After a spell of rain in NCR, air quality improved drastically in Noida, Greater Noida, Ghaziabad and Gurgaon to reach "poor" levels, while it reached "moderate" category in Faridabad on Monday, according to a government agency.
Concentration of major air pollutant PM 2.5 although remained in the five immediate neighbours of Delhi, even as PM 10 got washed off from the skies, 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 Monday was 186 in Faridabad, 207 in Ghaziabad, 226 in Greater Noida, 243 in Noida and 246 in Gurgaon, according to CPCB's Sameer app.
On Sunday, it was 448 in Ghaziabad, 441 in Noida, 417 in Greater Noida, 425 in Gurgaon and 414 in Faridabad.
On Saturday, the average AQI was 456 in Ghaziabad, 425 in Noida, 394 in Greater Noida, 378 in Faridabad and 358 in Gurgaon.
The CPCB states that an AQI in the "poor" category may cause breathing discomfort to most people on prolonged exposure, while "moderate" may cause breathing discomfort to people with asthma, lung and heart diseases.
Parts of NCR received light to moderate rains a day after Diwali, while according to the IMD, another western disturbance - the weather phenomenon that causes rains in the region - is expected around November 18-19, which will further hit the mercury due to snowfall on the northern mountainous states.
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.
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