there, according to the app.The CPCB states that an AQI in the "very poor" category can lead to respiratory illness on prolonged exposure, while "poor" can cause breathing discomfort to most people on prolonged exposure.
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